Libyan Desert Glass: An extraordinary highly translucent 239.1-gram Libyan Desert Glass individual covered in pseudo regmaglypts, which are strikingly similar in appearance to the thumbprints found on certain meteorites. Some impact specialists have theorized that at the time of impact, molten jelly-like blobs of desert glass were thrown far up into the air, and then fell back to earth acquiring regmaglypts in the process. A more widely accepted view is that pseudo regmaglypts are the result of long term desert erosion by wind and sand. However they are formed, their resemblance to meteoritic regmaglypts is remarkable. Photograph by Leigh Anne DelRay, copyright Aerolite Meteorites.
From moon rocks to meteorites, and from space dust to a dinosaur-destroying impact, the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) has a well-storied expertise in exploring samples of extraterrestrial origin.
This research – which has helped us to understand the makeup and origins of objects within and beyond our solar system – stems from the Lab’s long-standing core capabilities and credentials in structural and chemical analyses and measurement at the microscale and nanoscale.
Berkeley Lab’s participation in a new study, detailed June 11 in the journal Proceedings of the National Academy of Sciences (see related news release), focused on the chemical composition of tiny glassy grains of interplanetary particles – likely deposited in Earth’s upper atmosphere by comets – that contain dust leftover from the formative period of our solar system.
Petrographic relationship between organic carbon and amorphous silicates in cometary IDPs. (A) High-angle annular darkfield (HAADF) image of a section through the middle of a single GEMS grain in U217B19 and (B) corresponding carbon element map showing organic rims on subgrains within the GEMS grain. (C) HAADF image of a section through the middle of a GEMS grain in LT39 and (D) corresponding carbon element map showing a higher brightness organic carbon rim mantling the GEMS exterior surface. The higher brightness rim corresponds to higher-density organic carbon with higher C/O ratio (SI Appendix). (E) HAADF image of PAH-rich nanoglobules (ng) comprised of higher-density organic carbon and (F) element map. Red, C; blue, Mg; green, Fe; and yellow, S. One nanoglobule has a partial GEMS mantle shown in Inset. (G) HAADF image of a nanoglobule heavily decorated with GEMS. (H) Brightfield image of two carbon-rich GEMS, with one on right a torus with an organic carbon interior and inorganic exterior. [From above cited science paper.]
That study involved experiments at the Lab’s Molecular Foundry, a nanoscale research facility, and the Advanced Light Source (ALS), which supplies different types of light, from infrared light to X-rays, for dozens of simultaneous experiments.
More than a decade ago, NASA’s Stardust spacecraft mission, which had a rendezvous with comet 81P/Wild 2, returned samples of cometary and interstellar dust to Earth. Ever since, researchers have been working to study this material in detail.
In one study, published in 2014 [Science], scientists used X-rays and infrared light to study particles from this mission. In another study [Wiley], published in 2015, researchers studied two comet particles using several high-resolution electron microscopes and a focused ion beam at Berkeley Lab’s National Center for Electron Microscopy (NCEM), which is now part of the Molecular Foundry.
LBNL National Center for Electron Microscopy (NCEM)
LBNL Molecular Foundry – No image credits found
They found that the microscopic rocks, named Iris and Callie, had formed from molten droplets that crystallized rapidly in outer space.
Interplanetary dust particles were also the focus of a 2014 study that involved NCEM and the ALS. That study [PNAS]explored pockets of water that were directly formed on the dust particles via irradiation by the solar wind, and their findings suggest that this mechanism could be responsible for transporting water throughout the solar system.
In other studies, the ALS has been used to reveal liquid water and complex organic compounds like hydrocarbons and amino acids in meteorites – one of which may have traveled here from a dwarf planet – and ALS scientists have been working with NASA to study the microscopic makeup of asteroids to better understand how meteoroids break apart in Earth’s atmosphere.
The Lab also had a role in analyzing dust from moon rocks collected in the Apollo 11 and Apollo 12 moon missions – the late Melvin Calvin, who was a former associate director at the Lab, participated in a study of carbon compounds in lunar samples that was published [<em>PSLSC] in 1971.
And in the 1970s, Berkeley Lab Nobel laureate Luis Alvarez teamed with his son, Walter Alvarez, then an associate professor of geology at UC Berkeley, to unravel the mystery of the dinosaur die-off some 65 million years ago. The Alvarezes, working with Lab nuclear chemists Frank Asaro and Helen Michel, used a technique known as neutron activation analysis to precisely measure an unusual abundance in the element iridium in sedimentary deposits that dated back to the time of the dinosaurs’ disappearance and the mass extinction of many other species. [LBL Science Beat]
Iridium, which is rare on Earth, was known to be associated with extraterrestrial objects such as asteroids, and later studies [Science] would confirm that a massive meteorite impact is the most likely cause of that ancient extinction event.
Besides studying materials of extraterrestrial origin, Berkeley Lab researchers have also worked to synthesize and simulate the chemistry, materials, conditions, and effects found outside of Earth – from lab-treated materials that are analogous to exotic minerals that formed in space from the presence of corrosive gases in the early solar system to simulated mergers of neutron stars and black holes, and the creation of simulated Martian meteorites.
The tectonic plates of the world were mapped in 1996, USGS.
A new study suggests that rapid cooling within the Earth’s mantle through plate tectonics played a major role in the development of the first life forms, which in turn led to the oxygenation of the Earth’s atmosphere. The study was published in the March 2018 issue of Earth and Planetary Science Letters.
Scientists at the University of Adelaide and Curtin University in Australia, and the University of California at Riverside, California, USA, gathered and analyzed data on igneous rocks from geological and geochemical data repositories in Australia, Canada, New Zealand, Sweden and the United States. They found that over the 4.5 billion years of the Earth’s development, rocks rich in phosphorus accumulated in the Earth’s crust. They then looked at the relationship of this accumulation with that of oxygen in the atmosphere.
Phosphorus is essential for life as we know it. Phosphates, which are compounds containing phosphorus and oxygen, are part of the backbones of DNA and RNA as well as the membranes of cells, and help control cell growth and function.
To find out how the level of phosphorus in the Earth’s crust has increased over time, the scientists studied how rock formed as the Earth’s mantle cooled. They performed modeling to find out how mantle-derived rocks changed composition as a consequence of the long-term cooling of the mantle.
Their results suggest that during an early, hotter period in Earth’s history – the Archaean period between four and 2.5 billion years ago – there was a larger amount of molten mantle. Phosphorus would have been too dilute in these rocks. However, over time, the Earth cooled sufficiently, aided by the onset of plate tectonics, in which the colder outer crust of the planet is subducted back into the hot mantle. With this cooling, partial mantle melts became smaller.
As Dr. Grant Cox, an earth scientist at the University of Adelaide and a co-author of the study, explains, the result is that “phosphorus will be concentrated in small percentage melts, so as the mantle cools, the amount of melt you extract is smaller but that melt will have higher concentrations of phosphorus in it.”
