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  • richardmitnick 3:15 pm on April 11, 2017 Permalink | Reply
    Tags: , Earth's Wobbly Path Gives Clues to Its Core, , , Geosciences, Nutation, Precession   

    From Eos: “Earth’s Wobbly Path Gives Clues to Its Core” 

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    Understanding the Earth Core and Nutation; Brussels, Belgium, 19–21 September 2016

    4.11.17
    Veronique Dehant
    Richard Gross

    1
    The way that Earth precesses (large white cones) and nutates (red wavy line) in space gives clues to processes in its interior. At a recent workshop, scientists discussed the fluid, gravitational, and magnetic factors that cause these motions. The white circle indicates the ecliptic (the Sun’s apparent path across Earth’s surface), and the gold circle indicates Earth’s equator. Adapted from Dehant and Mathews (2015), Precession, Nutation, and Wobble of the Earth, 551 pp., Cambridge University Press, New York.

    The gravitational pull of the Sun and Moon on the Earth, as well as many other smaller geophysical effects (including motions of Earth’s fluid core), cause Earth to wobble. Earth is not a perfect sphere but an ellipsoid flattened at its poles, so the forces acting upon Earth alter both its speed of rotation and the orientation of the axis on which it spins. The term “precession” describes the long-term trend of this latter motion, which is roughly circular and analogous to the motion of a spinning top. “Nutation” is the name given to shorter-term periodic variations: wobbles along this circular track.

    Last September, scientists gathered for a workshop in Brussels, Belgium, to discuss the role of Earth’s core in its nutation and to gain further insight into Earth’s interior processes. This was the first such workshop to be held within the framework of the newly established RotaNut project in the frame of an ERC (European Research Council) Advanced Grant.

    Precession causes the rotation axis of Earth to move in space at about 1.5 kilometers each year. Nutation introduces periodic variations on the order of 600 meters back and forth around the precession circle (from a vantage point looking down on the planet’s pole). Present observations allow these motions to be measured at the centimeter level. Speakers noted how such observations show that there are significant differences on the order of a few centimeters (1 milliarc second, or about 3 centimeters) between observations and the standard theoretical model of precession and nutation. The theoretical model was adopted by the International Astronomical Union in 2000 and by the International Union of Geodesy and Geophysics in 2003.

    2
    As Earth rotates on its axis, it precesses like a wobbly spinning top, but it also nutates, or wobbles along the circular precession path. This illustration shows Earth’s precession and nutation, as well as the orbital paths of a Galileo satellite constellation. Adapted from J. Huart, European Space Agency

    The theoretical model is based on the idea that Earth reacts as a deformable object with a deformable inner core, a fluid outer core, a deformable mantle that is both viscous and elastic (it can flow and stretch), an atmosphere, and oceans. But the theoretical model is not perfect, attendees discussed. In particular, scientists still don’t understand the interactions between the inner core, fluid outer core, and mantle well enough to properly model them.

    Because the core transfers angular momentum to the mantle, interactions between the two regions play an important role in nutation modeling, meeting participants agreed. The current nutation model incorporates the effect of the flattening of the core due to Earth’s rotation and the fluid pressure and gravitational effects on that flattened boundary, as well as the effects of a simple uniform, dipolar magnetic field.

    Today, we understand that there are important contributions from other components of the magnetic field and possibly other effects, like the viscosity of the inner core, the viscosity of the outer core, and core stratification. In addition, the core-mantle boundary is not smooth, and pressure forces acting on these topographical features could also play an important role.

    The workshop shed light on all of the mechanisms that might be influencing Earth’s nutation, including the possible interaction between rotational modes and inertial modes inside the liquid core. Future meetings will highlight outcomes and new insights that emerge from the discussions held during this meeting.

    The work of Veronique Dehant was performed at the Royal Observatory of Belgium under funding from the European Research Council under the European Union’s Horizon 2020 research and innovation program (advanced grant agreement 670874). The work of Richard Gross was performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA.

    —Veronique Dehant, Royal Observatory of Belgium, Brussels; and Richard Gross (email: richard.gross@jpl.nasa.gov), Jet Propulsion Laboratory, California Institute of Technology, Pasadena

    See the full article here .

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  • richardmitnick 1:43 pm on January 4, 2017 Permalink | Reply
    Tags: , , , Geosciences, ,   

    From AGU via EOS: “Pinpointing the Trigger Behind Yellowstone’s Last Supereruption” 

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    Eos

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    1.4.17
    Aylin Woodward
    aylin.y.woodward.gr@dartmouth.edu

    Geologists suggest that mixing of magma melt pockets could have caused the explosion a little more than 600,000 years ago.

    1
    View of the Grand Canyon of Yellowstone National Park. The canyon walls consist of rhyolitic tuff and lava. Crystals in such tuff may hold clues to magma conditions just prior to Yellowstone’s eruptions. Credit: Steven R. Brantley/USGS

    Yellowstone National Park is renowned for more than just its hot springs and Old Faithful. The area is famous in the volcanology community for being the site of three explosive supereruptions, the last of which was 631,000 years ago.

