Tagged: Geology Toggle Comment Threads | Keyboard Shortcuts

  • richardmitnick 8:41 am on October 14, 2016 Permalink | Reply
    Tags: , , , Geology, Microtektites, Signs of comet collision found in 5.5-million-year-old rocks, Spherules   

    From COSMOS: “Signs of comet collision found in 5.5-million-year-old rocks” 

    Cosmos Magazine bloc


    14 October 2016
    Amy Middleton

    Glass blobs in rocks found along the US east coast point to a comet collision a few million years ago. Marc Ward / Stocktrek Images / Getty Images

    Glassy spheres discovered in sedimentary rock have tipped off geologists about a previously unknown prehistoric comet crash – one that may have triggered a period of intense global warming.

    Morgan Schaller at the Rensselaer Polytechnic Institute in New York and colleagues found marble-like glassy spherules, known as microtektites, which they believe to be fragments of debris scattered into the air after an object collided with the Earth some 5.5 million years ago.

    They published their work in Science.

    Examples of a few of the spherules examined in the study. M F Schaller et al, Science 2016

    The distinct structures and unique appearances of spherules, as well as the way they’re positioned in sediment, can offer clues about historic impact events.

    Schaller’s spherules were found in marine shelf sites on the Atlantic Coastal Plain, along the east coast of the US, dating back to the boundary between the Paleocene and Eocene epochs.

    This is known as the Paleocene-Eocene Thermal Maximum (PETM), one of the most dramatic climate events known to science.

    During this period, the global average temperature was 8 °C higher than it is today and the world largely devoid of ice. Massive amounts of carbon were injected into the atmosphere and oceans and many of the world’s organisms experienced drastic shifts in their evolution.

    This intense warming is particularly relevant to us, because it marks the closest comparative event to the global warming evident today.

    What may have kick-started the PETM is hotly debated, and theories stretch from volcanic degassing to the cycle of Earth’s orbit. Now, the possibility of a meteorite impact may be thrown into the mix.

    To draw clues from the spherules, the researchers analysed the size, structure, layout and abundance of the particles they had uncovered, and compared the data to evidence of other impact sites.

    Shape and colour of the fragments also offered clues about their origins.

    “The spherules often have surface pits and in some cases microcraters,” the researchers write, “indicating relative velocities high enough to fracture the spherules on impact with one another, or other objects, after solidification.”

    Not everyone’s convinced, though.

    Christian Koeberl, an impact specialist at the University of Vienna in Austria, said the spherules could have come from another time and been reworked into the PETM sediments.

    The researchers did not directly use radiometric dating on the spherules themselves – just the surrounding sediment.

    But the next step, according to the research team, is to uncover spherules in more locations and start to figure out how far the debris spread. This will help them eventually narrow down a potential crater location to mark the comet’s impact.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

  • richardmitnick 8:09 am on October 12, 2016 Permalink | Reply
    Tags: , , Geology, , , , ,   

    From Symmetry: “Recruiting team geoneutrino” 

    Symmetry Mag

    Leah Crane

    Illustration by Sandbox Studio, Chicago with Corinne Mucha

    Physicists and geologists are forming a new partnership to study particles from inside the planet.

    The Earth is like a hybrid car.

    Deep under its surface, it has two major fuel tanks. One is powered by dissipating primordial energy left over from the planet’s formation. The other is powered by the heat that comes from radioactive decay.

    We have only a shaky understanding of these heat sources, says William McDonough, a geologist at the University of Maryland. “We don’t have a fuel gauge on either one of them. So we’re trying to unravel that.”

    One way to do it is to study geoneutrinos, a byproduct of the process that burns Earth’s fuel. Neutrinos rarely interact with other matter, so these particles can travel straight from within the Earth to its surface and beyond.

    Geoneutrinos hold clues as to how much radioactive material the Earth contains. Knowing that could lead to insights about how our planet formed and its modern-day dynamics. In addition, the heat from radioactive decay plays a key role in driving plate tectonics.

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

    Understanding the composition of the planet and the motion of the plates could help geologists model seismic activity.

    To effectively study geoneutrinos, scientists need knowledge both of elementary particles and of the Earth itself. The problem, McDonough says, is that very few geologists understand particle physics, and very few particle physicists understand geology. That’s why physicists and geologists have begun coming together to build an interdisciplinary community.

    “There’s really a need for a beyond-superficial understanding of the physics for the geologists and likewise a nonsuperficial understanding of the Earth by the physicists,” McDonough says, “and the more that we talk to each other, the better off we are.”

    There are hurdles to overcome in order to get to that conversation, says Livia Ludhova, a neutrino physicist and geologist affiliated with Forschungzentrum Jülich and RWTH Aachen University in Germany. “I think the biggest challenge is to make a common dictionary and common understanding—to get a common language. At the basic level, there are questions on each side which can appear very naïve.”

    In July, McDonough and Gianpaolo Bellini, emeritus scientist of the Italian National Institute of Nuclear Physics and retired physics professor at the University of Milan, led a summer institute for geology and physics graduate students to bridge the divide.

    “In general, geology is more descriptive,” Bellini says. “Physics is more structured.”

    This can be especially troublesome when it comes to numerical results, since most geologists are not used to working with the defined errors that are so important in particle physics.

    At the summer institute, students began with a sort of remedial “preschool,” in which geologists were taught how to interpret physical uncertainty and the basics of elementary particles and physicists were taught about Earth’s interior. Once they gained basic knowledge of one another’s fields, the scientists could begin to work together.

    This is far from the first interdisciplinary community within science or even particle physics. Ludhova likens it to the field of radiology: There is one expert to take an X-ray and another to determine a plan of action once all the information is clear. Similarly, particle physicists know how to take the necessary measurements, and geologists know what kinds of questions they could answer about our planet.

    Right now, only two major experiments are looking for geoneutrinos: KamLAND at the Kamioka Observatory in Japan and Borexino at the Gran Sasso National Laboratory in Italy. Between the two of them, these observatories detect fewer than 20 geoneutrinos a year.

    KamLAND at the Kamioka Observatory in Japan

    INFN/Borexino Solar Neutrino detector, Gran Sasso, Italy
    INFN/Borexino Solar Neutrino detector, Gran Sasso, Italy

    Between the two of them, these observatories detect fewer than 20 geoneutrinos a year.

    Because of the limited results, geoneutrino physics is by necessity a small discipline: According to McDonough, there are only about 25 active neutrino researchers with a deep knowledge of both geology and physics.

    Over the next decade, though, several more neutrino detectors are anticipated, some of which will be much larger than KamLAND or Borexino. The Jiangmen Underground Neutrino Observatory (JUNO) in China, for example, should be ready in 2020.

    JUNO Neutrino detector China
    JUNO Neutrino detector China

    Whereas Borexino’s detector is made up of 300 tons of active material, and KamLAND’s contains 1000, JUNO’s will have 20,000 tons.

    The influx of data over the next decade will allow the community to emerge into the larger scientific scene, Bellini says. “There are some people who say ‘now this is a new era of science’—I think that is exaggerated. But I do think that we have opened a new chapter of science in which we use the methods of particle physics to study the Earth.”

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    Symmetry is a joint Fermilab/SLAC publication.

  • richardmitnick 1:15 pm on October 10, 2016 Permalink | Reply
    Tags: , , Geology, Intertropical Convergence Zone, Paleoceanography, Paleography   

    From Eos: “Simulating the Climate 145 Million Years Ago” 

    Eos news bloc


    Shannon Hall

    A new model shows that the Intertropical Convergence Zone wasn’t always a single band around the equator, which had drastic effects on climate.

    Upper Jurassic (145- to 160-million-year-old) finely laminated organic carbon-rich shale interspersed with homogeneous, low-carbon mudrock of the Kimmeridge Clay Formation in Kimmeridge Bay, England. Variation in rock type reflects the ocean response to a monsoon-like climate 30°N during the Late Jurassic. Credit: Howard Armstrong

    The United Kingdom was once a lush oasis. That can be read from sediments within the Kimmeridge Clay Formation, which were deposited around 160 to 145 million years ago on Dorset’s “Jurassic Coast.” A favorite stomping ground for fossil hunters and the source rock for North Sea oil, the formation is rich in organic matter, which suggests that it likely formed when global greenhouse conditions were at least 4 times higher than present levels.

    Normally, organic matter disappears rapidly after an organism dies, as the nutrients are consumed by other life forms and the carbon decays. However, when the seas are starved of oxygen, which occurs when plankton numbers swell owing to increasing levels of carbon dioxide, then organic matter is preserved. An abundance of so-called black shales, or organic-rich muds, within the Kimmeridge Clay Formation points to this past.

    Here Armstrong et al. used those black shales to build new climate simulations that better approximate the climate toward the end of the Jurassic period. The model simulated 1422 years of time that suggested a radically different Intertropical Convergence Zone—the region where the Northern and Southern Hemisphere trade winds meet—than the one today. The convergence of these trade winds produces a global belt of clouds near the equator and is responsible for most of the precipitation on Earth.

    This figure shows the path (in red) of the Intertropical Convergence Zone as it forks, where the Pacific Ocean met the western coast of the American continents. Credit: Armstrong et al. [2016]

    Today the Intertropical Convergence Zone in the Atlantic strays, at most, 12° away from the equator. However, 145 million years ago, when the continents were still much closer together, the model showed that the zone split, like a fork in the road, where the Pacific Ocean met the western coast of the American continents. The zone was driven apart by the proto-Appalachian mountain range to the north and the North African mountains to the south. The northern fork, which was much stronger than the southern one, extended as far as about 30° north, passing over the United Kingdom and the location of the Kimmeridge Clay Formation.

    Not only were the researchers able to verify that the United Kingdom was once a tropical oasis, but they were also able to simulate and map the climate 145 million years ago—research that will help scientists better understand how Earth will react to anthropogenic warming today and in the future. (Paleoceanography, doi:10.1002/2015PA002911, 2016)

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    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.

  • richardmitnick 5:26 pm on October 7, 2016 Permalink | Reply
    Tags: , , Geology, New insights into early terrestrial planet formation,   

    From Tokyo Tech: “New insights into early terrestrial planet formation” 


    Tokyo Institute of Technology

    October 7, 2016
    No writer credit

    Scientists at Tokyo Tech have demonstrated that the relatively high levels of precious metals (gold, platinum, etc.) in the Earth’s mantle likely originated from one large-scale planetary impact prior to the formation of the Earth’s crust. This implies that the early Earth was a more benign place than previously thought, with fewer impacts from space.

    The debate surrounding the formation of the planets in our solar system, particularly the terrestrial (‘rocky’) planets, has been ongoing for many years. Scientists have long used computer models coupled with analysis of ancient meteorites to piece together the most likely scenarios that led to the planets forming as we know them today. A few puzzles still remain, including why Mars is much smaller than most models predict, and why the Earth in particular has a large amount of iron-loving, or ‘siderophile’, material in its mantle. Metals like gold, platinum and palladium would ordinarily be sequestered in the metallic core. The existing explanation for the latter is that the Earth was pummelled by meteors in its early life, leaving the highly siderophile elements (HSE) beneath the crust.

    Now, Ramon Brasser and Shigeru Ida at the Earth-Life Science Institute at Tokyo Institute of Technology, Japan, together with an international team of researchers from the University of Colorado (USA), the University of Dundee (UK) and the University of Oslo (Norway), have shown that the Earth’s HSE budget was most likely the result of a single, large-scale impact from space rather than the slow accumulation of material from many smaller meteors. This single impact may or may not have been the same one that created the Moon.

    Brasser’s team simulated the evolution of the terrestrial planets up to 300 million years after their first formation, a much longer time-scale than in previous studies. They collated information regarding the precious metal budget of Earth, Moon and Mars, and data on lunar cratering, and ran simulations to determine the circumstances that would fit the observations.

    Their results show that the total mass of planetesimals – accumulations of planet-forming material floating in space – at the time of the event that formed the Moon was less than previously thought. Mars accumulated 0.06% of its total mass in meteors during the period of the late veneer on Earth. The single, large-scale impact that created Earth’s HSE complement was unique to Earth, and must have occurred before the crust had begun to form around 4.45 billion years ago. Brasser and his team have shown that the early Earth at the time of life’s emergence was not under a constant, intense bombardment from meteors as previously thought.

    The early solar system

    There is still much debate around the early formation and behaviour of the planets that orbit our Sun. While the initial formation processes for the terrestrial planets — accumulation of material into ‘planetesimals’ followed by the gradual growth into full-size planets — is well-researched, it has proven difficult to solve some of the more complex enigmas about the inner solar system.

    Recently, the ‘Grand Tack’ theory was proposed in which Jupiter shifted its path inwards towards the sun before tracking back to its current position. This movement, together with the formation of Saturn and its associated resonance with Jupiter, meant that the two gas planets pulled an immense amount of debris and material away from the inner solar system when they shifted back outwards. This accounts for the smaller size of Mars and for the current composition of the asteroid belt.

    Questions regarding the unexplained high levels of iron-loving material (highly siderophile element, or HSE) in the Earth’s mantle, and indeed beneath the crust of Mars, still remain.

    Implications of the current study

    By combining data from various sources and simulating the early evolution of the terrestrial planets using computer models incorporating the Grand Tack theory, Brasser and his team have provided new insights into the HSE conundrum. Their simulations suggest that the Earth’s mantle composition was altered primarily by one large-scale impact — possibly the same impact that created the Moon — rather than by a multitude of small meteor impacts. Their results also show that there was far less debris and material floating in the inner solar system by the time the Moon-forming event occurred than scientists had anticipated. This implies that the early Earth may have been a more benign place than previously thought, and the team suggest that their findings should be incorporated into future simulations of the early solar system.

    The crescent Earth rises above the lunar horizon in this spectacular photograph taken from the Apollo 17 spacecraft in lunar orbit during final lunar landing mission in the Apollo program. Image Credit: NASA

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition


    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.

  • richardmitnick 7:23 am on October 7, 2016 Permalink | Reply
    Tags: , Case of Earth’s missing continental crust solved: It sank, Geology, ,   

    From U Chicago: “Case of Earth’s missing continental crust solved: It sank” 

    U Chicago bloc

    University of Chicago

    October 4, 2016
    Carla Reiter

    Mantle swallowed massive chunk of Eurasia and India, study finds

    UChicago scientists have concluded that half the original mass of Eurasia and India disappeared into the Earth’s interior before the two continents began their slow-motion collision approximately 60 million years ago. The participating UChicago scientists are (from left) Miquela Ingalls, doctoral student in geophysical sciences; David Rowley, professor in geophysical sciences; and Albert Colman, assistant professor in geophysical sciences. Rowley holds a rock of the type they believe sank into the interior. Photo by Jean Lachat

    How do you make half the mass of two continents disappear? To answer that question, you first need to discover that it’s missing.

    That’s what a trio of University of Chicago geoscientists and their collaborator did, and their explanation for where the mass went significantly changes prevailing ideas about what can happen when continents collide. It also has important implications for our understanding of when the continents grew to their present size and how the chemistry of the Earth’s interior has evolved.

    The study, published online Sept. 19 in Nature Geoscience, examines the collision of Eurasia and India, which began about 60 million years ago, created the Himalayas and is still in (slow) progress. The scientists computed with unprecedented precision the amount of landmass, or “continental crust,” before and after the collision.

    “What we found is that half of the mass that was there 60 million years ago is missing from the earth’s surface today,“ said Miquela Ingalls, a graduate student in geophysical sciences who led the project as part of her doctoral work.

    The result was unexpectedly large. After considering all other ways the mass might be accounted for, the researchers concluded that so huge a mass discrepancy could only be explained if the missing chunk had gone back down into the Earth’s mantle—something geoscientists had considered more or less impossible on such a scale.

    When tectonic plates come together, something has to give.

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

    According to plate tectonic theory, the surface of the Earth comprises a mosaic of about a dozen rigid plates in relative motion. These plates move atop the upper mantle, and plates topped with thicker, more buoyant continental crust ride higher than those topped with thinner oceanic crust. Oceanic crust can dip and slide into the mantle, where it eventually mixes together with the mantle material. But continental crust like that involved in the Eurasia-India collision is less dense, and geologists have long believed that when it meets the mantle, it is pushed back up like a beach ball in water, never mixing back in.

    Geology 101 miscreant

    “We’re taught in Geology 101 that continental crust is buoyant and can’t descend into the mantle,” Ingalls said. The new results throw that idea out the window.

    “We really have significant amounts of crust that have disappeared from the crustal reservoir, and the only place that it can go is into the mantle,” said David Rowley, a professor in geophysical sciences who is one of Ingalls’ advisors and a collaborator on the project. “It used to be thought that the mantle and the crust interacted only in a relatively minor way. This work suggests that, at least in certain circumstances, that’s not true.”

    The scientists’ conclusion arose out of meticulous calculations of the amount of mass there before and after the collision, and a careful accounting of all possible ways it could have been distributed. Computing the amount of crust “before” is a contentious problem involving careful dating of the ages of strata and reconstructions of past plate positions, Ingalls said. Previous workers have done similar calculations but have often tried to force the “before” and “after” numbers to balance, “trying to make the system match up with what we think we already know about how tectonics works.”

    Ingalls and collaborators made no such assumptions. They used recently revised estimates about plate movements to figure out how large the two plates were at the onset of collision, and synthesized more than 20 years’ worth of data on the geology of various regions of the Earth to calculate how thick the crust would have been.

    “By looking at all of the relevant data sets, we’ve been able to say what the mass of the crust was at the beginning of collision,” Rowley said.

    Limited options

    There were only a few places for the displaced crust to go after the collision: Some was thrust upward, forming the Himalayas, some was eroded and deposited as enormous sedimentary deposits in the oceans, and some was squeezed out the sides of the colliding plates, forming Southeast Asia.

    “But accounting for all of these different types of mass loss, we still find that half of the continental crust involved in this collision is missing today,” Ingalls said. “If we’ve accounted for all possible solutions at the surface, it means the remaining mass must have been recycled wholesale into the mantle.”

    If large areas of continental crust are recycled back into the mantle, scientists can at last explain some previously puzzling geochemistry. Elements including lead and uranium are periodically erupted from the mantle through volcanic activity. Such elements are relatively abundant in continental crust, but scarce in the mantle. Yet the composition of some mantle-derived rocks indicates that they have been contaminated by continental crust. So how did continental material mix back into the mantle?

    “The implication of our work is that, if we’re seeing the India-Asia collision system as an ongoing process over Earth’s history, there has been a continuous mixing of the continental crustal elements back into the mantle,” said Rowley. “And they can then be re-extracted and seen in some of those volcanic materials that come out of the mantle today.”

    Funding: National Science Foundation

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    U Chicago Campus

    An intellectual destination

    One of the world’s premier academic and research institutions, the University of Chicago has driven new ways of thinking since our 1890 founding. Today, UChicago is an intellectual destination that draws inspired scholars to our Hyde Park and international campuses, keeping UChicago at the nexus of ideas that challenge and change the world.

  • richardmitnick 9:55 am on September 4, 2016 Permalink | Reply
    Tags: Anthropocene – the Age of Humans, , Geology   

    From EarthSky: “Experts declare Anthropocene has begun” 



    August 31, 2016
    Deborah Byrd

    Nuclear test at Bikini Atoll, 1946. Image via U.S. Dept. of Energy.

    Has humanity become so prevalent and powerful on Earth that we’re now globally affecting the geologic record, the actual rock record used by geologists to divide the past into named blocks? If the answer is yes, should scientists declare we’ve entered a new geologic epoch? This week, a group of 35 scientists said, yes, we are globally affecting the rock record and, yes, we should officially consider a new epoch. They would name it the Anthropocene, meaning Age of Humans, a word first introduced by two scientists in the year 2000 that’s now gaining wider scientific acceptance. The Anthropocene Work Group reported this conclusion on Monday (August 29, 2016) to the 35th International Geological Congress going on this week in Cape Town, South Africa.

    If scientists decide to accept the Anthropocene into the Geologic Time Scale, they’ll have to decide when it began. Scientists speak of golden spikes in Earth’s sediment layers, events laid down in the rocks that clearly demarcate one geologic epoch from another.

    A widely known example of a golden spike occurred with the demise of the dinosaurs, 65 million years ago. Most scientists believe an asteroid strike ended their dominance, due to the discovery in the late 1970s of iridium in the rock record on all parts of Earth. Iridium is rare on Earth (found mostly in Earth’s core), but common in the rest of the solar system. This layer of iridium in the rock record is said to mark the time of the asteroid impact; it’s the golden spike that marks the end of the Cretaceous epoch.

    What would be the golden spike separating the Anthropocene – the Age of Humans – from the rest of history? The answer is arbitrary, and members of the Anthropocene Work Group do not entirely agree.

    But 28 of the 35 scientists do agree that the golden spike for the Anthropocene comes around the 1950s. That’s when the great acceleration began on Earth, when our human impacts intensified and began to happen globally, not just locally, scientists say.

    About 10 members of the Anthropocene Work Group said they felt the start of the Anthropocene would coincide with the beginning of nuclear bomb testing. It started in the late 1940s and caused radioactive elements to be dispersed across Earth and thus laid down in the rock record.

    Other group members pointed to other ongoing signs of the Age of Humans, however, which will ultimately find their way into the rock record, including plastic pollution, soot from power stations, aluminium and concrete particles and high levels of nitrogen and phosphate in soils, derived from artificial fertilizers.

    And so defining when and how the Anthropocene began – assuming scientists do accept it and include it in the Geologic Time Scale – is a task that lies ahead.