A cross section of the Earth, showing the exterior crust, the molten mantle beneath it and the core at the center of the planet. Image credit: NASA/JPL-Université Paris Diderot – Institut de Physique du Globe de Paris.
Phosphorus’ role in the oxidation of Earth
The phosphorus was concentrated and crystallized into a mineral called apatite, which became part of the igneous rocks that were created from the cooled mantle. Eventually, these rocks reached the Earth’s surface and formed a large proportion of the crust. When phosphorus minerals derived from the crust mixed with the water in lakes, rivers and oceans, apatite broke down into phosphates, which became available for development and nourishment of primitive life.
The scientists estimated the mixing of elements from the Earth’s crust with seawater over time. They found that higher levels of bio-essential elements parallel major increases in the oxygenation of the Earth’s atmosphere: the Great Oxidation Event (GOE) 2.4 billion years ago, and the Neoproterozoic Oxygen Event, 800 million years ago, after which oxygen levels were presumed to be high enough to support multicellular life.
Even before the GOE, from approximately 3.5 to 2.5 billion years ago, some of the earliest life forms possibly generated oxygen through photosynthesis. However, during that time, most of this oxygen reacted with iron and sulfur in igneous rocks. To understand how these reactions affected oxygen levels in the atmosphere over a period of four billion years, the scientists measured the amounts of sulfur and iron in igneous rocks, and figured out how much oxygen had reacted. They compared all of these events with changes in levels of atmospheric oxygen. The scientists found that decreases in sulfur and iron along with increases in phosphorus paralleled the Great Oxidation Event and the Neoproterozoic Oxygen Event.
An explosion of life
All of these events support a scenario in which the cooling of the Earth’s mantle led to the increase of phosphorus-rich rocks in the Earth’s crust. These rocks then mixed with the oceans, where phosphorus-containing minerals broke down and leached into the water. Once phosphorus levels in seawater were high enough, primitive life forms thrived and their numbers increased, so they could generate enough oxygen that most of it reached the atmosphere. Oxygen reached levels sufficient to support multicellular life.
Dr. Peter Cawood, a geologist at Monash University inMelbourne, Australia, comments to Astrobiology Magazine that, “it’s intriguing to think that the [oxygen] on which we depend for life owes its ultimate origin to secular decreases in mantle temperature, which are thought to have decreased from some 1,550 degrees Celsius some three billion years ago to around 1,350 degrees Celsius today.”
Could a similar scenario be playing out on a possible exo-Earth? With the Kepler discoveries of a growing number of possibly Earth-like planets, could any of these support life? Cawood suggests that the finding is potentially significant for the development of aerobic life (i.e. life that evolves in an oxygen-rich environment) on exoplanets. “This is provided that [phosphorus] within the igneous rocks on the surface of the planet is undergoing weathering to ensure its bio-availability,” says Cawood. “Significantly, the phosphorus content of igneous rocks is highest in those rocks low in silica [rocks formed by rapid cooling] and rocks of this composition dominate the crusts of Venus and Mars and likely also on exoplanets.”
Cox concludes by saying that, “This relationship [between rising oxygen levels and mantle cooling] has implications for any terrestrial planet. All planets will cool, and those with efficient plate tectonic convection will cool more rapidly. We are left concluding that the speed of such cooling may affect the rate and pattern of biological evolution on any potentially habitable planet.”
The research was supported by the NASA Astrobiology Institute (NAI) element of the NASA Astrobiology Program, as well as the National Science Foundation Frontiers in Earth System Dynamics Program and the Australian Research Council.
Interesting science relative to chemical and geologic observation of early Earth conditions. But, the continuous overly optimistic speculation about origin of life,OoL, in this case based on molecular formation and migration which are such a minuscule aspect of OoL origination suggests a level of desperation of naturalists to find any positive aspects of the present chaotic mess of naturalistic OoL..
Rice University’s 3D model suggests new role for asthenosphere in plate movements.
A graphic showing the convective heat cycle (red arrows) that drive plate tectonic motion (black arrows) on Earth. Heat flows toward subduction zones through the uppermost mantle layer, the asthenosphere. A realistic new computer model from Rice University finds that the asthenosphere moves and drags plates along with it rather than acting as a brake on plate movements as had been widely believed. (Image courtesy of Surachit/Wikimedia Commons)
New simulations of Earth’s asthenosphere find that convective cycling and pressure-driven flow can sometimes cause the planet’s most fluid layer of mantle to move even faster than the tectonic plates that ride atop it.
That’s one conclusion from a new study by Rice University geophysicists who modeled flow in the 100-mile-thick layer of mantle that begins at the base of Earth’s tectonic plates, or lithosphere.
The study, in the journal Earth and Planetary Science Letters, takes aim at a much-debated question in geophysics: What drives the movement of Earth’s tectonic plates, the 57 interlocking slabs of the lithosphere that slip, grind and bump against one another in a seismic dance that causes earthquakes, builds continents and gradually reshapes the planet’s surface every few million years?
The tectonic plates of the world were mapped in 1996, USGS.
“Tectonic plates float on top of the asthenosphere, and the leading theory for the past 40 years is that the lithosphere moves independently of the asthenosphere, and the asthenosphere only moves because the plates are dragging it along,” said graduate student Alana Semple, lead co-author of the new study. “Detailed observations of the asthenosphere from a Lamont research group returned a more nuanced picture and suggested, among other things, that the asthenosphere has a constant speed at its center but is changing speeds at its top and base, and that it sometimes appears to flow in a different direction than the lithosphere.”
Computational modeling carried out at Rice offers a theoretical framework that can explain these puzzling observations, said Adrian Lenardic, a study co-author and professor of Earth, environmental and planetary sciences at Rice.
“We’ve shown how these situations can occur through a combination of plate- and pressure-driven flow in the asthenosphere,” he said. “The key was realizing that a theory developed by former Rice postdoc Tobias Höink had the potential to explain the Lamont observations if a more accurate representation of the asthenosphere’s viscosity was allowed for. Alana’s numerical simulations incorporated that type of viscosity and showed that the modified model could explain the new observations. In the process, this offered a new way of thinking about the relationship between the lithosphere and asthenosphere.”
Though the asthenosphere is made of rock, it is under intense pressure that can cause its contents to flow.
“Thermal convection in Earth’s mantle generates dynamic pressure variations,” Semple said. “The weakness of the asthenosphere, relative to tectonic plates above, allows it to respond differently to the pressure variations. Our models show how this can lead to asthenosphere velocities that exceed those of plates above. The models also show how flow in the asthenosphere can be offset from that of plates, in line with the observations from the Lamont group”
The oceanic lithosphere is formed at mid-ocean ridges and flows toward subduction zones where one tectonic plate slides beneath another. In the process, the lithosphere cools and heat from Earth’s interior is transferred to its surface. Subduction recycles cooler lithospheric material into the mantle, and the cooling currents flow back into the deep interior.
Semple’s 3D model simulates both this convective cycle and the asthenosphere. She credited Rice’s Center for Research Computing (CRC) for its help running simulations — some of which took as long as six weeks — on Rice’s DAVinCI supercomputer.
Rice DAVinCI IBM iDataPlex supercomputer
Semple said the simulations show how convective cycling and pressure-driven flow can drive tectonic movement.
“Our paper suggests that pressure-driven flow in the asthenosphere can contribute to the motion of tectonic plates by dragging plates along with it,” she said. “A notable contribution does come from ‘slab-pull,’ a gravity-driven process that pulls plates toward subduction zones. Slab-pull can still be the dominant process that moves plates, but our models show that asthenosphere flow provides a more significant contribution to plate movement than previously thought.”
The research was supported by the National Science Foundation. DAVinCI is administered by CRC and was procured in partnership with Rice’s Ken Kennedy Institute for Information Technology.
In his 1912 inaugural address, Rice University president Edgar Odell Lovett set forth an ambitious vision for a great research university in Houston, Texas; one dedicated to excellence across the range of human endeavor. With this bold beginning in mind, and with Rice’s centennial approaching, it is time to ask again what we aspire to in a dynamic and shrinking world in which education and the production of knowledge will play an even greater role. What shall our vision be for Rice as we prepare for its second century, and how ought we to advance over the next decade?
This was the fundamental question posed in the Call to Conversation, a document released to the Rice community in summer 2005. The Call to Conversation asked us to reexamine many aspects of our enterprise, from our fundamental mission and aspirations to the manner in which we define and achieve excellence. It identified the pressures of a constantly changing and increasingly competitive landscape; it asked us to assess honestly Rice’s comparative strengths and weaknesses; and it called on us to define strategic priorities for the future, an effort that will be a focus of the next phase of this process.
University of Washington (UW) Graduate Student Megan (Meg) Whitney applies a plaster jacket to a fossil in Antarctica. Photo: Christian Sidor/Burke Museum
The Antarctic fossil record is one of the least understood in the world, due in large part to its remoteness, ice cover, and extreme conditions. There is much to learn, but Antarctic research is often difficult to do.
“It’s logistically intensive fieldwork,” said Dr. Christian Sidor, Burke Museum curator of vertebrate paleontology and University of Washington (UW) Professor of Biology. He recently led a multi-institution research team to Antarctica for an 11-week expedition funded by the National Science Foundation, which manages the U.S. Antarctic Program.
Christian is very familiar with the logistics involved; this was his fourth research trip to Antarctica in the past 15 years to better understand how life recovered after the Permo-Triassic mass extinction, which happened about 252 million years ago and ushered in the era of dinosaurs.
Megan (Meg) Whitney, a graduate student in the UW Department of Biology, joined Christian for her first trip to Antarctica. Meg’s interest is in anatomy, but she didn’t want to be a medical doctor. “I wasn’t a dinosaur kid—I fell into [paleontology].” Meg is studying the anatomy of fossil bones and teeth at a microscopic scale to understand how animals were affected by extreme seasonality at polar latitudes as part of her PhD.
Christian and Meg were joined by paleontologists and geologists from the Natural History Museum of Los Angeles County, the Field Museum, Southern Methodist University, and the Iziko South African Museum.
Members of the expedition team. From left to right: Christian Sidor, Roger Smith, Akiko Shinya, Peter Makovicky, Julia McIntosh, Nathan Smith, Hank Wooley, Peter Braddock, Megan Whitney. Photo: Mike Niedzwiecki
After arriving at McMurdo Station and completing two weeks of trainings, the team flew to what would be their home for the next 45 days—the temporary Shackleton Glacier camp about 300 miles from the South Pole in the Transantarctic Mountains.
The base camp was a pop-up community for the research season. Camp staff are brought in to prepare food, maintain supplies, monitor the weather, offer medical support, pilot the helicopters and planes, and help with everything the 12 research teams might need to operate for months at a time.
Camp staff and fellow researchers become close friends—an extended family of sorts—especially since the research team celebrated the Christmas and New Years holidays thousands of miles away from home.
Meg Whitney (left) and Roger Smith (right) with their gear before taking it to the helicopter to head out for the day. Photo: Christian Sidor/Burke Museum
Each day, the paleontologists loaded all of their safety gear to take with them in case bad weather rolled in. Two weather forecasters in the camp kept an eye on any approaching weather that might impact the team’s ability to get in and out in the field safely. They also had a mountaineer accompanying them for safety.
The only way to reach the mountainsides where they were working was by helicopter.
The helicopter lands to pick up the team and their gear at the end of the day. Photo: Christian Sidor/Burke Museum
It’s “kind of like catching an Uber,” added Meg. “Some days were longer, some shorter, dependent on availability of helicopters that day and the weather.” The weather worked in their favor most of the trip and they only had to cancel three field days. In addition to the weather, light conditions play an important role in spotting fossils.
“We’re working on the mountainsides—the tips of mountain sticking through the glacier,” said Christian. “We use our knowledge of the geology and sedimentology to understand where fossils are likely to be found.”
“When we find a fossil, hopefully we’re finding the beginning of a skeleton and can trace that to the hillside and excavate a big block, including the fossil but also some of the rock surrounding it so it’s protected,” he said.
A fossil of an early reptile called Procolophon still embedded in rock.
Photo: Christian Sidor/Burke Museum
They focused their efforts on the Fremouw Formation, a rock formation that is about 250–240 million years old and use rock saws to excavate fossils to speed up the process.
“After we’ve cut out and chiseled out all of this rock, we put a plaster jacket on top which is an interesting thing to do in Antarctica, because it requires putting your hand in water, so you’re freezing your hand to make the jacket,” said Meg.
The Shackleton Glacier area was previously explored by paleontologists only three other times, in 1970–71, 1977–78 and 1995–96. “I was worried that it might have been picked over [by the previous teams],” said Christian. Thankfully that wasn’t the case.
The team found fossil bones, trace fossils including tracks and burrows, and plant impressions—all indications of what life was like about 250 million years ago.
A fossil burrow where an animal would’ve dug into its den back in the Triassic. Photo: Christian Sidor/Burke Museum
The skeletal material includes small, salamander-like amphibians (temnospondyls), early reptiles such as Prolacerta and Procolophon, in addition to mammal relatives like Lystrosaurus and Thrinaxodon. They also found several other species that will need additional research to determine what they were.
Fossils collected in Antarctica fall under the Antarctic Treaty, of which the United States is a signatory. This means that scientific observations and research must be made freely available. So the fossils will be cared for in the Burke Museum collection, but they will be accessible to any visiting researcher.
Not much is known about Antarctic amphibians, but Christian believes that will change after this expedition. “In the past, we’ve known which families of amphibians have been there but not which species,” he said. “Because we have so many [amphibian fossils] and they’re so well-preserved, we’ll be able to tackle that question and know what species of amphibians were in Antarctica after the mass extinction.”
In addition, they collected the first identifiable vertebrate fossils from the middle of the Fremouw Formation, which will help narrow down the age of those rocks. Fossils were previously found in the lower and upper parts of the Fremouw Formation, but not in the middle.
In all, the Burke Museum team found 56 new localities and more than 100 specimens, including two new localities, where vertebrate fossils had never been collected before.
The work is just getting started back at the museum now that the fossils arrived.
“Antarctica provides our only window into what happened to life at high latitudes after the Permo-Triassic mass extinction, and so I’m excited to be back at the Burke and get the lab work started,” said Sidor.
The University of Washington is one of the world’s preeminent public universities. Our impact on individuals, on our region, and on the world is profound — whether we are launching young people into a boundless future or confronting the grand challenges of our time through undaunted research and scholarship. Ranked number 10 in the world in Shanghai Jiao Tong University rankings and educating more than 54,000 students annually, our students and faculty work together to turn ideas into impact and in the process transform lives and our world. For more about our impact on the world, every day.
So what defines us —the students, faculty and community members at the University of Washington? Above all, it’s our belief in possibility and our unshakable optimism. It’s a connection to others, both near and far. It’s a hunger that pushes us to tackle challenges and pursue progress. It’s the conviction that together we can create a world of good. Join us on the journey.
Gravity of Jupiter and Venus elongates Earth’s orbit every 405,000 years, Rutgers-led study confirms.
Every 405,000 years, gravitational tugs from Jupiter and Venus slightly elongate Earth’s orbit, an amazingly consistent pattern that has influenced our planet’s climate for at least 215 million years and allows scientists to more precisely date geological events like the spread of dinosaurs, according to a Rutgers-led study.
Rutgers University–New Brunswick Professor Dennis Kent with part of a 1,700-foot-long rock core through the Chinle Formation in Petrified Forest National Park in Arizona. The background includes boxed archives of cores from the Newark basin that were compared with the Arizona core.
Photo: Nick Romanenko/Rutgers University
“It’s an astonishing result because this long cycle, which had been predicted from planetary motions through about 50 million years ago, has been confirmed through at least 215 million years ago,” said lead author Dennis V. Kent, a Board of Governors professor in the Department of Earth and Planetary Sciences at Rutgers University–New Brunswick. “Scientists can now link changes in the climate, environment, dinosaurs, mammals and fossils around the world to this 405,000-year cycle in a very precise way.”
The scientists linked reversals in the Earth’s magnetic field – when compasses point south instead of north and vice versa – to sediments with and without zircons (minerals with uranium that allow radioactive dating) as well as to climate cycles.
“The climate cycles are directly related to how the Earth orbits the sun and slight variations in sunlight reaching Earth lead to climate and ecological changes,” said Kent, who studies Earth’s magnetic field. “The Earth’s orbit changes from close to perfectly circular to about 5 percent elongated especially every 405,000 years.”
The scientists studied the long-term record of reversals in the Earth’s magnetic field in sediments in the Newark basin, a prehistoric lake that spanned most of New Jersey, and in sediments with volcanic detritus including zircons in the Chinle Formation in Petrified Forest National Park in Arizona. They collected a core of rock from the Triassic Period, some 202 million to 253 million years ago. The core is 2.5 inches in diameter and about 1,700 feet long, Kent said.
The results showed that the 405,000-year cycle is the most regular astronomical pattern linked to the Earth’s annual turn around the sun, he said.
The study was conducted by National Science Foundation-funded scientists at Rutgers–New Brunswick; Lamont–Doherty Earth Observatory at Columbia University, where Kent is also an adjunct senior research scientist and where longtime research collaborator and co-author Paul E. Olsen works; and other institutions. Christopher J. Lepre, a lecturer in Rutgers’ Department of Earth and Planetary Sciences, and seven others co-authored the study, and the cores were sampled at the Rutgers Core Repository.
Rutgers, The State University of New Jersey, is a leading national research university and the state’s preeminent, comprehensive public institution of higher education. Rutgers is dedicated to teaching that meets the highest standards of excellence; to conducting research that breaks new ground; and to providing services, solutions, and clinical care that help individuals and the local, national, and global communities where they live.
Founded in 1766, Rutgers teaches across the full educational spectrum: preschool to precollege; undergraduate to graduate; postdoctoral fellowships to residencies; and continuing education for professional and personal advancement.
As a ’67 graduate of University college, second in my class, I am proud to be a member of
Alpha Sigma Lamda, National Honor Society of non-tradional students.
In Silent Spring, Rachel Carson considers the Western sagebrush. “For here the natural landscape is eloquent of the interplay of forces that have created it,” she writes. “It is spread before us like the pages of an open book in which we can read why the land is what it is, and why we should preserve its integrity. But the pages lie unread.” She is lamenting the disappearance of a threatened landscape, but she may just as well be talking about markers of paleoclimate.
To know where you’re going, you have to know where you’ve been. That’s particularly true for climate scientists, who need to understand the full range of the planet’s shifts in order to chart the course of our future. But without a time machine, how do they get this kind of data?
Like Carson, they have to read the pages of the Earth. Fortunately, the Earth has kept diaries. Anything that puts down yearly layers—ocean corals, cave stalagmites, long-lived trees, tiny shelled sea creatures—faithfully records the conditions of the past. To go further, scientists dredge sediment cores and ice cores from the bottom of the ocean and the icy poles, which write their own memoirs in bursts of ash and dust and bubbles of long-trapped gas.
In a sense, then, we do have time machines: Each of these proxies tells a slightly different story, which scientists can weave together to form a more complete understanding of Earth’s past.
In March, the Smithsonian Institution’s National Museum of Natural History held a three-day Earth’s Temperature History Symposium that brought teachers, journalists, researchers and the public together to enhance their understanding of paleoclimate. During an evening lecture, Gavin Schmidt, climate modeler and director of NASA’s Goddard Institute for Space Studies, and Richard Alley, a world-famous geologist at Pennsylvania State University, explained how scientists use Earth’s past climates to improve the climate models we use to predict our future.
Here is your guide to Earth’s climate pasts—not just what we know, but how we know it.
How do we look into Earth’s past climate?
It takes a little creativity to reconstruct Earth’s past incarnations. Fortunately, scientists know the main natural factors that shape climate. They include volcanic eruptions whose ash blocks the sun, changes in Earth’s orbit that shift sunlight to different latitudes, circulation of oceans and sea ice, the layout of the continents, the size of the ozone hole, blasts of cosmic rays, and deforestation. Of these, the most important are greenhouse gases that trap the sun’s heat, particularly carbon dioxide and methane.
As Carson noted, Earth records these changes in its landscapes: in geologic layers, fossil trees, fossil shells, even crystallized rat pee—basically anything really old that gets preserved. Scientists can open up these diary pages and ask them what was going on at that time. Tree rings are particularly diligent record-keepers, recording rainfall in their annual rings; ice cores can keep exquisitely detailed accounts of seasonal conditions going back nearly a million years.
Ice cores reveal annual layers of snowfall, volcanic ash and even remnants of long-dead civilizations. (NASA’s Goddard / Ludovic Brucker)
What else can an ice core tell us?
“Wow, there’s so much,” says Alley, who spent five field seasons coring ice from the Greenland ice sheet. Consider what an ice core actually is: a cross-section of layers of snowfall going back millennia.
When snow blankets the ground, it contains small air spaces filled with atmospheric gases. At the poles, older layers become buried and compressed into ice, turning these spaces into bubbles of past air, as researchers Caitlin Keating-Bitonti and Lucy Chang write in Smithsonian.com. Scientists use the chemical composition of the ice itself (the ratio of the heavy and light isotopes of oxygen in H2O) to estimate temperature. In Greenland and Antarctica, scientists like Alley extract inconceivably long ice cores—some more than two miles long!
Ice cores tell us how much snow fell during a particular year. But they also reveal dust, sea salt, ash from faraway volcanic explosions, even the pollution left by Roman plumbing. “If it’s in the air it’s in the ice,” says Alley. In the best cases, we can date ice cores to their exact season and year, counting up their annual layers like tree rings. And ice cores preserve these exquisite details going back hundreds of thousands of years, making them what Alley calls “the gold standard” of paleoclimate proxies.
Wait, but isn’t Earth’s history much longer than that?
Yes, that’s right. Paleoclimate scientists need to go back millions of years—and for that we need things even older than ice cores. Fortunately, life has a long record. The fossil record of complex life reaches back to somewhere around 600 million years. That means we have definite proxies for changes in climate going back approximately that far. One of the most important is the teeth of conodonts—extinct, eel-like creatures—which go back 520 million years.
But some of the most common climate proxies at this timescale are even more miniscule. Foraminifera (known as “forams”) and diatoms are unicellular beings that tend to live on the ocean seafloor, and are often no bigger than the period at the end of this sentence. Because they are scattered all across the Earth and have been around since the Jurassic, they’ve left a robust fossil record for scientists to probe past temperatures. Using oxygen isotopes in their shells, we can reconstruct ocean temperatures going back more than 100 million years ago.
“In every outthrust headland, in every curving beach, in every grain of sand there is a story of the earth,” Carson once wrote. Those stories, it turns out, are also hiding in the waters that created those beaches, and in creatures smaller than a grain of sand.
Foraminifera. (Ernst Haeckel)
How much certainty do we have for deep past?
For paleoclimate scientists, life is crucial: if you have indicators of life on Earth, you can interpret temperature based on the distribution of organisms.
But when we’ve gone back so far that there are no longer even any conodont teeth, we’ve lost our main indicator. Past that we have to rely on the distribution of sediments, and markers of past glaciers, which we can extrapolate out to roughly indicate climate patterns. So the further back we go, the fewer proxies we have, and the less granular our understanding becomes. “It just gets foggier and foggier,” says Brian Huber, a Smithsonian paleobiologist who helped organize the symposium along with fellow paleobiologist research scientist and curator Scott Wing.
How does paleoclimate show us the importance of greenhouse gases?
Greenhouse gases, as their name suggests, work by trapping heat. Essentially, they end up forming an insulating blanket for the Earth. (You can get more into the basic chemistry here.) If you look at a graph of past Ice Ages, you can see that CO2 levels and Ice Ages (or global temperature) align. More CO2 equals warmer temperatures and less ice, and vice versa. “And we do know the direction of causation here,” Alley notes. “It is primarily from CO2 to (less) ice. Not the other way around.”
We can also look back at specific snapshots in time to see how Earth responds to past CO2 spikes. For instance, in a period of extreme warming during Earth’s Cenozoic era about 55.9 million years ago, enough carbon was released to about double the amount of CO2 in the atmosphere. The consequentially hot conditions wreaked havoc, causing massive migrations and extinctions; pretty much everything that lived either moved or went extinct. Plants wilted. Oceans acidified and heated up to the temperature of bathtubs.
Unfortunately, this might be a harbinger for where we’re going. “This is what’s scary to climate modelers,” says Huber. “At the rate we’re going, we’re kind of winding back time to these periods of extreme warmth.” That’s why understanding carbon dioxide’s role in past climate change helps us forecast future climate change.
That sounds pretty bad.
Yep.
I’m really impressed by how much paleoclimate data we have. But how does a climate model work?
Great question! In science, you can’t make a model unless you understand the basic principles underlying the system. So the mere fact that we’re able to make good models means that we understand how this all works. A model is essentially a simplified version of reality, based on what we know about the laws of physics and chemistry. Engineers use mathematical models to build structures that millions of people rely on, from airplanes to bridges.
Our models are based on a framework of data, much of which comes from the paleoclimate proxies scientists have collected from every corner of the world. That’s why it’s so important for data and models to be in conversation with each other. Scientists test their predictions on data from the distant past, and try to fix any discrepancies that arise. “We can go back in time and evaluate and validate the results of these models to make better predictions for what’s going to happen in the future,” says Schmidt.
Here’s a model:
It’s pretty. I hear the models aren’t very accurate, though.
By their very nature, models are always wrong. Think of them as an approximation, our best guess.
But ask yourself: do these guesses give us more information than we had previously? Do they provide useful predictions we wouldn’t otherwise have? Do they allow us to ask new, better questions? “As we put all of these bits together we end up with something that looks very much like the planet,” says Schmidt. “We know it’s incomplete. We know there are things that we haven’t included, we know that we’ve put in things that are a little bit wrong. But the basic patterns we see in these models are recognizable … as the patterns that we see in satellites all the time.”
So we should trust them to predict the future?
The models faithfully reproduce the patters we see in Earth’s past, present—and in some cases, future. We are now at the point where we can compare early climate models—those of the late 1980s and 1990s that Schmidt’s team at NASA worked on—to reality. “When I was a student, the early models told us how it would warm,” says Alley. “That is happening. The models are successfully predictive as well as explanatory: they work.” Depending on where you stand, that might make you say “Oh goody! We were right!” or “Oh no! We were right.”
To check models’ accuracy, researchers go right back to the paleoclimate data that Alley and others have collected. They run models into the distant past, and compare them to the data that they actually have.
“If we can reproduce ancient past climates where we know what happened, that tells us that those models are a really good tool for us to know what’s going to happen in the future,” says Linda Ivany, a paleoclimate scientist at Syracuse University. Ivany’s research proxies are ancient clams, whose shells record not only yearly conditions but individual winters and summers going back 300 million years—making them a valuable way to check models. “The better the models get at recovering the past,” she says, “the better they’re going to be at predicting the future.”
Paleoclimate shows us that Earth’s climate has changed dramatically. Doesn’t that mean that, in a relative sense, today’s changes aren’t a big deal?
When Richard Alley tries to explain the gravity of manmade climate change, he often invokes a particular annual phenomenon: the wildfires that blaze in the hills of Los Angeles every year. These fires are predictable, cyclical, natural. But it’d be crazy to say that, since fires are the norm, it’s fine to let arsonists set fires too. Similarly, the fact that climate has changed over millions of years doesn’t mean that manmade greenhouse gases aren’t a serious global threat.
“Our civilization is predicated on stable climate and sea level,” says Wing, “and everything we know from the past says that when you put a lot of carbon in the atmosphere, climate and sea level change radically.”
Since the Industrial Revolution, human activities have helped warm the globe 2 degrees F, one-quarter of what Schmidt deems an “Ice Age Unit”—the temperature change that the Earth goes through between an Ice Age and a non-Ice Age. Today’s models predict another 2 to 6 degrees Celsius of warming by 2100—at least 20 times faster than past bouts of warming over the past 2 million years.
______________________________________________________________
From NASA Earth Observatory
How is Today’s Warming Different from the Past?
Earth has experienced climate change in the past without help from humanity. We know about past climates because of evidence left in tree rings, layers of ice in glaciers, ocean sediments, coral reefs, and layers of sedimentary rocks. For example, bubbles of air in glacial ice trap tiny samples of Earth’s atmosphere, giving scientists a history of greenhouse gases that stretches back more than 800,000 years. The chemical make-up of the ice provides clues to the average global temperature.
See the Earth Observatory’s series Paleoclimatology for details about how scientists study past climates.
Glacial ice and air bubbles trapped in it (top) preserve an 800,000-year record of temperature & carbon dioxide. Earth has cycled between ice ages (low points, large negative anomalies) and warm interglacials (peaks). (Photograph courtesy National Snow & Ice Data Center. NASA graph by Robert Simmon, based on data from Jouzel et al., 2007.)
Using this ancient evidence, scientists have built a record of Earth’s past climates, or “paleoclimates.” The paleoclimate record combined with global models shows past ice ages as well as periods even warmer than today. But the paleoclimate record also reveals that the current climatic warming is occurring much more rapidly than past warming events.
As the Earth moved out of ice ages over the past million years, the global temperature rose a total of 4 to 7 degrees Celsius over about 5,000 years. In the past century alone, the temperature has climbed 0.7 degrees Celsius, roughly ten times faster than the average rate of ice-age-recovery warming.
Temperature histories from paleoclimate data (green line) compared to the history based on modern instruments (blue line) suggest that global temperature is warmer now than it has been in the past 1,000 years, and possibly longer. (Graph adapted from Mann et al., 2008.)
Models predict that Earth will warm between 2 and 6 degrees Celsius in the next century. When global warming has happened at various times in the past two million years, it has taken the planet about 5,000 years to warm 5 degrees. The predicted rate of warming for the next century is at least 20 times faster. This rate of change is extremely unusual.
See the full NASA Earth Observatory article here .
______________________________________________________________
Of course there are uncertainties: “We could have a debate about whether we’re being a little too optimistic or not,” says Alley. “But not much debate about whether we’re being too scary or not.” Considering how right we were before, we should ignore history at our own peril.
Smithsonian magazine and Smithsonian.com place a Smithsonian lens on the world, looking at the topics and subject matters researched, studied and exhibited by the Smithsonian Institution — science, history, art, popular culture and innovation — and chronicling them every day for our diverse readership.
A natural geyser hearing by nuclear fission in a uranium deposit may have provided the ideal conditions for biomolecules to form. SOPA Images / Getty.
Life may not have originated in the primordial soup of an ancient pond, according to scientists, but rather in a “nuclear geyser” powered by an ancient uranium deposit.
Shigenori Maruyama of Tokyo Institute of Technology says the idea came from what chemists know about crucial compounds in our own bodies.
Many of these compounds – including DNA and proteins – are polymers formed from chains of smaller building blocks.
Each of these molecules serves a different purpose in the body, but something they all have in common, says Nicholas Hud, a chemist from Georgia Institute of Technology, Atlanta, is that a molecule of water is released when each new building block is added.
“There is a theme here,” he said last week at a NASA-sponsored symposium on the early solar system and the origins of life. To a chemist, this suggests that these biopolymers must have originated under relatively dry conditions.
Otherwise, Hud says, the presence of water would have forced the reactions to run backwards, breaking chains apart. But, there’s a problem: most scientists assume life started in water.
The solution to this paradox, according to Hud, comes from realizing that water comes and goes. The major chemicals of life, and presumably life itself, may have formed in an environment that was alternately wet and dry. “It could be seasonal,” he says. “It could be tides. It could be aerosols that go up [into the air] and come back down.”
Some prebiotic chemical reactions occur easily at moderate temperatures, but others, says Robert Pascal, a physical organic chemist from the University of Montpellier, France, require a more concentrated source of energy. This energy may have come from the sun, which in the early solar system was considerably more active than today. But another source is radiation.
Which brings us back to nuclear geysers.
Based on analyses similar to Hud’s and Pascal’s, Maruyama has identified nine requirements for the birthplace of life. One place where all can occur at once, Maruyama says, is in the plumbing of a nuclear geyser [Geoscience Frontiers].
This would not only produce heat to power the geyser, but produce radiation strong enough to break the recalcitrant molecular bonds of water, nitrogen, and carbon dioxide, all of which must be cleaved in order to produce critical prebiotic compounds. Periodic eruptions of the geyser would also produce alternating wet and dry cycles, and water draining from the surface would bring back dissolved gases from the atmosphere. The rocks lining the geyser’s subterranean channels would provide a source of minerals such as potassium and calcium.
“This is the place I recommend [for the origin of life],” Maruyama says.
Once life originated, he says, it would have been spewed onto the surface and from there into the oceans. From there, it spread to every known habitable niche on the modern Earth.
Extraterrestrial life (or at least life as we know it), he says, would need similar conditions in which to originate.
That, he thinks, means the best place to look for it in our solar system is Mars. However habitable the subsurface oceans of outer moons such as Ganymede, Europa, and Titan may be for bacteria, they likely lack the conditions needed for the origin of life as we know it, he says.
As for exoplanets? Similar conditions are also needed there, he says, including not only an energy source to power pre-biotic reactions, but a “triple junction” between rock, air, and water, where all the needed materials can come together simultaneously.
Tokyo Tech is the top national university for science and technology in Japan with a history spanning more than 130 years. Of the approximately 10,000 students at the Ookayama, Suzukakedai, and Tamachi Campuses, half are in their bachelor’s degree program while the other half are in master’s and doctoral degree programs. International students number 1,200. There are 1,200 faculty and 600 administrative and technical staff members.
In the 21st century, the role of science and technology universities has become increasingly important. Tokyo Tech continues to develop global leaders in the fields of science and technology, and contributes to the betterment of society through its research, focusing on solutions to global issues. The Institute’s long-term goal is to become the world’s leading science and technology university.
22 March 2018
Susanna Falsaperla
Marco Neri
Giuseppe Di Grazia
Horst Langer
Salvatore Spampinato
Readings from a sensor for the radioactive gas near summit craters of the Italian volcano reveal signatures of such processes as seismic rock fracturing and sloshing of groundwater and other fluids.
Mount Etna in Sicily, Italy, spews lava from a Strombolian and effusive eruption on 24 April 2012. The church Santa Maria della Provvidenza stands in the foreground in the town of Zafferana Etnea on the mountain’s eastern flank. New research from a team studying the volcano finds that variations in its radon emissions provide insights into volcanic and tectonic influences inside the mountain and, for some seismic activity, up to tens of kilometers away. Credit: Marco Neri.
Some researchers view radon emissions as a precursor to earthquakes, especially those of high magnitude [e.g., Wang et al., 2014; Lombardi and Voltattorni, 2010], but the debate in the scientific community about the applicability of the gas to surveillance systems remains open. Yet radon “works” at Italy’s Mount Etna, one of the world’s most active volcanoes, although not specifically as a precursor to earthquakes. In a broader sense, this naturally radioactive gas from the decay of uranium in the soil, which has been analyzed at Etna in the past few years, acts as a tracer of eruptive activity and also, in some cases, of seismic-tectonic phenomena.
To deepen the understanding of tectonic and eruptive phenomena at Etna, scientists analyzed radon escaping from the ground and compared those data with measurements gathered continuously by instrumental networks on the volcano (Figure 1). Here Etna is a boon to scientists—it’s traced by roads, making it easy to access for scientific observation.
Fig. 1. Panoramic view of the volcano as it appeared during 2008 and 2009. No image credit.
Dense monitoring networks, managed by the Istituto Nazionale di Geofisica e Vulcanologia, Catania-Osservatorio Etneo (INGV-OE), have been continuously observing the volcano for more than 40 years. This continuous dense monitoring made the volcano the perfect open-air laboratory for deciphering how eruptive activity may influence radon emissions.
Tower of the Philosopher
Volcanologist Marco Neri during the winter of 2008–2009 downloads data onto a laptop from the ERN1 radon sensor at the site (later buried in lava) known as the Tower of the Philosopher. Behind him, less than 1 kilometer away, ash billows from the summit craters of the volcano. Credit: Marco Neri.
In a recently published study [Falsaperla et al., 2017], we analyzed a period of dynamic and variable volcanic activity of Etna between January 2008 and July 2009. In those 19 months, the volcano produced seismic swarms, surface ground fractures, a vigorous lava fountain, and an eruption lasting 419 days.
In short, the volcano delivered enough diverse behaviors to test whether radon detected by a station located near the top of Etna, at an altitude of about 3,000 meters, showed any patterns that matched eruptive behavior recorded by the networks. The station is at a place formerly known as the Torre del Filosofo (Tower of the Philosopher), which in 2013 became buried below meters of lava flows that completely changed the location’s appearance.
The network’s data are plentiful and are related to physical occurrences, such as the vibrations produced by magma movements in the feed conduits, or so-called volcanic tremor, as well as the tremor source’s localization within the volcano; isolated seismic events or swarms; and ground fractures accompanying the opening of eruptive fissures and associated explosive and effusive events. We conducted an analysis of this enormous amount of data through a statistical-mathematical approach that revealed possible correlations and, in many cases, obvious synchronicities with radon emissions.
What Did We Discover?
Our study revealed that essentially two processes influenced radon levels at the monitoring station. The first, easily imaginable given the location of the measuring probe less than a kilometer from the summit craters of Etna, is linked to the rise of magma in the volcano’s central conduit. Short, intense radon bursts, which researchers refer to as gas pulses, occur when a carrier gas that conveys the radon to the surface also bursts from the volcano (Figure 2). In the area in question, this carrier consists mainly of water vapor that feeds the local fumarolic activity.
Fig. 2. Volcanic processes may have influenced the flux of radon recorded by the ERN1 probe during Mount Etna’s 2008–2009 flank eruption. Variations in magmatic activity could have caused gas pulses near the feeding dike, as well as the rapid increase in radon values recorded by the ERN1 station probe. Conceptual model by the authors (2017).
The second process is rock fracturing from an earthquake or seismic swarm. Radon rising from rock fractures is a well-known, recurrent phenomenon caused by greater permeability of the ground following earthquake-induced breakage of rock.
Action at a Distance
We have also discovered that the radon probe of the Torre del Filosofo was sensitive even to relatively small earthquakes taking place several kilometers away. We noted a clear synchronism between seismic swarms more than 10 kilometers away from the probe and significant variations of radon, impossible to explain by the diffusion of radon gas to rocks and toward the surface. We therefore had to find a different solution, which we identified as a sloshing phenomenon, like the lapping of waves.
Slosh dynamics describes the movement of liquids within a container [Ibrahim, 2005]. Experimental observations prove that sloshing may occur inside the conduits of volcanoes, promoting magma oscillations [Namiki et al., 2016].
Applied to Etna, sloshing may explain how rock shaking induced by a seismic swarm can cause oscillatory motion in the groundwater and in the magmatic fluids contained within the volcano (Figure 3). These oscillations can propagate quickly inside the mountain, reaching far greater distances than had been imagined in relatively short times. Sloshing may also be favored by flank instability affecting the eastern and southeastern sectors of the volcano, as it can produce tensile stresses both on the summit and on the rift zones, increasing the permeability of the rocks in those areas [Acocella et al., 2016].
Fig. 3. Along with volcanic triggers (Fig. 2), tectonic activity may have influenced the flux of radon recorded by the ERN1 probe during Mount Etna’s 2008–2009 flank eruption. Seismicity in the rift zone could have caused microfracturing of the rocks, changing their porosity and permeability. Resulting gas migration inside the highly fractured zone related to the rift may have led to fluctuations in radon emissions recorded by the ERN1 station. Conceptual model by the authors (2017).
In some ways, these remote influences are an unforeseen discovery that implicitly reveals that the volcano is in a perpetually precarious balance and therefore easily disturbed. Reminiscent of a butterfly effect, even a small phenomenon occurring, for example, on the north side of Mount Etna can make its effects felt on the opposite side.
Acknowledgments
We are grateful to Stephen Conway for his help in the English editing of this article. This work was supported by the Mediterranean Supersite Volcanoes (MED-SUV) project, which has received funding from the European Union’s Seventh Framework Programme for research, technological development, and demonstration under grant agreement 308665.
References
Acocella, V., et al. (2016), Why does a mature volcano need new vents? The case of the new Southeast Crater at Etna, Front. Earth Sci., 4, 67, https://doi.org/10.3389/feart.2016.00067.
Falsaperla, S., et al. (2017), What happens to in-soil radon activity during a long-lasting eruption? Insights from Etna by multidisciplinary data analysis, Geochem. Geophys. Geosyst., 18(6), 2,162–2,176, https://doi.org/10.1002/2017GC006825.
Ibrahim, R. A. (2005), Liquid Sloshing Dynamics: Theory and Applications, 948 pp., Cambridge Univ. Press, Cambridge, U.K., https://doi.org/10.1017/CBO9780511536656.
Lombardi, S., and N. Voltattorni (2010), Rn, He and CO2 soil gas geochemistry for the study of active and inactive faults, Appl. Geochem., 25, 1,206–1,220, https://doi.org/10.1016/j.apgeochem.2010.05.006.
Namiki, A., et al. (2016), Sloshing of a bubbly magma reservoir as a mechanism of triggered eruptions, J. Volcanol. Geotherm. Res., 320, 156–171, https://doi.org/10.1016/j.jvolgeores.2016.03.010.
Wang, X., et al. (2014), Correlations between radon in soil gas and the activity of seismogenic faults in the Tangshan area, north China, Radiat. Meas., 60, 8–14, https://doi.org/10.1016/j.radmeas.2013.11.001.
Author Information
Susanna Falsaperla (email: susanna.falsaperla@ingv.it), Marco Neri, Giuseppe Di Grazia, Horst Langer, and Salvatore Spampinato, Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Catania, Italy
Eos is the leading source for trustworthy news and perspectives about the Earth and space sciences and their impact. Its namesake is Eos, the Greek goddess of the dawn, who represents the light shed on understanding our planet and its environment in space by the Earth and space sciences.
Colorful forests fill the landscape in the Berkshires of western Massachusetts.
Photograph by Berthold Steinhilber, laif, Redux, courtesy of natgeo.com, which also provided the link to the article in Geology, which Scientific American was to lazy to do. Looking for the link is how I found the photo.
Credit: Thomas Fuchs
For the past 200 million years New England has been a place without intense geologic change. With few exceptions, there have been no rumbling volcanoes or major earthquakes. But it might be on the verge of awakening.
Findings published this January in Geologyshow a bubble of hot rock rising underneath the northern Appalachian Mountains. The feature was first detected in 2016 by EarthScope, a collection of thousands of seismic instruments sprinkled throughout the U.S. Vadim Levin, a geophysicist at Rutgers University, says this wealth of sensors lets earth scientists peer under the North American continent, just as the Hubble Space Telescope has enabled astronomers to gaze deep into the night sky. Should the broiling rock breach the surface—which could happen, though not until tens of millions of years from now—it would transform New England into a burbling volcanic landscape.
The finding has sparked many questions, given that New England is not located along an active plate margin (where one tectonic plate rubs against another) but sits squarely in the middle of the North American plate. The exact source of the hot rock bubble, for example, is unclear. Because the edge of the North American continent is colder than a plate near an active margin, Levin suspects this edge is cooling the mantle—the layer just below the crust that extends toward the earth’s core. As cold chunks of mantle sink, they may displace hotter segments, which would rise toward the surface. Scientists believe they have now imaged such an ascending piece. Although it sounds simple, this scenario “is a story that at present does not have a place in a textbook,” Levin says.
Or perhaps pieces of the North American continent are breaking off and sinking into the mantle (which would also push the warmer mantle upward), observes William Menke, a geophysicist at Columbia University, who was not part of the study.
Scientists do not yet know which model is correct or if an entirely different one may be involved. Levin and his colleagues are eager to collect more data to bring this unusual hotspot into sharper focus and, in doing so, flesh out the theory of plate tectonics. “We know little about the interior of our planet, and every time we look with a new light … we find things we did not expect,” Levin says. “When we do, we need to rethink our understanding of how the planet functions.”
Rutgers, The State University of New Jersey, is a leading national research university and the state’s preeminent, comprehensive public institution of higher education. Rutgers is dedicated to teaching that meets the highest standards of excellence; to conducting research that breaks new ground; and to providing services, solutions, and clinical care that help individuals and the local, national, and global communities where they live.
Founded in 1766, Rutgers teaches across the full educational spectrum: preschool to precollege; undergraduate to graduate; postdoctoral fellowships to residencies; and continuing education for professional and personal advancement.
As a ’67 graduate of University college, second in my class, I am proud to be a member of
Alpha Sigma Lamda, National Honor Society of non-tradional students.
An extensional detachment fault in western Norway. In a new study, researchers examine how crustal-scale extensional faults successively link and interact to produce the architecture of a rifted margin. Credit: Per Terje Osmundsen.
Earth’s surface is continuously reconfigured by the assembly and breakup of supercontinents. As part of this cycle, landmasses split apart at continental rifts, linear zones where the lithosphere is stretched and lowered and new oceanic crust forms.
Geologists have long understood that rifted margins are characterized by several types of normal faults that accommodate this extension, including steep faults with up to a few kilometers of vertical displacement and lower-angle faults that can accommodate tens of kilometers of horizontal motion. Although the growth of these steeper faults has been systematically studied in rift margins, the role that the lower-angle faults plays in these settings is not as well understood.
To bridge this gap, Osmundsen and Péron-Pinvidic [Tectonics] studied the range of faults present along the mid-Norwegian margin, an important oil- and natural gas–producing area that experienced multiple episodes of rifting between the late Paleozoic and early Cenozoic. Using several sources of seismic reflection data collected in the Norwegian Sea between 1984 and 2008, the researchers identified five structural domains that formed via the linkage of large extensional faults.
The faults combined into what the authors call “breakaway complexes,” which distinguish the margin’s proximal and necking domains, with thicker continental crust and higher-angle faults, from its distal and outermost portions, which are recognized by increasingly isolated slivers of crystalline continental crust and the presence of lower-angle faults. Seaward of the outermost breakaway complex, nearly flat detachment faults prevail. The 3-D architecture of the rifted margin develops mainly through the lateral and downdip interaction between these faults.
By defining these structural domains in a novel way, this study places low-angle, high-displacement faults within a broader framework. This perspective will help researchers better understand the lateral variability of rift-forming processes and, ultimately, how these margins—and their economically important sedimentary deposits—evolve.
Eos is the leading source for trustworthy news and perspectives about the Earth and space sciences and their impact. Its namesake is Eos, the Greek goddess of the dawn, who represents the light shed on understanding our planet and its environment in space by the Earth and space sciences.
Reply