    2
    Map of the known ashfall boundaries for major eruptions from Yellowstone, with ashfall from the Long Valley Caldera and Mount St. Helens for comparison. Credit: USGS

    During that eruption, approximately 1000 cubic kilometers of rock, dust, and volcanic ash blasted into the sky. Debris rained across the continental United States, spanning a rough triangle that stretches from today’s Canadian border down to California and over to Louisiana. In places, ash reached more than a meter thick.

    “If something like this happened today, it would be catastrophic,” said Hannah Shamloo, a geologist at Arizona State University’s School of Earth and Space Exploration in Tempe. “We want to understand what triggers these eruptions, so we can set up warning systems. That’s the big-picture goal.”

    Now, Shamloo and her coauthor think they’ve found a clue. By examining trace elements in crystals that they found in the volcanic leftovers of Yellowstone’s last supereruption, they might be able to pinpoint what triggered it.

    Outer Rims

    Just outside Yellowstone National Park is a thick multicolored, multilayered rock formation called the Lava Creek Tuff. Tuffs are igneous rocks formed by the volcanic debris left behind by an explosive eruption.

    Minerals in these tuffs can tell scientists about conditions inside the volcano before it erupted, and identifying these preeruptive conditions may help inform current hazard assessments.

    3
    Arizona State University’s Christy Till points at an ash layer within the Lava Creek Tuff at the study site near Flagg Ranch, Wyo., just south of the Yellowstone boundary. Samples from this site are giving scientists information on what might have triggered Yellowstone’s most recent supereruption. Credit: Hannah Shamloo

    Shamloo and her Ph.D. adviser at Arizona State University, geologist Christy Till, examined two crystals of feldspar that they found embedded in the tuff. These crystals, called phenocrysts, form as magma cools slowly beneath the volcano.

    These phenocrysts, measuring between 1 and 2 millimeters in diameter, were too large to have formed when hot material was flung up during the eruption.

    Instead, as Shamloo explained, they grew gradually over time in Yellowstone’s magma chamber, each crystal beginning with a core that slowly and steadily enlarged outward, layer upon layer. As surrounding magma conditions—temperature, pressure, and water content— changed, trace elements surrounding the growing phenocrysts also changed and became incorporated into subsequent layers.

    In this way, the differences in chemical composition between the phenocryst core and successive layers serve as a map of changing conditions deep within the volcano over time. What’s more, the phenocrysts’ outermost rims represent the magma that surrounded the crystal right before Yellowstone erupted.

    Thus, by analyzing the outer rims, Shamloo and Till could gather both temperature and trace element information just prior to the massive explosion.

    Bubble, Bubble, Toil and Trouble

    5
    Feldspar phenocrysts from the Lava Creek Tuff. The outermost layers, which contain tiny bits of glass, are to the left. The phenocryst may be a fraction of a larger crystal that grew within the magma chamber or may have adhered to a different crystal on the right, explaining why layers are roughly vertical rather than concentric. Red represents the path of an electron microprobe, which cut through layers to collect chemical compositions. Credit: Hannah Shamloo

    Temperature information locked in a phenocryst’s outer rims can be extracted using a technique called feldspar thermometry. The technique relies on the fact that certain minerals vary their compositions in known ways as temperatures change. Thus, scientists can work backward from the exact compositions of minerals present in these outer rims to estimate the surrounding temperature when the crystal rim formed.

    The duo found signatures in the rims that point to an increase in temperature and uptick in the element barium in the magma just before the eruption. They presented their research on 13 December at the American Geophysical Union’s Fall Meeting in San Francisco, Calif.

    To verify their layer by layer analysis of temperature and chemical composition, Shamloo and Till used MELTS, a software program that models how the crystal composition changed as a function of temperature, pressure, and water content in the magma chamber. They assumed that the magma had the same bulk composition as the Lava Creek Tuff. Their results and the model agreed well but pointed to a low water content for the magma chamber involved in the recent supereruption. In contrast, an older eruption from Yellowstone that produced the Bishop Tuff had 5% water by weight, 5 times more than the one that produced the Lava Creek Tuff.

    The low water content is surprising, Shamloo explained, because water and steam create pressures that can trigger eruptions. But Shamloo said that the phenocrysts’ story of hotter temperatures and more barium in the magma chamber just prior to the eruption suggests a possible culprit behind the explosion: the mixing of neighboring pockets of semimelted magma, called an injection event. “There are multiple ways to trigger an eruption, but as of now, we’re seeing evidence for a magma injection,” she said.

    Magma, molten or semimolten rock that exists in layers of the Earth’s crust, can also reach the Earth’s surface. Because it is less dense than surrounding rocks, magma can move upward through cracks in the Earth’s crust, but when its motion is stymied, it pools into magma chambers. These chambers expand thanks to magma injections, when hotter material from deeper volcanic reservoirs feeds into shallower ones. This injection of hotter material just before the eruption may explain the temperature increase recorded in the phenocrysts.

    But the presence of barium in the phenocrysts is a smoking gun, said Shamloo. “Barium doesn’t like to be in the crystal. It likes to hang out in the melt, so this tells us the barium must’ve been introduced from a different source.” The duo thinks this source is a deeper reservoir inside the volcano.

    Eric Christiansen, a volcanologist from Brigham Young University in Provo, Utah, who was not involved with the study, was skeptical of Shamloo’s use of the MELTS software and thinks this type of modeling isn’t as reliable as “real experiments with real rocks.” However, he asserted, “her work is sound, and her analysis is solid. She’s got interesting trace element data with the barium, a late addition to the chamber, which suggests it accompanies what triggered the eruption.”

    Geologic Crystal Ball

    “The public is always afraid of the ‘next big one,’” Shamloo said. “And I like to ask, ‘Can we really forecast that?’” Shamloo and Till hope that they can.

    Knowing the eruption trigger is just the first step, according to Shamloo. The next step is understanding what order of time—days, months, even years—these changes can take before an eruption like the one that produced the Lava Creek Tuff.

    Such information could help Shamloo, Till, and others to correctly read signs of volcanic unrest at Yellowstone and to create a model for predicting future supereruptions.

    See the full article here .

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  • richardmitnick 7:41 pm on April 11, 2016 Permalink | Reply
    Tags: , Geosciences, U Wyoming   

    From U Wyoming: “UW Researcher Part of Team That Defined Links Within Two Supercontinents” 

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    University of Wyoming

    A University of Wyoming researcher contributed to a paper that has apparently solved an age-old riddle of how constituent continents were arranged in two Precambrian supercontinents — then known as Nuna-Columbia and Rodinia. It’s a finding that may have future economic implications for mining companies.

    Specifically, the article describes a technique Kevin Chamberlain, a UW research professor in the Department of Geology and Geophysics, and other researchers used to test reconstructions of ancient continents. The paper argues that the rocks or crust now exposed in southern Siberia were once connected to northern North America for nearly a quarter of the Earth’s history. Those two continental blocks now form the cores of the modern continents of Asia and North America.

    Chamberlain was co-author of the paper, titled “Long-Lived Connection between Southern Siberia and Northern Laurentia in the Proterozoic,” that appeared* in today’s (April 11) online issue of Nature Geoscience. The monthly multi-disciplinary journal focuses on bringing together top-quality research across the entire spectrum of the Earth sciences, along with relevant work in related areas. The journal’s content reflects all the disciplines within the geosciences, encompassing field work, modeling and theoretical studies.

    “The article highlights a technique that our project (http://www.supercontinent.org) has been using to test pre-Pangea or ancient continental reconstructions,” Chamberlain says. “We have been using the ages, orientations and paleo-magnetic characteristics of short-lived (1 million to 10 million years in duration) igneous, mafic dike swarms as piercing points to determine nearest-neighbor continents in the past.”

    Mafic dikes are dark-colored rocks or minerals that are in a dike formation, which is a sheet of rock that formed in a fracture in a pre-existing rock body. Chamberlain says mafic dikes, like those studied in the paper, can be found in Wyoming. Mafic dikes in the state include the black vein that can be seen in Mount Moran in the Teton Range; the black, horizontal band on the east face of Medicine Bow Peak; and those that crisscross the Granitic Mountains in central Wyoming.

    Using labs at UW and UCLA, Chamberlain says his role in the project was to determine the magmatic ages of numerous mafic dikes through uranium-lead radiometric dating. He was one of four geochronology labs on the team and the only one based in the United States.

    The linear dikes from these igneous events (large igneous provinces, or LIPs) are relatively narrow, roughly 100 meters or less, but can be 1,000 to 1,500 kilometers in length. They erupt in a radial pattern.

    During later rifting, the continents broke into fragments, which later combined into subsequent new continents, such as our modern-day seven continents.

    “There may have been four or five cycles of supercontinent formation,” Chamberlain says.

    Each continental fragment preserves a dike swarm record, he explains. By comparing the temporal records called bar codes (since a plot of dike date vs. time looks like a bar code) of older fragments known as cratons (the cores of modern continents), Chamberlain says he was able to test whether the cratons were close enough to share LIP dike swarms. He adds the research team also can determine when the two cratons joined, as well as when they split apart.

    “In this new study, we believe that northern Laurentia (North America) and southern Siberia were joined for nearly 1.2 billion years from 1.9 billion years ago to 700 million years ago,” he says. “Geologists are like detectives. It seems like we come to the crime scene after the fact and put together the pieces.”

    This finding disproves previous constructions of Nuna-Columbia and Rodinia, and establishes new arrangements of the continental blocks within them, he says.

    The project determined the ages of nearly 250 mafic dikes worldwide, a number Chamberlain says is large enough to build a database comparison between all of the older continental fragments from roughly 500 million years ago to 2,700 million years ago. The research group also worked on more recent LIPs — about 400 million to 100 million years ago — which have importance for oil and gas exploration, and hydrocarbon maturation models.

    A consortium of mining companies funded the research project for five years. Their reasoning: That the continental reconstructions for times when major, known metal deposits formed would be useful for prospecting new finds on the conjugate continents, Chamberlain says. These new deposits may be buried under hundreds of meters of younger rock. So, by establishing which continents were next to the known deposits when they formed, the hope is that additional minerals may be found in the future.

    “A lot of the major metal deposits in the earth formed in the early part of Earth’s history,” Chamberlain says.

    Chamberlain collaborated on the paper with researchers at Carleton University in Ottawa, Canada; Tomsk State University in Tomsk, Russia; University of Toronto in Toronto, Canada; Lund University in Lund, Sweden; Queens University in Kingston, Canada; Institute of the Earth’s Crust, Siberian Branch of the RAS, in Irkutsk, Russia; Diamond and Precious Metal Geology Institute in Yakutsk, Russia; Institute of Geochemistry in Irkutsk, Russia; Geological Survey of Canada in Ottawa; and the Kosygin Institute of Tectonics and Geophysics in Khabarovsk, Russia.

    A print version of the paper is scheduled to appear in the May issue of Nature Geoscience.

    *Science paper:
    Long-lived connection between southern Siberia and northern Laurentia in the Proterozoic

    Science team and affiliations:

    Affiliations

    Department of Earth Sciences, Carleton University, Ottawa, Ontario K1S 5B6, Canada
    R. E. Ernst
    Faculty of Geology and Geography, Tomsk State University, Tomsk 634050, Russia
    R. E. Ernst
    Jack Satterly Geochronology Laboratory, University of Toronto, Toronto, Ontario M5S 3B1, Canada
    M. A. Hamilton
    Department of Earth and Ecosystem Sciences, Lund University, 223 62 Lund, Sweden
    U. Söderlund
    Department of Geological Sciences and Geological Engineering, Queen’s University, Kingston, Ontario K7L 3N6, Canada
    J. A. Hanes
    Institute of the Earth’s Crust, Siberian Branch of the RAS, Irkutsk 664033, Russia
    D. P. Gladkochub
    Diamond and Precious Metal Geology Institute, Yakutsk 677000, Russia
    A. V. Okrugin
    Institute of Geochemistry, Irkutsk 664033, Russia
    T. Kolotilina & A. S. Mekhonoshin
    Geological Survey of Canada, Ottawa, Ontario K1S 0E8, Canada
    W. Bleeker & K. L. Buchan
    Geological Survey of Canada (retired), 5592 Van Vliet Road, Manotick, Ontario K4M 1J4, Canada
    A. N. LeCheminant
    Department of Geology and Geophysics, University of Wyoming, Laramie, Wyoming 82071, USA
    K. R. Chamberlain
    Kosygin Institute of Tectonics and Geophysics, Khabarovsk 680063, Russia
    A. N. Didenko

    Contributions

    R.E.E. led and coordinated the research and manuscript preparation. M.A.H. and U.S. produced key ID-TIMS U–Pb ages and their interpretation. J.A.H. produced key Ar–Ar ages and their interpretation. K.R.C. assisted in the interpretation of the geochronology results. A.V.O., T.K., A.S.M. and A.N.L. provided key samples for U–Pb dating and assisted in the interpretation of their results. D.P.G. and A.N.D. assisted in the interpretation of the Russian data and its geological context. W.B. provided insight into the LIP correlations and their limitations. K.L.B. provided the background palaeomagnetic context. M.A.H., K.L.B. and A.N.L. were also heavily involved in aspects of preparation, revision and/or finalizing of the overall manuscript.

    See the full article here .

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    U Wyoming campus

    The University of Wyoming consists of seven colleges: agriculture and natural resources, arts and sciences, business, education, engineering and applied sciences, health sciences, and law. The university offers over 190 undergraduate, graduate and certificate programs including Doctor of Pharmacy and Juris Doctor.

    In addition to on-campus classes in Laramie, the university’s Outreach School offers more than 41[8] degree, certificate and endorsement programs to distance learners across the state and beyond.[9] These programs are delivered through the use of technology, such as online and video conferencing classes. The Outreach School has nine regional centers across the state, with several on community college campuses, to give Wyoming residents access to a university education without relocating to Laramie.[10]

    The university is a hub of cultural events in Laramie. It offers a variety of performing arts events, ranging from rock concerts in the Arena Auditorium to classical concerts and performances by the university’s theater and dance department at the Fine Arts Center. Wyoming also boasts a competitive athletic program, one which annually challenges for conference and national championships. University of Wyoming offers many extracurricular activities, including over 200 student clubs and organizations that include a wide range of social, professional and academic groups. The Wyoming Union is the hub of the campus, with the University Store and numerous student facilities.

     
  • richardmitnick 12:07 pm on December 20, 2015 Permalink | Reply
    Tags: , Geosciences,   

    From UC Berkeley: “Earth’s magnetic field could flip within a human lifetime” 2014 but very informative 

    UC Berkeley

    UC Berkeley

    October 14, 2014
    Robert Sanders

    Imagine the world waking up one morning to discover that all compasses pointed south instead of north.

    It’s not as bizarre as it sounds. Earth’s magnetic field has flipped – though not overnight – many times throughout the planet’s history. Its dipole magnetic field, like that of a bar magnet, remains about the same intensity for thousands to millions of years, but for incompletely known reasons it occasionally weakens and, presumably over a few thousand years, reverses direction.

    1
    Left to right, Biaggio Giaccio, Gianluca Sotilli, Courtney Sprain and Sebastien Nomade sitting next to an outcrop in the Sulmona basin of the Apennine Mountains that contains the Matuyama-Brunhes magnetic reversal. A layer of volcanic ash interbedded with the lake sediments can be seen above their heads. Sotilli and Sprain are pointing to the sediment layer in which the magnetic reversal occurred. (Photo by Paul Renne)

    Now, a new study by a team of scientists from Italy, France, Columbia University and the University of California, Berkeley, demonstrates that the last magnetic reversal 786,000 years ago actually happened very quickly, in less than 100 years – roughly a human lifetime.

    “It’s amazing how rapidly we see that reversal,” said UC Berkeley graduate student Courtney Sprain. “The paleomagnetic data are very well done. This is one of the best records we have so far of what happens during a reversal and how quickly these reversals can happen.”

    Sprain and Paul Renne, director of the Berkeley Geochronology Center and a UC Berkeley professor-in- residence of earth and planetary science, are coauthors of the study, which will be published in the November issue of Geophysical Journal International and is now available online.

    Flip could affect electrical grid, cancer rates

    The discovery comes as new evidence indicates that the intensity of Earth’s magnetic field is decreasing 10 times faster than normal, leading some geophysicists to predict a reversal within a few thousand years.

    Though a magnetic reversal is a major planet-wide event driven by convection in Earth’s iron core, there are no documented catastrophes associated with past reversals, despite much searching in the geologic and biologic record. Today, however, such a reversal could potentially wreak havoc with our electrical grid, generating currents that might take it down.

    And since Earth’s magnetic field protects life from energetic particles from the sun and cosmic rays, both of which can cause genetic mutations, a weakening or temporary loss of the field before a permanent reversal could increase cancer rates. The danger to life would be even greater if flips were preceded by long periods of unstable magnetic behavior.

    “We should be thinking more about what the biologic effects would be,” Renne said.

    Dating ash deposits from windward volcanoes

    The new finding is based on measurements of the magnetic field alignment in layers of ancient lake sediments now exposed in the Sulmona basin of the Apennine Mountains east of Rome, Italy. The lake sediments are interbedded with ash layers erupted from the Roman volcanic province, a large area of volcanoes upwind of the former lake that includes periodically erupting volcanoes near Sabatini, Vesuvius and the Alban Hills.

    2
    Leonardo Sagnotti, standing, and coauthor Giancarlo Scardia collecting a sample for paleomagnetic analysis.

    Italian researchers led by Leonardo Sagnotti of Rome’s National Institute of Geophysics and Volcanology measured the magnetic field directions frozen into the sediments as they accumulated at the bottom of the ancient lake.

    Sprain and Renne used argon-argon dating, a method widely used to determine the ages of rocks, whether they’re thousands or billions of years old, to determine the age of ash layers above and below the sediment layer recording the last reversal. These dates were confirmed by their colleague and former UC Berkeley postdoctoral fellow Sebastien Nomade of the Laboratory of Environmental and Climate Sciences in Gif-Sur-Yvette, France.

    Because the lake sediments were deposited at a high and steady rate over a 10,000-year period, the team was able to interpolate the date of the layer showing the magnetic reversal, called the Matuyama-Brunhes transition, at approximately 786,000 years ago. This date is far more precise than that from previous studies, which placed the reversal between 770,000 and 795,000 years ago.

    “What’s incredible is that you go from reverse polarity to a field that is normal with essentially nothing in between, which means it had to have happened very quickly, probably in less than 100 years,” said Renne. “We don’t know whether the next reversal will occur as suddenly as this one did, but we also don’t know that it won’t.”

    Unstable magnetic field preceded 180-degree flip

    Whether or not the new finding spells trouble for modern civilization, it likely will help researchers understand how and why Earth’s magnetic field episodically reverses polarity, Renne said.

    3
    The ‘north pole’ — that is, the direction of magnetic north — was reversed a million years ago. This map shows how, starting about 789,000 years ago, the north pole wandered around Antarctica for several thousand years before flipping 786,000 years ago to the orientation we know today, with the pole somewhere in the Arctic. No image credit.

    The magnetic record the Italian-led team obtained shows that the sudden 180-degree flip of the field was preceded by a period of instability that spanned more than 6,000 years. The instability included two intervals of low magnetic field strength that lasted about 2,000 years each. Rapid changes in field orientations may have occurred within the first interval of low strength. The full magnetic polarity reversal – that is, the final and very rapid flip to what the field is today – happened toward the end of the most recent interval of low field strength.

    Renne is continuing his collaboration with the Italian-French team to correlate the lake record with past climate change.

    Renne and Sprain’s work at the Berkeley Geochronology Center was supported by the Ann and Gordon Getty Foundation.

    See the full article here .

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  • richardmitnick 12:03 pm on December 19, 2015 Permalink | Reply
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    From Eos: “NSF Director Cautions Against Politicizing Science” 

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    Eos

    France Córdova says that elected officials are generally supportive of science and technology but that the political environment can be challenging.

    1
    National Science Foundation Director France Córdova, who spoke at the American Geophysical Union’s Fall Meeting on 15 December, called for scientists to continue setting their own priorities for goals and challenges to meet in the sciences. Credit: Gary Wagner

    17 December 2015
    Randy Showstack

    “It has been a tough time for geosciences on [Capitol] Hill,” National Science Foundation (NSF) Director France Córdova said in a 15 December speech at the American Geophysical Union’s (AGU) Fall Meeting in San Francisco, Calif.

    Earlier in 2015, for instance, some members of Congress had proposed restricting funding for geosciences within NSF and questioned climate change.

    However, a bipartisan omnibus spending bill for fiscal year (FY) 2016 introduced by the House Appropriations Committee in the early morning hours of 16 December—less than a day after Córdova’s lecture—would help to provide additional support for the geosciences at NSF. The bill would increase NSF’s funding by 1.6% above the FY 2015 enacted level.

    During a media availability following her AGU speech, Córdova said that the appropriations package that was then in the works includes a number of NSF priorities, “and just about all of them have to do with the geosciences.”

    Challenges to the Geosciences

    “Some would challenge [geosciences’] goal to understand our planet as not of the highest priority for the science agencies,”Córdova said during the Union Agency Lecture. “Some would find a hypothetical ocean on a distant moon of more interest than our own ocean, whose mysteries have barely been tapped.”

    “It is your challenge as scientists to ride this questioning tide with your best tools: your quest for truth; your application of the scientific method to increase our knowledge about our planet; and your ability to communicate in all directions the beauty, the value, the importance of the geosciences,” she said. Her speech also touched on NSF’s priorities, funding, investments, and instruments.

    Setting Priorities for Discovery

    During the media availability following her speech, Córdova elaborated on her concerns. Elected officials are “very enamored of science and technology, innovation in particular, and very supportive in general,” she said, adding, “They do have individual predilections about what they think is important to do.”

    The NSF director said it is “helpful to have the perspective that our major discoveries over history, over time, have been multidisciplinary discoveries. So, leaving out one branch of science in favor of others is just not a good thing to do for the progress of science. We have to appreciate that it’s interdisciplinary.”

    “Science and scientists should be setting the priorities for what are the big goals, the big challenges in the discovery space,” she said. “If that decision about what to prioritize becomes political, then who knows where it will all end. It will be unstable and certainly not flexible for the disciplines. And we can’t raise the next generation of scientists and engineers unless we do have support and flexibility.”

    Citation: Showstack, R. (2015), NSF director cautions against politicizing science, Eos, 96, doi:10.1029/2015EO042063. Published on 17 December 2015.

    See the full article here .

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  • richardmitnick 5:24 pm on December 12, 2015 Permalink | Reply
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    From Caltech: “Developing a Picture of the Earth’s Mantle” 

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    Caltech

    12/11/2015
    Katie Neith

    1
    This illustration shows a bridgmanite sample that is being laser-heated between two diamond anvils. This set-up allows researchers to measure a sample at compressions over 1 million times the earth’s atmospheric pressure, while being heated to thousands of degrees Celsius.
    Credit: Aaron Wolf and Jennifer Jackson, Caltech

    2
    This schematic shows different scenarios of bridgmanite provinces that Jennifer Jackson and colleagues explored in their research. Their results found that the scenario at right aligns most closely with geophysical constraints of the lower mantle.Credit: Aaron Wolf and Jennifer Jackson, Caltech

    Deep inside the earth, seismic observations reveal that three distinct structures make up the boundary between the earth’s metallic core and overlying silicate mantle at a depth of about 2,900 kilometers—an area whose composition is key to understanding the evolution and dynamics of our planet. These structures include remnants of subducted plates that originated near the earth’s surface, ultralow-velocity zones believed to be enriched in iron, and large dense provinces of unknown composition and mineralogy. A team led by Caltech’s Jennifer Jackson, professor of mineral physics has new evidence for the origin of these features that occur at the core-mantle boundary.

    “We have discovered that bridgmanite, the most abundant mineral on our planet, is a reasonable candidate for the material that makes up these dense provinces that occupy about 20 percent of the core-mantle boundary surface, and rise up to a depth of about 1,500 kilometers. Integrated by volume that’s about the size of our moon!” says Jackson, coauthor of a study that outlines these findings and appears online in the Journal of Geophysical Research: Solid Earth. “This finding represents a breakthrough because although bridgmanite is the earth’s most abundant mineral, we only recently have had the ability to precisely measure samples of it in an environment similar to what we think the materials are experiencing inside the earth.”

    Previously, says Jackson, it was not clear whether bridgmanite, a perovskite structured form of (Mg,Fe)SiO3, could explain seismic observations and geodynamic modeling efforts of these large dense provinces. She and her team show that indeed they do, but these structures need to be propped up by external forces, such as the pinching action provided by cold and dense subducted slabs at the base of the mantle.

    Jackson, along with then Caltech graduate student Aaron Wolf (PhD ’13), now a research scientist at the University of Michigan at Ann Arbor, and researchers from Argonne National Laboratory, came to these conclusions by taking precise X-ray measurements of synthetic bridgmanite samples compressed by diamond anvil cells to over 1 million times the earth’s atmospheric pressure and heated to thousands of degrees Celsius.

    The measurements were done utilizing two different beamlines at the Advanced Photon Source [APS] of Argonne National Laboratory in Illinois, where the team used powerful X-rays to measure the state of bridgmanite under the physical conditions of the earth’s lower mantle to learn more about its stiffness and density under such conditions.

    ANL APS interior
    ANL APS
    APS

    The density controls the buoyancy—whether or not these bridgmanite provinces will lie flat on the core-mantle boundary or rise up. This information allowed the researchers to compare the results to seismic observations of the core-mantle boundary region.

    “With these new measurements of bridgmanite at deep-mantle conditions, we show that these provinces are very likely to be dense and iron-rich, helping them to remain stable over geologic time,” says Wolf.

    Using a technique known as synchrotron Mössbauer spectroscopy, the team also measured the behavior of iron in the crystal structure of bridgmanite, and found that iron-bearing bridgmanite remained stable at extreme temperatures (more than 2,000 degrees Celsius) and pressure (up to 130 gigapascals). There had been some reports that iron-bearing bridgmanite breaks down under extreme conditions, but the team found no evidence for any breakdown or reactions.

    “This is the first study to combine high-accuracy density and stiffness measurements with Mössbauer spectroscopy, allowing us to pinpoint iron’s behavior within bridgmanite,” says Wolf. “Our results also show that these provinces cannot possibly contain a large complement of radiogenic elements, placing strong constraints on their origin. If present, these radiogenic elements would have rapidly heated and destabilized the piles, contradicting many previous simulations that indicate that they are likely hundreds of millions of years old.”

    In addition, the experiments suggest that the rest of the lower mantle is not 100 percent bridgmanite as had been previously suggested. “We’ve shown that other phases, or minerals, must be present in the mantle to satisfy average geophysical observations,” says Jackson. “Until we made these measurements, the thermal properties were not known with enough precision and accuracy to uniquely constrain the mineralogy.”

    “There is still a lot of work to be done, such as identifying the dynamics of subducting slabs, which we believe plays a role in providing an external force to shape these large bridgmanite provinces,” she says. “We know that the earth did not start out this way. The provinces had to evolve within the global system, and we think these findings may help large-scale geodynamic modeling that involves tectonic plate reconstructions.”

    The results of the study were published in a paper titled The thermal equation of state of (Mg,Fe)SiO3bridgmanite (perovskite) and implications for lower mantle structures. In addition to Jackson and Wolf, other authors on the study are Przemeslaw Dera and Vitali B. Prakapenka from the Center for Advanced Radiation Sources at Argonne National Laboratory. Support for this research was provided by the National Science Foundation, the Turner Postdoctoral Fellowship at the University of Michigan, and the California Institute of Technology.

    See the full article here .

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    The California Institute of Technology (commonly referred to as Caltech) is a private research university located in Pasadena, California, United States. Caltech has six academic divisions with strong emphases on science and engineering. Its 124-acre (50 ha) primary campus is located approximately 11 mi (18 km) northeast of downtown Los Angeles. “The mission of the California Institute of Technology is to expand human knowledge and benefit society through research integrated with education. We investigate the most challenging, fundamental problems in science and technology in a singularly collegial, interdisciplinary atmosphere, while educating outstanding students to become creative members of society.”
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  • richardmitnick 3:32 pm on January 30, 2015 Permalink | Reply
    Tags: , Geosciences,   

    From U Arizona: “Iceland Rises as Its Glaciers Melt From Climate Change” 

    U Arizona bloc

    University of Arizona

    January 29, 2015
    Mari N. Jensen

    1
    This global positioning satellite receiver is part of Iceland’s network of 62 such receivers that geoscientists are using to detect movements of the Icelandic crust that are as small as one millimeter per year. Langjokull glacier is in the background. (Photo: Richard A. Bennett/UA Department of Geosciences)

    With the country’s glaciers melting faster, the crust near the glaciers is rebounding at an accelerated rate, according to a UA-led team of geoscientists.

    2
    Iceland’s glaciers (white) are melting faster and faster. As a result, the Icelandic crust near the glaciers is rebounding at an accelerated rate — in some cases, as much as 1.4 inches per year, a UA-led team of geoscientists found. The researchers used Iceland’s geodesy network of sensitive GPS receivers (red triangles) to determine how fast the land is rising. (Credit: Kathleen Compton/UA Department of Geosciences)

    The Earth’s crust under Iceland is rebounding as global warming melts the island’s great ice caps, a University of Arizona-led team reports in an upcoming issue of Geophysical Research Letters.

    The paper is the first to show the current fast uplift of the Icelandic crust is a result of accelerated melting of the island’s glaciers and coincides with the onset of warming that began about 30 years ago, the scientists said.

    Some sites in south-central Iceland are moving upward as much as 1.4 inches per year — a speed that surprised the researchers.

    “Our research makes the connection between recent accelerated uplift and the accelerated melting of the Icelandic ice caps,” said first author Kathleen Compton, a UA geosciences doctoral candidate.

    Geologists have long known that as glaciers melt and become lighter, the Earth rebounds as the weight of the ice decreases.

    Whether the current rebound geologists detect is related to past deglaciation or modern ice loss has been an open question until now, said co-author Richard Bennett, a UA associate professor of geosciences.

    “Iceland is the first place we can say accelerated uplift means accelerated ice mass loss,” Bennett said.

    To figure out how fast the crust was moving upward, the team used a network of 62 global positioning satellite receivers fastened to rocks throughout Iceland. By tracking the position of the GPS receivers year after year, the scientists “watch” the rocks move and can calculate how far they have traveled — a technique called geodesy.

    The new work shows that, at least for Iceland, the land’s current accelerating uplift is directly related to the thinning of glaciers and to global warming.

    “What we’re observing is a climatically induced change in the Earth’s surface,” Bennett said.

    He added there is geological evidence that during the past deglaciation roughly 12,000 years ago, volcanic activity in some regions of Iceland increased thirtyfold.

    Others have estimated the Icelandic crust’s rebound from warming-induced ice loss could increase the frequency of volcanic eruptions such as the 2010 eruption of Eyjafjallajökull, which had negative economic consequences worldwide.

    The article Climate driven vertical acceleration of Icelandic crust measured by CGPS geodesy by Compton, Bennett and their co-author Sigrun Hreinsdóttir of GNS Science in Avalon, New Zealand, was accepted for publication Jan. 14, 2015, and is soon to be published online. The National Science Foundation and the Icelandic Center for Research funded the research.

    Some of Iceland’s GPS receivers have been in place since 1995. Bennett, Hreinsdóttir and colleagues had installed 20 GPS receivers in Iceland in 2006 and 2009, thus boosting the coverage of the nation’s geodesy network. In central and southern Iceland, where five of the largest ice caps are located, the receivers are 18 miles or less apart on average.

    The team primarily used the geodesy network to track geological activity such as earthquakes and volcanic eruptions.

    In 2013, Bennett noticed one of the long-running stations in the center of the country was showing that site was rebounding at an accelerated rate. He wondered about it, so he and his colleagues checked the nearby stations to see if they had recorded the same changes.

    “The striking answer was, yes, they all do,” he said. “We wondered what in the world could be causing this?”

    The team began systematically analyzing years of signals from the entire network and found the fastest uplift was the region between several large ice caps. The rate of uplift slowed the farther the receiver was from the ice cap region.

    Other researchers had been measuring ice loss and observed a notable uptick in the rate of melting since 1995. Temperature records for Iceland, some of which go back to the 1800s, show temperatures increasing since 1980.

    To determine whether the same rate of ice loss year after year could cause such an acceleration in uplift, Compton tested that idea using mathematical models. The answer was no: The glaciers had to be melting faster and faster every year to be causing more and more uplift.

    Compton found the onset of rising temperatures and the loss of ice corresponded tightly with her estimates of when uplift began.

    “I was surprised how well everything lined up,” she said.

    Bennett said, “There’s no way to explain that accelerated uplift unless the glacier is disappearing at an accelerated rate.”

    Estimating ice loss is laborious and difficult, he said. “Our hope is we can use current GPS measurements of uplift to more easily quantify ice loss.”

    The team’s next step is to analyze the uplift data to reveal the seasonal variation as the ice caps grow during the winter snow season and melt during the summer.

    See the full article here.

    Please help promote STEM in your local schools.

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    U Arizona campus

    The University of Arizona (UA) is a place without limits-where teaching, research, service and innovation merge to improve lives in Arizona and beyond. We aren’t afraid to ask big questions, and find even better answers.

    In 1885, establishing Arizona’s first university in the middle of the Sonoran Desert was a bold move. But our founders were fearless, and we have never lost that spirit. To this day, we’re revolutionizing the fields of space sciences, optics, biosciences, medicine, arts and humanities, business, technology transfer and many others. Since it was founded, the UA has grown to cover more than 380 acres in central Tucson, a rich breeding ground for discovery.

    Where else in the world can you find an astronomical observatory mirror lab under a football stadium? An entire ecosystem under a glass dome? Visit our campus, just once, and you’ll quickly understand why the UA is a university unlike any other.

     
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