    Plastics aren’t permanent. They’ll eventually break down into fragments that’ll become buried in Earth’s sediments. When future geologists uncover these fragments, they might point to the start of the Anthropocene. Image via Plastic Ocean Gyre blog.

    Colin Waters from the British Geological Survey is secretary to the Anthropocene Work Group. He told the BBC:

    “This is an update on where we are in our discussions.

    We’ve got to a point where we’ve listed what we think the Anthropocene means to us as a working group.

    The majority of us think it is real; that there is clearly something happening; that there are clearly signals in the environment that are recognizable and make the Anthropocene a distinct unit; and the majority of us think it would be justified to formally recognise it.

    That doesn’t mean it will be formalized, but we’re going to go through the procedure of putting in a submission.”

    If the Anthropocene were formally defined as a geological epoch beginning in 1945, then newer structures – such as the Grant Marsh Interstate 94 bridge over the Missouri River in Bismarck, N.D. (foreground) – would be classified as Anthropocene. Older structures with or without recent updates, such as the Bismarck railroad bridge (center) would be classified as Holocene and Anthropocene. Photo via Joel M. Galloway, USGS.

    So the word Anthropocene, though not a part of the official scientific lexicon yet, is gaining acceptance among scientists. You can read more about the history of the word, which was coined in the year 2000 by atmospheric chemist Paul Crutzen and ecologist Eugene Stoermer in this article: What is the Anthropocene?

    By the way, scientists now speak of our geologic age – basically everything since the end of the last major Ice Age, corresponding to the rise of complex human civilizations – as the Holocene. Holo is from a Greek root meaning whole or entire. You sometimes hear the Holocene called the Recent age.

    Some have argued that the word Holocene is good enough to describe our human impact and that we don’t need the new term Anthropocene. There are arguments for and against including the Anthropocene in the Geologic Time Scale under the subheads multiple meanings and contrasting philosophies – and also hierarchy – in this article.

    In the meantime, just remember the word Anthropocene.

    You’ll be hearing more about it in the years ahead.

    The Geologic Time Spiral from the U.S. Geologic Survey.

    Bottom line: The Anthropocene Work Group reported their conclusions on August 29, 2016 to the 35th International Geological Congress in Cape Town, South Africa. The group said that the new epoch Anthropocene should be considered for official inclusion in the Geological Time Scale.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

  • richardmitnick 2:18 pm on September 1, 2016 Permalink | Reply
    Tags: Geology, Melting Glaciers Are Wreaking Havoc on Earth's Crust,   

    From Smithsonian: “Melting Glaciers Are Wreaking Havoc on Earth’s Crust” 


    September 1, 2016
    Jenny Chen

    A beach in Juneau, Alaska. Sea levels in Alaska are not rising, but dropping precipitously due to a phenomenon known as glacial isostatic adjustment. (Joseph, Flickr CC BY-SA)

    You’ve no doubt by now been inundated with the threat of global sea level rise. At the current estimated rate of one-tenth of an inch each year, sea level rise could cause large swaths of cities like New York, Galveston and Norfolk to disappear underwater in the next 20 years. But a new study out in the Journal of Geophysical Research shows that in places like Juneau, Alaska, the opposite is happening: sea levels are dropping about half an inch every year.

    How could this be? The answer lies in a phenomenon of melting glaciers and seesawing weight across the earth called “glacial isostatic adjustment.” You may not know it, but the Last Ice Age is still quietly transforming the Earth’s surface and affecting everything from the length of our days to the topography of our countries.

    During the glacier heyday 19,000 years ago, known as the Last Glacial Maximum, the Earth groaned under the weight of heavy ice sheets thousands of feet thick, with names that defy pronunciation: the Laurentide Ice Sheet, the Cordilleran Ice Sheet, the Fennoscandian Ice Sheet, and many more. These enormous hunks of frozen water pressed down on the Earth’s surface, displacing crustal rock and causing malleable mantle substance underneath to deform and flow out, changing the Earth’s shape—the same way your bottom makes a depression on a couch if you sit on it long enough. Some estimates suggest that an ice sheet about half a mile thick could cause a depression 900 feet deep—about the of an 83-story building.

    The displaced mantle flows into areas surrounding the ice sheet, causing that land to rise up, the way stuffing inside a couch will bunch up around your weight. These areas, called “forebulges,” can be quite small, but can also reach more than 300 feet high. The Laurentide Ice Sheet, which weighed down most of Canada and the northern United States, for example, caused an uplift in the central to southern parts of the U.S. Elsewhere, ancient glaciers created forebulges around the Amazon delta area that are still visible today even though the ice melted long ago.

    As prehistoric ice sheets began to melt around 11,700 years ago, however, all this changed. The surface began to spring back, allowing more space for the mantle to flow back in. That caused land that had previously been weighed down, like Glacier Bay Park in Alaska and the Hudson Bay in Canada, to rise up. The most dramatic examples of uplift are found in places like Russia, Iceland and Scandinavia, where the largest ice sheets existed. In Sweden, for example, scientists have found that the rising land severed an ancient lake called Malaren from the sea, turning it into a freshwater lake.

    At the same time, places that were once forebulges are now sinking, since they are no longer being pushed up by nearby ice sheets. For example, as Scotland rebounds, England sinks approximately seven-tenths of an inch into the North Sea each year. Similarly, as Canada rebounds about four inches each decade, the eastern coast of the U.S. sinks at a rate of approximately three-tenths of an inch each year—more than half the rate of current global sea level rise. A study published in 2015 predicted that Washington, D.C. would drop by six or more inches in the next century due to forebulge collapse, which might put the nation’s monuments and military installations at risk.

    Some of the most dramatic uplift is found in Iceland. (Martin De Lusenet, Flickr CC BY).

    Recent estimates suggest that land in southeast Alaska is rising at a rate of 1.18 inches per year, a rate much faster than previously suspected. Residents already feel the dramatic impacts of this change. On the positive side, some families living on the coast have doubled or tripled their real estate: As coastal glaciers retreat and land once covered by ice undergoes isostatic rebound, lowland areas rise and create “new” land, which can be an unexpected boon for families living along the coast. One family was able to build a nine-hole golf course on land that has only recently popped out of the sea, a New York Times article reported in 2009. Scientists have also tracked the gravitational pull on Russell Island, Alaska, and discovered that it’s been weakening every year as the land moves farther from the Earth’s center.

    Uplift will increase the amount of rocky sediment in areas previously covered in water. For example, researchers predict that uplift will cause estuaries in the Alaskan town of Hoonah to dry up, which will increase the amount of red algae in the area, which in turn, could damage the fragile ecosystems there. In addition, some researchers worry that the rapid uplift in Alaska will also change the food ecosystem and livelihood for salmon fishers.

    At the same time, there are a lot of new salmon streams opening up in Glacier Bay, says Eran Hood, professor of environmental science at the University of Alaska. “As glaciers are melting and receding, the land cover is changing rapidly,” he says. “A lot of new areas becoming forested. As the ice recedes, salmon is recolonizing. It’s not good or bad, just different.”

    The rate of uplift due to glacial isostatic adjustment around the world; Antarctica and Canada are expected to rise the most. (By Erik Ivins, JPL. [Public domain], via Wikimedia Commons)

    Although not as visible, all the changes caused by glacier melt and shifting mantle is also causing dramatic changes to the Earth’s rotation and substances below the earth’s surface.

    As our gargantuan glaciers melted, the continents up north lost weight quickly, causing a rapid redistribution of weight. Recent research from NASA scientists show that this causes a phenomenon called “true polar wander” where the lopsided distribution of weight on the Earth causes the planet to tilt on its axis until it finds its balance. Our north and south poles are moving towards the landmasses that are shrinking the fastest as the Earth’s center of rotation shifts. Previously, the North Pole was drifting towards Canada; but since 2000, it’s been drifting towards the U.K. and Europe at about four inches per year. Scientists haven’t had to change the actual geographic location of the North Pole yet, but that could change in a few decades.

    Redistribution of mass is also slowing down the Earth’s rotation. In 2015, Harvard geophysicist Jerry Mitrovica published a study in Science Advances showing that glacial melt was causing ocean mass to pool around the Earth’s center, slowing down the Earth’s rotation. He likened the phenomenon to a spinning figure skater extending their arms to slow themselves down.

    Glacial melt may also be re-awakening dormant earthquakes and volcanoes. Large glaciers suppressed earthquakes, but according to a study published in 2008 in the journal Earth and Planetary Science Letters, as the Earth rebounds, the downward pressure on the plates is released and shaky pre-existing faults could reactivate. In Southeast Alaska, where uplift is most prevalent, the Pacific plate slides under the North American plate, causing a lot of strain. Researchers say that glaciers had previously quelled that strain, but the rebound is allowing those plates to grind up against each other again. “The burden of the glaciers was keeping smaller earthquakes from releasing tectonic stress,” says Erik Ivins, a geophysicist at NASA’s Jet Propulsion Laboratory.

    Melting glaciers may also make way for earthquakes in the middle of plates. One example of that phenomenon is the series of New Madrid earthquakes that rocked the Midwestern United States in the 1800s. While many earthquakes occur on fault lines where two separate plates slide on top of each other, scientists speculate that the earthquakes in the New Madrid area occurred at a place where hot, molten rock underneath the Earth’s crust once wanted to burst through, but was quelled by the weight of massive ice sheets. Now that the ice sheets have melted, however, the mantle is free to bubble up once again.

    Scientists have also found a link between deglaciation and outflows of magma from the Earth, although they’re not sure why one causes the other. In the past five years, Iceland has suffered three major volcanic eruptions, which is unusual for the area. Some studies suggest that the weight of the glaciers suppressed volcanic activity and the recent melting is 20-30 times more likely to trigger volcanic eruptions in places like Iceland and Greenland.

    The wandering poles: Until recently earth’s axis had been slowly moving toward Canada, as shown in this graphic; now, melting ice and other factors are shifting Earth’s axis toward Europe. (NASA/JPL-Caltech)

    Much of the mystery pertaining to ancient glaciers is still unsolved. Scientists are still trying to create an accurate model of glacial isostatic adjustment, says Richard Snay, the lead author of the most recent study in the Journal of Geophysical Research. “There’s been such software since the early ’90s for longitude and latitude measurements but vertical measurements have always been difficult,” says Snay. He and colleagues have developed new equations for measuring isostatic adjustment based off of a complex set of models first published by Dick Peltier, a professor at the University of Toronto. Peltier’s models don’t only take into account mantle viscosity, but also past sea level histories, data from satellites currently orbiting the Earth and even ancient records translated from Babylonian and Chinese texts. “We’re trying to look at glaciation history as a function of time and elasticity of the deep earth,” says Peltier. “The theory continues to be refined. One of the main challenges of this work is describing the effects that are occurring in the earth’s system today, that are occurring as a result of the last Ice Age thousands of years ago.”

    Added on to all the unknowns, researchers also don’t know exactly how this prehistoric process will be affected by current patterns of global warming, which is accelerating glacial melt at an unprecedented rate. In Alaska, global warming means less snow in the wintertime, says Hood.

    “There is a much more rapid rate of ice loss here compared to many regions of the world,” he says. “The human fingerprint of global warming is just exacerbating issues and increasing the rate of glacial isostatic adjustment.”

    And while the effects may vary from city to city—local sea levels may be rising or dropping—it’s clear that the effects are dramatic, wherever they may be. Although many of glaciers have long gone, it’s clear that the weight of their presence still lingers on the Earth, and on our lives.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    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.

  • richardmitnick 1:35 pm on August 24, 2016 Permalink | Reply
    Tags: , , Geology, Kleine Gaisl: a large rockfall in the Italian Dolomites   

    From AGU: “Kleine Gaisl: a large rockfall in the Italian Dolomites” 

    AGU bloc

    American Geophysical Union

    23 August 2016
    Posted by dr-dave

    Kleine Gaisl rockfall

    Kleine Gaisl (Piccola Croda Rossa), is a large (2859 m) mountain in the Braies Valley in the South Tyrol in the northern Italian Dolomites. At the end of last week a large rockfall occurred in a series of stages over two days between 18th and 20th August. There is a good report on Planet Mountain, although they have the volume wrong by three orders of magnitude. From other sources the estimated volume is 600,000 to 700,000 cubic metres.

    Mountain guide Roman Valentini captured a part of the rockfall in a video that has been uploaded to Youtube. But note that this is not the main collapse event, as Planet Mountain notes:

    “The footage below was filmed by Roman Valentini, a mountain guide working for Alta Badia Guides, who was in the area on Thursday, August 18 at around 12:30. Although this is only the first, smaller part of the landslide, Valentini told planetmountain.com “It was ‘spectacular’ … I’ve never seen anything quite like it. It looked like a river in spate, with rocks half the size of houses tumbling down.”

    Although the main rockfall event occurred later (the seismic data will be interesting here in order to understand the sequence of events), there is a significant collapse event at about three minutes into the video:

    The rockfall had been anticipated as a large tension crack had been observed prior to the collapse event. Stol.it has a nice article, in German, though Google Translate does a good job, that includes an interview with the Deputy Mayor, Erwin Steiner, which also includes this good image of the source area of the rockfall:

    The rockfall scar on Kleine Gaisl, image by Erwin Steiner

    Whilst another article on the same site has another view of the source zone that also captures some of the rockfall deposit::

    Image of the Kleine Gaisl rockfall zone, including a part of the deposit. Image by Tourismusbüro Prags

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    The purpose of the American Geophysical Union is to promote discovery in Earth and space science for the benefit of humanity.

    To achieve this mission, AGU identified the following core values and behaviors.

    Core Principles

    As an organization, AGU holds a set of guiding core values:

    The scientific method
    The generation and dissemination of scientific knowledge
    Open exchange of ideas and information
    Diversity of backgrounds, scientific ideas and approaches
    Benefit of science for a sustainable future
    International and interdisciplinary cooperation
    Equality and inclusiveness
    An active role in educating and nurturing the next generation of scientists
    An engaged membership
    Unselfish cooperation in research
    Excellence and integrity in everything we do

    When we are at our best as an organization, we embody these values in our behavior as follows:

    We advance Earth and space science by catalyzing and supporting the efforts of individual scientists within and outside the membership.
    As a learned society, we serve the public good by fostering quality in the Earth and space science and by publishing the results of research.
    We welcome all in academic, government, industry and other venues who share our interests in understanding the Earth, planets and their space environment, or who seek to apply this knowledge to solving problems facing society.
    Our scientific mission transcends national boundaries.
    Individual scientists worldwide are equals in all AGU activities.
    Cooperative activities with partner societies of all sizes worldwide enhance the resources of all, increase the visibility of Earth and space science, and serve individual scientists, students, and the public.
    We are our members.
    Dedicated volunteers represent an essential ingredient of every program.
    AGU staff work flexibly and responsively in partnership with volunteers to achieve our goals and objectives.

  • richardmitnick 12:52 pm on August 12, 2016 Permalink | Reply
    Tags: , , Geology, , , Theia   

    From Smithsonian: “New Moon-Formation Theory Also Raises Questions About Early Earth” 


    Nola Taylor Redd

    A new model of the impact that created the moon might upend theories about earth, too

    Visualization of the giant impact that formed the moon (William Hartmann)

    A new theory about how the moon formed might also tweak our understanding of early life on Earth.

    The presence of gold and platinum in Earth’s mantle has previously been assumed to be the result of a heavy shower of meteors raining down on early Earth, but new research suggests another source—one enormous impact with the object that crashed into the planet to create the moon.

    Around 4 billion years ago the Earth was under constant attack, according to geophysicists. Asteroids and meteors continuously smashed into the planet for about 100 million years, a period known as the Late Heavy Bombardment. Any life on the planet at that time would be in constant peril.

    We know about these impacts not because of the craters they left—erosion and plate tectonics have long spirited those away—but because of the presence of certain metals in the Earth’s mantle. The pockmarked surface of the moon, which is not tectonically active, also helps bolster this theory.

    But new research suggests that the bombardment may have been milder than expected, because the metals found in Earth’s mantle could instead be from the moon-forming impact, about 500 million years earlier.

    Early in the life of the solar system, a growing world known to scientists as Theia collided with the young Earth. The violent impact liquefied Earth’s outer layers and pulverized Theia, creating a ring of debris that swirled around the scarred world. Iron from Theia’s core drew together to form the heart of the moon. The remaining heavy material rained back down on Earth, and gravity drew the lighter components together to create the moon.

    But new research suggests not all of Theia’s iron built the lunar core. Instead, some may have settled on Earth’s crust, and was later drawn into the mantle through plate tectonics. Elements such as gold and platinum, which are drawn to iron, may have been pulled into the mantle along with it. Such elements are sparse in the lunar mantle, presumably because all of the iron delivered to the moon created its core while Earth’s original core remained intact after the collision.

    That could mean good news for life on the early Earth. If Theia’s core brought in traces of iron that attracted scarcer, iron-loving elements, the rain of asteroids and meteors couldn’t have been as heavy as previously estimated.

    “The Earth is not going to be completely unhabitable for a long period of time because the bombardment is relatively benign,” says Norman Sleep, a geophysicist at Stanford University. Sleep investigated the idea that Theia could have brought platinum and similar elements to Earth’s mantle, comparing it with previous suggestions that meteors delivered the material. In a recent paper published in the journal Geochemistry, Geophysics, Geosystems, he found that Theia could have brought in enough iron-loving elements to suggest later bombardment was milder than previously considered.

    “It was certainly not anything we would survive, but we’re dealing with microbes,” he says.

    However, without a heavy bombardment of meteorites, a new problem arises. The collision between Theia and the young Earth would have vaporized any water on the planet. The leading theory for how Earth got its water back is via collisions with water-carrying meteorites, but meteorites would also have delivered more iron-loving elements along with iron, leaving behind too much gold and platinum than measured. That means Sleep’s calculations would require another method of bringing water to the planet.

    That doesn’t make the theory a deal-breaker. “There’s no guarantee that there’s one event that solves every problem,” says Tim Swindle, who studies planetary materials at the University of Arizona. Water could have come from another source unrelated to Theia.

    Figuring out exactly what happened in the early life of Earth and its moon may require a return to our satellite. “We’ve got to go back to the moon and get a better handle on the age of the basins,” Swindle says, especially those on the back side of the moon. “We might be able to get an age with a rover that could answer the questions, but I think we’d do better to bring the samples back.” That doesn’t necessarily mean humans have to be onboard the lunar mission, but, as Swindle points out, people do a great job.

    Sleep agrees, calling for a visit to the South Pole Aiken basin, the largest and oldest of those on the moon. That basin has never been sampled, and should provide insight into the timing of the bombardment, which would give clues into how much material rained down on Earth.

    According to Edward Young, a planetary scientist at the University of California at Los Angeles, the biggest result of Sleep’s research is the mental shift it requires for the scientists studying Earth and the moon. “I think what he’s doing is exposing the soft underbelly of what we do,” Young says, adding that geochemical arguments are filled with basic assumptions of the processes that go into building the Earth and moon. “He’s challenging some of those assumptions.”

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    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.

  • richardmitnick 1:11 pm on August 9, 2016 Permalink | Reply
    Tags: , , , Geology, Rocks in Chile Help Scientists Hunt for Life on Mars   

    From Eos: “Rocks in Chile Help Scientists Hunt for Life on Mars” 

    Eos news bloc


    Mika McKinnon

    A view of the Salar Grande basin, with pre-Andean ranges in the background. Techniques tested within this basin could help rovers on Mars search for life. Credit: David Fernández-Remolar

    Robots like Viking, Phoenix, and Curiosity have found indirect evidence of oxalate minerals on Mars. New techniques tested in the Chile’s Atacama Desert could help future Mars rovers analyze these minerals for possible by-products of life.

    Organic oxalates tie up carbon, creating carbon sinks that are extremely resistant to most physical and chemical weathering. On Earth, oxalates are primarily broken down by biological weathering; fungus and bacteria consume oxalate, recycling carbon back into the environment. But Mars’s carbon cycle is not as well understood. Developing better techniques to identify trace concentrations of oxalates may provide insights into the processes at play on the Red Planet.

    A close-up of cemented deposits within Chile’s Salar Grande basin, which hosts hardy lichen. Oxalate minerals found here were formed by biological activity, and different techniques tested whether instruments could detect such minerals at low concentrations. Successful detections could help future Mars rovers search for traces of life. Credit: Guillermo Chong

    In a new paper, Cheng et al. used samples from a terrestrial analogue of Mars—the Salar Grande basin in the Atacama Desert—to test out various techniques for detecting and characterizing oxalate-bearing rocks. They found that although X-ray diffraction could detect insoluble oxalate concentrates of approximately 2%–4% or higher, only ion chromatography could detect lower concentrations of soluble oxalates.

    The team specifically tuned their instruments to search for weddellite and whewellite oxalate minerals formed by biological activity. They found concentrations of weddellite and whewellite in samples collected in the sediment record infilling the Salar Grande basin, which demonstrates the great preservation potential for oxalate compounds sourced in biological activity. This suggests that any similar oxalate-bearing deposits on Mars are worth closer investigation in the ongoing search for life.

    Oxalate minerals can be formed by meteoritic, primordial, geothermal, and biological processes and so are not inherently indicators of life, but their resistance to most forms of nonbiological weathering make them a noteworthy aspect of the carbon cycle. Future research could use the techniques tested in Chile for more sensitive detection of oxalates on Mars. This in turn could lead to insights into Martian carbon sinks and sources. (Journal of Geophysical Research: Biogeosciences, doi:10.1002/2016JG003439, 2016)

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    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.

Compose new post
Next post/Next comment
Previous post/Previous comment
Show/Hide comments
Go to top
Go to login
Show/Hide help
shift + esc
%d bloggers like this: