Tagged: Eos Toggle Comment Threads | Keyboard Shortcuts

  • richardmitnick 11:53 am on March 23, 2017 Permalink | Reply
    Tags: , , Eos, Neotectonics   

    From Eos: “Neotectonics and Earthquake Forecasting” 

    AGU bloc

    AGU
    Eos news bloc

    Eos

    3.23.17
    Ibrahim Çemen
    Yücel Yilmaz

    The editors of a new book describe the evolution of major earthquake producing fault zones in the eastern Mediterranean region and explore how earthquake forecasting could improve.

    1
    Digital elevation map of the Eastern Mediterranean region showing major neotectonics structural features, volcanic centers, and epicenters of the earthquakes since 1950. Credit: Çemen and Yilmaz, 2017

    A research symposium on “Neotectonics and Earthquake Potential of the Eastern Mediterranean Region” at the AGU Fall Meeting in 2013 drew researchers from around the world. A new book arising from that symposium has just been published by the American Geophysical Union. The symposium organizers and book editors, Ibrahim Çemen and Yücel Yilmaz, answers some questions about the book and the relevance of research in this field.

    What is neotectonics and why is it important?

    Neotectonics is a branch of Earth Sciences that studies the present-day motions of the Earth’s tectonics plates. When these motions reach a certain level they cause sudden ground shaking, i.e. earthquakes. Neotectonics studies are important to provide evidence for locations of major earthquakes along active fault zones of the world, such as the San Andreas in California, USA. Therefore, neotectonics and earthquake prediction are intimately associated subjects, important for scientists and the people living in areas where earthquakes have occurred in the past and likely to occur in the future.

    What different methods are used in the study of neotectonics?

    Neotectonics studies draw data from range of geological and geophysical methods, including GPS studies, geodesy, and passive source seismology. They also combine data from different sources including field work, seismic, experimental, computer-based, and theoretical studies. In addition, morphotectonic studies are extensively used in neotectonics. Morphotectonics focusses on landforms and involves combining geological and morphological data to evaluate how the Earth’s crust is currently being deformed and therefore modifying the land surface.

    Why the focus on the eastern Mediterranean region?

    The region is one of the most seismically-active areas of the world and has experienced many devastating earthquakes throughout history. Furthermore, many large earthquakes are expected to occur during the twenty-first century and beyond, creating a societal need for research on neotectonics and earthquake potential. Moreover, the findings specific to the eastern Mediterranean are relevant to other seismically-active regions of the earth including the western Mediterranean, western North America (including California), central and western South America, and central and southeastern Asia.

    With evolution of geophysical methods and techniques, is there hope for improving earthquake forecasting capabilities over time?

    Crustal movements along major fault zones lead to occurrence of earthquakes. New geophysical methods and techniques are being developed to monitor these movements. Eventually, earthquake scientists will be able to identify the tipping points related to these movements along the faults before an earthquake occurs. These tipping points include the build-up of stress and amount of displacements along the faults over the years (usually decades). Once these tipping points are identified, scientists will be able to more accurately forecast when an earthquake will occur along a given fault, within a certain period of time. These forecasts may be given with a percentage of chance, similar to weather forecasting.

    What kind of future research may be necessary to address some of the remaining questions in this field?

    There are still many important questions to be answered relating to neotectonics and earthquakes including: How did the major earthquake producing fault zones evolve in recent geologic time? What are the depths of these fault zones in the Earth’s crust? What is the state of stress along the zones? New insights to these questions can be provided if detailed crustal geometry of the major earthquake producing faults can be imaged precisely by combining modern geophysical techniques such as seismic tomography and 3D gravity modelling.

    Active Global Seismology: Neotectonics and Earthquake Potential of the Eastern Mediterranean Region, 2017, 306 pp., ISBN: 978-1-118-94498-1, list price $199.95 (hardcover)

    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 1:59 pm on March 17, 2017 Permalink | Reply
    Tags: , , Eos, , Mapping the Topographic Fingerprints of Humanity Across Earth   

    From Eos: “Mapping the Topographic Fingerprints of Humanity Across Earth” 

    AGU bloc

    AGU
    Eos news bloc

    Eos

    16 March 2017
    Paolo Tarolli
    Giulia Sofia
    Erle Ellis

    1
    Fig. 1. Three-dimensional view of Bingham Canyon Mine, Utah, a human-made topographic signature, based on a free, open-access high-resolution data set. Credit: Data from Utah AGRC

    Since geologic time began, Earth’s surface has been evolving through natural processes of tectonic uplift, volcanism, erosion, and the movement of sediment. Now a new force of global change is altering Earth’s surface and morphology in unprecedented ways: humanity.

    Human activities are leaving their fingerprints across Earth (Figure 1), driven by increasing populations, technological capacities, and societal demands [e.g., Ellis, 2015; Brown et al., 2017; Waters et al., 2016]. We have altered flood patterns, created barriers to runoff and erosion, funneled sedimentation into specific areas, flattened mountains, piled hills, dredged land from the sea, and even triggered seismic activity [Tarolli and Sofia, 2016]. These and other changes can pose broad threats to the sustainability of human societies and environments.

    If increasingly globalized societies are to make better land management decisions, the geosciences must globally evaluate how humans are reshaping Earth’s surface. A comprehensive mapping of human topographic signatures on a planet-wide scale is required if we are to understand, model, and forecast the geological hazards of the future.

    Understanding and addressing the causes and consequences of anthropogenic landform modifications are a worldwide challenge. But this challenge also poses an opportunity to better manage environmental resources and protect environmental values [DeFries et al., 2012].

    The Challenge of Three Dimensions

    “If life happens in three dimensions, why doesn’t science?” This question, posed more than a decade ago in Nature [Butler, 2006], resonates when assessing human reshaping of Earth’s landscapes.

    Landforms are shaped in three dimensions by natural processes and societal demands [e.g., Sidle and Ziegler, 2012; Guthrie, 2015]; societies in turn are shaped by the landscapes they alter. Understanding and modeling these interacting forces across Earth are no small challenge.

    For example, observing and modeling the direct effects of some of the most widespread forms of human topographic modification, such as soil tillage and terracing [Tarolli et al., 2014], are possible only with very fine spatial resolutions (i.e., ≤1 meter). Yet these features are common all over the world. High-resolution three-dimensional topographic data at global scales are needed to observe and appraise them.

    The Need for a Unified, Global Topographic Data Set

    High-resolution terrain data such as lidar [Tarolli, 2014], aerial photogrammetry [Eltner et al., 2016], and satellite observations [Famiglietti et al., 2015] are increasingly available to the scientific community. These data sets are also becoming available to land planners and the public, as governments, academic institutions, and others in the remote sensing community seize the opportunity for high-resolution topographic data sharing (Figure 2) [Wulder and Coops, 2014; Verburg et al., 2015]

    2
    Fig. 2. High-resolution geodata reveal the topographic fingerprints of humanity: (a) terraces in the Philippines, (b) agricultural practices in Germany, and (c) roads in Antarctica. The bottom images are lidar images of the same landscapes. Credit: Data from University of the Philippines TCAGP/Freie und Hansestadt Hamburg/Noh and Howat [2015]. Top row: © Google, DigitalGlobe

    Thanks to these geodata, anthropogenic signatures are widely observable across the globe, under vegetation cover (Figure 2a), at very fine spatial scales (e.g., agricultural practices and plowing; Figure 2b) and at large spatial scales (e.g., major open pit mines; Figure 3), and far from contemporary human settlements (Figure 2c). So the potential to assess the global topographic fingerprints of humanity using high-resolution terrain data is a tantalizing prospect.

    However, despite a growing number of local projects at fine scales, a global data set remains nonetheless elusive. This lack of global data is largely the result of technical challenges to sharing very large data sets and issues of data ownership and permissions.

    But once a global database exists, advances in the technical capacity to handle and analyze large data sets could be utilized to map anthropogenic signatures in detail (e.g., using a close-range terrestrial laser scanner) and across larger areas (e.g., using satellite data). Together with geomorphic analyses, the potential is clear for an innovative, transformative, and global-scale assessment of the extent to which humans shape Earth’s landscapes.

    For example, a fine-scale analysis of terrain data can detect specific anthropogenic configurations in the organization of surface features (Figure 3b) [Sofia et al., 2014], revealing modifications that humans make across landscapes (Figure 3c). Such fine-scale geomorphic changes are generally invisible to coarser scales of observation and analysis, making it appear that natural landforms and natural hydrological and sedimentary processes are unaltered. Failure to observe such changes misrepresents the true extent and form of human modifications of terrain, with huge consequences when inaccurate data are used to assess risks from runoff, landslides, and other geologic hazards to society [Tarolli, 2014].

    3
    Fig. 3. This potential detection of anthropogenic topographic signatures has been derived from satellite data. (a) This satellite image shows an open-pit mine in North Korea. (b) That image has been processed in an autocorrelation analysis, a measure of the organization of the topography (slope local length of autocorrelation, SLLAC [Sofia et al., 2014]). The variation in the natural landscape is noisy (e.g., top right corner), whereas anthropogenic structures are more organized and leave a clear topographic signature. (c) The degree of landscape organization can be empirically related to the amount of human-made alterations to the terrain, as demonstrated by Sofia et al. [2014]. Credit: Data from CNES© Distribution Airbus DS

    Topography for Society

    A global map of the topographic signatures of humanity would create an unparalleled opportunity to change both scientific and public perspectives on the human role in reshaping Earth’s land surface. A worldwide inventory of anthropogenic geomorphologies would enable geoscientists to assess the extent to which human societies have reshaped geomorphic processes globally and provide a tool for monitoring these changes over time.

    Such monitoring would facilitate unprecedented insights into the dynamics and sensitivity of landscapes and their responses to human forcings at global scale. In turn, these insights would help cities, resource managers, and the public better understand and mediate their social and environmental actions.

    As we move deeper into the Anthropocene, a comprehensive mapping of human topographic signatures will be increasingly necessary to understand, model, and forecast the geological hazards of the future. These hazards will likely be manifold.

    4
    Fig. 4. (a) This road, in the HJ Andrews Experimental Forest in Oregon’s Cascade Range, was constructed in 1952. A landslide occurred in 1964, and its scar was still visible in 1994, when the image was acquired. The landslide starts from the road and flows toward the top right corner of the image. (b) An index called the relative path impact index (RPII) [Tarolli et al., 2013] is evaluated here using a lidar data set from 2008. The RPII analyzes the potential water surface flow accumulation based on the lidar digital terrain model, and the index is highest where the flows are increased because of the presence of anthropogenic features. High values beyond one standard deviation (σ) highlight potential road-induced erosion. Credit: Data from NSF LTER, USFS Research, OSU; background image © Google, USGS.

    For example, landscapes across the world face altered flooding regimes in densely populated floodplains, erosion rates associated with road networks, altered runoff and erosion due to agricultural practices, and sediment release and seismic activity from mining [Tarolli and Sofia, 2016]. Modifications in land use (e.g., urbanization and changes in agricultural practices) alter water infiltration and runoff production, increasing flooding risks in floodplains. Increases in road density cause land degradation and erosion (Figure 4), especially when roads are poorly planned and constructed without well-designed drainage systems, leading to destabilized hillslopes and landslides. Erosion from agricultural fields can exceed rates of soil production, causing soil degradation and reducing crop yields, water quality, and food production. Mining areas, even years after reclamation, can induce seismicity, landslides, soil erosion, and terrain collapse, damaging environments and surface structures.

    Without accurate data on anthropogenic topography, communities will find it difficult to develop and implement strategies and practices aimed at reducing or mitigating the social and environmental impacts of anthropogenic geomorphic change.

    Earth Science Community’s Perspective Needed

    Technological advances in Earth observation have made possible what might have been inconceivable just a few years ago. A global map and inventory of human topographic signatures in three dimensions at high spatial resolution can now become a reality.

    Collecting and broadening access to high spatial resolution (meter to submeter scale), Earth science–oriented topography data acquired with lidar and other technologies would promote scientific discovery while fostering international interactions and knowledge exchange across the Earth science community. At the same time, enlarging the search for humanity’s topographical fingerprints to the full spectrum of environmental and cultural settings across Earth’s surface will require a more generalized methodology for discovering and assessing these signatures.

    These two parallel needs are where scientific efforts should focus. It is time for the Earth science community to come together and bring the topographic fingerprints of humanity to the eyes and minds of the current and future stewards, shapers, curators, and managers of Earth’s land surface.
    Acknowledgments

    Data sets for Figure 1 are from Utah Automated Geographic Reference Center (AGRC), Geospatial Information Office. Data sets for Figures 2(a)–2(c) are from the University of the Philippines Training Center for Applied Geodesy and Photogrammetry (TCAGP), Noh and Howat [2015], and Freie und Hansestadt Hamburg (from 2014), respectively. Data sets for Figure 3 are from Centre National d’Études Spatiales (CNES©), France, Distribution Airbus DS. Data sets for Figure 4 are from the HJ Andrews Experimental Forest research program, National Science Foundation’s Long-Term Ecological Research Program (NSF LTER, DEB 08-23380), U.S. Forest Service (USFS) Pacific Northwest Research Station, and Oregon State University (OSU).
    References

    Butler, D. (2006), Virtual globes: The web-wide world, Nature, 439, 776–778, https://doi.org/10.1038/439776a.

    Brown, A. G., et al. (2017), The geomorphology of the Anthropocene: Emergence, status and implications, Earth Surf. Processes Landforms, 42, 71–90, https://doi.org/10.1002/esp.3943.

    DeFries, R. S., et al. (2012), Planetary opportunities: A social contract for global change science to contribute to a sustainable future, BioScience, 62, 603–606, https://doi.org/10.1525/bio.2012.62.6.11.

    Ellis, E. C. (2015), Ecology in an anthropogenic biosphere, Ecol. Monogr., 85, 287–331, https://doi.org/10.1890/14-2274.1.

    Eltner, A., et al. (2016), Image-based surface reconstruction in geomorphometry—Merits, limits and developments, Earth Surf. Dyn., 4, 359–389, https://doi.org/10.5194/esurf-4-359-2016.

    Famiglietti, J. S., et al. (2015), Satellites provide the big picture, Science, 349, 684–685, https://doi.org/10.1126/science.aac9238.

    Guthrie, R. (2015), The catastrophic nature of humans, Nat. Geosci. 8, 421–422, https://doi.org/10.1038/ngeo2455.

    Noh, M. J., and I. M. Howat (2015), Automated stereo-photogrammetric DEM generation at high latitudes: Surface Extraction with TIN-based Search-space Minimization (SETSM) validation and demonstration over glaciated regions, GIScience Remote Sens., 52(2), 198–217, https://doi.org/10.1080/15481603.2015.1008621.

    Sidle, R. C., and A. D. Ziegler (2012), The dilemma of mountain roads, Nat. Geosci, 5, 437–438, https://doi.org/10.1038/ngeo1512.

    Sofia, G., F. Marinello, and P. Tarolli (2014), A new landscape metric for the identification of terraced sites: The slope local length of auto-correlation (SLLAC), ISPRS J. Photogramm. Remote Sens., 96, 123–133, https://doi.org/10.1016/j.isprsjprs.2014.06.018.

    Tarolli, P. (2014), High-resolution topography for understanding Earth surface processes: Opportunities and challenges, Geomorphology, 216, 295–312, https://doi.org/10.1016/j.geomorph.2014.03.008.

    Tarolli, P., and G. Sofia (2016), Human topographic signatures and derived geomorphic processes across landscapes, Geomorphology, 255, 140–161, https://doi.org/10.1016/j.geomorph.2015.12.007.

    Tarolli, P., et al. (2013), Recognition of surface flow processes influenced by roads and trails in mountain areas using high-resolution topography, Eur. J. Remote Sens., 46, 176–197.

    Tarolli, P., F. Preti, and N. Romano (2014), Terraced landscapes: From an old best practice to a potential hazard for soil degradation due to land abandonment, Anthropocene, 6, 10–25, https://doi.org/10.1016/j.ancene.2014.03.002.

    Verburg, P. H., et al. (2015), Land system science and sustainable development of the Earth system: A global land project perspective, Anthropocene, 12, 29–41, https://doi.org/10.1016/j.ancene.2015.09.004.

    Waters, C. N., et al. (2016), The Anthropocene is functionally and stratigraphically distinct from the Holocene, Science, 351, aad2622, https://doi.org/10.1126/science.aad2622.

    Wulder, M. A., and N. C. Coops (2014), Satellites: Make Earth observations open access, Nature, 513, 30–31, https://doi.org/10.1038/513030a.

    —Paolo Tarolli (email: paolo.tarolli@unipd.it; @TarolliP) and Giulia Sofia (@jubermensch2), Department of Land, Environment, Agriculture, and Forestry, University of Padova, Legnaro, Italy; and Erle Ellis (@erleellis), Department of Geography and Environmental Systems, University of Maryland, Baltimore County, Baltimore
    Citation: Tarolli, P., G. Sofia, and E. Ellis (2017), Mapping the topographic fingerprints of humanity across Earth, Eos, 98, https://doi.org/10.1029/2017EO069637. Published on 16 March 2017.
    © 2017. The authors. CC BY-NC-ND 3.0

    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 10:02 am on March 13, 2017 Permalink | Reply
    Tags: , Eos, Stromboli volcano,   

    From Eos: “Tracking Volcanic Bombs in Three Dimensions” 

    AGU bloc

    AGU
    Eos news bloc

    Eos

    3.13.17
    Leah Crane

    1
    Off the north coast of Sicily, an eruption of the Stromboli volcano sends decametric lava fragments flying into the air. A new method allows researchers to track these “bombs” and to reconstruct their flight trajectories in three dimensions. Credit: Florian Becker/Vulkankultour

    In explosive volcanic eruptions, bits of fragmented magma can be shot through the air by the release and expansion of pressurized gas. The trajectory map of these centimetric to decametric fragments, called “bombs,” is an important parameter in the study of explosive eruptions and the dangers that they present: Understanding how fast the debris is moving, how far it moves, and in which direction pieces travel could help scientists assess the hazards of volcanic eruptions or man-made explosions. In a new paper, Gaudin et al . present a method for studying the motion of volcanic bombs in three dimensions, allowing for more precise trajectory reconstructions.

    There are several conditions that make observing active volcanic vents and bombs difficult, including the obvious difficulty of getting cameras close to the vents. The most significant of the problems is the large number of bombs from each explosive event that may change shape in flight and whose flight paths overlap with one another.

    2
    When observing a bubble bursting in Halema‘uma‘u lava lake in Hawaii, researchers manually tracked selected pieces of debris on stills of a video. These two images of the resulting set of trajectories could then be combined to produce a three-dimensional map. Credit: Gaudin et al. [2016]

    These limitations make any automatic tracking difficult or impossible, so the scientists simplified their procedure by relying on manual tracking of a few representative bombs rather than a computerized account of every single one. By placing two or more high-speed video cameras at well-documented positions around the volcanic vent, they were able to manually determine an object’s location in all of the images, computing the object’s position in three dimensions.

    The human component of this manual process can be a major source of error since the person tracking the bombs makes a series of subjective choices, like deciding where exactly on the object to select as a representative point in each frame. If the cameras are tilted at all, that can also be a significant component of uncertainty in the measurements.

    In the new study, the team was able to reduce uncertainty to 10° in angle and 20% in speed of the bombs. They used three events as examples: a bursting bubble at the Halema‘uma‘u lava lake in Hawaii, in-flight bomb collision, and an explosive ejection event at Stromboli volcano in Italy. A video showing the bursting bubble followed by the explosive ejection and their model in action is given below.


    In Stromboli’s case, the reliability of the trajectory reconstruction was demonstrated by comparing the 3-D reconstruction with the low-speed, low-resolution cameras of the Stromboli permanent monitoring network. These case studies demonstrated just a few of the numerous contexts in which this 3-D tracking method could be useful, both within and beyond the study of volcanic vents and magma. (Geochemistry, Geophysics, Geosystems, https://doi.org/10.1002/2016GC006560, 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 10:46 am on March 8, 2017 Permalink | Reply
    Tags: , , California Fault System Could Produce Magnitude 7.3 Quake, , Eos, Newport-Inglewood/Rose Canyon fault mostly offshore but never more than four miles from the San Diego Orange County and Los Angeles County coast,   

    From Eos: “California Fault System Could Produce Magnitude 7.3 Quake” 

    AGU bloc

    AGU
    Eos news bloc

    Eos

    Mar 7, 2017

    A new study finds rupture of the offshore Newport-Inglewood/Rose Canyon fault that runs from San Diego to Los Angeles is possible.

    1
    A Scripps research vessel tows a hydrophone array used to collect high-resolution bathymetric to better understand offshore California faults. Credit: Scripps Institution of Oceanography, UC San Diego

    A fault system that runs from San Diego to Los Angeles is capable of producing up to magnitude 7.3 earthquakes if the offshore segments rupture and a 7.4 if the southern onshore segment also ruptures, according to a new study led by Scripps Institution of Oceanography at the University of California San Diego.

    The Newport-Inglewood and Rose Canyon faults had been considered separate systems but the study shows that they are actually one continuous fault system running from San Diego Bay to Seal Beach in Orange County, then on land through the Los Angeles basin.

    “This system is mostly offshore but never more than four miles from the San Diego, Orange County, and Los Angeles County coast,” said study lead author Valerie Sahakian, who performed the work during her doctorate at Scripps and is now a postdoctoral fellow with the U.S. Geological Survey in Menlo Park, California. “Even if you have a high 5- or low 6-magnitude earthquake, it can still have a major impact on those regions which are some of the most densely populated in California.”

    The new study was accepted for publication in the Journal of Geophysical Research: Solid Earth, a journal of the American Geophysical Union.

    In the new study, researchers processed data from previous seismic surveys and supplemented it with high-resolution bathymetric data gathered offshore by Scripps researchers between 2006 and 2009 and seismic surveys conducted aboard former Scripps research vessels New Horizon and Melville in 2013. The disparate data have different resolution scales and depth of penetration providing a “nested survey” of the region. This nested approach allowed the scientists to define the fault architecture at an unprecedented scale and thus to create magnitude estimates with more certainty.

    2
    Locations of NIRC fault zone as observed in seismic profiles. Credit: AGU/Journal of Geophysical Research: Solid Earth

    They identified four segments of the strike-slip fault that are broken up by what geoscientists call stepovers, points where the fault is horizontally offset. Scientists generally consider stepovers wider than three kilometers more likely to inhibit ruptures along entire faults and instead contain them to individual segments—creating smaller earthquakes. Because the stepovers in the Newport-Inglewood/Rose Canyon (NIRC) fault are two kilometers wide or less, the Scripps-led team considers a rupture of all the offshore segments is possible, said Neal Driscoll, a geophysicist at Scripps and co-author of the new study.

    The team used two estimation methods to derive the maximum potential a rupture of the entire fault, including one onshore and offshore portions. Both methods yielded estimates between magnitude 6.7 and magnitude 7.3 to 7.4.

    The fault system most famously hosted a 6.4-magnitude quake in Long Beach, California that killed 115 people in 1933. Researchers have found evidence of earlier earthquakes of indeterminate size on onshore portions of the fault, finding that at the northern end of the fault system, there have been between three and five ruptures in the last 11,000 years. At the southern end, there is evidence of a quake that took place roughly 400 years ago and little significant activity for 5,000 years before that.

    Driscoll has recently collected long sediment cores along the offshore portion of the fault to date previous ruptures along the offshore segments, but the work was not part of this study.

    “Further study is warranted to improve the current understanding of hazard and potential ground shaking posed to urban coastal areas from Tijuana to Los Angeles from the NIRC fault,” the study concludes.

    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 2:16 pm on February 18, 2017 Permalink | Reply
    Tags: , , , , Eos, Hall electric field, kinetic Alfvén waves,   

    From AGU Eos: “Plasma Waves Pinpointed at the Site of Magnetic Reconnection” This is Really Cool 

    AGU bloc

    AGU

    Eos news bloc

    Eos

    17 February 2017
    Mark Zastrow

    NASA/MMS

    nasa-mms-satellites
    An artist’s illustration of the four NASA MMS spacecraft, flying in formation through the fringes of Earth’s magnetic field. Credit: NASA

    Some of the most mysterious physics in all of space occurs tens of thousands of kilometers above the Earth, where the Sun’s magnetic field merges with that of Earth. This region pulses with currents and fields as the two fields tangle and reconnect, especially during solar storms, when reconnection soars and sends currents surging down into Earth’s magnetic field, causing hazardous geomagnetic storms.

    Scientists have labored for decades to understand what happens here, but in October 2015 they got a significant break: For the first time, a fleet of NASA satellites flew directly through a reconnection event. Now a new study by Dai et al. explains these data further and suggests that one electric field important to reconnection is triggered by a certain type of plasma wave. The work advances our understanding of magnetic reconnection, which is critical to forecasting geomagnetic storms.

    NASA’s Magnetospheric Multiscale (MMS) mission consists of four spacecraft launched in March 2015. Flying in a tight pyramid-shaped formation, they soar through the fringes of Earth’s magnetic field hunting for reconnection sites, taking high-resolution measurements as they fly in and out of the swirling currents and fields.

    One of the most prominent fields that appears during reconnection is the Hall electric field, which points across the boundary of Earth’s magnetic bubble. MMS revealed that this field is caused by the pressure of solar wind ions outside of Earth’s magnetic field pushing against it. The Earth’s magnetic field generates the Hall electric field to balance against the intruding ions.

    Magnetosphere of Earth, original bitmap from NASA. SVG rendering by Aaron Kaase
    Magnetosphere of Earth, original bitmap from NASA. SVG rendering by Aaron Kaase

    But what allows these ions to intrude in the first place? And why only positively charged ions and not electrons, too, which would result in no separation of charge and no electric field? As the authors detail, this change in ion pressure is mathematically related to the vibrations in the magnetic field lines themselves. These vibrations, called kinetic Alfvén waves, are akin to those caused by plucking on a string.

    According to the equations that govern plasma particles, both electrons and ions gyrate around the field lines. But protons have roughly 2000 times the mass of electrons, with a corresponding amount of additional inertia. So although electrons in the solar wind remain tightly coiled around the Sun’s magnetic field lines (typically within a few kilometers), positively charged ions perform gyrations as wide as hundreds of kilometers. This allows them to penetrate farther into regions than electrons. This effect also shows up in the equations for kinetic Alfvén waves, suggesting that these waves trigger the Hall electric field in reconnection events.

    The authors note that kinetic Alfvén wave physics can also explain several other phenomena observed at magnetic reconnection sites, including currents that flow along the magnetic field as well as the formation of additional smaller magnetic fields that run perpendicular to those of the Earth and Sun. In addition, the strength of the Hall electric field relative to these perpendicular magnetic fields happens to be very close to the speed of kinetic Alfvén waves as they propagate along magnetic field lines, strengthening the case that they play an important role in magnetic reconnection. (Geophysical Research Letters, https://doi.org/10.1002/2016GL071044, 2017)

    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 1:47 pm on January 28, 2017 Permalink | Reply
    Tags: Data Illuminate a Mountain of Molehills Facing Women Scientists, Eos,   

    From Eos: Women in STEM “Data Illuminate a Mountain of Molehills Facing Women Scientists” 

    Eos news bloc

    Eos

    25 January 2017
    Julia Rosen
    julia.rosen@nasw.org
    @ScienceJulia

    From the peer-review process to our very concept of what it means to be brilliant, studies show that women face subtle biases and structural barriers to success in the geosciences.

    1
    iStock.com/swissmediavision

    Every female scientist has a story.

    One woman was warned not to wear her wedding ring to job interviews. Another noticed that her adviser showered more praise on his male students. On one occasion, a woman sat silent while the man next to her turned his back to talk to other (male) colleagues for the entire duration of a professional dinner.

    What should the women on the receiving end of such slights make of them? They might be random, nothing more than the everyday ups and downs of life as a professional scientist. They could be isolated incidents of sexism. Or they could be symptomatic of broader trends that hinder women in science.

    In cases like these, it’s impossible to know. “As an individual, you don’t really have the sample size to come up with this sort of conclusion,” said Jory Lerback, a graduate student at the University of Utah. But now, researchers like Lerback have harnessed the power of data to zoom out and identify systemic problems within the Earth sciences.

    In one study, led by Lerback and published today in Nature, researchers found that women make up a disproportionately small percentage of reviewers for Earth science journals. Another revealed that female geoscientists are less likely to receive glowing letters of recommendation when applying to postdoctoral fellowships.

    Researchers say the new results don’t reflect overt discrimination, which has declined dramatically in recent decades. Instead, women face more insidious challenges, such as subtle, unconscious bias held by people of both genders and built-in barriers to success.

    And they add up. Psychologist Virginia Valian of Hunter College calls this the “accumulation of disadvantage.” She argues that countless molehills pile up to create formidable mountains standing in the way of female scientists. In the geosciences, women still make up just 20% of faculty in the United States, despite earning almost a third of Ph.D. degrees in 2000 and more than 40% today.

    By using hard data to illuminate lingering problems, many hope that the geoscience community can start bulldozing the remaining molehills. After all, to realize its full potential for innovation and success, science needs all kinds of scientists, said Tracey Holloway, an atmospheric scientist at the University of Wisconsin–Madison and president of the Earth Science Women’s Network.

    “For the well-being of the human enterprise, we want all hands on deck.”

    2
    Heather Ford, an independent research fellow at Cambridge University studying paleoclimatology, examines a sediment core on the R/V Melville. Ford says that she enjoys reviewing papers, but new data show that women are underrepresented as reviewers in geoscience journals. Credit: Ajay Singh

    Wanted: A Detailed Database

    Reviewing papers may not be glamorous, but it plays a fundamental role in the scientific process.

    “I like reviewing papers because I have an opportunity to improve the quality, breadth, and impact of a manuscript,” said Heather Ford, an independent research fellow at Cambridge University studying paleoclimatology. Reviewing also provides important opportunities for early-career scientists like Ford to network with journal editors and interact with fellow scientists.

    But it’s hard to determine whether women are well represented among geoscience authors and reviewers, Lerback says. Most publishers don’t ask scientists for their gender, and assigning it based on names can be tricky business. Considering age is also important because the proportion of women decreases among older scientists—a consequence of historic barriers to entry.

    The American Geophysical Union (AGU), however, was in a unique position to do such an analysis. It publishes a suite of scientific journals and possesses gender and age information for more than 38,000 geoscientists who belong to the organization or have participated in AGU-sponsored activities, like its sprawling Fall Meeting.

    Merging these two data sets offered the chance to evaluate both the gender ratio of authors and reviewers for AGU’s journals and how those ratios stacked up against the field’s demographic breakdown. Lerback undertook the task with Brooks Hanson, AGU’s director of publications, and uncovered a complex landscape of small but significant gender differences in geoscience publishing.

    Lerback and Hanson’s results show that women published less than men, submitting an average of 0.79 fewer first-author papers to AGU’s journals in the 4-year period between 2012 and 2015.

    However, women were better represented among first authors (26%) compared to total authors (23%), in contrast to previous studies that found women tended to be listed between the respected first and last author positions. Overall, women also enjoyed a slightly higher acceptance rate than men: 61% vs. 57%.

    The researchers attribute this greater success rate either to reverse discrimination (i.e., reviewers actually favoring female scientists) or, more likely, to the fact that women perfect their papers before submission, anticipating heightened scrutiny. “When someone is faced with that sort of mentality, you cover all your bases,” Lerback said. “You check and check and check.”

    A Gender Gap in Peer Review

    Most worryingly, Lerback and Hanson found that women were chronically underrepresented as reviewers. In total, women made up only 20% of reviewers, even though they comprise 28% of AGU’s membership and 29% of all scientists who have created accounts with AGU.

    “That’s a pretty big gap of women who aren’t reviewing,” Lerback said. On its own, this disparity wouldn’t make or break anyone’s career, she added, but it’s problematic because it plays into the larger pattern of gender inequality in the Earth sciences.

    3
    A study published today in Nature found that women were underrepresented as reviewers for AGU’s journals. The proportion of female reviewers (20%) was smaller than the proportion of published female first authors (27%) and female AGU members (28%). Credit: Lerback and Hanson, 2017, doi:10.1038/541455a

    The researchers found that several factors were to blame: Authors didn’t suggest enough female reviewers for their papers, editors didn’t invite enough female reviewers, and women declined to do reviews more often than men.

    What’s more, these disparities persisted across age groups. This eliminated the possibility that authors and editors simply sought reviewers from older and more experienced cohorts with fewer female members.

    No comparable analyses have been carried out for journals published by the Geological Society of America or the European Geosciences Union. But the new results, based on an analysis of nearly 25,000 authors and 15,000 reviewers, are hard to dismiss as unrepresentative, said Mary Anne Holmes, a sedimentary geologist at the University of Nebraska–Lincoln and a leading advocate for gender equality in the Earth sciences. “The volume of data is pretty overwhelming.”

    Brilliant or Intelligent?

    Another recent study tells a similar story about differences in the quality of reference letters for male and female geoscientists.

    Researchers first realized that letters often reflect gender stereotypes decades ago, and disparities have been clearly documented in numerous studies. But a new analysis, published last fall in Nature Geoscience, is the first to look specifically at the Earth sciences and relies on a larger data set than previous work.

    Researchers evaluated more than 1200 letters sent on behalf of scientists applying for postdoctoral fellowships at Columbia University’s Lamont-Doherty Earth Observatory (LDEO) between 2007 and 2012. The letters came from male and female recommenders scattered across 54 countries.

    4
    Cynthia Gerlein-Safdi, a Ph.D. student at Princeton University who studies how plants respond to climate, takes a soil sample in Kenya. She is currently applying for postdoc positions and was disheartened to hear reports of gender bias in recommendation letters. Credit: Ekomwa Akuwam

    The analysis revealed that letters for men and women differed significantly in tone. Roughly a quarter of male applicants received what the authors classified as excellent letters, which included phrases like “brilliant scientist” and “scientific leader,” compared to 15% of female applicants. Instead, more than 80% of women got letters that praised them in more staid terms, calling them “highly intelligent” and “very knowledgeable.”

    After adjusting the results to reflect regional variations between the home country of recommenders and letter length, the researchers found that women were about half as likely to receive excellent letters. This disadvantages women at a critical stage in their careers, the authors wrote.

    “It certainly makes me feel highly discouraged and pessimistic,” says Cynthia Gerlein-Safdi, a Ph.D. student at Princeton University studying how plants respond to climate. She is currently in the process of applying for postdoc positions and was disheartened when she heard the results of the study.

    Because of the archival nature of the study, the researchers could not control for differences in the qualifications of the applicants. However, that probably doesn’t explain the results, said Kuheli Dutt, assistant director of academic affairs at LDEO and lead author of the study.

    “It is highly unlikely that all over the world, there is a systemic deficit in the quality of just the women applicants,” she said.

    A Competitive Disadvantage

    Women remain at a competitive disadvantage even when they have the exact same qualifications as their male counterparts, according to previous studies.

    Take the now-famous study [PNAS]where identical job applications were sent out under different names. Faculty rated the applicants with male names as significantly more competent and hirable for a potential lab manager position than applicants with female names. They offered to pay them more too. Another study [PNAS]found that men were twice as likely to be selected to perform a mathematical calculation on the basis of their appearance alone.

    Holmes also points to the story of gender bias in orchestras. Few female musicians made the cut when judges could see them perform during auditions. But when they played from behind a screen, Holmes said, “the number of women who were hired just rose dramatically.”

    Researchers attribute such patterns of discrimination not to intentional exclusion but to the effects of implicit or unconscious biases. These are deep-seated beliefs about groups of people—in this case, women—that stem from common stereotypes and may even conflict with our conscious thoughts and attitudes, according to Mikki Hebl, an applied social psychologist at Rice University.

    For instance, many people may support women in science but subconsciously react to the ways in which female stereotypes conflict with stereotypes about scientists.

    In a 2008 Nature Geoscience study led by Holmes, some participants in a focus group tasked with examining why women choose to leave Earth science suggested that it is because they don’t like doing fieldwork or have low interest in the subject matter, ideas that echo long-held ideas about feminine fragility and disposition. However, as “congenital players in the dirt,” Holmes and her coauthors wrote that they don’t believe these are major drivers.

    Problems also stem from the fact that stereotypes about scientists evolved decades ago, when most were men. “We have so many cultural preconceptions of what a genius looks like, what a scientist looks like, what kind of behavior is indicative of somebody being truly devoted to their career,” Holloway said.

    “Sometimes, it’s very difficult to differentiate what are characteristics of a good scientist from what are characteristics of a male scientist.”

    An Equal Opportunity Challenge

    Men aren’t the only ones who fall prey to these subtle biases, however.

    In Dutt’s study, female recommenders were equally likely to write stronger letters on behalf of male applicants. And although female editors and authors at AGU’s journals identified a higher proportion of women to review papers than male editors did, the gender ratio of those reviewers still failed to reflect the demographics of the field.

    Both men and women can harbor unconscious bias because it’s based on “culturally learned information,” Hebl said. “When we come into the world, we learn that girls wear pink and boys wear blue.” As a result, psychologists have found that we tend to penalize anyone—male or female—who doesn’t conform to our subconscious expectations.

    For example, in one 2016 study where male and female subjects were asked to rate the brilliance of various scientific discoveries, researchers found that people of both genders rated discoveries as more exceptional if they were described in ways that fit stereotypes of women as caregivers and men as geniuses.

    “It’s not really about who’s to blame,” Lerback said. It’s recognizing that everyone is part of the problem.

    Both men and women can harbor unconscious bias because it’s based on “culturally learned information,” Hebl said. “When we come into the world, we learn that girls wear pink and boys wear blue.” As a result, psychologists have found that we tend to penalize anyone—male or female—who doesn’t conform to our subconscious expectations.

    For example, in one 2016 study where male and female subjects were asked to rate the brilliance of various scientific discoveries, researchers found that people of both genders rated discoveries as more exceptional if they were described in ways that fit stereotypes of women as caregivers and men as geniuses.

    For men, that meant having a flash of brilliance, and for women, it meant nurturing the seed of an idea as it grew. Discoveries described with the opposite pairings (i.e., women having a flash of brilliance) received more tepid ratings.

    Subtle though they may be, these biases make scientists less likely to think of their female colleagues when inviting colloquia speakers, according to Hebl’s research. This may also explain why fewer women get nominated for awards and honors or get asked to author perspective pieces for prestigious journals. A 2012 analysis found that women wrote just 4% of Earth science News and Views articles in Nature.

    It’s no surprise, then, that these biases may also arise when authors or editors of a scientific paper brainstorm possible reviewers, Lerback said. “Who makes it through to the forefront of your mind?”

    Navigating Hidden Barriers

    Unconscious biases aren’t the only impediments to success. Women must also contend with troubling levels of sexual harassment and assault, a lack of mentors, isolation in male-dominated research groups, and a litany of other challenges. Sometimes, the very architecture of science—designed mostly by and for men—can stand in the way. This becomes particularly evident as women progress beyond graduate school.

    For instance, it has long been seen as advantageous for young scientists to move to a new institution immediately after finishing a Ph.D. Until recently, it was actually a requirement for recipients of the National Science Foundation’s prestigious postdoctoral fellowships.

    But uprooting can be harder for women than men, said Holloway. Women generally marry and have children at a younger age, and female scientists are more likely to have a partner in academia.

    4
    Jennifer Hertzberg, paleoceanographer and postdoctoral fellow at the University of Connecticut in Avery Point, inspects a sediment core aboard the R/V Melville in the eastern Pacific. She’s currently looking for a job but notes that the researcher’s life of chasing funding could bleed into family time. Credit: Franco Marcantonio

    The demands of certain faculty jobs that require constantly chasing funding can also be daunting to women as they consider starting families, said Jennifer Hertzberg. Hertzberg is a paleoceanographer and postdoctoral fellow at the University of Connecticut in Avery Point, who is currently applying for jobs. “If I were having to write research grants all the time, I know that that would fall into afterhours and on the weekends.” She’s not sure it would be doable with kids.

    Academic jobs often require long hours, and data suggest women have fewer to spare. Female scientists with male partners tend to do more housework, according to a survey conducted through the Earth Science Jobs Network, a listserv run by the Earth Science Women’s Network that includes both male and female geoscientists. Sixty percent of women reported doing the majority of household upkeep, compared to 20% of men. Fifty percent of women with children also did the majority of parenting work, compared to 9% of men.

    In addition, research suggests that women may also juggle more obligations at the office. Female associate professors, in particular, typically shoulder heavier administrative, mentoring, and teaching duties at the expense of research. They often serve on many doctoral committees, for example, as one of a few female faculty members in high demand from larger numbers of female students, Holmes said.

    All this may explain the small but telling finding in Lerback’s study that even when women were asked to review papers, they declined more often than men. “Maybe women aren’t stepping up to do these reviews because they’re too damn busy,” Holmes said.

    Data Pave a Path to Progress

    At the end of the day, the many challenges facing female scientists weigh on women just starting in their careers. Some feel lucky just to have made it as far as they have, given that the deck is often stacked against them.

    “It’s exhausting,” said Ford.

    “I feel like I have to work harder than a male at the same point in my career,” said Hertzberg.

    Many agree that the first step in addressing these problems is raising awareness. And the recent studies should help.

    “Data are undeniable facts,” said Claudia Jesus-Rydin, a program officer for Earth system sciences at the European Research Council who coordinates its gender balance initiatives. Scientists, of all people, should be persuaded of the problem.

    But what can scientists do about it?

    Knocking Down Barriers

    Unconscious bias and structural barriers can take many forms, and the solutions may be as diverse as the problems themselves.

    Because unconscious biases are, by definition, unconscious, people can’t just decide to change them. However, research suggests that simply recognizing the presence of implicit bias is an important way to reduce its effects. Harvard offers online bias tests, and many organizations, including universities and professional societies, now offer implicit bias training for awards and hiring committees.

    Voluntary training proved most effective at reducing bias, along with strategies like implementing mentoring programs and fostering social accountability, according to an analysis of diversity programs in the Harvard Business Review. However, the authors found that forcing people to participate in bias training can actually spark a backlash.

    For AGU’s part, Hanson said that the organization is “trying to expand the diversity of our editorial teams and reviewers.” And since recommendation letter differences have come to light, many universities have compiled tips for reducing bias. They include emphasizing accomplishments over effort and steering clear of personal details, which crop up disproportionately in letters for female applicants.

    Holloway has worked with AGU to increase the diversity of its awards, primarily by encouraging a more diverse pool of people to do the nominating. Award committees also stopped emphasizing a candidate’s h-index—a measure of their citations—after studies showed that men self-cite more than women. And in 2016, female scientists represented 30% of nominees and winners, twice the ratio in 2014 and roughly equal to the proportion of female AGU members. A similar effort is under way within the European Geosciences Union.

    Holmes cites other innovative efforts at places like Lehigh University and the University of California, Irvine, where men are trained to be so-called equity advisers. The idea is that men can then serve as advocates for women, for instance, on hiring committees.

    “I really like that idea,” Holmes said. “Ya’ll step up to the plate and take some of the burden.”

    Finding a Way Forward

    Gender equality is always a touchy subject, and addressing it as a community will require a careful balancing act, Hebl said. Scientists have to hold each other accountable whenever unconscious bias rears its head. But they should also be tolerant as people learn how to recognize and acknowledge it.

    “We all make mistakes,” Hebl said. “If there are not safe spaces to make mistakes and learn, it can harbor pools of hatred.”

    5
    Elizabeth Orr, a Ph.D. student at the University of Cincinnati studying glacial geomorphology, collects samples to date the timing of glacial retreat in the Pir Panjal Range of northern India. Despite gender-based obstacles standing in the way of female geoscientists, she says she’s committed to science. Credit: Sourav Saha

    And as scientists work to address the challenges facing women, they shouldn’t forget that that the road is even harder for people of color and those with different sexual orientations and gender identities, said Robyn Dahl, a paleontologist at Western Washington University in Bellingham. Dahl is biracial and a lesbian and works on increasing diversity in fields involving science, technology, engineering, and math.

    Policies and structures may need to change too, and that may entail a bit of trial and error. Some well-intentioned strategies, like paid parental leave for both men and women at research universities, appears to have backfired. A recent study suggested that it did not level the playing field, as hoped, but actually helped male faculty gain tenure while reducing women’s chances.

    Nonetheless, any efforts to increase flexibility mark a step in the right direction, Holmes said. The academic career path is often described as a pipeline toward professorhood from which women disproportionately “leak” out. But times are changing.

    “The new metaphor is something more like an interstate expressway,” Holmes said. “There are a lot of on ramps, a lot of rest areas, and other destinations to go to.”

    Many early-career researchers are fueled up and ready for the ride, despite the curves ahead.

    “I love my job, and I can’t imagine myself doing anything else in life other than working in the geosciences,” said Elizabeth Orr, a Ph.D. student at the University of Cincinnati studying glacial geomorphology.

    “I am here to stay.”

    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 1:43 pm on January 4, 2017 Permalink | Reply
    Tags: , , Eos, , ,   

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

    Eos news bloc

    Eos

    AGU bloc

    AGU

    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 .

    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 6:26 am on December 3, 2016 Permalink | Reply
    Tags: , Eos, Megathrust earthquakes,   

    From Eos: “Understanding Tectonic Processes Following Great Earthquakes” 

    Eos news bloc

    Eos

    12.2.16
    Sarah Witman

    1
    A building torn in two in Concepción, Chile, following a magnitude 8.8 earthquake in 2010. Credit: hdur, CC BY-NC 2.0

    The most powerful and destructive earthquakes (magnitude 8 and higher) happen about once per year. Earthquakes at those magnitudes can do a lot of damage, often causing tsunamis and inflicting devastation across an entire region. The biggest quakes, such as Chile’s 1960 magnitude 9.5 tremor and Japan’s 2011 magnitude 9 event, typically occur in a subduction zone, a section of the Earth’s crust where one massive tectonic plate is sliding beneath another.

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

    The pent-up energy of these two plates pressing against one another eventually gives way, creating a colossal earthquake known as a megathrust.

    A recent study by Bedford et al. [Journal of Geophysical Research] presents a new approach to analyzing signals detected via satellite in the months following a megathrust earthquake. These signals, related to deformation in the tectonic plates caused by stress and strain, can be used to shed light on the tectonic processes that continue to unfold after disaster has struck.

    In many recent megathrust earthquakes, continuous GPS monitoring has allowed scientists to observe a two-part process following each quake: afterslip (slow, quiet movement along the interface of the two plates) and viscoelastic relaxation (the process of malleable, deforming rock adjusting to its new state of stress). However, when modeling GPS data collected in the 4 years after a magnitude 8.8 earthquake struck Chile in 2010, the team of researchers noticed something odd.

    2
    A schematic showing the straightening process in action. Viscoelastic relaxation and relocking predictions are subtracted from the curved original signal to leave behind a straight signal that is assumed to be the isolated afterslip signal. The color scale shows the time that has elapsed since the great earthquake. Millimeter scales on the x and y axes denote motions in the east and north horizontal directions, respectively. Credit: Jonathan Bedford

    Usually, before an earthquake, the horizontal ground motion of a continental plate is in roughly the same direction as the subducting oceanic plate because the oceanic plate sticks against—and drags along—the continental plate. During the quake, this observed surface motion is reversed when the sticking point between the two plates suddenly slips.

    Instead of this usual pattern of horizontal motion due to afterslip and viscoelastic relaxation, however, the researchers saw a distinct curvature in the surface signals. Almost immediately after the quake, the GPS motions started to curve around, starting from roughly the opposite direction of the downgoing plate and shifting toward a direction more in line with the pre-earthquake motion.

    The researchers thought that maybe, in addition to afterslip and viscoelastic relaxation, some relocking at the interface of the plates (pumping the brakes, so to speak) might be contributing to the observed curvature. After all, the plate interface must eventually relock in preparation for the next large earthquake. The researchers wondered whether relocking could be a dominant process so soon after a great earthquake. And, if so, how big was its impact relative to the other two processes?

    To find out, the researchers applied a novel approach to separating out three different processes: afterslip, viscoelastic relaxation, and plate interface relocking. Their approach, called straightening, assumes that the afterslip motion comes from a nonmigrating afterslip distribution on the plate interface that decays linearly with time. Under these assumptions, the individual contributions of each process can be teased out by finding the combination of relocking and viscoelastic relaxation model predictions that when subtracted from the recorded signal, best reproduces the expected unstraightened afterslip signal features. In other words, they held afterslip to a fixed pattern so that they could vary other parameters to estimate the other components.

    Following this method, the researchers discovered that plate interface relocking was indeed the dominant process causing curvature in the signal. Moreover, they were also able to confirm the results of past lab experiments proposing that relocking occurs rapidly, less than a year after an earthquake takes place.

    Overall, the study helps provide a more accurate picture of the tectonic processes underlying signals detected after a megathrust earthquake. The researchers hope that in the future their method can be tested at the sites of other megathrust earthquakes, especially those that are well observed by GPS networks.

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

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

    Eos news bloc

    Eos

    10.10.16
    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.

    1
    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.

    2
    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 1:39 pm on September 29, 2016 Permalink | Reply
    Tags: , , Eos, Radio waves, Surface plasmons   

    From Eos: “Earthquakes Could Funnel Radio Waves to Dark Zones in Mountains” 

    Eos news bloc

    Eos

    9.29.16
    Leah Crane

    1
    Just like visible light, radio waves leave shadows on the opposite sides of obstacles like mountains. Modeling based on the Tsurugidake peak in Japan, pictured here, shows that radio waves could still travel into these shadowed areas with the help of surface plasmons. Credit: Alpsdake

    Similar to how a mountain in the sunlight casts a shadow, large obstacles can create dark zones for radio waves. Unlike with visible light, though, scientists think radio waves could travel along the ground up a mountain peak and into the “shadowed” area, thanks to a natural phenomenon known as a surface plasmon. Because surface plasmons are related to underground stress, this could be used to help monitor seismic activity.

    Surface plasmons, also called surface plasma waves, are products of electromagnetic waves moving over Earth’s surface. If mobile positive electrical charges (similar to electrons, but positively charged instead of negatively) can travel, they could interact with radio signals and flow to the tops of nearby mountains, oscillating in time with the radio waves. This collective oscillation is the surface plasmon, moving like a breeze over a lake.

    Because surface plasmons need energy to oscillate, they can be induced only when the plasma frequencies of the surface electrical charges are higher than that of the radio wave passing by: The greater the difference between the plasma frequency and the radio wave frequency is, the stronger the surface plasmon is.

    The positive charges necessary for a surface plasmon are released when rocks underground are subjected to stress. This seismic stress forces positive charge carriers to the surface, creating a plasma layer at the highest parts of the landscape. Because strong seismic activity corresponds to more tectonic stress and therefore more charge carriers (and thus a higher plasma frequency), there can be no surface plasmon without an earthquake. If there are enough of these positive charges on the ground’s surface, they could absorb and reradiate the energy from radio waves, causing them to randomly scatter from a mountain’s rough terrain.

    In a new study, Fujii shows that when a surface plasmon is made up of a particularly high density of positive charges, it could propagate up over a mountain peak and down the other side, reradiating electromagnetic waves into the shadowed region of the mountain. Using both an ideal cone structure and a model of the Tsurugidake peak in Japan, the team’s supercomputer shows that surface plasmons scattered over surface bumps and mountain peaks that randomly reradiate incoming radio waves into a narrowly convergent, beam-like wave, focused on a small area.

    The reradiated waves can reach areas that would have been inaccessible to the original signal. By monitoring these anomalous radio waves, researchers expect that scientists could monitor seismic activity over larger areas. (Radio Science, doi:10.1002/2016RS006068, 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.

     
c
Compose new post
j
Next post/Next comment
k
Previous post/Previous comment
r
Reply
e
Edit
o
Show/Hide comments
t
Go to top
l
Go to login
h
Show/Hide help
shift + esc
Cancel
%d bloggers like this: