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  • richardmitnick 8:38 am on May 17, 2019 Permalink | Reply
    Tags: "From Earth’s deep mantle, Bermuda has a unique volcanic past., , Geochemical signatures, Geology, scientists discover a new way volcanoes form", , The mantle’s transition zone – between 250 to 400 miles beneath our planet’s crust, The peculiar and extreme isotopes measured in the Bermuda lava core had not been observed before., There is enough water in the transition zone to form at least three oceans according to Gazel but it is the water that helps rock to melt in the transition zone.,   

    From Cornell Chronicle: “From Earth’s deep mantle, scientists discover a new way volcanoes form” 

    From Cornell Chronicle

    May 15, 2019
    Blaine Friedlander
    bpf2@cornell.edu

    1
    Bermuda has a unique volcanic past. About 30 million years ago, a disturbance in the mantle’s transition zone supplied the magma to form the now-dormant volcanic foundation on which the island sits. Wendy Kenigsberg/Clive Howard – Cornell University, modified from Mazza et al. (2019)

    Far below Bermuda’s pink sand beaches and turquoise tides, Cornell geoscientists have discovered the first direct evidence that material from deep within Earth’s mantle transition zone – a layer rich in water, crystals and melted rock – can percolate to the surface to form volcanoes.

    2
    In a cross-polarized microscopic slice of a core sample, the blue and yellow crystal is titanium-augite, surrounded by a ground mass of minerals, which include feldspars, phlogopite, spinel, perovskite and apatite. This assemblage suggests that the mantle source – rich in water – produced this lava. Gazel Lab/Provided

    Scientists have long known that volcanoes form when tectonic plates (traveling on top of the Earth’s mantle) converge, or as the result of mantle plumes that rise from the core-mantle boundary to make hotspots at Earth’s crust.

    The tectonic plates of the world were mapped in 1996, USGS.

    But obtaining evidence that material emanating from the mantle’s transition zone – between 250 to 400 miles beneath our planet’s crust – can cause volcanoes to form is new to geologists.

    “We found a new way to make volcanoes. This is the first time we found a clear indication from the transition zone deep in the Earth’s mantle that volcanoes can form this way,” said senior author Esteban Gazel, Cornell associate professor in the Department of Earth and Atmospheric Sciences. The research published in Nature on May 15.

    “We were expecting our data to show the volcano was a mantle plume formation – an upwelling from the deeper mantle – just like it is in Hawaii,” Gazel said. But 30 million years ago, a disturbance in the transition zone caused an upwelling of magma material to rise to the surface, form a now-dormant volcano under the Atlantic Ocean and then form Bermuda.

    Using a 2,600-foot core sample – drilled in 1972, housed at Dalhousie University, Nova Scotia – co-author Sarah Mazza of the University of Münster, Germany, assessed the cross-section for signature isotopes, trace elements, evidence of water content and other volatile material. The assessment provided a geologic, volcanic history of Bermuda.

    “I first suspected that Bermuda’s volcanic past was special as I sampled the core and noticed the diverse textures and mineralogy preserved in the different lava flows,” Mazza said. “We quickly confirmed extreme enrichments in trace element compositions. It was exciting going over our first results … the mysteries of Bermuda started to unfold.”

    From the core samples, the group detected geochemical signatures from the transition zone, which included larger amounts of water encased in the crystals than were found in subduction zones. Water in subduction zones recycles back to Earth’s surface. There is enough water in the transition zone to form at least three oceans, according to Gazel, but it is the water that helps rock to melt in the transition zone.

    The geoscientists developed numerical models with Robert Moucha, associate professor of Earth sciences at Syracuse University, to discover a disturbance in the transition zone that likely forced material from this deep mantle layer to melt and percolate to the surface.

    Despite more than 50 years of isotopic measurements in oceanic lavas, the peculiar and extreme isotopes measured in the Bermuda lava core had not been observed before. Yet, these extreme isotopic compositions allowed the scientists to identify the unique source of the lava.

    “If we start to look more carefully, I believe we’re going to find these geochemical signatures in more places,” said co-author Michael Bizimis, associate professor at the University of South Carolina.

    Gazel explained that this research provides a new connection between the transition zone layer and volcanoes on the surface of Earth. “With this work we can demonstrate that the Earth’s transition zone is an extreme chemical reservoir,” he said. “We are now just now beginning to recognize its importance in terms of global geodynamics and even volcanism.”

    Said Gazel: “Our next step is to examine more locations to determine the difference between geological processes that can result in intraplate volcanoes and determine the role of the mantle’s transition zone in the evolution of our planet.”

    Gazel is a fellow at Cornell’s Atkinson Center for a Sustainable Future and a fellow at Cornell’s Carl Sagan Institute. In addition to Gazel, Mazza, Bizimis and Moucha, co-authors of “Sampling the Volatile-Rich Transition Zone Beneath Bermuda,” are Paul Béguelin, University of South Carolina; Elizabeth A. Johnson, James Madison University; Ryan J. McAleer, United States Geological Survey; and Alexander V. Sobolev, the Russian Academy of Sciences.

    The National Science Foundation provided funding for this research.

    See the full article here .


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    Please help promote STEM in your local schools.

    Stem Education Coalition

    Once called “the first American university” by educational historian Frederick Rudolph, Cornell University represents a distinctive mix of eminent scholarship and democratic ideals. Adding practical subjects to the classics and admitting qualified students regardless of nationality, race, social circumstance, gender, or religion was quite a departure when Cornell was founded in 1865.

    Today’s Cornell reflects this heritage of egalitarian excellence. It is home to the nation’s first colleges devoted to hotel administration, industrial and labor relations, and veterinary medicine. Both a private university and the land-grant institution of New York State, Cornell University is the most educationally diverse member of the Ivy League.

    On the Ithaca campus alone nearly 20,000 students representing every state and 120 countries choose from among 4,000 courses in 11 undergraduate, graduate, and professional schools. Many undergraduates participate in a wide range of interdisciplinary programs, play meaningful roles in original research, and study in Cornell programs in Washington, New York City, and the world over.

     
  • richardmitnick 11:36 am on May 4, 2019 Permalink | Reply
    Tags: "When it comes to planetary habitability it’s what’s inside that counts", A true picture of planetary habitability must consider how a planet’s atmosphere is linked to and shaped by what’s happening in its interior, , , , , , Geology, , , ,   

    From Carnegie Institution for Science: “When it comes to planetary habitability, it’s what’s inside that counts” 

    Carnegie Institution for Science
    From Carnegie Institution for Science

    May 01, 2019

    Which of Earth’s features were essential for the origin and sustenance of life? And how do scientists identify those features on other worlds?

    A team of Carnegie investigators with array of expertise ranging from geochemistry to planetary science to astronomy published this week in Science an essay urging the research community to recognize the vital importance of a planet’s interior dynamics in creating an environment that’s hospitable for life.

    With our existing capabilities, observing an exoplanet’s atmospheric composition will be the first way to search for signatures of life elsewhere. However, Carnegie’s Anat Shahar, Peter Driscoll, Alycia Weinberger, and George Cody argue that a true picture of planetary habitability must consider how a planet’s atmosphere is linked to and shaped by what’s happening in its interior.

    1
    Reprinted with permission from Shahar et. al., Science Volume 364:3(2019).

    For example, on Earth, plate tectonics are crucial for maintaining a surface climate where life can thrive. What’s more, without the cycling of material between its surface and interior, the convection that drives the Earth’s magnetic field would not be possible and without a magnetic field, we would be bombarded by cosmic radiation.

    “We need a better understanding of how a planet’s composition and interior influence its habitability, starting with Earth,” Shahar said. “This can be used to guide the search for exoplanets and star systems where life could thrive, signatures of which could be detected by telescopes.”

    It all starts with the formation process. Planets are born from the rotating ring of dust and gas that surrounds a young star. The elemental building blocks from which rocky planets form—silicon, magnesium, oxygen, carbon, iron, and hydrogen—are universal. But their abundances and the heating and cooling they experience in their youth will affect their interior chemistry and, in turn, things like ocean volume and atmospheric composition.

    “One of the big questions we need to ask is whether the geologic and dynamic features that make our home planet habitable can be produced on planets with different compositions,” Driscoll explained.

    The Carnegie colleagues assert that the search for extraterrestrial life must be guided by an interdisciplinary approach that combines astronomical observations, laboratory experiments of planetary interior conditions, and mathematical modeling and simulations.

    2
    Artist’s impression of the surface of the planet Barnard’s Star b courtesy of ESO/M. Kornmesser.

    “Carnegie scientists are long-established world leaders in the fields of geochemistry, geophysics, planetary science, astrobiology, and astronomy,” said Weinberger. “So, our institution is perfectly placed to tackle this cross-disciplinary challenge.”

    In the next decade as a new generation of telescopes come online, scientists will begin to search in earnest for biosignatures in the atmospheres of rocky exoplanets. But the colleagues say that these observations must be put in the context of a larger understanding of how a planet’s total makeup and interior geochemistry determines the evolution of a stable and temperate surface where life could perhaps arise and thrive.

    “The heart of habitability is in planetary interiors,” concluded Cody.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Carnegie Institution of Washington Bldg

    Carnegie Institution for Science

    Andrew Carnegie established a unique organization dedicated to scientific discovery “to encourage, in the broadest and most liberal manner, investigation, research, and discovery and the application of knowledge to the improvement of mankind…” The philosophy was and is to devote the institution’s resources to “exceptional” individuals so that they can explore the most intriguing scientific questions in an atmosphere of complete freedom. Carnegie and his trustees realized that flexibility and freedom were essential to the institution’s success and that tradition is the foundation of the institution today as it supports research in the Earth, space, and life sciences.

    6.5 meter Magellan Telescopes located at Carnegie’s Las Campanas Observatory, Chile.
    6.5 meter Magellan Telescopes located at Carnegie’s Las Campanas Observatory, Chile


    Carnegie Las Campanas 2.5 meter Irénée Dupont telescope, Atacama Desert, over 2,500 m (8,200 ft) high approximately 100 kilometres (62 mi) northeast of the city of La Serena,Chile


    Carnegie Institution Swope telescope at Las Campanas, Chile, 100 kilometres (62 mi) northeast of the city of La Serena. near the north end of a 7 km (4.3 mi) long mountain ridge. Cerro Las Campanas, near the southern end and over 2,500 m (8,200 ft) high, at Las Campanas, Chile

    [/caption]

     
  • richardmitnick 10:10 am on April 28, 2019 Permalink | Reply
    Tags: , , , , , Geology, , Jupiter's Europa moon, , , OPAG-Outer Planet Assessment Group   

    From Nautilus: “Why Europa Is the Place to Go for Alien Life” 

    Nautilus

    From Nautilus

    April 18, 2019
    Corey S. Powell

    1
    This image shows a view of the trailing hemisphere of Jupiter’s ice-covered satellite, Europa, in approximate natural color. Long, dark lines are fractures in the crust, some of which are more than 3,000 kilometers (1,850 miles) long. The bright feature containing a central dark spot in the lower third of the image is a young impact crater some 50 kilometers (31 miles) in diameter. This crater has been provisionally named “Pwyll” for the Celtic god of the underworld. Europa is about 3,160 kilometers (1,950 miles) in diameter, or about the size of Earth’s moon. This image was taken on September 7, 1996, at a range of 677,000 kilometers (417,900 miles) by the solid state imaging television camera onboard the Galileo spacecraft during its second orbit around Jupiter. The image was processed by Deutsche Forschungsanstalt fuer Luftund Raumfahrt e.V., Berlin, Germany. NASA/JPL/DLR.

    NASA/Galileo 1989-2003

    I have seen the future of space exploration, and it looks like a cue ball covered with brown scribbles. I am talking about Europa, the 1,940-mile-wide, nearly white, and exceedingly smooth satellite of Jupiter. It is an enigmatic world that is, in many ways, almost a perfect inversion of Earth. It is also one of the most plausible places to look for alien life. If it strikes you that those two statements sound rather contradictory—why yes, they do. And therein lies the reason why Europa just might be the most important world in the solar system right now. The Europa Clipper spacecraft is scheduled to launch in 2023 to probe the mysterious moon, according to NASA’s 2020 budget proposal.

    NASA/Europa Clipper annotated

    The unearthly aspects of Europa are literally un-earthly : This is an orb sculpted from water ice, not from rock. It has ice tectonics in place of shifting continents, salty ocean in place of mantle, and vapor plumes in place of volcanoes. The surface scribbles may be dirty ocean material that leaked up through the icy equivalent of an earthquake fault.

    From a terrestrial perspective, Europa is built all wrong, with its solid crust up top and water down below. From the perspective of alien life, though, that might be a perfectly dandy arrangement. Beneath its frozen crust, Europa holds twice as much liquid water as exists in all of our planet’s oceans combined. Astrobiologists typically flag water as life’s number-one requirement; well, Europa is drowning in it. Just below the ice line, conditions might resemble the environment on the underside of Antarctic ice sheets. At the bottom of its buried ocean, Europa may have an active system of hydrothermal vents. Both of these are vibrant habitats on Earth.

    Adding a new twist to the story, Europa’s water may sometimes escape its icy confines. On at least four occasions, the Hubble Space Telescope has detected what appear to be large plumes of water vapor erupting from Europa. That detection has confirmed and expanded on the scientific ideas about what makes Europa such a dynamic world. Europa travels in a slightly oval orbit around Jupiter, causing it to get alternately squeezed and stretched by the giant planet’s gravity. The flexing creates intense friction inside the satellite and generates enough heat to maintain a warm ocean beneath Europa’s frozen outer shell. The presence of a plume suggests that the stretching of Europa also opens and closes a network of fissures that allow buried water to erupt as geysers.

    If the geysers consist of ocean water shooting all the way through the crust, they could carry traces of aquatic life with them. And if the plumes rise high enough, a future spacecraft could fly right through them, sniffing for biochemicals.

    2
    SIGNS FROM BELOW: Salty seawater appears to have breached Europa’s frozen exterior, creating a network of red-brown streaks. Perhaps traces of aquatic life were carried along in the process? This scene is 100 miles wide. NASA/JPL-Caltech/SETI Institute

    You can see why people were giddy at a 2015 OPAG meeting held at NASA’s Ames Research Center. A regular forum for geeking out about ice worlds, the OPAG gatherings—short for Outer Planet Assessment Group—feel halfway between the corporate swarm of a MacWorld expo and a vinyl record fair. They are where true believers mingle with the newbies, showing off the latest science, kicking around speculative ideas, and developing strategies for exploration. With each new bit of data, they have grown increasingly convinced that Europa, not Mars, is the place to go to search for alien life. Finding the plume on Europa was another shot of adrenaline. The room went fervently silent as Lorenz Roth of Sweden’s Royal Institute of Technology, calling in via a fuzzy phone line, reported on the latest search for a recurrence of such water eruptions (no luck yet, alas).

    Another significant piece of news was hanging over the OPAG meeting: The discovery that Europa has plate tectonics, like Earth and unlike any other world we know of. Tectonics describes a process in which the crust moves about and cycles back and forth into the interior. Louise Prockter of Johns Hopkins University’s Applied Physics Laboratory co-discovered this style of activity on Europa by painstakingly reconstructing old images from the Galileo spacecraft, which circled Jupiter from 1995 to 2003. (Analysis of other Galileo data suggests the probe flew right past a Europan water plume in 1997, but scientists didn’t realize it at the time.)

    As Prockter explained to me at the meeting, a mobile crust potentially does two important things. It cycles surface ice, along with all the compounds it develops during exposure to the sun, down into the dark ocean; that chemical flow could be crucial for supplying the ocean with nutrients. The motion of the crust also brings ocean material up to the surface, where prying human eyes can seek clues about the Europan ocean without actually drilling down into it.

    Bolstered by these discoveries, the cult of Europa has now escaped the confines of the OPAG meetings. A successful mission to Europa would bring into focus the incredible ice-and-ocean environment of Europa. It would also help scientists understand ice worlds in general. Icy moons, dwarf planets, and giant asteroids are the norm in the vast outer zone of the solar system, and if they repeat the pattern of Europa they may contain much of the solar system’s habitable real estate. There is good reason to think that ice worlds are similarly abundant around other stars as well. Putting all of these new ideas together suggests that the Milky Way may collectively contain tens of billions of life-friendly iceboxes.

    But if these stunning extrapolations seem to suggest that scientists are starting to get a handle on how Europa works, allow me to suggest otherwise. Europa is still largely a big, icy ball of confusion.

    3
    Under the Ice: An artist’s conception of Europa (foreground), Jupiter (right) and Jupiter’s innermost large moon, Io (middle), shows salts bubbling up from Europa’s liquid ocean to reach its frozen surface. NASA/JPL-Caltech.

    Almost everything we know about the surface of Europa comes from NASA’s Galileo mission, which reached Jupiter in 1995. During its eight-year mission, Galileo mapped most of Europa, but at a crude resolution of about one mile per pixel. For comparison, today’s best Mars images show features as small as three feet. Elizabeth “Zibi” Turtle of the Hopkins Applied Physics Lab promises that the camera on NASA’s upcoming Europa probe will achieve a similar level of clarity. Until then, imagine trying to navigate using a map that doesn’t show anything smaller than one mile and you will get a sense of how far the Europa scientists have to go.

    What’s more, at a very basic level, planetary scientists still do not have a good handle on how geology (or maybe we should say “glaciology?”) works in frozen settings. Ice, you see, is not just ice. Robert Pappalardo of NASA’s Jet Propulsion Laboratory, the ponytail-wielding mission scientist for the agency’s upcoming Europa probe, spelled out some of the complexities to me. On Europa, surface temperatures on a warm day at the equator might rise up to -210 degrees Fahrenheit; at the poles, the lows plunge to -370 degrees Fahrenheit. Under those conditions, water is properly thought of as a mineral, and ice has approximately the consistency of concrete. In many ways it is remarkably similar to rock in how it fractures, faults, and shatters. But even in such a deep freeze, surface ice can sublimate—evaporate directly from solid to gas—in a way that rock does not. Icy material tends to boil off from darker, warmer regions and collect on lighter, cooler ones, producing an exotic kind of weathering that rearranges the landscape without any wind or rain.

    All sorts of other things are happening on the surface of Europa. Jupiter has a huge, potent magnetic field that bombards its satellite with radiation: about 500 rem per day on average, which you can more easily judge as a dose strong enough to make you sick in one hour and to kill you in 24. That radiation quickly breaks down any organic compounds, greatly complicating the search for life, but produces all kinds of other complex chemistry. A lab experiment at the Jet Propulsion Laboratory suggests that the colors of Europa’s streaks are produced by irradiated ocean salts. These and other fragmented molecules, along with a steady rain of organic material delivered by comet impacts, could be used as energy sources for life when they circulate back down into the ocean, where any living things would be well protected.

    The movement of Europa’s crust—its icy outer shell—is another broad area of mystery. On ice worlds, Pappalardo notes, water takes on the role of magma and hot rock deep below the surface, but once again ice and rock are not quite the same. Warm ice turns soft, almost slushy, under high pressure and slowly flows. There could be complicated circulation patterns contained entirely within the crust, which is perhaps 10 to 15 miles thick (or maybe more or less; that is yet another mystery that the Europa mission will investigate). Pools of liquid water might exist trapped within the shell, cut off from the underlying ocean. Plumes of water at the surface might not originate directly from the ocean; it is possible that they come from these intermediate lakes, analogous to the largely unexplored Lake Vostok in Antarctica.

    At the OPAG meeting, seemingly narrow arguments about the circulation of ice sparked colorful debates about prospects for life on Europa and, by extension, on the myriad other ice worlds out there. Britney Schmidt of Georgia Tech wondered if the active geology (glaciology) on Europa occurs entirely within the crust. If material does not circulate at all between surface and ocean, Europa is sealed tight. Life could not get any fresh chemicals from up above, and if it somehow manages to survive anyway we might never know unless we find a way to dig a hole all the way through. Several researchers at OPAG suggested that meaningful answers will require a surface lander; one energetic audience member repeatedly argued for sending an impactor—a high-speed bowling ball, essentially—to smack the surface and shake loose any possible buried microbes.

    As for the Europan ocean itself, that runs even deeper into what you might call aqua incognita . If the surface truly is streaked with salts, as the recent experiments indicate, that suggests a mineral-rich ocean in which waters interact vigorously with a rocky seafloor at the bottom. A likely source of such interaction is a network of hydrothermal vents powered by Europa’s internal heat; such vents could provide chemical energy to sustain Europan life, as they do on Earth. But how much total hydrothermal activity goes on? Are the acidity and salinity conducive to life? How much organic material is down there? The scientists egged each other on with provocative questions that, as yet, have no answers.

    When (or if) we will find out will depend, in large part, on how much of Europa’s inner nature is evident from the outside. The conversations at OPAG sometimes devolved into something resembling a college existential argument: If an alien swims in Europa’s ocean and nobody is able to see it, is it really alive?

    The Europa faithful have been waiting a long time for a mission that would wipe away those kinds of arguments, or at least ground them in hard data. That wait has been full of whipsaw swings between optimism and disappointment. NASA’s planned Europa Orbiter got a green light in 1999, only to be cancelled in 2002. The agency rebounded with a proposal for an even more ambitious, nuclear-propelled Jupiter Icy Moons Orbiter, which looked incredible until it got delayed and finally cancelled in 2006. A proposed joint venture with the European Space Agency never even got that far, though the Europeans are going ahead with their part of the project, which will send a probe to Ganymede, another one of Jupiter’s icy moons, in 2030.

    The Europa Clipper, outfitted with scientific instruments that include cameras and spectrometers, will swoop repeatedly past the moon and produce images that determine its composition. There is a chance the Europa mission will include a lander. Funding does not exist yet, but Adam Steltzner—the hearty engineer who figured out how to land the two-ton Curiosity rover safely on Mars—assures me that from a technical standpoint it would not be difficult to design a small probe equipped with rockets to allow a soft touchdown on Europa. There it could drill into the surface and search for possible organic material that has not been degraded by the radiation blasts from Jupiter.

    What you won’t see, the OPAG boffins all sadly agreed, is one of those cool Europa submarines that show up on the speculative “future mission concept” NASA web pages. Getting a probe into Lake Vostok right here on Earth has proven a daunting challenge. Drilling through 10 miles or more of Europan ice and exploring an alien ocean by remote control is something we still don’t know how to do, and certainly not with any plausible future NASA budget.

    No matter. Even the no-frills version of NASA’s current Europa plan will unleash a flood of information about how ice worlds work, and about how likely they are to support life. If the answers are as exciting as many scientists hope—and as I strongly expect—it will bolster the case for future missions to Titan, Enceladus, and some of Europa’s other beckoning cousins. It will reshape the search for habitable worlds around other stars as well. Right now astronomers are mostly focused on finding other Earthlike planets, but maybe that is not where most of the action is. Perhaps most of the life in the universe is locked away, safe but almost undetectable, beneath shells of ice.

    Whether or not Europa is home to alien organisms, it will tell us about the range of what life can be, and where it can be. That one icy moon will help cure science of its rocky-planet chauvinism. Hey, who you calling cue ball?

    See the full article here .

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    Welcome to Nautilus. We are delighted you joined us. We are here to tell you about science and its endless connections to our lives. Each month we choose a single topic. And each Thursday we publish a new chapter on that topic online. Each issue combines the sciences, culture and philosophy into a single story told by the world’s leading thinkers and writers. We follow the story wherever it leads us. Read our essays, investigative reports, and blogs. Fiction, too. Take in our games, videos, and graphic stories. Stop in for a minute, or an hour. Nautilus lets science spill over its usual borders. We are science, connected.

     
  • richardmitnick 10:52 am on April 1, 2019 Permalink | Reply
    Tags: "Annals of the Former World-The Day the Dinosaurs Died", , Cretaceous period, Geology, Paleogene period, Paleontologist Robert DePalma, , The colossal “Deccan” volcanic eruptions, The Hell Creek Formation, The KT boundary marks the dividing line between the Cretaceous period and the Tertiary period., The KT layer was laced with the rare metal iridium which they hypothesized was from the dusty remains of an asteroid impact-so geologist Walter Alvarez and his father Luis Alvarez, , The Tertiary has been redefined as the Paleogene,   

    From The New Yorker via U Washington: “Annals of the Former World-The Day the Dinosaurs Died” 

    U Washington

    University of Washington

    new-yorker-bloc-rea-irvin
    Rea Irvin

    From The New Yorker

    April 8, 2019
    Douglas Preston

    1
    A field assistant, Rudy Pascucci, left, and the paleontologist Robert DePalma, right, at DePalma’s dig site. Of his discovery, DePalma said, “It’s like finding the Holy Grail clutched in the bony fingers of Jimmy Hoffa, sitting on top of the Lost Ark.”

    If, on a certain evening about sixty-­six million years ago, you had stood somewhere in North America and looked up at the sky, you would have soon made out what appeared to be a star. If you watched for an hour or two, the star would have seemed to grow in brightness, although it barely moved. That’s because it was not a star but an asteroid, and it was headed directly for Earth at about forty-five thousand miles an hour. Sixty hours later, the asteroid hit. The air in front was compressed and violently heated, and it blasted a hole through the atmosphere, generating a supersonic shock wave. The asteroid struck a shallow sea where the Yucatán peninsula is today. In that moment, the Cretaceous period ended and the Paleogene period began.

    A few years ago, scientists at Los Alamos National Laboratory used what was then one of the world’s most powerful computers, the so-called Q Machine, to model the effects of the impact.

    2
    The ASCI Q machine at LANL.

    The result was a slow-motion, second-by-second false-color video of the event. Within two minutes of slamming into Earth, the asteroid, which was at least six miles wide, had gouged a crater about eighteen miles deep and lofted twenty-five trillion metric tons of debris into the atmosphere. Picture the splash of a pebble falling into pond water, but on a planetary scale. When Earth’s crust rebounded, a peak higher than Mt. Everest briefly rose up. The energy released was more than that of a billion Hiroshima bombs, but the blast looked nothing like a nuclear explosion, with its signature mushroom cloud. Instead, the initial blowout formed a “rooster tail,” a gigantic jet of molten material, which exited the atmosphere, some of it fanning out over North America. Much of the material was several times hotter than the surface of the sun, and it set fire to everything within a thousand miles. In addition, an inverted cone of liquefied, superheated rock rose, spread outward as countless red-hot blobs of glass, called tektites, and blanketed the Western Hemisphere.

    Some of the ejecta escaped Earth’s gravitational pull and went into irregular orbits around the sun. Over millions of years, bits of it found their way to other planets and moons in the solar system. Mars was eventually strewn with the debris—just as pieces of Mars, knocked aloft by ancient asteroid impacts, have been found on Earth. A 2013 study in the journal Astrobiology estimated that tens of thousands of pounds of impact rubble may have landed on Titan, a moon of Saturn, and on Europa and Callisto, which orbit Jupiter—three satellites that scientists believe may have promising habitats for life. Mathematical models indicate that at least some of this vagabond debris still harbored living microbes. The asteroid may have sown life throughout the solar system, even as it ravaged life on Earth.

    The asteroid was vaporized on impact. Its substance, mingling with vaporized Earth rock, formed a fiery plume, which reached halfway to the moon before collapsing in a pillar of incandescent dust. Computer models suggest that the atmosphere within fifteen hundred miles of ground zero became red hot from the debris storm, triggering gigantic forest fires. As the Earth rotated, the airborne material converged at the opposite side of the planet, where it fell and set fire to the entire Indian subcontinent. Measurements of the layer of ash and soot that eventually coated the Earth indicate that fires consumed about seventy per cent of the world’s forests. Meanwhile, giant tsunamis resulting from the impact churned across the Gulf of Mexico, tearing up coastlines, sometimes peeling up hundreds of feet of rock, pushing debris inland and then sucking it back out into deep water, leaving jumbled deposits that oilmen sometimes encounter in the course of deep-sea drilling.

    The damage had only begun. Scientists still debate many of the details, which are derived from the computer models, and from field studies of the debris layer, knowledge of extinction rates, fossils and microfossils, and many other clues. But the over-all view is consistently grim. The dust and soot from the impact and the conflagrations prevented all sunlight from reaching the planet’s surface for months. Photosynthesis all but stopped, killing most of the plant life, extinguishing the phytoplankton in the oceans, and causing the amount of oxygen in the atmosphere to plummet. After the fires died down, Earth plunged into a period of cold, perhaps even a deep freeze. Earth’s two essential food chains, in the sea and on land, collapsed. About seventy-five per cent of all species went extinct. More than 99.9999 per cent of all living organisms on Earth died, and the carbon cycle came to a halt.

    Earth itself became toxic. When the asteroid struck, it vaporized layers of limestone, releasing into the atmosphere a trillion tons of carbon dioxide, ten billion tons of methane, and a billion tons of carbon monoxide; all three are powerful greenhouse gases. The impact also vaporized anhydrite rock, which blasted ten trillion tons of sulfur compounds aloft. The sulfur combined with water to form sulfuric acid, which then fell as an acid rain that may have been potent enough to strip the leaves from any surviving plants and to leach the nutrients from the soil.

    Today, the layer of debris, ash, and soot deposited by the asteroid strike is preserved in the Earth’s sediment as a stripe of black about the thickness of a notebook. This is called the KT boundary, because it marks the dividing line between the Cretaceous period and the Tertiary period. (The Tertiary has been redefined as the Paleogene, but the term “KT” persists.) Mysteries abound above and below the KT layer. In the late Cretaceous, widespread volcanoes spewed vast quantities of gas and dust into the atmosphere, and the air contained far higher levels of carbon dioxide than the air that we breathe now. The climate was tropical, and the planet was perhaps entirely free of ice. Yet scientists know very little about the animals and plants that were living at the time, and as a result they have been searching for fossil deposits as close to the KT boundary as possible.

    One of the central mysteries of paleontology is the so-called “three-­metre problem.” In a century and a half of assiduous searching, almost no dinosaur remains have been found in the layers three metres, or about nine feet, below the KT boundary, a depth representing many thousands of years. Consequently, numerous paleontologists have argued that the dinosaurs were on the way to extinction long before the asteroid struck, owing perhaps to the volcanic eruptions and climate change. Other scientists have countered that the three-metre problem merely reflects how hard it is to find fossils. Sooner or later, they’ve contended, a scientist will discover dinosaurs much closer to the moment of destruction.

    Locked in the KT boundary are the answers to our questions about one of the most significant events in the history of life on the planet. If one looks at the Earth as a kind of living organism, as many biologists do, you could say that it was shot by a bullet and almost died. Deciphering what happened on the day of destruction is crucial not only to solving the three-­metre problem but also to explaining our own genesis as a species.

    On August 5, 2013, I received an e-mail from a graduate student named Robert DePalma. I had never met DePalma, but we had corresponded on paleontological matters for years, ever since he had read a novel I’d written that centered on the discovery of a fossilized Tyrannosaurus rex killed by the KT impact. “I have made an incredible and unprecedented discovery,” he wrote me, from a truck stop in Bowman, North Dakota. “It is extremely confidential and only three others know of it at the moment, all of them close colleagues.” He went on, “It is far more unique and far rarer than any simple dinosaur discovery. I would prefer not outlining the details via e-mail, if possible.” He gave me his cell-phone number and a time to call.

    I called, and he told me that he had discovered a site like the one I’d imagined in my novel, which contained, among other things, direct victims of the catastrophe. At first, I was skeptical. DePalma was a scientific nobody, a Ph.D. candidate at the University of Kansas, and he said that he had found the site with no institutional backing and no collaborators. I thought that he was likely exaggerating, or that he might even be crazy. (Paleontology has more than its share of unusual people.) But I was intrigued enough to get on a plane to North Dakota to see for myself.

    DePalma’s find was in the Hell Creek geological formation, which outcrops in parts of North Dakota, South Dakota, Montana, and Wyoming, and contains some of the most storied dinosaur beds in the world.

    3
    Hell Creek Formation near Ft. Peck Reservoir, Montana. Anky-man.

    At the time of the impact, the Hell Creek landscape consisted of steamy, subtropical lowlands and floodplains along the shores of an inland sea. The land teemed with life and the conditions were excellent for fossilization, with seasonal floods and meandering rivers that rapidly buried dead animals and plants.

    Dinosaur hunters first discovered these rich fossil beds in the late nineteenth century. In 1902, Barnum Brown, a flamboyant dinosaur hunter who worked at the American Museum of Natural History, in New York, found the first Tyrannosaurus rex here, causing a worldwide sensation. One paleontologist estimated that in the Cretaceous period Hell Creek was so thick with T. rexes that they were like hyenas on the Serengeti. It was also home to triceratops and duckbills.

    4
    DePalma’s thesis adviser estimated that the site will keep specialists busy for half a century. “Robert’s got so much stuff that’s unheard of,” he said. “It will be in the textbooks.”
    Photograph by Richard Barnes for The New Yorker.

    The Hell Creek Formation spanned the Cretaceous and the Paleogene periods, and paleontologists had known for at least half a century that an extinction had occurred then, because dinosaurs were found below, but never above, the KT layer. This was true not only in Hell Creek but all over the world. For many years, scientists believed that the KT extinction was no great mystery: over millions of years, volcanism, climate change, and other events gradually killed off many forms of life. But, in the late nineteen-seventies, a young geologist named Walter Alvarez and his father, Luis Alvarez, a nuclear physicist, discovered that the KT layer was laced with unusually high amounts of the rare metal iridium, which, they hypothesized, was from the dusty remains of an asteroid impact. In an article in Science, published in 1980, they proposed that this impact was so large that it triggered the mass extinction, and that the KT layer was the debris from that event. Most paleontologists rejected the idea that a sudden, random encounter with space junk had drastically altered the evolution of life on Earth. But as the years passed the evidence mounted, until, in a 1991 paper, the smoking gun was announced: the discovery of an impact crater buried under thousands of feet of sediment in the Yucatán peninsula, of exactly the right age, and of the right size and geochemistry, to have caused a worldwide cataclysm. The crater and the asteroid were named Chicxulub, after a small Mayan town near the epicenter.

    One of the authors of the 1991 paper, David Kring, was so frightened by what he learned of the impact’s destructive nature that he became a leading voice in calling for a system to identify and neutralize threatening asteroids. “There’s no uncertainty to this statement: the Earth will be hit by a Chicxulub-size asteroid again, unless we deflect it,” he told me. “Even a three-hundred-metre rock would end world agriculture.”

    In 2010, forty-one researchers in many scientific disciplines announced, in a landmark Science article, that the issue should be considered settled: a huge asteroid impact caused the extinction. But opposition to the idea remains passionate. The main competing hypothesis is that the colossal “Deccan” volcanic eruptions, in what would become India, spewed enough sulfur and carbon dioxide into the atmosphere to cause a climatic shift. The eruptions, which began before the KT impact and continued after it, were among the biggest in Earth’s history, lasting hundreds of thousands of years, and burying half a million square miles of the Earth’s surface a mile deep in lava. The three-­metre gap below the KT layer, proponents argued, was evidence that the mass extinction was well under way by the time of the asteroid strike.

    In 2004, DePalma, at the time a twenty-­two-year-old paleontology undergraduate, began excavating a small site in the Hell Creek Formation. The site had once been a pond, and the deposit consisted of very thin layers of sediment. Normally, one geological layer might represent thousands or millions of years. But DePalma was able to show that each layer in the deposit had been laid down in a single big rainstorm. “We could see when there were buds on the trees,” he told me. “We could see when the cypresses were dropping their needles in the fall. We could experience this in real time.” Peering at the layers was like flipping through a paleo-history book that chronicled decades of ecology in its silty pages. DePalma’s adviser, the late Larry Martin, urged him to find a similar site, but one that had layers closer to the KT boundary.

    Today, DePalma, now thirty-seven, is still working toward his Ph.D. He holds the unpaid position of curator of vertebrate paleontology at the Palm Beach Museum of Natural History, a nascent and struggling museum with no exhibition space. In 2012, while looking for a new pond deposit, he heard that a private collector had stumbled upon an unusual site on a cattle ranch near Bowman, North Dakota. (Much of the Hell Creek land is privately owned, and ranchers will sell digging rights to whoever will pay decent money, paleontologists and commercial fossil collectors alike.) The collector felt that the site, a three-foot-deep layer exposed at the surface, was a bust: it was packed with fish fossils, but they were so delicate that they crumbled into tiny flakes as soon as they met the air. The fish were encased in layers of damp, cracked mud and sand that had never solidified; it was so soft that it could be dug with a shovel or pulled apart by hand. In July, 2012, the collector showed DePalma the site and told him that he was welcome to it.

    “I was immediately very disappointed,” DePalma told me. He was hoping for a site like the one he’d excavated earlier: an ancient pond with fine-grained, fossil-bearing layers that spanned many seasons and years. Instead, everything had been deposited in a single flood. But as DePalma poked around he saw potential. The flood had entombed everything immediately, so specimens were exquisitely preserved. He found many complete fish, which are rare in the Hell Creek Formation, and he figured that he could remove them intact if he worked with painstaking care. He agreed to pay the rancher a certain amount for each season that he worked there. (The specifics of the arrangement, as is standard practice in paleontology, are a closely guarded secret. The site is now under exclusive long-term lease.)

    The following July, DePalma returned to do a preliminary excavation of the site. “Almost right away, I saw it was unusual,” he told me. He began shovelling off the layers of soil above where he’d found the fish. This “overburden” is typically material that was deposited long after the specimen lived; there’s little in it to interest a paleontologist, and it is usually discarded. But as soon as DePalma started digging he noticed grayish-white specks in the layers which looked like grains of sand but which, under a hand lens, proved to be tiny spheres and elongated ­droplets. “I think, Holy shit, these look like microtektites!” DePalma recalled. Micro­tektites are the blobs of glass that form when molten rock is blasted into the air by an asteroid impact and falls back to Earth in a solidifying drizzle. The site appeared to contain micro­tektites by the million.

    As DePalma carefully excavated the upper layers, he began uncovering an extraordinary array of fossils, exceedingly delicate but marvellously well preserved. “There’s amazing plant material in there, all interlaced and interlocked,” he recalled. “There are logjams of wood, fish pressed against cypress-­tree root bundles, tree trunks smeared with amber.” Most fossils end up being squashed flat by the pressure of the overlying stone, but here everything was three-dimensional, including the fish, having been encased in sediment all at once, which acted as a support. “You see skin, you see dorsal fins literally sticking straight up in the sediments, species new to science,” he said. As he dug, the momentousness of what he had come across slowly dawned on him. If the site was what he hoped, he had made the most important paleontological discovery of the new century.

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    In a century and a half of assiduous searching, almost no dinosaur remains have been found in the layers three metres, or about nine feet, below the KT boundary, a depth representing many thousands of years. Photograph by Richard Barnes for The New Yorker.

    DePalma grew up in Boca Raton, Florida, and as a child he was fascinated by bones and the stories they contained. His father, Robert, Sr., practices endodontic surgery in nearby Delray Beach; his great-uncle Anthony, who died in 2005, at the age of a hundred, was a renowned orthopedic surgeon who wrote several standard textbooks on the subject. (Anthony’s son, Robert’s cousin, is the film director Brian De Palma.)

    “Between the ages of three and four, I made a visual connection with the gracefulness of individual bones and how they fit together as a system,” DePalma told me. “That really struck me. I went after whatever on the dinner table had bones in it.” His family ­buried their dead pets in one spot and put the burial markers in another, so that he wouldn’t dig up the corpses; he found them anyway. He froze dead lizards in ice-cube trays, which his mother would discover when she had friends over for iced tea. “I was never into sports,” he said. “They tried to get me to do that so I would get along with the other kids. But I was digging up the baseball field looking for bones.”

    DePalma’s great-uncle Anthony, who lived in Pompano Beach, took him under his wing. “I used to visit him every other weekend and show him my latest finds,” DePalma said. When he was four, someone at a museum in Texas gave him a fragment of dinosaur bone, which he took to his great-uncle. “He taught me that all those little knobs and rough patches and protrusions on a bone had names, and that the bone also had a name,” DePalma said. “I was captivated.” At six or seven, on trips to Central Florida with his family, he started finding his own fossilized bones from mammals dating back to the Ice Age. He found his first dinosaur bone when he was nine, in Colorado.

    In high school, during the summer and on weekends, DePalma collected fossils, made dinosaur models, and mounted skeletons for the Graves Museum of Archaeology and Natural History, in Dania Beach. He loaned the museum his childhood fossil collection for display, but in 2004 the museum went bankrupt and many of the specimens were carted off to a community college. DePalma had no paperwork to prove his ownership, and a court refused to return his fossils, which numbered in the hundreds. They were mostly locked away in storage, unavailable for public display and enjoyment.

    Dismayed by what he called the “wasteful mismanagement” of his collection, DePalma adopted some unusual collecting practices. Typically, paleontologists cede the curation and the care of their specimens to the institutions that hold them. But DePalma insists on contractual clauses that give him oversight of the management of his specimens. He never digs on public land, because of what he considers excessive government red tape. But, without federal support for his work, he must cover almost all the costs himself. His out-of-pocket expenses for working the Hell Creek site amount to tens of thousands of dollars. He helps defray the expenses by mounting fossils, doing reconstructions, and casting and selling replicas for museums, private collectors, and other clients. At times, his parents have chipped in. “I squeak by,” he said. “If it’s a ­tossup between getting more PaleoBond”—an expensive liquid glue used to hold fossils together—“or changing the air-conditioning filter, I’m getting the PaleoBond.” He is single, and shares a three-bedroom apartment with casts of various dinosaurs, including one of a Nanotyrannus. “It’s hard to have a life outside of my work,” he said.

    DePalma’s control of his research collection is controversial. Fossils are a big business; wealthy collectors pay hundreds of thousands of dollars, even millions, for a rare specimen. (In 1997, a T. rex nicknamed Sue was sold at a Sotheby’s auction, to the Field Museum of Natural History, in Chicago, for more than $8.3 million.) The American market is awash in fossils illegally smuggled out of China and Mongolia. But in the U.S. fossil collecting on private property is legal, as is the buying, selling, and exporting of fossils. Many scientists view this trade as a threat to paleontology and argue that important fossils belong in museums. “I’m not allowed to have a private collection of anything I’m studying,” one prominent curator told me. DePalma insists that he maintains “the best of both worlds” for his fossils. He has deposited portions of his collection at several nonprofit institutions, including the University of Kansas, the Palm Beach Museum of Natural History, and Florida Atlantic University; some specimens are temporarily housed in various analytical labs that are conducting tests on them—all overseen by him.

    In 2013, DePalma briefly made news with a paper he published in the Proceedings of the National Academy of Sciences. Four years earlier, in Hell Creek, he and a field assistant, Robert Feeney, found an odd, lumpy growth of fossilized bone that turned out to be two fused vertebrae from the tail of a hadrosaur, a duck-billed dinosaur from the Cretaceous period. DePalma thought that the bone might have grown around a foreign object and encased it. He took it to Lawrence Memorial Hospital, in Kansas, where a CT technician scanned it for free in the middle of the night, when the machine was idle. Inside the nodule was a broken tyrannosaur tooth; the hadrosaur had been bitten by a tyrannosaur and escaped.

    The discovery helped refute an old hypothesis, revived by the formidable paleontologist Jack Horner, that T. rex was solely a scavenger. Horner argued that T. rex was too slow and lumbering, its arms too puny and its eyesight too poor, to prey on other creatures. When DePalma’s find was picked up by the national media, Horner dismissed it as “speculation” and merely “one data point.” He suggested an alternative scenario: the T. rex might have accidentally bitten the tail of a sleeping hadrosaur, thinking that it was dead, and then “backed away” when it realized its mistake. “I thought that was absolutely preposterous,” DePalma told me. At the time, he told the Los Angeles Times, “A scavenger doesn’t come across a food source and realize all of a sudden that it’s alive.” Horner eventually conceded that T. rex may have hunted live prey. But, when I asked Horner about DePalma recently, he said at first that he didn’t remember him: “In the community, we don’t get to know students very well.”

    Without his Ph.D., DePalma remains mostly invisible, awaiting the stamp of approval that signals the beginning of a serious research career. Several paleontologists I talked to had not heard of him. Another, who asked not to be named, said, “Finding that kind of fossil was pretty cool, but not life-­changing. People sometimes think I’m dumb because I often say I don’t have the answers—we weren’t there when a fossil was formed. There are other people out there who say they do know, and he’s one of those people. I think he can overinterpret.”

    After receiving DePalma’s e-mail, I made arrangements to visit the Hell Creek site; three weeks later I was in Bowman. DePalma pulled up to my hotel in a Toyota 4Runner, its stereo blasting the theme to “Raiders of the Lost Ark.” He wore a coarse cotton work shirt, cargo pants with canvas ­suspenders, and a suède cowboy hat with the left brim snapped up. His face was tanned from long days in the sun and he had a five-day-old beard.

    I got in, and we drove for an hour or so, turning through a ranch gate and following a maze of bone-rattling roads that eventually petered out in a grassy basin. The scattered badlands of Hell Creek form an otherworldly landscape. This is far-flung ranching and farming country; prairies and sunflower fields stretch to the horizon, domed by the great blue skies of the American West. Roads connect small towns—truck stop, church, motel, houses and trailers—and lonely expanses roll by in between. Here and there in the countryside, abandoned farmhouses lean into the ground. Over millions of years, the Hell Creek layer has been heavily eroded, leaving only remnants, which jut from the prairie like so many rotten teeth. These lifeless buttes and pinnacles are striped in beige, chocolate, yellow, maroon, russet, gray, and white. Fossils, worked loose by wind and rain, spill down the sides.

    When we arrived, DePalma’s site lay open in front of us: a desolate hump of gray, cracked earth, about the size of two soccer fields. It looked as if a piece of the moon had dropped there. One side of the deposit was cut through by a sandy wash, or dry streambed; the other ended in a low escarpment. The dig was a three-foot-deep rectangular hole, sixty feet long by forty feet wide. A couple of two-by-fours, along with various digging tools and some metal pipe for taking core samples, leaned against the far side of the hole. As we strolled around the site, I noticed on DePalma’s belt a long fixed-blade knife and a sheathed bayonet—a Second World War relic that his uncle gave him when he was twelve, he said.

    He recalled the moment of discovery. The first fossil he removed, earlier that summer, was a five-foot-long freshwater paddlefish. Paddlefish still live today; they have a long bony snout, with which they probe murky water in search of food. When DePalma took out the fossil, he found underneath it a tooth from a mosasaur, a giant carnivorous marine reptile. He wondered how a freshwater fish and a marine reptile could have ended up in the same place, on a riverbank at least several miles inland from the nearest sea. (At the time, a shallow body of water, called the Western Interior Seaway, ran from the proto-­Gulf of Mexico up through part of North America.) The next day, he found a two-foot-wide tail from another marine fish; it looked as if it had been violently ripped from the fish’s body. “If the fish is dead for any length of time, those tails decay and fall apart,” DePalma said. But this one was perfectly intact, “so I knew that it was transported at the time of death or around then.” Like the mosasaur tooth, it had somehow ended up miles inland from the sea of its origin. “When I found that, I thought, There’s no way, this can’t be right,” DePalma said. The discoveries hinted at an extraordinary conclusion that he wasn’t quite ready to accept. “I was ninety-eight per cent con­vinced at that point,” he said.

    The following day, DePalma noticed a small disturbance preserved in the sediment. About three inches in diameter, it appeared to be a crater formed by an object that had fallen from the sky and plunked down in mud. Similar formations, caused by hailstones hitting a muddy surface, had been found before in the fossil record. As DePalma shaved back the layers to make a cross-­section of the crater, he found the thing itself—not a hailstone but a small white sphere—at the bottom of the crater. It was a tektite, about three millimetres in diameter—the fallout from an ancient asteroid impact. As he continued excavating, he found another crater with a tektite at the bottom, and another, and another. Glass turns to clay over millions of years, and these tektites were now clay, but some still had glassy cores. The microtektites he had found earlier might have been carried there by water, but these had been trapped where they fell—on what, DePalma believed, must have been the very day of the disaster.

    “When I saw that, I knew this wasn’t just any flood deposit,” DePalma said. “We weren’t just near the KT boundary—this whole site is the KT boundary!” From surveying and mapping the layers, DePalma hypothesized that a massive inland surge of water flooded a river valley and filled the low-lying area where we now stood, perhaps as a result of the KT-impact tsunami, which had roared across the proto-Gulf and up the Western Interior Seaway. As the water slowed and became slack, it deposited everything that had been caught up in its travels—the heaviest material first, up to whatever was floating on the surface. All of it was quickly entombed and preserved in the muck: dying and dead creatures, both marine and freshwater; plants, seeds, tree trunks, roots, cones, pine needles, flowers, and pollen; shells, bones, teeth, and eggs; tektites, shocked minerals, tiny diamonds, iridium-laden dust, ash, charcoal, and amber-smeared wood. As the sediments settled, blobs of glass rained into the mud, the largest first, then finer and finer bits, until grains sifted down like snow.

    “We have the whole KT event preserved in these sediments,” DePalma said. “With this deposit, we can chart what happened the day the Cretaceous died.” No paleontological site remotely like it had ever been found, and, if DePalma’s hypothesis proves correct, the scientific value of the site will be immense. When Walter Alvarez visited the dig last summer, he was astounded. “It is truly a magnificent site,” he wrote to me, adding that it’s “surely one of the best sites ever found for telling just what happened on the day of the impact.”

    When DePalma finished showing me the dig, he introduced me to a field assistant, Rudy Pascucci, the director of the Palm Beach Museum. Pascucci, a muscular man in his fifties, was sunburned and unshaven, and wore a sleeveless T-shirt, snakeproof camouflage boots, and a dusty Tilley hat. The two men gathered their tools, got down on the floor of the hole, and began probing the three-foot-high walls of the deposit.

    For rough digging, DePalma likes to use his bayonet and a handheld Marsh pick, popularized by the nineteenth-­century Yale paleontologist Othniel C. Marsh, who pioneered dinosaur-hunting in the American West and dis­covered eighty new species. The pick was given to him by David Burnham, his thesis adviser at Kansas, when he completed his master’s degree. For fine work, DePalma uses X-Acto knives and brushes—the typical tools of a paleontologist—as well as dental instruments given to him by his father.

    The deposit consisted of dozens of thin layers of mud and sand. Lower down, it graded into a more turbulent band of sand and gravel, which contained the heavier fish fossils, bones, and bigger tektites. Below that layer was a hard surface of sandstone, the original Cretaceous bedrock of the site, much of which had been scoured smooth by the flood.

    Paleontology is maddening work, its progress typically measured in millimetres. As I watched, DePalma and Pascucci lay on their stomachs under the beating sun, their eyes inches from the dirt wall, and picked away. DePalma poked the tip of an X-Acto into the thin laminations of sediment and loosened one dime-size flake at a time; he’d examine it closely, and, if he saw nothing, flick it away. When the chips accumulated, he gathered them into small piles with a paintbrush; when those piles accumulated, Pascucci swept them into larger piles with a broom and then shovelled them into a heap at the far end of the dig.

    Occasionally, DePalma came across small plant fossils—flower petals, leaves, seeds, pine needles, and bits of bark. Many of these were mere impressions in the mud, which would crack and peel as soon as they were exposed to the air. He quickly squirted them with PaleoBond, which soaked into the fossils and held them together. Or, us­ing another technique, he mixed a batch of plaster and poured it on the spec­imen before it fell apart. This would preserve, in plaster, a reverse image of the fossil; the original was too short-lived to be saved.

    When the mosquitoes got bad, DePalma took out a briar pipe and packed it with Royal Cherry Cavendish tobacco. He put a lighter to it and vigorously puffed, wreathing himself in sickly-­sweet smoke, then went back to work. “I’m like a shopaholic in a shoe store,” he said. “I want everything!”

    He showed me the impression of a round object about two inches wide. “This is either a flower or an echinoderm,” he said, referring to a group of marine life-forms that includes sea urchins and starfish. “I’ll figure it out in the lab.” He swiftly entombed it in Paleo­Bond and plaster. Next, he found a perfect leaf, and near that a seed from a pinecone. “Cretaceous mulch,” he said, dismissively; he already had many similar examples. He found three more small craters with tektites in them, which he sectioned and photographed. Then his X-Acto blade turned up a tiny brown bone—a jaw, less than a quarter inch in length. He held it up between his fingers and peered at it with a lens.

    “A mammal,” he said. “This one was already dead when it was buried.” Weeks later, in the lab, he identified the jaw as probably belonging to a mam­mal distantly related to primates—including us.

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    In one fell swoop, DePalma may have filled in the gap in the fossil record. Photograph by Richard Barnes for The New Yorker.

    Half an hour later, DePalma discovered a large feather. “Every day is Christmas out here,” he said. He exposed the feather with precise movements. It was a crisp impression in the layer of mud, perhaps thirteen inches long. “This is my ninth feather,” he said. “The first fossil feathers ever found at Hell Creek. I’m convinced these are dinosaur feathers. I don’t know for sure. But these are primitive feathers, and most are a foot long. There are zero birds that big from Hell Creek with feathers this primitive. It’s more parsimonious to suggest it was a known dinosaur, most likely a theropod, possibly a raptor.” He kept digging. “Maybe we’ll find the raptor that these feathers came from, but I doubt it. These feathers could have floated from a long way off.”

    His X-Acto knife unearthed the edge of a fossilized fin. Another paddlefish came to light; it later proved to be nearly six feet long. DePalma probed the sediment around it, to gauge its position and how best to extract it. As more of it was exposed, we could clearly see that the fish’s two-foot-long snout had broken when it was forced—probably by the flood’s surge—against the branches of a submerged araucaria tree. He noted that every fish he’d found in the site had died with its mouth open, which may indicate that the fish had been gasping as they suffocated in the sediment-laden water.

    “Most died in a vertical position in the sediment, didn’t even tip over on their sides,” he said. “And they weren’t scavenged, because whatever would have dug them up afterward was probably gone.” He chipped away around the paddlefish, exposing a fin bone, then a half-dollar-size patch of fossilized skin with the scales perfectly visible. He treated these by saturating them with his own special blend of hardener. Because of the extreme fragility of the fossils, he would take them back to his lab, in Florida, totally encased in sediment, or “matrix.” In the lab, he would free each fossil under a magnifying glass, in precisely controlled conditions, away from the damaging effects of sun, wind, and aridity.

    As DePalma worked around the paddlefish, more of the araucaria branch came to light, including its short, spiky needles. “This tree was alive when it was buried,” he said. Then he noticed a golden blob of amber stuck to the branch. Amber is preserved tree resin and often contains traces of whatever was in the air at the time, trapping the atmospheric chemistry and even, sometimes, insects and small reptiles. “This is Cretaceous flypaper,” he said. “I can’t wait to get this back to the lab.”

    An hour later, he had chiselled all the way around the fish, leaving it encased in matrix, supported by a four-inch-tall pedestal of rock. “I’m pretty sure this is a species new to science,” he said. Because the soft tissue had also fossilized, he said, even the animal’s stomach contents might still be present.

    He straightened up. “Time to plaster,” he said. He took off his shirt and began mixing a five-gallon bucket of plaster with his hands, while Pascucci tore strips of burlap. DePalma took a two-by-four and sawed off two foot-long pieces and placed them like splints on either side of the sediment-encased fossil. One by one, he dipped the burlap strips in the plaster and draped them across the top and the sides of the specimen. He added rope handles and plastered them in. An hour later, when the plaster had cured, he chiselled through the rock pedestal beneath the fossil and flipped the specimen over, leaving the underside exposed. Back in the lab, he would go through this surface to access the fossil, with the plaster jacket acting as a cradle below. Using the rope handles, DePalma and Pascucci lugged the specimen, which weighed perhaps two hundred pounds, to the truck and loaded it into the back. Later, DePalma would store it behind a friend’s ranch house, where all his jacketed fossils from the season were laid out in rows, covered with tarps.

    DePalma resumed digging. Gusts of wind stirred up clouds of dust, and rain fell; when the weather cleared, the late-afternoon sun spilled across the prairie. DePalma was lost in another day, in another time. “Here’s a piece of wood with bark-beetle traces,” he said. Plant fossils from the first several million years after the impact show almost no signs of such damage; the insects were mostly gone. The asteroid had likely struck in the fall, DePalma speculated. He had reached this conclusion by comparing the juvenile paddlefish and sturgeon he’d found with the species’ known growth rates and hatching seasons; he’d also found the seeds of conifers, figs, and certain flowers. “When we analyze the pollen and diatomaceous particles, that will narrow it down,” he said.

    7
    A core sample from DePalma’s site. The site may hold a precise geological transcript of the asteroid strike that almost wiped out life on the planet. Photograph by Richard Barnes for The New Yorker.

    8
    It solves the question of whether dinosaurs went extinct at exactly that level or whether they declined before,” the paleontologist Jan Smit said. “And this is the first time we see direct victims.” Photograph by Richard Barnes for The New Yorker.

    In the week that followed, fresh riches emerged: more feathers, leaves, seeds, and amber, along with several other fish, three to five feet long, and a dozen more craters with tektites. I have visited many paleontological sites, but I had never seen so many specimens found so quickly. Most digs are boring; days or weeks may pass with little found. DePalma seemed to make a noteworthy discovery about every half hour.

    When DePalma first visited the site, he noted, partially embedded on the surface, the hip bone of a dinosaur in the ceratopsian family, of which triceratops is the best-known member. A commercial collector had tried to remove it years earlier; it had been abandoned in place and was crumbling from years of exposure. DePalma initially dismissed it as “trash” and decried the irresponsibility of the collector. Later, though, he wondered how the bone, which was heavy, had arrived there, very close to the high-water mark of the flood. It must have floated, he said, and to have done so it must have been encased in desiccated tissue—suggesting that at least one dinosaur species was alive at the time of the impact. He later found a suitcase-size piece of fossilized skin from a ceratopsian attached to the hip bone.

    At one point, DePalma set off to photograph the layers of the deposit which had been cut through and exposed by the sandy wash. He scraped smooth a vertical section and misted it with water from a spray bottle to bring out the color. The bottom layer was jumbled; the first rush of water had ripped up layers of mud, gravel, and rocks and tumbled them about with pieces of burned (and burning) wood.

    Then DePalma came to a faint jug-shaped outline in the wall of the wash. He examined it closely. It started as a tunnel at the top of the KT layer, went down, and then widened into a round cavity, filled with soil of a different color, which stopped at the hard sandstone of the undisturbed bedrock layer below. It looked as though a small animal had dug through the mud to create a hideout. “Is that a burrow?” I asked.

    DePalma scraped the area smooth with his bayonet, then sprayed it. “You’re darn right it is,” he said. “And this isn’t the burrow of a small dinosaur. It’s a mammal burrow.” (Burrows have characteristic shapes, depending on the species that inhabit them.) He peered at it, his eyes inches from the rock, probing it with the tip of the bayonet. “Gosh, I think it’s still in there!”

    He planned to remove the entire burrow intact, in a block, and run it through a CT scanner back home, to see what it contained. “Any Cretaceous mammal burrow is incredibly rare,” he said. “But this one is impossible—it’s dug right through the KT boundary.” Perhaps, he said, the mammal survived the impact and the flood, burrowed into the mud to escape the freezing darkness, then died. “It may have been born in the Cretaceous and died in the Paleocene,” he said. “And to think—sixty-­six million years later, a stinky monkey is digging it up, trying to figure out what happened.” He added, “If it’s a new species, I’ll name it after you.”

    When I left Hell Creek, DePalma pressed me on the need for secrecy: I was to tell no one, not even close friends, about what he’d found. The history of paleontology is full of tales of bribery, backstabbing, and double-­dealing. In the nineteenth century, ­Othniel C. Marsh and Edward Drinker Cope, the nation’s two leading paleontologists, engaged in a bitter competition to collect dinosaur fossils in the American West. They raided each other’s quarries, bribed each other’s crews, and vilified each other in print and at scientific meetings. In 1890, the New York Herald began a series of sensational articles about the controversy with the headline “Scientists Wage Bitter Warfare.” The rivalry has since become known as the Bone Wars. The days of skulduggery in paleontology have not passed; DePalma was deeply concerned that the site would be expropriated by a major museum.

    DePalma knew that a screwup with this site would probably end his career, and that his status in the field was so uncertain that he needed to fortify the find against potential criticism. He had already experienced harsh judgment when, in 2015, he published a paper on a new species of dinosaur called a Dakotaraptor, and mistakenly inserted a fossil turtle bone in the reconstruction. Although rebuilding a skeleton from thousands of bone fragments that have commingled with those of other species is not easy, DePalma was mor­tified by the attacks. “I never want to go through that again,” he told me.

    For five years, DePalma continued excavations at the site. He quietly shared his findings with a half-dozen luminaries in the field of KT studies, including Walter Alvarez, and enlisted their help. During the winter months, when not in the field, DePalma prepared and analyzed his specimens, a few at a time, in a colleague’s lab at Florida Atlantic University, in Boca Raton. The lab was a windowless, wedge­like room in the geology building, lined with bubbling aquarium tanks and shelves heaped with books, scientific journals, pieces of coral, mastodon teeth, seashells, and a stack of .50-­calibre machine-gun rounds, dating from the Second World War, that the lab’s owner had recovered from the bottom of the Atlantic Ocean. DePalma had carved out a space for himself in a corner, just large enough for him to work on one or two jacketed fossils at a time.

    When I first visited the lab, in April, 2014, a block of stone three feet long by eighteen inches wide lay on a table under bright lights and a large magnifying lens. The block, DePalma said, contained a sturgeon and a paddlefish, along with dozens of smaller fossils and a single small, perfect crater with a tektite in it. The lower parts of the block consisted of debris, fragments of bone, and loose tektites that had been dislodged and caught up in the turbulence. The block told the story of the impact in microcosm. “It was a very bad day,” DePalma said. “Look at these two fish.” He showed me where the sturgeon’s scutes—the sharp, bony plates on its back—had been forced into the body of the paddlefish. One fish was impaled on the other. The mouth of the paddlefish was agape, and jammed into its gill rakers were microtektites—sucked in by the fish as it tried to breathe. DePalma said, “This fish was likely alive for some time after being caught in the wave, long enough to gasp frenzied mouthfuls of water in a vain attempt to survive.”

    Gradually, DePalma was piecing together a potential picture of the disaster. By the time the site flooded, the surrounding forest was already on fire, given the abundance of charcoal, charred wood, and amber he’d found at the site. The water arrived not as a curling wave but as a powerful, roiling rise, packed with disoriented fish and plant and animal debris, which, DePalma hypothesized, were laid down as the water slowed and receded.

    In the lab, DePalma showed me magnified cross-sections of the sediment. Most of its layers were horizontal, but a few formed curlicues or flamelike patterns called truncated flame structures, which were caused by a combination of weight from above and mini-surges in the incoming water. DePalma found five sets of these patterns. He turned back to the block on his table and held a magnifying lens up to the tektite. Parallel, streaming lines were visible on its surface—Schlieren lines, formed by two types of molten glass swirling together as the blobs arced through the atmosphere. Peering through the lens, DePalma picked away at the block with a dental probe. He soon exposed a section of pink, pearlescent shell, which had been pushed up against the sturgeon. “Ammonite,” he said. Ammonites were marine mollusks that somewhat resemble the present-day nautilus, although they were more closely related to squid and octopi. As DePalma uncovered more of the shell, I watched its vibrant color fade. “Live ammonite, ripped apart by the tsunami—they don’t travel well,” he said. “Genus Sphenodiscus, I would think.” The shell, which hadn’t previously been documented in the Hell Creek Formation, was another marine victim tossed inland.

    He stood up. “Now I’m going to show you something special,” he said, opening a wooden crate and removing an object that was covered in aluminum foil. He unwrapped a sixteen-inch fossil feather, and held it in his palms like a piece of Lalique glass. “When I found the first feather, I had about twenty seconds of disbelief,” he said. DePalma had studied under Larry Martin, a world authority on the Cretaceous predecessors of birds, and had been “exposed to a lot of fossil feathers. When I encountered this damn thing, I immediately understood the importance of it. And now look at this.”

    From the lab table, he grabbed a fossil forearm belonging to Dakotaraptor, the dinosaur species he’d discovered in Hell Creek. He pointed to a series of regular bumps on the bone. “These are probably quill knobs,” he said. “This dinosaur had feathers on its forearms. Now watch.” With precision calipers, he measured the diameter of the quill knobs, then the diameter of the quill of the fossil feather; both were 3.5 millimetres. “This matches,” he said. “This says a feather of this size would be associated with a limb of this size.”

    There was more, including a piece of a partly burned tree trunk with am­ber stuck to it. He showed me a photo of the amber seen through a micro­scope. Trapped inside were two impact particles—another landmark discovery, because the amber would have preserved their chemical composition. (All other tektites found from the impact, exposed to the elements for millions of years, have chemically changed.) He’d also found scores of beautiful examples of lonsdaleite, a hexagonal form of diamond that is associated with impacts; it forms when carbon in an asteroid is compressed so violently that it crystallizes into trillions of microscopic grains, which are blasted into the air and drift down.

    Finally, he showed me a photograph of a fossil jawbone; it belonged to the mammal he’d found in the burrow. “This is the jaw of Dougie,” he said. The bone was big for a Cretaceous mammal—three inches long—and almost complete, with a tooth. After my visit to Hell Creek, DePalma had removed the animal’s burrow intact, still encased in the block of sediment, and, with the help of some women who worked as cashiers at the Travel Center, in Bowman, hoisted it into the back of his truck. He believes that the jaw belonged to a marsupial that looked like a weasel. Using the tooth, he could conduct a stable-isotope study to find out what the animal ate—“what the menu was after the disaster,” he said. The rest of the mammal remains in the burrow, to be researched later.

    9
    DePalma says that he’s discovered more than a dozen new species of animals and plants, and identified the broken teeth and bones, including hatchling remains, of almost every dinosaur group known from Hell Creek. Photograph by Richard Barnes for The New Yorker.

    DePalma listed some of the other discoveries he’s made at the site: several flooded ant nests, with drowned ants still inside and some chambers packed with microtektites; a possible wasp burrow; another mammal ­burrow, with multiple tunnels and galleries; shark teeth; the thigh bone of a large sea turtle; at least three new fish species; a gigantic ginkgo leaf and a plant that was a relative of the banana; more than a dozen new species of animals and plants; and several other burrow types.

    At the bottom of the deposit, in a mixture of heavy gravel and tektites, DePalma identified the broken teeth and bones, including hatchling remains, of almost every dinosaur group known from Hell Creek, as well as pterosaur remains, which had previously been found only in layers far below the KT boundary. He found, intact, an unhatched egg containing an embryo—a fossil of immense research value. The egg and the other remains suggested that dinosaurs and major reptiles were probably not staggering into extinction on that fateful day. In one fell swoop, DePalma may have solved the three-metre problem and filled in the gap in the fossil record.

    By the end of the 2013 field season, DePalma was convinced that the site had been created by an impact flood, but he lacked conclusive evidence that it was the KT impact. It was possible that it resulted from another giant asteroid strike that occurred at around the same time. “Extraordinary discoveries require extraordinary evidence,” he said. If his tektites shared the same geochemistry as tektites from the Chicxulub asteroid, he’d have a strong case. Deposits of Chicxulub tektites are rare; the best source, discovered in 1990, is a small outcrop in Haiti, on a cliff above a road cut. In late January, 2014, DePalma went there to gather tektites and sent them to an independent lab in Canada, along with tektites from his own site; the samples were analyzed at the same time, with the same equipment. The results indicated a near-perfect geochemical match.

    In the first few years after DePalma’s discoveries, only a handful of scientists knew about them. One was David Burnham, DePalma’s thesis adviser at Kansas, who estimates that DePalma’s site will keep specialists busy for at least half a century. “Robert’s got so much stuff that’s unheard of,” Burnham told me. “Amber with tektites embedded in it—holy cow! The dinosaur feathers are crazy good, but the burrow makes your head reel.” In paleontology, the term Lagerstätte refers to a rare type of fossil site with a large variety of specimens that are nearly perfectly preserved, a sort of fossilized ecosystem. “It will be a famous site,” Burnham said. “It will be in the textbooks. It is the Lagerstätte of the KT extinction.”

    Jan Smit, a paleontologist at Vrije University, in Amsterdam, and a world authority on the KT impact, has been helping DePalma analyze his results, and, like Burnham and Walter Alvarez, he is a co-author of a scientific paper that DePalma is publishing about the site. (There are eight other co-authors.) “This is really a major discovery,” Smit said. “It solves the question of whether dinosaurs went extinct at exactly that level or whether they declined before. And this is the first time we see direct victims.” I asked if the results would be controversial. “When I saw his data with the paddlefish, sturgeon, and ammonite, I think he’s right on the spot,” Smit said. “I am very sure he has a pot of gold.”

    In September of 2016, DePalma gave a brief talk about the discovery at the annual meeting of the Geological Society of America, in Colorado. He mentioned only that he had found a deposit from a KT flood that had yielded glass droplets, shocked minerals, and fossils. He had christened the site Tanis, after the ancient city in Egypt, which was featured in the 1981 film “Raiders of the Lost Ark” as the resting place of the Ark of the Covenant. In the real Tanis, archeologists found an inscription in three writing systems, which, like the Rosetta stone, was crucial in translating ancient Egyptian. DePalma hopes that his Tanis site will help decipher what happened on the first day after the impact.

    The talk, limited though it was, caused a stir. Kirk Cochran, a professor at the School of Marine and Atmospheric Science at Stony Brook University, in New York, recalled that when DePalma presented his findings there were gasps of amazement in the audience. Some scientists were wary. Kirk Johnson, the director of the Smithsonian’s National Museum of Natural History, told me that he knew the Hell Creek area well, having worked there since 1981. “My warning lights were flashing bright red,” he told me. “I was so skeptical after the talk I was convinced it was a fabrication.” Johnson, who had been mapping the KT layer in Hell Creek, said that his research indicated that Tanis was at least forty-five feet below the KT boundary and perhaps a hundred thousand years older. “If it’s what it’s said to be,” Johnson said, “it’s a fabulous discovery.” But he declared himself “uneasy” until he could see DePalma’s paper.

    One prominent West Coast paleontologist who is an authority on the KT event told me, “I’m suspicious of the findings. They’ve been presented at meetings in various ways with various associated extraordinary claims. He could have stumbled on something amazing, but he has a reputation for making a lot out of a little.” As an example, he brought up DePalma’s paper on Dakotaraptor, which he described as “bones he basically collected, all in one area, some of which were part of a dinosaur, some of which were part of a turtle, and he put it all together as a skeleton of one animal.” He also objected to what he felt was excessive secrecy surrounding the Tanis site, which has made it hard for outside scientists to evaluate DePalma’s claims.

    Johnson, too, finds the lack of transparency, and the dramatic aspects of DePalma’s personality, unnerving. “There’s an element of showmanship in his presentation style that does not add to his credibility,” he said. Other paleontologists told me that they were leery of going on the record with criticisms of DePalma and his co-authors. All expressed a desire to see the final paper, which will be published next week, in the Proceedings of the National Academy of Sciences, so that they could evaluate the data for themselves.

    After the G.S.A. talk, DePalma realized that his theory of what had happened at Tanis had a fundamental problem. The KT tsunami, even moving at more than a hundred miles an hour, would have taken many hours to travel the two thousand miles to the site. The rainfall of glass blobs, however, would have hit the area and stopped within about an hour after the impact. And yet the tektites fell into an active flood. The timing was all wrong.

    This was not a paleontological question; it was a problem of geophysics and sedimentology. Smit was a sedimentologist, and another researcher whom DePalma shared his data with, Mark Richards, now of the University of Washington, was a geophysicist. At dinner one evening in Nagpur, India, where they were attending a conference, Smit and Richards talked about the problem, looked up a few papers, and later jotted down some rough calculations. It was immediately apparent to them that the KT tsunami would have arrived too late to capture the falling tektites; the wave would also have been too diminished by its long journey to account for the thirty-­five-foot rise of water at Tanis. One of them proposed that the wave might have been created by a curious phenomenon known as a seiche. In large earthquakes, the shaking of the ground sometimes causes water in ponds, swimming pools, and bathtubs to slosh back and forth. Richards recalled that the 2011 Japanese earthquake produced bizarre, five-foot seiche waves in an absolutely calm Norwegian fjord thirty minutes after the quake, in a place unreachable by the tsunami.

    Richards had previously estimated that the worldwide earthquake generated by the KT impact could have been a thousand times stronger than the biggest earthquake ever experienced in human history. Using that gauge, he calculated that potent seismic waves would have arrived at Tanis six minutes, ten minutes, and thirteen minutes after the impact. (Different types of seismic waves travel at different speeds.) The brutal shaking would have been enough to trigger a large seiche, and the first blobs of glass would have started to rain down seconds or minutes afterward. They would have continued to fall as the seiche waves rolled in and out, depositing layer upon layer of sediment and each time ­sealing the tektites in place. The Tanis site, in short, did not span the first day of the impact: it probably recorded the first hour or so. This fact, if true, renders the site even more fabulous than previously thought. It is almost beyond credibility that a precise geological transcript of the most important sixty minutes of Earth’s history could still exist millions of years later—a sort of high-speed, high-resolution video of the event recorded in fine layers of stone. DePalma said, “It’s like finding the Holy Grail clutched in the bony fingers of Jimmy Hoffa, sitting on top of the Lost Ark.” If Tanis had been closer to or farther from the impact point, this beautiful coincidence of timing could not have happened. “There’s nothing in the world that’s ever been seen like this,” Richards told me.

    One day sixty-six million years ago, life on Earth almost came to a shattering end. The world that emerged after the impact was a much simpler place. When sunlight finally broke through the haze, it illuminated a hellish landscape. The oceans were empty. The land was covered with drifting ash. The forests were charred stumps. The cold gave way to extreme heat as a greenhouse effect kicked in. Life mostly consisted of mats of algae and growths of fungus: for years after the impact, the Earth was covered with little other than ferns. Furtive, ratlike mammals lived in the gloomy understory.

    But eventually life emerged and blossomed again, in new forms. The KT event continues to attract the interest of scientists in no small part because the ashen print it left on the planet is an existential reminder. “We wouldn’t be here talking on the phone if that meteorite hadn’t fallen,” Smit told me, with a laugh. DePalma agreed. For the first hundred million years of their existence, before the asteroid struck, mammals scurried about the feet of the dinosaurs, amounting to little. “But when the dinosaurs were gone it freed them,” DePalma said. In the next epoch, mammals underwent an explosion of adaptive radiation, evolving into a dazzling variety of forms, from tiny bats to gigantic titanotheres, from horses to whales, from fearsome creodonts to large-brained primates with hands that could grasp and minds that could see through time.

    “We can trace our origins back to that event,” DePalma said. “To actually be there at this site, to see it, to be connected to that day, is a special thing. This is the last day of the Cretaceous. When you go one layer up—the very next day—that’s the Paleocene, that’s the age of mammals, that’s our age.”

    See the full article here .


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    From Nautilus: “Glaciers May Have Covered the Entire Planet—Twice” 

    Nautilus

    From Nautilus

    Mar 26, 2019
    Laura Poppick

    1
    Ancient rocks suggest that ice entirely covered our planet on at least two occasions. Those events may help explain the rise of complex life that followed. Photo Illustration by pryzmat / Shutterstock.

    The Earth has endured many changes in its 4.5-billion-year history, with some tumultuous twists and turns along the way. One especially dramatic episode appears to have come between 700 million and 600 million years ago, when scientists think ice smothered the entire planet, from the poles to the equator—twice in quick succession.

    Drawing on evidence across multiple continents, scientists say these Snowball Earth events may have paved the way for the Cambrian explosion of life that followed—the period when complex, multicellular organisms began to diversify and spread across the planet.

    When Caltech geologist Joe Kirschvink coined the term Snowball Earth in 1989—merging ideas that some geologists, climate physicists and planetary chemists had been thinking about for decades—many earth scientists were skeptical that these cataclysmic events could really have occurred. But with mounting evidence in support of the theory and new data that help pin down the timing of events, more scientists have warmed up to the idea.

    Paul Hoffman, a geologist at the University of Victoria in British Columbia, has helped pioneer Snowball Earth research over the past 25 years. Among other things, he amassed 50 months’ worth of fieldwork in Namibia, where he gathered evidence of ancient glacial activity in rocks that are interspersed with limestone. Since limestone tends to form in the warmest parts of the ocean, this sandwich-like pattern supports the idea that glaciers covered all of the Earth, cold as well as warm spots, during Snowball Earth episodes. Knowable spoke with Hoffman, who recounts his life work in the Annual Review of Earth and Planetary Sciences, about the evolution of the Snowball Earth theory and what questions remain. This conversation has been edited for length and clarity.

    3
    Snowologist: Paul Hoffman says he is still doing fieldwork in Namibia, as a 77-year-old. “It’s just a large and fascinating problem,” he said. “It’s hard to pull myself away.”
    Illustration by James Provost / Creative Commons.

    What did the planet look like during Snowball Earth?

    The name describes its appearance from outer space—a glistening white ball. The ice surface is mostly coated with frost and tiny ice crystals that settled out of the cold dry air, which is far below freezing everywhere. Gale-force winds howl in low latitudes. Beneath the floating ice shelf, a dark and briny ocean is continually stirred by tides and turbulent eddies generated by geothermal heat slowly entering from the ocean floor.

    What tipped off geologists to the possibility of a Snowball Earth?

    Geologists were struggling to understand what they saw in the geologic record—that not too long before the first appearance of complex life, there was unmistakable evidence of glaciation even in the warmest areas of the Earth. Geologists had a very difficult time understanding how this was possible.

    The deposits that glaciers leave behind are very distinctive. They look like cement that has been dumped out of a cement truck. These Snowball ice sheets would have flowed from the continents out onto the ocean, so we have a lot of deposits that formed in the marine environment where you get what are known as dropstones: pebbles or boulders that are out of place. Very often, you see structures related to the impact, as if the stone was somehow dropped and then plunked into the underlying sediment. It’s difficult to imagine what, other than floating ice, could have possibly transported this debris; trees, which can carry soil and stones out to sea in their roots, had not yet evolved.

    3
    A Seafloor Embrace: A glacial dropstone from Namibia, in rocks that date to the second Snowball Earth. The stone was likely carried and dropped by a floating ice shelf, and when it plunked into seafloor sediment below, that sediment folded around it. (Penny [upper right] shown for scale.)Courtesy of Paul Hoffman.

    How did you start studying Snowball Earth?

    I had known about the hypothesis since even before I was interested in working on the problem myself. Joe Kirschvink at Caltech told me about it a few months after he had the idea in 1989, but he never did anything more with it at that time. I liked it because I like ideas, but there was a credibility gap, so before our work, the hypothesis was dormant.

    The biggest problem was that because the conditions were so different from any other time in Earth’s history, we didn’t understand the implications of the hypothesis well enough to know whether any given bit of geologic evidence was either for or against it. We had to have climate models to see what actually happens under Snowball conditions, and that modeling, developed later, has been extremely important.

    My main contribution was making the case that it was a credible scientific hypothesis by arguing, from different disciplines within geoscience, that there was a lot of geological evidence consistent with the predictions. As I often like to say, new ideas or hypotheses are like small children: It’s best not to judge them too early because you don’t know what they are going to be like as adults. Very often, the problem with new ideas is not that they are wrong, but that they are incomplete.

    What triggered the runaway growth of ice on Earth?

    That’s the “why” question and that’s maybe the most difficult one. I don’t think there is a consensus on this. There are a number of factors that contributed, and it is useful to look at this in two ways. First of all, what was the general condition that made for a colder climate and therefore made the Earth more susceptible to this runaway ice growth phenomenon? And then what was the immediate trigger that tipped it over the edge?

    4
    Snowball Earth Snooping: On a field expedition with Paul Hoffman in 2002, geoscientists Galen Halverson (now at McGill University) and Matthew Hurtgen (now at Northwestern University) collect carbonate rocks from a mountainside in northeastern Svalbard, Norway. The carbonate rocks rest directly above glacial deposits from the second Snowball Earth event. This juxtaposition of carbonates—which form only in warm parts of the ocean—and glacial rocks supports the theory that ice covered the entire planet during the Snowball Earth episodes. Courtesy of Paul Hoffman.

    When the Snowball events occurred, the supercontinent Rodinia was in the process of breaking up. A supercontinent is a state in which all of the continents are clustered together in one group. The reason why people think there is a connection there is that the breakup of a supercontinent would increase rainfall in the continental areas, and that would increase the weathering of crustal rocks. The weathering of rocks actually consumes carbon dioxide, so that would lead to less carbon dioxide in the atmosphere and therefore a colder climate.

    As for what actually caused the immediate trigger, attention has focused in recent years on a sequence of very large volcanic eruptions that occurred in what is now the high arctic of Canada. These eruptions occurred around 717 million and 719 million years ago. When you get fire fountains—lava that comes out of one place over a period of weeks or months—you get a strong thermal upwelling in the atmosphere from the heating effect of that lava. These upwellings can loft sulfur aerosols into the stratosphere where they hang around for a significant amount of time. These sulfur gas particles reflect incoming solar radiation and have a strong cooling effect. Because of the coincidence in timing between these eruptions and the onset of the first and longer of the two Snowball Earths, it’s been postulated that that may have been the immediate trigger.

    What did life on Snowball Earth look like, and how did it change as a consequence of runaway ice growth?

    There were certainly bacteria and there were also algae and unicellular primitive animals, or protists.

    There is also evidence that the first multicellular animals originated at this time, probably something like sponges. Why is a matter of speculation: There are a number of ideas on this, but they are difficult to test. One idea is that on Snowball Earth, ecosystems may have been more isolated from one another and this might be a situation that would be helpful for evolving new forms of life, and particularly forms of life that are altruistic—ones with cells that find that there is an advantage in working together rather than working individually. So more isolation of different ecosystems might have allowed certain ecosystems that had a higher proportion of these multicellular altruists to establish a foothold.

    How was the Snowball theory received by other geologists?

    I underestimated how emotional people would get about it and how wedded people were to the idea that the Earth has never really been greatly different than it is today. In the 19th century, people had a difficult time believing that most of northern Europe and North America were covered by an ice sheet only 20,000 years ago. That was as hard for a 19th-century geologist to accept as Snowball Earth has been for 20th-century geologists.

    For a long time we had a lot of evidence for glaciation at low latitude and in the warmest parts of the Earth, but we didn’t really have a good idea of the dates of these events. It was sort of embarrassing. But between 2010 and 2014 that situation dramatically changed. We now have pretty precise estimates from two very different dating techniques, and it’s impressive that they are giving highly consistent results. Working out the timescale [GeoScienceWorld] has caused a majority of geologists working on the problem to now accept the Snowball hypothesis.

    Alternative theories have arisen over the years, including what is called the Slushball theory—a less extreme version of Snowball Earth. How does pinning down the dates help sort out these alternative theories?

    In the Slushball scenario, carbon dioxide would start building up very quickly, so the glaciation would be short-lived and the ice would retreat gradually. This is not what we see in the geologic record. We now know that the first Snowball lasted for 58 million years and that is completely inconsistent with the Slushball idea. Also, we see the Snowball glaciations terminate extremely abruptly and they are followed by clear evidence of a complete and abrupt climate reversal, a very hot period. That is not explained by the Slushball model.

    I don’t think there are any other alternatives that satisfy the evidence.

    4
    It Was a Seafloor in Another Life: Hoffman has spent a cumulative 50 months collecting evidence of Snowball Earth in the desert mountain ranges of Namibia. The landscape shown here is comprised of an ancient seafloor punctuated with dropstones—sporadically placed stones that researchers believe were carried by ice floating out at sea.Courtesy of Paul Hoffman.

    What other questions about Snowball Earth remain?

    The dating has created a new set of problems. One thing the dating revealed was that the two Snowball Earths occurred in rapid succession and were very unequal in duration. The first one lasted 58 million years [PNAS] and the second one only lasted 5 million to 15 million years. So we don’t know why there is this great disparity in how long the glaciations lasted. And why was it that there was just this short interval between the two? There’s only about 10 million years when there was no ice at all and then suddenly the planet went back into Snowball Earth. So why two in rapid succession? And why wasn’t there a third one or a fourth one? These are new questions that have arisen as a result of our understanding of the timing.

    Could Snowball Earth return?

    I don’t think we are in a very good position to say whether or not it’s likely to happen in the future. The future is a long time. We can say it is not going to happen in the next several tens of thousands of years.

    Why study Earth history?

    The history of our planet is one of the greatest stories. Because we live here and we are dependent on this place, it is very important to understand that the Earth has not always been the way it is today. Snowball Earth is an example of the kinds of amazing things that the Earth has been through that we would never have suspected if we didn’t investigate the geologic record.

    Dealing with Snowball Earth has been fantastic—it’s been the most intense learning experience of my life, and I never anticipated that it would be accepted in my lifetime.

    And you’re still at it, after 25 years?

    I’m still doing fieldwork in Namibia, as a 77-year-old. It’s just a large and fascinating problem. It’s hard to pull myself away.

    See the full article here .

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    Welcome to Nautilus. We are delighted you joined us. We are here to tell you about science and its endless connections to our lives. Each month we choose a single topic. And each Thursday we publish a new chapter on that topic online. Each issue combines the sciences, culture and philosophy into a single story told by the world’s leading thinkers and writers. We follow the story wherever it leads us. Read our essays, investigative reports, and blogs. Fiction, too. Take in our games, videos, and graphic stories. Stop in for a minute, or an hour. Nautilus lets science spill over its usual borders. We are science, connected.

     
  • richardmitnick 8:16 am on March 22, 2019 Permalink | Reply
    Tags: ARC-Australian Research Council, , , Geology   

    From Curtin University: “New ARC-funded research uses new tool to examine world’s oldest rocks” 

    From Curtin University

    19 March 2019

    Yasmine Phillips
    Media Relations Manager, Public Relations
    Tel: +61 8 9266 9085
    Mob: +61 401 103 877
    yasmine.phillips@curtin.edu.au

    Curtin University researchers will develop a new fingerprinting tool capable of delving deeper into the Earth’s rock layers, in what promises to be an important development for Australia’s mining and petroleum sectors.

    The research will enhance industry’s understanding of the Earth’s sedimentary rocks by investigating case studies at the Yilgarn Craton, Australia’s premier gold and nickel province spanning from Meekatharra to WA’s South-West including Kalgoorlie, as well as the Canning Basin, located in the Kimberley, and the Northern Carnarvon Basin.

    The project secured $352,000 from the Australian Research Council’s Linkage Project scheme as part of the latest funding announcement made by the Federal Minister for Education, the Hon. Dan Tehan, today.

    Curtin University Acting Deputy Vice-Chancellor Research Professor Garry Allison said the research had potentially important implications for the mining and petroleum sectors.

    “Western Australia’s mineral and petroleum exports are major contributors to the Australian economy, but in recent years the number of significant discoveries has fallen and those that have been identified tend to be at greater depths,” Professor Allison said.

    “This new research will develop a new fingerprinting tool capable of shedding more light on some of the world’s oldest rocks with the aim of helping Australian mining and petroleum explorers to uncover major new mineral and hydrocarbon deposits.”

    The state-wide isotope-based research project will be led by Associate Professor Chris Kirkland and Professor Chris Elders, both from the School of Earth and Planetary Sciences at Curtin University.

    Curtin University researchers will work with Northern Star Resources and the Geological Survey of Western Australia, within the Department of Mines, Industry Regulation and Safety, on the project.

    As part of the latest round of ARC grants announced today, Curtin University researchers will also work on an international project, led by The University of Western Australia, that will test and review the success of teaching Einstein’s theories of space, time, matter, light and gravity. That project was awarded $898,560 in ARC funding.

    See the full article here .

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    Curtin University (formerly known as Curtin University of Technology and Western Australian Institute of Technology) is an Australian public research university based in Bentley and Perth, Western Australia. The university is named after the 14th Prime Minister of Australia, John Curtin, and is the largest university in Western Australia, with over 58,000 students (as of 2016).

    Curtin was conferred university status after legislation was passed by the Parliament of Western Australia in 1986. Since then, the university has been expanding its presence and has campuses in Singapore, Malaysia, Dubai and Mauritius. It has ties with 90 exchange universities in 20 countries. The University comprises five main faculties with over 95 specialists centres. The University formerly had a Sydney campus between 2005 & 2016. On 17 September 2015, Curtin University Council made a decision to close its Sydney campus by early 2017.

    Curtin University is a member of Australian Technology Network (ATN), and is active in research in a range of academic and practical fields, including Resources and Energy (e.g., petroleum gas), Information and Communication, Health, Ageing and Well-being (Public Health), Communities and Changing Environments, Growth and Prosperity and Creative Writing.

    It is the only Western Australian university to produce a PhD recipient of the AINSE gold medal, which is the highest recognition for PhD-level research excellence in Australia and New Zealand.

    Curtin has become active in research and partnerships overseas, particularly in mainland China. It is involved in a number of business, management, and research projects, particularly in supercomputing, where the university participates in a tri-continental array with nodes in Perth, Beijing, and Edinburgh. Western Australia has become an important exporter of minerals, petroleum and natural gas. The Chinese Premier Wen Jiabao visited the Woodside-funded hydrocarbon research facility during his visit to Australia in 2005.
    Contents

     
  • richardmitnick 5:25 pm on March 13, 2019 Permalink | Reply
    Tags: , , , Comet, Controversial from the time it was proposed the hypothesis even now continues to be contested by those who prefer to attribute the end-Pleistocene reversal in warming entirely to terrestrial causes., , Geology, Kennett and fellow stalwarts of the Younger Dryas Boundary (YDB) Impact Hypothesis have recently received a major boost:, , The discovery of a very young 31-kilometer-wide impact crater beneath the Greenland ice sheet which they believe may have been one of the many comet fragments that impacted Earth at the onset of the Y, The layer containing these spherules also show peak concentrations of platinum and gold and native iron particles rarely found in nature, The Pilauco dig site in a suburb of the Osorno province in Chile, The presence of microscopic spherules interpreted to have been formed by melting due to the extremely high temperatures associated with impact, They believe this may have been one of the many comet fragments that impacted Earth at the onset of the Younger Dryas., UC Santa Barbara geology professor emeritus James Kennett, , Younger Dryas Impact Hypothesis   

    From UC Santa Barbara: “The Day the World Burned” 

    UC Santa Barbara Name bloc
    From UC Santa Barbara

    March 8, 2019
    Sonia Fernandez

    1
    2
    The researchers found evidence of cosmic impact at the Pilauco dig site in a suburb of the Osorno province in Chile. Photo Credit: Courtesy Image

    When UC Santa Barbara geology professor emeritus James Kennett and colleagues set out years ago to examine signs of a major cosmic impact that occurred toward the end of the Pleistocene epoch, little did they know just how far-reaching the projected climatic effect would be.

    3
    James Kennett. Photo Credit: Sonia Fernandez

    “It’s much more extreme than I ever thought when I started this work,” Kennett noted. “The more work that has been done, the more extreme it seems.”

    He’s talking about the Younger Dryas Impact Hypothesis, which postulates that a fragmented comet slammed into the Earth close to 12,800 years ago, causing rapid climatic changes, megafaunal extinctions, sudden human population decrease and cultural shifts and widespread wildfires (biomass burning). The hypothesis suggests a possible triggering mechanism for the abrupt changes in climate at that time, in particular a rapid cooling in the Northern Hemisphere, called the Younger Dryas, amid a general global trend of natural warming and ice sheet melting evidenced by changes in the fossil and sediment record.

    Controversial from the time it was proposed, the hypothesis even now continues to be contested by those who prefer to attribute the end-Pleistocene reversal in warming entirely to terrestrial causes. But Kennett and fellow stalwarts of the Younger Dryas Boundary (YDB) Impact Hypothesis, as it is also known, have recently received a major boost: the discovery of a very young, 31-kilometer-wide impact crater beneath the Greenland ice sheet, which they believe may have been one of the many comet fragments that impacted Earth at the onset of the Younger Dryas.

    Now, in a paper published in the journal Nature Scientific Reports, Kennett and colleagues, led by Chilean paleontologist Mario Pino, present further evidence of a cosmic impact, this time far south of the equator, that likely lead to biomass burning, climate change and megafaunal extinctions nearly 13,000 years ago.

    “We have identified the YDB layer at high latitudes in the Southern Hemisphere at near 41 degrees south, close to the tip of South America,” Kennett said. This is a major expansion of the extent of the YDB event.” The vast majority of evidence to date, he added, has been found in the Northern Hemisphere.

    This discovery began several years ago, according to Kennett, when a group of Chilean scientists studying sediment layers at a well-known Quaternary paleontological and archaeological site, Pilauco Bajo, recognized changes known to be associated with YDB impact event. They included a “black mat” layer, 12,800 years in age, that coincided with the disappearance of South American Pleistocene megafauna fossils, an abrupt shift in regional vegetation and a disappearance of human artifacts.

    “Because the sequencing of these events looked like what had already been described in the YDB papers for North America and Western Europe, the group decided to run analyses of impact-related proxies in search of the YDB layer,” Kennett said. This yielded the presence of microscopic spherules interpreted to have been formed by melting due to the extremely high temperatures associated with impact. The layer containing these spherules also show peak concentrations of platinum and gold, and native iron particles rarely found in nature.

    “Among the most important spherules are those that are chromium-rich,” Kennett explained. The Pilauco site spherules contain an unusual level of chromium, an element not found in Northern Hemisphere YDB impact spherules, but in South America. “It turns out that volcanic rocks in the southern Andes can be rich in chromium, and these rocks provided a local source for this chromium,” he added. “Thus, the cometary objects must have hit South America as well.”

    Other evidence, which, Kennett noted, is consistent with previous and ongoing documentation of the region by Chilean scientists, pointed to a “very large environmental disruption at about 40 degrees south.” These included a large biomass burning event evidenced by, among other things, micro-charcoal and signs of burning in pollen samples collected at the impact layer. “It’s by far the biggest burn event in this region we see in the record that spans thousands of years,” Kennett said. Furthermore, he went on, the burning coincides with the timing of major YDB-related burning events in North America and western Europe.

    The sedimentary layers at Pilauco contain a valuable record of pollen and seeds that show change in character of regional vegetation — evidence of a shifting climate. However, in contrast to the Northern Hemisphere, where conditions became colder and wetter at the onset of the Younger Dryas, the opposite occurred in the Southern Hemisphere.

    “The plant assemblages indicate that there was an abrupt and major shift in the vegetation from wet, cold conditions at Pilauco to warm, dry conditions,” Kennett said. According to him, the atmospheric zonal climatic belts shifted “like a seesaw,” with a synergistic mechanism, bringing warming to the Southern Hemisphere even as the Northern Hemisphere experienced cooling and expanding sea ice. The rapidity — within a few years — with which the climate shifted is best attributed to impact-related shifts in atmospheric systems, rather than to the slower oceanic processes, Kennett said.

    Meanwhile, the impact with its associated major environmental effects, including burning, is thought to have contributed to the extinction of local South American Pleistocene megafauna — including giant ground sloths, sabretooth cats, mammoths and elephant-like gomphotheres — as well as the termination of the culture similar to the Clovis culture in the north, he added. The amount of bones, artifacts and megafauna-associated fungi that were relatively abundant in the soil at the Pilauco site declined precipitously at the impact layer, indicating a major local disruption.

    The distance of this recently identified YDB site — about 6,000 kilometers from the closest well-studied site in South America — and its correlation with the many Northern Hemispheric sites “greatly expands the extent of the YDB impact event,” Kennett said. The sedimentary and paleo-vegetative evidence gathered at the Pilauco site is in line with previous, separate studies conducted by Chilean scientists that indicate a widespread burn and sudden major climate shifts in the region at about YDB onset. This new study further bolsters the hypothesis that a cosmic impact triggered the atmospheric and oceanic conditions of the Younger Dryas, he said.

    “This is further evidence that the Younger Dryas climatic onset is an extreme global event, with major consequences on the animal life and the human life at the time,” Kennett said. “And this Pilauco section is consistent with that.”

    Research on this study was also conducted by Ana Abarzúa, Giselle Astorga, Alejandra Martel-Cea, Nathalie Cossio, Maria Paz Lira and Rafael Labarca of Universidad Austral de Chile; R. Ximena Navarro of Universidad Católica de Temuco; and Malcolm A. LeCompte and Victor Adedeji of Elizabeth City State University. Christopher Moore of University of South Carolina; Ted E. Bunch and Charles Mooney of Northern Arizona University; and Wendy S. Wolbach of DePaul University contributed research, as did Allen West of Comet Research Group.

    See the full article here .


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    Please help promote STEM in your local schools.

    Stem Education Coalition

    UC Santa Barbara Seal
    The University of California, Santa Barbara (commonly referred to as UC Santa Barbara or UCSB) is a public research university and one of the 10 general campuses of the University of California system. Founded in 1891 as an independent teachers’ college, UCSB joined the University of California system in 1944 and is the third-oldest general-education campus in the system. The university is a comprehensive doctoral university and is organized into five colleges offering 87 undergraduate degrees and 55 graduate degrees. In 2012, UCSB was ranked 41st among “National Universities” and 10th among public universities by U.S. News & World Report. UCSB houses twelve national research centers, including the renowned Kavli Institute for Theoretical Physics.

     
  • richardmitnick 7:38 am on March 13, 2019 Permalink | Reply
    Tags: "Old stone walls record the changing location of magnetic North", , , Geology, Geomagnetism,   

    From The Conversation: “Old stone walls record the changing location of magnetic North” 

    Conversation
    From The Conversation

    March 12, 2019
    John Delano

    1
    The orientations of the stone walls that crisscross the Northeastern U.S. can tell a geomagnetic tale as well as a historical one. John Delano, CC BY-ND

    When I was a kid living in southern New Hampshire, my family home was on the site of an abandoned farmstead consisting of massive stone foundations of quarried granite where dwellings once stood. Stone walls snaked throughout the forest. As I explored the deep woods of tall oaks and maples, I wondered about who had built these walls, and why. What stories did these walls contain?

    Decades later, while living in a rural setting in upstate New York and approaching retirement as a geologist, my long dormant interest was rekindled by treks through the neighboring woods. By now I knew that stone walls in New England and New York are iconic vestiges from a time when farmers, in order to plant crops and graze livestock, needed to clear the land of stones. Tons and tons of granite had been deposited throughout the region during the last glaciation that ended about 10,000 years ago.

    By the late 1800s, nearly 170,000 subsistence farming families had built an estimated 246,000 miles of stone walls across the Northeast. But by then, the Industrial Revolution had already started to contribute to the widespread abandonment of these farms in the northeastern United States. They were overgrown by forests within a few decades.

    During my more recent walks through the woods, on a whim I used a hand-held GPS unit to map several miles of stone walls. And that was how I realized that in addition to being part of an American legacy, their locations record a centuries-long history of the Earth’s wandering magnetic field.

    Connecting the walls with historical maps

    The complex array of walls that emerged from my GPS readings made no sense to me until I found an old map of my town’s property boundaries at the local historical society. Suddenly I saw that some of the stone walls on my map lay along property lines from 1790. They marked boundaries.

    My subsequent searches of church records and decades of the federal census revealed the names of these farm families and details of their lives, including annual yields from their harvests. I started to feel like the stone walls were letting me connect with the long-gone folks who had worked this land.

    Now the wheels in my scientist’s mind really started spinning. Did the original land surveys from the 18th and 19th centuries in this part of town still exist? What were the magnetic compass-bearings of those boundaries on the original surveys?

    2
    Historical maps and surveys underscore the orderly way plots were divvied up from the landscape in a grid. Charles Peirce/Stoddard, New Hampshire

    I knew that the location of magnetic north drifts over time due to changes in the Earth’s core. Could I determine its drift using stone walls and the old land surveys? My preliminary map of stone walls and a few historical surveys showed that the approach had potential.

    To have any scientific value, though, this work had to encompass much larger areas. I needed a different strategy for finding and mapping stone walls. Luckily I found two troves of useful information. First, the New York State Archives had hundreds of the original land surveys from the 18th and 19th centuries. And secondly, airborne LiDAR (light detection and ranging) images were publicly available that could reveal stone walls hidden beneath the forest canopy over much larger areas than I could cover on my own by foot.

    3
    Magnetic north and geographic north aren’t the same – and their difference changes over time. Siberian Art/Shutterstock.com

    Tracking magnetic north’s drift over time

    The Earth rotates on its axis once every 24 hours. The location of that spin axis in the Northern Hemisphere is called true north, and wanders very slowly. The location of true north can be considered stationary, though, on a timescale of a few centuries.

    But that’s not where a compass aims when it points north. The location of the north magnetic pole is not only at a different location from true north, but also changes rapidly – currently about one degree per 10 years in New England.

    The difference in direction between true north and magnetic north (at a specific time and location on the Earth) is known as the magnetic declination. Global information about historic variations in magnetic declination is currently based on thousands of magnetic compass-bearings recorded in ships’ navigational logs from 1590 onwards.

    But now my work on 726 miles of stone walls provides an independent check [JGR Solid Earth] on magnetic declination between 1685 and 1910.

    Here’s the logic. When settlers were piling up those stones along the boundaries of their plots, they were using property lines that had been laid out according to the surveyors’ compass readings. Using LiDAR images, the bearings of those stone walls could be determined with respect to true north and compared with the surveyors’ magnetic bearings. The difference is the magnetic declination at the time of the original survey.

    For example, the original surveys divided New Hampshire’s Stoddard township into hundreds of lots with boundaries with magnetic compass-bearings of N80 degrees W and N14 degrees E in 1768. As the land was cleared for farming, owners built stone walls along and within those 1768 surveyed boundaries.

    4
    Lidar reveals the stone walls hidden beneath the canopy. Comparing their orientation with true north provides the magnetic declination at this location when boundaries were surveyed in 1768. CC BY-ND

    Now one can compare the bearings of those stone wall-defined boundaries relative to magnetic north and true north today. The difference shows that the magnetic declination at this location in 1768 was 7.6 ± 0.3 degrees W. That’s a good match for scientists’ current geophysical model. Since the magnetic declination at this location today is 14.2 degrees W, the direction to magnetic north at this location has moved about 6.6 degrees further west since 1768.

    Data from these stone walls strengthen the current geophysical model about the Earth’s magnetic field.

    See the full article here .

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    Please help promote STEM in your local schools.

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    The Conversation launched as a pilot project in October 2014. It is an independent source of news and views from the academic and research community, delivered direct to the public.
    Our team of professional editors work with university and research institute experts to unlock their knowledge for use by the wider public.
    Access to independent, high quality, authenticated, explanatory journalism underpins a functioning democracy. Our aim is to promote better understanding of current affairs and complex issues. And hopefully allow for a better quality of public discourse and conversation.

     
  • richardmitnick 11:15 am on March 12, 2019 Permalink | Reply
    Tags: "Scientists Track Deep History of Planets' Motions and Effects on Earth's Climate", , , , , Geology,   

    From Columbia University: “Scientists Track Deep History of Planets’ Motions, and Effects on Earth’s Climate” 

    Columbia U bloc

    From Columbia University

    March 4, 2019
    Kevin Krajick

    Newly Forming Map of Chaos in the Solar System.

    1
    Geologist Paul Olsen at Arizona’s Petrified Forest National Park, where 200 million-year-old rocks are helping reveal the long-ago motions of other planets. (Kevin Krajick/Earth Institute)

    Scientists have long posited that periodic swings in Earth’s climate are driven by cyclic changes in the distribution of sunlight reaching our surface. This is due to cyclic changes in how our planet spins on its axis, the ellipticity of its orbit, and its orientation toward the sun — overlapping cycles caused by subtle gravitational interplays with other planets, as the bodies whirl around the sun and by each other like gyrating hula-hoops.

    But planetary paths change over time, and that can change the cycles’ lengths. This has made it challenging for scientists to untangle what drove many ancient climate shifts. And the problem gets ever more difficult the further back in time you go; tiny changes in one planet’s motion may knock others’ askew — at first slightly, but as eons pass, these changes resonate against each other, and the system morphs in ways impossible to predict using even the most advanced math. In other words, it’s chaos out there. Up to now, researchers are able to calculate the relative motions of the planets and their possible effects on our climate with reasonable reliability back only about 60 million years — a relative eyeblink in the 4.5 billion-plus life of Earth.

    This week, in a new paper in the Proceedings of the National Academy of Sciences, a team of researchers has pushed the record way back, identifying key aspects of the planets’ motions from a period around 200 million years ago. The team is led by geologist and paleontologist Paul Olsen of Columbia University’s Lamont-Doherty Earth Observatory. Last year, by comparing periodic changes in ancient sediments drilled from Arizona and New Jersey, Olsen and colleagues identified a 405,000-year cycle in Earth’s orbit that apparently has not changed at all over at least the last 200 million years — a kind of metronome against which all other cycles can be measured. Using those same sediments in the new paper, they now have identified a cycle that started out lasting 1.75 million years, but is now operating every 2.4 million years. This, they say, allows them to extrapolate long-term changes in the paths of Jupiter and the inner planets (Mercury, Venus and Mars), the bodies most likely to affect our own orbit.

    Olsen’s ultimate aim: to use Earth’s rocks to create what he calls a “Geological Orrery” — a record of climatic changes on Earth that can be extrapolated back into a larger map of solar system motions over hundreds of millions of years. He says it would open a window not just onto our own climate, but the evolution of the solar system itself, including the possible existence of past planets, and its possible interactions with invisible dark matter.

    We spoke with Olsen about the Geological Orrery, his work, and the new paper.

    Most people have probably never even heard the word “orrery.” What is it, and how does it fit with our evolving understanding of celestial mechanics?

    In the early 1800s, mathematician Pierre-Simon de Laplace took Newton’s laws of gravitation and planetary motion and published his idea that it should be possible to develop a single great equation that would allow all the universe to be modeled. With only knowledge of the present, all the past and future could be known. This idea is embodied in the orrery, a mechanical model of the solar system. Clockwork mechanisms like this for predicting eclipses and the like go back to the ancient Greeks, but it’s now clear the problem is far more complicated, and interesting.

    We’ve since discovered that the solar system not a clockwork. It is in fact chaotic over long time scales, so Laplace’s grand equation was a mirage. This means you cannot unpack its history from calculations or models, no matter how precise, because the motions of the real solar system are incredibly sensitive. Varying any factor even a tiniest bit results in a different outcome after millions of years — even what the major asteroids, or minor planets, such as Ceres and Vesta, are doing. One of my coauthors, Jacques Laskar, has shown that computations can project forward or backward only 60 million years. After that, the predictions become utterly unreliable. Since Earth is about 4.6 billion years old, this means that only about 1.6 percent of its past or future orbit can be predicted. Over billions of years, the best calculations reveal many possible terrific events, such as one of the inner planets falling into the sun or being ejected from the solar system. Maybe even that Earth and Venus could collide one day. We can’t tell if any of these actually happened, or might happen in the future. So we need some other method to limit the possibilities.

    2
    View looking east toward the U.S. East Coast, Oct. 7, 2015, when the three planets most influential to Earth’s orbit lined up with the Moon. Lower left near Earth’s horizon, Jupiter (greenish); slightly higher, Mars (reddish); slightly higher and to right, Venus (bright white); and the Moon. On Earth’s surface, lights of the New York-Philadelphia metro region trace the area where scientists took rock cores revealing these planets’ motions. Inspired by a photo taken by U.S. astronaut Scott Kelly. (Painting by Paul Olsen; acrylic on clay board, digitally modified)

    So, what is the “Geological Orrery?” Are you trying again to boil everything down to one equation, or is this something different?

    The Geological Orrery is the opposite of an equation or model. It’s designed to provide a precise and accurate history of the solar system. We get that history right here on Earth, from the history of our climates, which is recorded in the geological record, especially in large, long-lived lakes.

    Earth’s orbit and axis orientation are constantly changing because they are being deformed by the gravitational attractions of other bodies. These changes affect the distribution of sunlight hitting our surface, which in turn affects climate, and the kinds of sediments that are deposited. That gives us the geological record of solar system behavior.

    Many scientists have used sediments to determine the effects of orbital deformations. That’s how we know that the ice ages of the last few million years were paced by them. Some researchers have tried to go back much further in time. What is new here is the systematic approach of taking rock cores spanning tens of millions of years, looking at the cyclical sedimentary record of climate and accurately dating those changes over multiple sites. That allows us to capture the full range of solar system-driven deformations of our orbit and axis over long time periods.

    3
    A mechanical orrery presented in 1713 by English inventor John Rowley to Charles Boyle, the Fourth Earl of Orrery — origin of the modern name. (Engraving from The Universal Magazine, 1749)

    What are the rocks telling you about how such cyclic changes affect our climate?

    With two major coring experiments to date, we’ve we learned that changes in tropical climates from wet to dry during the time of early dinosaurs, from about 252 to 199 million years ago, were paced by orbital cycles lasting about 20,000, 100,000 and 400,000 years. On top of that is a much longer cycle of about 1.75 million years. The shorter cycles are about the same today, but the 1.75 million year cycle is way off —it’s 2.4 million years today. We think the difference is caused by a gravitational dance between Earth and Mars. This difference is the fingerprint of solar system chaos. No existing set of models or calculations precisely duplicates these data.

    How far do you think we’re going to get with this problem during your lifetime?

    Next step is to combine our two finished coring experiments with cores taken at high latitudes. While our core data do a really good job of mapping some aspects of planetary orbits, they tell us nothing about others. For those, we need a core from an ancient lake above the paleo-Arctic or Antarctic circles. Such deposits exist in what are now China and Australia. We also would like to include deposits that extend the record up 20 million years or so towards the present, and another low-latitude core that we can precisely date. With those, we would be able to determine what if any changes have taken place in that Mars-Earth gravitational dance. That would be a full proof of concept of the Geological Orrery. I plan to certainly be around for that.

    4
    Digital elevation map of sediment strata formed on a lake bottom some 220 million years ago, near present day Flemington, N.J. The lakebed was later tilted so that its cross section now faces the sky. Purple sections are ridges — remains of hard, compressed sediments formed when climate was wet and the lake deep; alternating greenish sections are lower areas made of eroded-out softer sediments from dryer times. Each pair represents 405,000 years. Groups of ridges in lower part of image manifest a separate 1.7 million-year cycle that has today grown to 2.4 million years. Thee 40-square-mile area is dissected by parts of the modern Raritan and Neshanic rivers (blue). (LIDAR image by U.S. Geological Survey; digital colorization by Paul Olsen)

    Your paper mentions that this work might offer insights into the evolution of the solar system — maybe the even wider universe.

    If all this works out, we could plan the grand mission to use the Geological Orrery for at least the rest of the time between 60 and 190 million years age. This mission would be expensive by geology standards, because rock coring is expensive. But the results would have far-reaching implications. For sure we would have data to produce high-quality climate models for Earth. And there is no doubt we would have the parameters for past climates on Mars or other rocky planets. But more excitingly and more speculative is the possibility of exploring how we might need to tweak gravity theory, or test some controversial theories, such as the possible existence of a plane of dark matter in our galaxy that our solar system passes through periodically.

    We’re talking deep time here. Does this have any application to questions about modern-day climate change?

    It does have relevance to the present. in addition to the way climate is tuned to our orbit, it’s also affected by the amount of carbon dioxide in the air. Now we’re heading into a time when CO2 levels may be as high as they were 200 million years ago, early dinosaur times. This gives us a potential way to see how all the factors interact. It also has resonance with our search for life on Mars, or for habitable exoplanets.

    The paper is coauthored by Jacques Laskar, Observatoire de Paris; Dennis Kent and Sean Kinney, Lamont-Doherty Earth Observatory; David Reynolds, ExxonMobil Exploration; Jingeng Sha, Nanjing Institute of Geology and Paleontology; and Jessica Whiteside, University of Southampton.

    See the full article here .

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    Please help promote STEM in your local schools.

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    Columbia U Campus

    Columbia University was founded in 1754 as King’s College by royal charter of King George II of England. It is the oldest institution of higher learning in the state of New York and the fifth oldest in the United States.

     
  • richardmitnick 11:13 am on March 5, 2019 Permalink | Reply
    Tags: "I found these unusual rocks quite by accident all those years ago. On a hunch I prepared a bunch of samples and when I enhanced the images I was genuinely surprised by what I found.", , Geology, Hiding in a slab of northern Canada's ancient sea floor geologists have uncovered a 'superhighway' of prehistoric worm tunnels, It was thought that half a billion years ago the ocean floor was completely void of life an ancient dead zone without the necessary oxygen for survival, , , Serendipity is a common aspect to my kind of research" says Pratt, Thanks to a lucky new discovery scientists are now second-guessing that assumption, The Burgess shale also located in northern Canada is famous for its remarkably preserved Cambrian fossils, The Cambrian period is known for its explosion of life with multicellular organisms developing and spreading right across the globe, The discovery was made by Brian Pratt a geologist and palaeontologist from the University of Saskatchewan 35 years after he first collected the sedimentary rocks from the Mackenzie Mountains in northw, These fossilised tunnels date back to the Cambrian period - 270 million years before the first dinosaurs, These tunnels ranged from 0.5 to 15 millimetres (0.02 to 0.6 inches) which suggests there was quite a bit of diversity in worm life at this time and in this unexpected place., University of Saskatchewan   

    From Science Alert for University of Saskatchewan: “Scientists Discover an Ancient ‘Superhighway’ at The Bottom of The Ocean” 

    ScienceAlert

    From Science Alert

    for

    1

    University of Saskatchewan

    5 MAR 2019
    CARLY CASSELLA

    2
    (University of Saskatchewan)

    Half a billion years ago, the ocean floor was thought to be completely void of life, an ancient dead zone without the necessary oxygen for survival.

    Thanks to a lucky new discovery, scientists are now second-guessing that assumption. Hiding in a slab of northern Canada’s ancient sea floor, geologists have uncovered a ‘superhighway’ of prehistoric worm tunnels.

    These fossilised tunnels date back to the Cambrian period – 270 million years before the first dinosaurs – and they suggest that even the deepest seabeds held more life, and oxygen, than we once thought.

    The discovery was made by Brian Pratt, a geologist and palaeontologist from the University of Saskatchewan, 35 years after he first collected the sedimentary rocks from the Mackenzie Mountains in northwest Canada.

    “Serendipity is a common aspect to my kind of research,” says Pratt.

    “I found these unusual rocks quite by accident all those years ago. On a hunch I prepared a bunch of samples and when I enhanced the images I was genuinely surprised by what I found.”

    The burrows where these ancient worms once used to roam were not visible until Pratt used a flatbed scanner and image editing to bring them to life.

    There, in the slices of rock, was a nice surprise: an abundance of exceptionally well-defined burrows, criss-crossing each other in every which way.

    These tunnels ranged from 0.5 to 15 millimetres (0.02 to 0.6 inches), which suggests there was quite a bit of diversity in worm life at this time and in this unexpected place.

    Some of the prehistoric worms, for instance, are estimated at no more than a millimetre, while others are thought to be as long as a finger.

    3
    (Brian Pratt, University of Saskatchewan)

    The authors think the smaller tunnels were made by polychaetes, a simple creature also known as a bristle worm. Meanwhile, the larger burrows probably belonged to predators, who liked to attack unsuspecting arthropods and other surface-dwelling worms from their hiding spot.

    The Cambrian period is known for its explosion of life, with multicellular organisms developing and spreading right across the globe. The Burgess shale, also located in northern Canada, is famous for its remarkably preserved Cambrian fossils.

    Scientists thought these fossils had been so well preserved because they’d fallen to the bottom of the sea where there was little oxygen to speed up their decay, and also fewer animals around who’d eat the evidence.

    If the new research is right and there was, in fact, life in the seafloor, we may need to rethink some of our assumptions about ancient oceans and the continental shelves they sit upon.

    “This has a lot of implications which will now need to be investigated, not just in Cambrian shales but in younger rocks as well,” says Pratt.

    “People should try the same technique to see if it reveals signs of life in their samples.”

    This study has been published in Geology.

    See the full article here .


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