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  • richardmitnick 11:44 am on March 22, 2017 Permalink | Reply
    Tags: , Geology, , Remnants of Earth’s Original Crust Found in Canada   

    From NOVA: “Remnants of Earth’s Original Crust Found in Canada” 

    PBS NOVA

    NOVA

    16 Mar 2017
    Annette Choi

    Two geologists studying North America’s oldest rocks have uncovered ancient minerals that are remnants of the Earth’s original crust which first formed more than 4.2 billion years ago.

    These rocks appear to preserve the signature of an early Earth that presumably took shape within the first few hundred million years of Earth’s history.

    Jonathan O’Neil and Richard Carlson uncovered the samples on a trek to the northeastern part of Canada to study the Canadian Shield formation, a large area of exposed continental crust underlying, centered on Hudson Bay, which was already known to contain some of the oldest parts of North America. O’Neil calls it the core or nucleus of the North American continent. “That spot on the shore of Hudson Bay has this older flavor to it, this older chemical signature.”

    1
    A view of 2.7 billion-year-old continental crust produced by the recycling of more than 4.2 billion-year-old rocks. Image credit: Alexandre Jean

    To O’Neil, an assistant professor of geology at the University of Ottawa, rocks are like books that allow geologists to study their compositions and to learn about the conditions in which they form. But as far as rock records go, the first billion years of the Earth’s history is almost completely unrepresented.

    “We’re missing basically all the crust that was present about 4.4 billion years ago. The question we’re after with our study is: what happened to it?” said Carlson, director of the Carnegie Institution for Science. “Part of the goal of this was simply to see how much crust was present before and see what that material was.”

    While most of the samples are made up of a 2.7 billion-year-old granite, O’Neil said these rocks were likely formed by the recycling of a much older crust. “The Earth is very, very good at recycling itself. It constantly recycles and remelts and reworks its own crust,” O’Neil said. He and Carlson arrived at their conclusion by determining the age of the samples using isotopic dating and then adding on the estimate of how long it would have taken for the recycled bits to have originally formed.

    O’Neil and Carlson’s estimate relies on the theory that granite forms through the reprocessing of older rocks. “That is a possibility that they form that way, but that is not the only way you can form these rocks,” said Oliver Jagoutz, an associate professor of geology at the Massachusetts Institute of Technology. “Their interpretation really strongly depends on their assumption that that is the way these granites form.

    The nature of Earth’s first crust has largely remained a mystery because there simply aren’t very many rocks that have survived the processes that can erase their signature from the geologic record. Crust is often forced back into the Earth’s interior, which then melts it down, the geologic equivalent of sending silver jewelry back into the forge. That makes it challenging for geologists to reconstruct how the original looked.

    These new findings give geologists an insight into the evolution of the oldest elements of Earth’s outer layer and how it has come to form North America. “We’re recycling extremely, extremely old crust to form our stable continent,” O’Neil said.

    See the full article here .

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    NOVA is the highest rated science series on television and the most watched documentary series on public television. It is also one of television’s most acclaimed series, having won every major television award, most of them many times over.

     
  • richardmitnick 1:59 pm on March 17, 2017 Permalink | Reply
    Tags: , , , Geology, 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]

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    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 .

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    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 4:43 pm on March 1, 2017 Permalink | Reply
    Tags: 3.77-billion-year-old fossils stake new claim to oldest evidence of life, , , , Geology, , Hydrothermal vents, , ,   

    From Science: “3.77-billion-year-old fossils stake new claim to oldest evidence of life” 

    AAAS
    Science Magazine

    Mar. 1, 2017
    Carolyn Gramling

    1
    These tubelike structures, formed of an iron ore called hematite, may be microfossils of 3.77-billion-year-old life at ancient hydrothermal vents.

    Life on Earth may have originated in the sunless depths of the ocean rather than shallow seas. In a new study, scientists studying 3.77-billion-year-old rocks have found tubelike fossils similar to structures found at hydrothermal vents, which host thriving biological communities. That would make them more than 300 million years older than the most ancient signs of life on Earth—fossilized microbial mats called stromatolites that grew in shallow seas. Other scientists are skeptical about the new claims.

    “The authors offer a convincing set of observations that could signify life,” says Kurt Konhauser, a geomicrobiologist at the University of Alberta in Edmonton, Canada, who was not involved in the study. But “at present, I do not see a way in which we will definitively prove ancient life at 3.8 billion years ago.”

    When life first emerged on Earth has been an enduring and frustrating mystery. The planet is 4.55 billion years old, but thanks to plate tectonics and the constant recycling of Earth’s crust, only a handful of rock outcrops remain that are older than 3 billion years, including 3.7-billion-year-old formations in Greenland’s Isua Greenstone Belt. And these rocks tend to be twisted up and chemically altered by heat and pressure, making it devilishly difficult to detect unequivocal signs of life.

    “It’s a challenge in rocks that have been this messed up,” says Abigail Allwood, a geologist with NASA’s Jet Propulsion Laboratory in Pasadena, California, who was also not involved in the study. “There’s only so much you can do with them.”

    Nevertheless, researchers have searched through these most ancient rocks for structural or chemical relics that may have lingered. Last year, for example, scientists reported identifying odd reddish peaks in 3.7-billion-year-old rocks in Greenland that may be the product of stromatolites, though many doubted that interpretation. The best evidence for these fossilized algal mats comes from 3.4-billion-year-old rocks in Australia, generally thought of as the strongest evidence for early life on Earth.

    But some scientists think ocean life may have begun earlier—and deeper. In the modern ocean, life thrives in and around the vents that form near seafloor spreading ridges or subduction zones—places where Earth’s tectonic plates are pulling apart or grinding together. The vents spew seawater, superheated by magma in the ocean crust and laden with metal minerals such as iron sulfide. As the water cools, the metals settle out, forming towering spires and chimneys. The mysterious ecosystem that inhabits this sunless, harsh environment includes bacteria and giant tube worms that don’t derive energy from photosynthesis. Such hardy communities, scientists have suggested, may not only have thrived on early Earth, but may also be an analog for life on other planets.

    Now, a team led by geochemist Dominic Papineau of University College London and his Ph.D. student Matthew Dodd says it has found clear evidence of such ancient vent life. The clues come from ancient rocks in northern Quebec in Canada that are at least 3.77 billion years old and may be even older than 4 billion years. Dodd examined hair-thin slices of rock from this formation and found intriguing features: tiny tubes composed of an iron oxide called hematite, as well as filaments of hematite that branch out and sometimes terminate into large knobs.

    Filaments and tubes are common features in more recent fossils that are attributed to the activity of iron-oxidizing bacteria at seafloor hydrothermal vents. Papineau was initially skeptical. However, he says, “within a year [Dodd] had found so much compelling evidence that I was convinced.”

    The team also identified carbonate “rosettes,” tiny concentric rings that contain traces of life’s building blocks including carbon, calcium, and phosphorus; and tiny, round granules of graphite, a form of carbon. Such rosettes and granules had been observed previously in rocks of similar age, but whether they are biological in origin is hotly debated. The rosettes can form nonbiologically from a series of chemical reactions, but Papineau says the rosettes in the new study contain a calcium phosphate mineral called apatite, which strongly suggests the presence of microorganisms. The graphite granules may represent part of a complicated chemical chain reaction mediated by the bacteria, he says. Taken together, the structures and their chemistry point to a biological origin near a submarine hydrothermal vent, the team reports online today in Nature. That would make them among the oldest signs of life on Earth—and, depending on the actual age of the rocks, possibly the oldest.

    That doesn’t necessarily mean that life originated in deep waters rather than in shallow seas, Papineau says. “It’s not necessarily mutually exclusive—if we are ready to accept the fact that life diversified very early.” Both the iron-oxidizing bacteria and the photosynthetic cyanobacteria that build stromatolite mats could have evolved from an earlier ancestor, he says.

    But researchers like Konhauser remain skeptical of the paper’s conclusion. For example, he says, the observed hematite tubes and filaments are similar to structures associated with iron-oxidizing bacteria, “but of course that does not mean the [3.77-] billion-year-old structures are cells.” Moreover, he notes, if the tubes were formed by iron-oxidizing bacteria, they would need oxygen, in short supply at this early moment in Earth’s history. It implies that photosynthetic bacteria were already around to produce it. But it’s still unclear how oxygen would get down to the depths of early Earth’s ocean. The cyanobacteria that make stromatolites, on the other hand, make oxygen rather than consume it.

    The new paper makes “a more detailed case than has been presented previously,” Allwood says. Most previous reports of possible signs of life older than about 3.5 billion years have been questioned, she adds—not because life didn’t exist, but because it’s just so difficult to prove the further back in time you go in the rock record. “There’s still quite a bit of room for doubt.”

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  • richardmitnick 8:45 am on February 23, 2017 Permalink | Reply
    Tags: , , evidence of a ‘chaotic solar system’, From rocks in Colorado, Geology, The planets in our solar system behave differently than the prevailing theory that the they orbit like clockwork in a quasiperiodic manner   

    From Wisconsin: “From rocks in Colorado, evidence of a ‘chaotic solar system’” 

    U Wisconsin

    University of Wisconsin

    February 22, 2017
    Terry Devitt
    trdevitt@wisc.edu

    1
    Alternating layers of shale and limestone near Big Bend, Texas, characteristic of the rock laid down at the bottom of a shallow ocean during the late Cretaceous period. The rock holds definitive geologic evidence that the planets in our solar system behave differently than the prevailing theory that the they orbit like clockwork in a quasiperiodic manner. Photo: Bradley Sageman

    Plumbing a 90 million-year-old layer cake of sedimentary rock in Colorado, a team of scientists from the University of Wisconsin–Madison and Northwestern University has found evidence confirming a critical theory of how the planets in our solar system behave in their orbits around the sun.

    The finding, published Feb. 23, 2017 in the journal Nature, is important because it provides the first hard proof for what scientists call the “chaotic solar system,” a theory proposed in 1989 to account for small variations in the present conditions of the solar system. The variations, playing out over many millions of years, produce big changes in our planet’s climate — changes that can be reflected in the rocks that record Earth’s history.

    2
    Geoscience Professor Stephen Meyers. © Gigi Cohen

    The discovery promises not only a better understanding of the mechanics of the solar system, but also a more precise measuring stick for geologic time. Moreover, it offers a better understanding of the link between orbital variations and climate change over geologic time scales.

    Using evidence from alternating layers of limestone and shale laid down over millions of years in a shallow North American seaway at the time dinosaurs held sway on Earth, the team led by UW–Madison Professor of Geoscience Stephen Meyers and Northwestern University Professor of Earth and Planetary Sciences Brad Sageman discovered the 87 million-year-old signature of a “resonance transition” between Mars and Earth. A resonance transition is the consequence of the “butterfly effect” in chaos theory. It plays on the idea that small changes in the initial conditions of a nonlinear system can have large effects over time.

    In the context of the solar system, the phenomenon occurs when two orbiting bodies periodically tug at one another, as occurs when a planet in its track around the sun passes in relative proximity to another planet in its own orbit. These small but regular ticks in a planet’s orbit can exert big changes on the location and orientation of a planet on its axis relative to the sun and, accordingly, change the amount of solar radiation a planet receives over a given area. Where and how much solar radiation a planet gets is a key driver of climate.


    This animation shows a chaotic solar system and changing planetary orbits playing out over billions of years, illustrating the slight chance in the distant future of planetary collisions. Geologic evidence was recently found to confirm the idea that the planets in our solar system do not orbit the sun like clockwork in a quasiperiodic manner, as has been believed since the 18th century. Credit: Jacques Laskar

    “The impact of astronomical cycles on climate can be quite large,” explains Meyers, noting as an example the pacing of the Earth’s ice ages, which have been reliably matched to periodic changes in the shape of Earth’s orbit, and the tilt of our planet on its axis. “Astronomical theory permits a very detailed evaluation of past climate events that may provide an analog for future climate.”

    To find the signature of a resonance transition, Meyers, Sageman and UW–Madison graduate student Chao Ma, whose dissertation work this comprises, looked to the geologic record in what is known as the Niobrara Formation in Colorado. The formation was laid down layer by layer over tens of millions of years as sediment was deposited on the bottom of a vast seaway known as the Cretaceous Western Interior Seaway. The shallow ocean stretched from what is now the Arctic Ocean to the Gulf of Mexico, separating the eastern and western portions of North America.

    “The Niobrara Formation exhibits pronounced rhythmic rock layering due to changes in the relative abundance of clay and calcium carbonate,” notes Meyers, an authority on astrochronology, which utilizes astronomical cycles to measure geologic time. “The source of the clay (laid down as shale) is from weathering of the land surface and the influx of clay to the seaway via rivers. The source of the calcium carbonate (limestone) is the shells of organisms, mostly microscopic, that lived in the water column.”

    Meyers explains that while the link between climate change and sedimentation can be complex, the basic idea is simple: “Climate change influences the relative delivery of clay versus calcium carbonate, recording the astronomical signal in the process. For example, imagine a very warm and wet climate state that pumps clay into the seaway via rivers, producing a clay-rich rock or shale, alternating with a drier and cooler climate state which pumps less clay into the seaway and produces a calcium carbonate-rich rock or limestone.”

    The new study was supported by grants from the National Science Foundation. It builds on a meticulous stratigraphic record and important astrochronologic studies of the Niobrara Formation, the latter conducted in the dissertation work of Robert Locklair, a former student of Sageman’s at Northwestern.

    Dating of the Mars-Earth resonance transition found by Ma, Meyers and Sageman was confirmed by radioisotopic dating, a method for dating the absolute ages of rocks using known rates of radioactive decay of elements in the rocks. In recent years, major advances in the accuracy and precision of radioisotopic dating, devised by UW–Madison geoscience Professor Bradley Singer and others, have been introduced and contribute to the dating of the resonance transition.

    The motions of the planets around the sun has been a subject of deep scientific interest since the advent of the heliocentric theory — the idea that the Earth and planets revolve around the sun — in the 16th century. From the 18th century, the dominant view of the solar system was that the planets orbited the sun like clockwork, having quasiperiodic and highly predictable orbits. In 1988, however, numerical calculations of the outer planets showed Pluto’s orbit to be “chaotic” and the idea of a chaotic solar system was proposed in 1989 by astronomer Jacques Laskar, now at the Paris Observatory.

    Following Laskar’s proposal of a chaotic solar system, scientists have been looking in earnest for definitive evidence that would support the idea, says Meyers.

    “Other studies have suggested the presence of chaos based on geologic data,” says Meyers. “But this is the first unambiguous evidence, made possible by the availability of high-quality, radioisotopic dates and the strong astronomical signal preserved in the rocks.”

    See the full article here .

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    In achievement and prestige, the University of Wisconsin–Madison has long been recognized as one of America’s great universities. A public, land-grant institution, UW–Madison offers a complete spectrum of liberal arts studies, professional programs and student activities. Spanning 936 acres along the southern shore of Lake Mendota, the campus is located in the city of Madison.

     
  • richardmitnick 7:15 am on February 21, 2017 Permalink | Reply
    Tags: , Chemosynthesis, Geology, , , Strange Life Has Been Found Trapped Inside These Giant Cave Crystals   

    From Science Alert: “Strange Life Has Been Found Trapped Inside These Giant Cave Crystals” 

    ScienceAlert

    Science Alert

    20 FEB 2017
    BEC CREW

    1
    Alexander Van Driessche/Wikipedia

    A NASA scientist just woke them up.

    Strange microbes have been found inside the massive, subterranean crystals of Mexico’s Naica Mine, and researchers suspect they’ve been living there for up to 50,000 years.

    The ancient creatures appear to have been dormant for thousands of years, surviving in tiny pockets of liquid within the crystal structures. Now, scientists have managed to extract them – and wake them up.

    “These organisms are so extraordinary,” astrobiologist Penelope Boston, director of the NASA Astrobiology Institute, said on Friday at the annual meeting of the American Association for the Advancement of Science (AAAS) in Boston.

    The Cave of Crystals in Mexico’s Naica Mine might look incredibly beautiful, but it’s one of the most inhospitable places on Earth, with temperatures ranging from 45 to 65°C (113 to 149°F), and humidity levels hitting more than 99 percent.

    Not only are temperatures hellishly high, but the environment is also oppressively acidic, and confined to pitch-black darkness some 300 metres (1,000 feet) below the surface.

    2
    Peter Williams/Flickr

    In lieu of any sunlight, microbes inside the cave can’t photosynthesise – instead, they perform chemosynthesis using minerals like iron and sulphur in the giant gypsum crystals, some of which stretch 11 metres (36 feet) long, and have been dated to half a million years old.

    Researchers have previously found life living inside the walls of the cavern and nearby the crystals – a 2013 expedition to Naica reported the discovery of creatures thriving in the hot, saline springs of the complex cave system.

    But when Boston and her team extracted liquid from the tiny gaps inside the crystals and sent them off to be analysed, they realised that not only was there life inside, but it was unlike anything they’d seen in the scientific record.

    They suspect the creatures had been living inside their crystal castles for somewhere between 10,000 and 50,000 years, and while their bodies had mostly shut down, they were still very much alive.

    “Other people have made longer-term claims for the antiquity of organisms that were still alive, but in this case these organisms are all very extraordinary – they are not very closely related to anything in the known genetic databases,” Boston told Jonathan Amos at BBC News.

    What’s perhaps most extraordinary about the find is that the researchers were able to ‘revive’ some of the microbes, and grow cultures from them in the lab.

    “Much to my surprise we got things to grow,” Boston told Sarah Knapton at The Telegraph. “It was laborious. We lost some of them – that’s just the game. They’ve got needs we can’t fulfil.”

    At this point, we should be clear that the discovery has yet to be published in a peer-reviewed journal, so until other scientists have had a chance to examine the methodology and findings, we can’t consider the discovery be definitive just yet.

    The team will also need to convince the scientific community that the findings aren’t the result of contamination – these microbes are invisible to the naked eye, which means it’s possible that they attached themselves to the drilling equipment and made it look like they came from inside the crystals.

    “I think that the presence of microbes trapped within fluid inclusions in Naica crystals is in principle possible,” Purificación López-García from the French National Centre for Scientific Research, who was part of the 2013 study that found life in the cave springs, told National Geographic.

    “[But] contamination during drilling with microorganisms attached to the surface of these crystals or living in tiny fractures constitutes a very serious risk,” she says. I am very skeptical about the veracity of this finding until I see the evidence.”

    That said, microbiologist Brent Christner from the University of Florida in Gainesville, who was also not involved in the research, thinks the claim isn’t as far-fetched as López-García is making it out to be, based on what previous studies have managed with similarly ancient microbes.

    “[R]eviving microbes from samples of 10,000 to 50,000 years is not that outlandish based on previous reports of microbial resuscitations in geological materials hundreds of thousands to millions of years old,” he told National Geographic.

    For their part, Boston and her team say they took every precaution to make sure their gear was sterilised, and cite the fact that the creatures they found inside the crystals were similar, but not identical to those living elsewhere in the cave as evidence to support their claims.

    “We have also done genetic work and cultured the cave organisms that are alive now and exposed, and we see that some of those microbes are similar but not identical to those in the fluid inclusions,” she said.

    Only time will tell if the results will bear out once they’re published for all to see, but if they are confirmed, it’s just further proof of the incredible hardiness of life on Earth, and points to what’s possible out there in the extreme conditions of space.

    See the full article here .

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  • richardmitnick 2:11 pm on February 3, 2017 Permalink | Reply
    Tags: , , Geology, Gondwana, Mauritius a continent?, ,   

    From Smithsonian: “Researchers Think They’ve Found a Mini Continent in the Indian Ocean” 

    smithsonian
    Smithsonian.com

    February 2, 2017
    Jason Daley

    1
    The beautiful Mauritius island may be hiding a chunk of continent. (Sapsiwai via iStock)

    About 200 million years ago, the supercontinent of Gondwana—essentially an an agglomeration of Africa, South America, India, Australia and Antarctica—began slowly ripping apart into the continents recognizable today. But a new study suggests that Gondwana spun out another continent that is now lost beneath the Indian Ocean.

    1
    Assemblage of continents, which constitute Gondwana. Image Credit: Griem (2007)

    As Alice Klein reports for New Scientist, researchers studying the earth’s crust found that parts of the Indian Ocean’s seafloor had slightly stronger gravitaitonal fields, suggesting that the crust might be thicker there.

    The island of Mauritius exhibited this extra oomph, which led Lewis Ashwal, a geologist at the University of the Witwatersrand, South Africa, and his colleagues to propose that the island was sitting atop a sunken chunk of continent.

    The researchers studied the geology of the island and rocks spewed out during periods of ancient volcanism. One particular mineral they were looking for are zircons, tough minerals that contains bits of uranium and thorium. The mineral can last billions of years and geologists can use these to acurately date rocks.

    The search paid off. The researchers recovered zircons as old as 3 billion years, Ashwal says in a press release. But the island rocks are no older than 9 million years old. The researchers argue that the old rock is evidence that the island is sitting on a much older crust that was once part of a continent. The zircons are remnants of this much older rock and were likely pushed up by volcanic activity. They published their results in the journal Nature Communications.

    According to Paul Hetzel at Seeker, researchers had previously discovered zircons on Mauritius’ beaches, but were unable to rule out the possibility that they were brought there by the ocean. The new finding confirms that the zircon comes from the island itself.

    Mauritia was likely a small continent, about a quarter the size of Madagascar, reports Klein. As the Indian plate and the Madagascar plate pulled apart, it stretched and broke up the small continent, spreading chunks of it across the Indian Ocean.

    3
    One of the 3-billion-year-old zircon crystals discovered on Mauritius (Wits University )

    “According to the new results, this break-up did not involve a simple splitting of the ancient super-continent of Gondwana, but rather, a complex splintering took place with fragments of continental crust of variable sizes left adrift within the evolving Indian Ocean basin,” Ashwal says in the press release [phys.org].

    Klein reports that other islands in the Indian Ocean, including Cargados Carajos, Laccadive and the Chagos islands might also exist on top of fragments of the continent now dubbed Mauritia.

    Surprisingly, this may not be the only lost continent out there. In 2015, researchers at the University of Oslo found evidence that Iceland may sit on top of a sunken slice of crust. And in 2011, researchers found evidence that a micro-continent has existed off the coast of Scotland for about a million years.

    See the full article here .

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    Smithsonian magazine and Smithsonian.com place a Smithsonian lens on the world, looking at the topics and subject matters researched, studied and exhibited by the Smithsonian Institution — science, history, art, popular culture and innovation — and chronicling them every day for our diverse readership.

     
  • richardmitnick 9:18 am on January 23, 2017 Permalink | Reply
    Tags: , Complex cells that go back maybe 1 ¾ billion years, Conditions right for complex life may have come and gone in Earth’s distant past, Geology, Selenium, ,   

    From U Washington: “Conditions right for complex life may have come and gone in Earth’s distant past” 

    U Washington

    University of Washington

    January 17, 2017
    Peter Kelley

    1
    This is a 1.9-billion-year-old stromatolite — or mound made by microbes that lived in shallow water — called the Gunflint Formation in northern Minnesota. The environment of the oxygen “overshoot” described in research by Michael Kipp, Eva Stüeken and Roger Buick may have included this sort of oxygen-rich setting that is suitable for complex life.Eva Stüeken.

    Conditions suitable to support complex life may have developed in Earth’s oceans — and then faded — more than a billion years before life truly took hold, a new University of Washington-led study has found.

    The findings, based on using the element selenium as a tool to measure oxygen in the distant past, may also benefit the search for signs of life beyond Earth.

    In a paper published Jan. 18 in the Proceedings of the National Academy of Sciences, lead author Michael Kipp, a UW doctoral student in Earth and space sciences, analyzed isotopic ratios of the element selenium in sedimentary rocks to measure the presence of oxygen in Earth’s atmosphere between 2 and 2.4 billion years ago.

    Kipp’s UW coauthors are former Earth and space sciences postdoctoral researcher Eva Stüeken — now a faculty member at the University of St. Andrews in Scotland — and professor Roger Buick, who is also a faculty member with the UW Astrobiology Program. Their other coauthor is Andrey Bekker of the University of California, Riverside, whose original hypothesis this work helps confirm, the researchers said.

    “There is fossil evidence of complex cells that go back maybe 1 ¾ billion years,” said Buick. “But the oldest fossil is not necessarily the oldest one that ever lived – because the chances of getting preserved as a fossil are pretty low.

    “This research shows that there was enough oxygen in the environment to have allowed complex cells to have evolved, and to have become ecologically important, before there was fossil evidence.” He added, “That doesn’t mean that they did — but they could have.”

    Kipp and Stüeken learned this by analyzing selenium traces in pieces of sedimentary shale from the particular time periods using mass spectrometry in the UW Isotope Geochemistry Lab, to discover if selenium had been changed by the presence of oxygen, or oxidized. Oxidized selenium compounds can then get reduced, causing a shift in the isotopic ratios which gets recorded in the rocks. The abundance of selenium also increases in the rocks when lots of oxygen is present.

    Buick said it was previously thought that oxygen on Earth had a history of “none, then some, then a lot. But what it looks like now is, there was a period of a quarter of a billion years or so where oxygen came quite high, and then sunk back down again.”

    The oxygen’s persistence over a long stretch of time is an important factor, Kipp stressed: “Whereas before and after maybe there were transient environments that could have occasionally supported these organisms, to get them to evolve and be a substantial part of the ecosystem, you need oxygen to persist for a long time.”

    Stüeken said such an oxygen increase has been guessed at previously, but it was unclear how widespread it was. This research creates a clearer picture of what this oxygen “overshoot” looked like: “That it was moderately significant in the atmosphere and surface ocean – but not at all in the deep ocean.”

    What caused oxygen levels to soar this way only to crash just as dramatically?

    “That’s the million-dollar question,” Stüeken said. “It’s unknown why it happened, and why it ended.”

    “It is an unprecedented time in Earth’s history,” Buick said. “If you look at the selenium isotope record through time, it’s a unique interval. If you look before and after, everything’s different.”

    The use of selenium — named after the Greek word for moon — as an effective tool to probe oxygen levels in deep time could also be helpful in the search for oxygen — and so perhaps life — beyond Earth, the researchers said.

    Future generations of space-based telescopes, they note, will give astronomers information about the atmospheric composition of distant planets. Some of these could be approximately Earth-sized and potentially have appreciable atmospheric oxygen.

    “The recognition of an interval in Earth’s distant past that may have had near-modern oxygen levels, but far different biological inhabitants, could mean that the remote detection of an oxygen-rich world is not necessarily proof of a complex biosphere,” Kipp said.

    Buick concluded, “This is a new way of measuring oxygen in a planet’s historical past, to see whether complex life could have evolved there and persisted long enough to evolve into intelligent beings.”

    The research was funded by grants from the National Science Foundation, NASA and the NASA Astrobiology Institute and Canada’s Natural Sciences and Engineering Research Council.

    See the full article here .

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    The University of Washington is one of the world’s preeminent public universities. Our impact on individuals, on our region, and on the world is profound — whether we are launching young people into a boundless future or confronting the grand challenges of our time through undaunted research and scholarship. Ranked number 10 in the world in Shanghai Jiao Tong University rankings and educating more than 54,000 students annually, our students and faculty work together to turn ideas into impact and in the process transform lives and our world. For more about our impact on the world, every day.

    So what defines us — the students, faculty and community members at the University of Washington? Above all, it’s our belief in possibility and our unshakable optimism. It’s a connection to others, both near and far. It’s a hunger that pushes us to tackle challenges and pursue progress. It’s the conviction that together we can create a world of good. Join us on the journey.

     
  • richardmitnick 12:07 pm on December 22, 2016 Permalink | Reply
    Tags: , Explorers Find Passage to Earth’s Dark Age, Geology,   

    From Quanta: “Explorers Find Passage to Earth’s Dark Age” 

    Quanta Magazine
    Quanta Magazine

    December 22, 2016
    Natalie Wolchover

    1
    Earth scientists hope that their growing knowledge of the planet’s early history will shed light on poorly understood features seen today, from continents to geysers. Eric King

    Geochemical signals from deep inside Earth are beginning to shed light on the planet’s first 50 million years, a formative period long viewed as inaccessible to science.

    In August, the geologist Matt Jackson left California with his wife and 4-year-old daughter for the fjords of northwest Iceland, where they camped as he roamed the outcrops and scree slopes by day in search of little olive-green stones called olivine.

    A sunny young professor at the University of California, Santa Barbara, with a uniform of pearl-snap shirts and well-utilized cargo shorts, Jackson knew all the best hunting grounds, having first explored the Icelandic fjords two years ago. Following sketchy field notes handed down by earlier geologists, he covered 10 or 15 miles a day, past countless sheep and the occasional farmer. “Their whole lives they’ve lived in these beautiful fjords,” he said. “They look up to these black, layered rocks, and I tell them that each one of those is a different volcanic eruption with a lava flow. It blows their minds!” He laughed. “It blows my mind even more that they never realized it!”

    The olivine erupted to Earth’s surface in those very lava flows between 10 and 17 million years ago. Jackson, like many geologists, believes that the source of the eruptions was the Iceland plume, a hypothetical upwelling of solid rock that may rise, like the globules in a lava lamp, from deep inside Earth. The plume, if it exists, would now underlie the active volcanoes of central Iceland. In the past, it would have surfaced here at the fjords, back in the days when here was there — before the puzzle-piece of Earth’s crust upon which Iceland lies scraped to the northwest.

    Other modern findings [Nature]about olivine from the region suggest that it might derive from an ancient reservoir of minerals at the base of the Iceland plume that, over billions of years, never mixed with the rest of Earth’s interior. Jackson hoped the samples he collected would carry a chemical message from the reservoir and prove that it formed during the planet’s infancy — a period that until recently was inaccessible to science.

    After returning to California, he sent his samples to Richard Walker to ferret out that message. Walker, a geochemist at the University of Maryland, is processing the olivine to determine the concentration of the chemical isotope tungsten-182 in the rock relative to the more common isotope, tungsten-184. If Jackson is right, his samples will join a growing collection of rocks from around the world whose abnormal tungsten isotope ratios have completely surprised scientists. These tungsten anomalies reflect processes that could only have occurred within the first 50 million years of the solar system’s history, a formative period long assumed to have been wiped from the geochemical record by cataclysmic collisions that melted Earth and blended its contents.

    The anomalies “are giving us information about some of the earliest Earth processes,” Walker said. “It’s an alternative universe from what geochemists have been working with for the past 50 years.”

    2
    Matt Jackson and his family with a local farmer in northwest Iceland. Courtesy of Matt Jackson.

    The discoveries are sending geologists like Jackson into the field in search of more clues to Earth’s formation — and how the planet works today. Modern Earth, like early Earth, remains poorly understood, with unanswered questions ranging from how volcanoes work and whether plumes really exist to where oceans and continents came from, and what the nature and origin might be of the enormous structures, colloquially known as “blobs,” that seismologists detect deep down near Earth’s core. All aspects of the planet’s form and function are interconnected. They’re also entangled with the rest of the solar system. Any attempt, for instance, to explain why tectonic plates cover Earth’s surface like a jigsaw puzzle must account for the fact that no other planet in the solar system has plates. To understand Earth, scientists must figure out how, in the context of the solar system, it became uniquely earthlike. And that means probing the mystery of the first tens of millions of years.

    “You can think about this as an initial-conditions problem,” said Michael Manga, a geophysicist at the University of California, Berkeley, who studies geysers and volcanoes. “The Earth we see today evolved from something. And there’s lots of uncertainty about what that initial something was.”

    Pieces of the Puzzle

    On one of an unbroken string of 75-degree days in Santa Barbara the week before Jackson left for Iceland, he led a group of earth scientists on a two-mile beach hike to see some tar dikes — places where the sticky black material has oozed out of the cliff face at the back of the beach, forming flabby, voluptuous folds of faux rock that you can dent with a finger. The scientists pressed on the tar’s wrinkles and slammed rocks against it, speculating about its subterranean origin and the ballpark range of its viscosity. When this reporter picked up a small tar boulder to feel how light it was, two or three people nodded approvingly.

    A mix of geophysicists, geologists, mineralogists, geochemists and seismologists, the group was in Santa Barbara for the annual Cooperative Institute for Dynamic Earth Research (CIDER) workshop at the Kavli Institute for Theoretical Physics. Each summer, a rotating cast of representatives from these fields meet for several weeks at CIDER to share their latest results and cross-pollinate ideas — a necessity when the goal is understanding a system as complex as Earth.

    Earth’s complexity, how special it is, and, above all, the black box of its initial conditions have meant that, even as cosmologists map the universe and astronomers scan the galaxy for Earth 2.0, progress in understanding our home planet has been surprisingly slow. As we trudged from one tar dike to another, Jackson pointed out the exposed sedimentary rock layers in the cliff face — some of them horizontal, others buckled and sloped. Amazingly, he said, it took until the 1960s for scientists to even agree that sloped sediment layers are buckled, rather than having piled up on an angle. Only then was consensus reached on a mechanism to explain the buckling and the ruggedness of Earth’s surface in general: the theory of plate tectonics.

    Projecting her voice over the wind and waves, Carolina Lithgow-Bertelloni, a geophysicist from University College London who studies tectonic plates, credited the German meteorologist Alfred Wegener for first floating the notion of continental drift in 1912 to explain why Earth’s landmasses resemble the dispersed pieces of a puzzle. “But he didn’t have a mechanism — well, he did, but it was crazy,” she said.

    3
    Earth scientists on a beach hike in Santa Barbara County, California. Natalie Wolchover/Quanta Magazine

    A few years later, she continued, the British geologist Sir Arthur Holmes convincingly argued that Earth’s solid-rock mantle flows fluidly on geological timescales, driven by heat radiating from Earth’s core; he speculated that this mantle flow in turn drives surface motion. More clues came during World War II. Seafloor magnetism, mapped for the purpose of hiding submarines, suggested that new crust forms at the mid-ocean ridge — the underwater mountain range that lines the world ocean like a seam — and spreads in both directions to the shores of the continents. There, at “subduction zones,” the oceanic plates slide stiffly beneath the continental plates, triggering earthquakes and carrying water downward, where it melts pockets of the mantle. This melting produces magma that rises to the surface in little-understood fits and starts, causing volcanic eruptions. (Volcanoes also exist far from any plate boundaries, such as in Hawaii and Iceland. Scientists currently explain this by invoking the existence of plumes, which researchers like Walker and Jackson are starting to verify and map using isotope studies.)

    The physical description of the plates finally came together in the late 1960s, Lithgow-Bertelloni said, when the British geophysicist Dan McKenzie and the American Jason Morgan separately proposed a quantitative framework for modeling plate tectonics on a sphere.

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

    Other than their existence, almost everything about the plates remains in contention. For instance, what drives their lateral motion? Where do subducted plates end up — perhaps these are the blobs? — and how do they affect Earth’s interior dynamics? Why did Earth’s crust shatter into plates in the first place when no other planetary surface in the solar system did? Also completely mysterious is the two-tier architecture of oceanic and continental plates, and how oceans and continents came to ride on them — all possible prerequisites for intelligent life. Knowing more about how Earth became earthlike could help us understand how common earthlike planets are in the universe and thus how likely life is to arise.

    The continents probably formed, Lithgow-Bertelloni said, as part of the early process by which gravity organized Earth’s contents into concentric layers: Iron and other metals sank to the center, forming the core, while rocky silicates stayed in the mantle. Meanwhile, low-density materials buoyed upward, forming a crust on the surface of the mantle like soup scum. Perhaps this scum accumulated in some places to form continents, while elsewhere oceans materialized.

    Figuring out precisely what happened and the sequence of all of these steps is “more difficult,” Lithgow-Bertelloni said, because they predate the rock record and are “part of the melting process that happens early on in Earth’s history — very early on.”

    Until recently, scientists knew of no geochemical traces from so long ago, and they thought they might never crack open the black box from which Earth’s most glorious features emerged. But the subtle anomalies in tungsten and other isotope concentrations are now providing the first glimpses of the planet’s formation and differentiation. These chemical tracers promise to yield a combination timeline-and-map of early Earth, revealing where its features came from, why, and when.

    A Sketchy Timeline

    Humankind’s understanding of early Earth took its first giant leap when Apollo astronauts brought back rocks from the moon: our tectonic-less companion whose origin was, at the time, a complete mystery.

    The rocks “looked gray, very much like terrestrial rocks,” said Fouad Tera, who analyzed lunar samples at the California Institute of Technology between 1969 and 1976. But because they were from the moon, he said, they created “a feeling of euphoria” in their handlers. Some interesting features did eventually show up: “We found glass spherules — colorful, beautiful — under the microscope, green and yellow and orange and everything,” recalled Tera, now 85. The spherules probably came from fountains that gushed from volcanic vents when the moon was young. But for the most part, he said, “the moon is not really made out of a pleasing thing — just regular things.”

    In hindsight, this is not surprising: Chemical analysis at Caltech and other labs indicated that the moon formed from Earth material, which appears to have gotten knocked into orbit when the 60 to 100 million-year-old proto-Earth collided with another protoplanet in the crowded inner solar system. This “giant impact” hypothesis of the moon’s formation [Science Direct], though still hotly debated [Nature]in its particulars, established a key step on the timeline of the Earth, moon and sun that has helped other steps fall into place.

    5
    A panorama of the Taurus-Littrow Valley created from photographs by Apollo 17 astronaut Eugene Cernan. Astronaut Harrison Schmitt is shown using a rake to collect samples. NASA

    Chemical analysis of meteorites is helping scientists outline even earlier stages of our solar system’s timeline, including the moment it all began.

    First, 4.57 billion years ago, a nearby star went supernova, spewing matter and a shock wave into space. The matter included radioactive elements that immediately began decaying, starting the clocks that isotope chemists now measure with great precision. As the shock wave swept through our cosmic neighborhood, it corralled the local cloud of gas and dust like a broom; the increase in density caused the cloud to gravitationally collapse, forming a brand-new star — our sun — surrounded by a placenta of hot debris.

    Over the next tens of millions of years, the rubble field surrounding the sun clumped into bigger and bigger space rocks, then accreted into planet parts called “planetesimals,” which merged into protoplanets, which became Mercury, Venus, Earth and Mars — the four rocky planets of the inner solar system today. Farther out, in colder climes, gas and ice accreted into the giant planets.

    6
    The planets of the solar system as depicted by a NASA computer illustration. Orbits and sizes are not shown to scale.
    Credit: NASA

    7
    Researchers use liquid chromatography to isolate elements for analysis. Rock samples dissolved in acid flow down ion-exchange columns, like the ones in Rick Carlson’s laboratory at the Carnegie Institution in Washington, to separate the elements. Mary Horan.

    The last of the Earth-melting “giant impacts” appears to have been the one that formed the moon; while subtracting the moon’s mass, the impactor was also the last major addition to Earth’s mass. Perhaps, then, this point on the timeline — at least 60 million years after the birth of the solar system and, counting backward from the present, at most 4.51 billion years ago — was when the geochemical record of the planet’s past was allowed to begin. “It’s at least a compelling idea to think that this giant impact that disrupted a lot of the Earth is the starting time for geochronology,” said Rick Carlson, a geochemist at the Carnegie Institution of Washington. In those first 60 million years, “the Earth may have been here, but we don’t have any record of it because it was just erased.”

    Another discovery from the moon rocks came in 1974. Tera, along with his colleague Dimitri Papanastassiou and their boss, Gerry Wasserburg, a towering figure in isotope cosmochemistry who died in June, combined many isotope analyses of rocks from different Apollo missions on a single plot, revealing a straight line called an “isochron” that corresponds to time. “When we plotted our data along with everybody else’s, there was a distinct trend that shows you that around 3.9 billion years ago, something massive imprinted on all the rocks on the moon,” Tera said.

    As the infant Earth navigated the crowded inner solar system, it would have experienced frequent, white-hot collisions, which were long assumed to have melted the entire planet into a global “magma ocean.” During these melts, gravity differentiated Earth’s liquefied contents into layers — core, mantle and crust. It’s thought that each of the global melts would have destroyed existing rocks, blending their contents and removing any signs of geochemical differences left over from Earth’s initial building blocks.

    The last of the Earth-melting “giant impacts” appears to have been the one that formed the moon; while subtracting the moon’s mass, the impactor was also the last major addition to Earth’s mass. Perhaps, then, this point on the timeline — at least 60 million years after the birth of the solar system and, counting backward from the present, at most 4.51 billion years ago — was when the geochemical record of the planet’s past was allowed to begin. “It’s at least a compelling idea to think that this giant impact that disrupted a lot of the Earth is the starting time for geochronology,” said Rick Carlson, a geochemist at the Carnegie Institution of Washington. In those first 60 million years, “the Earth may have been here, but we don’t have any record of it because it was just erased.”

    Another discovery from the moon rocks came in 1974. Tera, along with his colleague Dimitri Papanastassiou and their boss, Gerry Wasserburg, a towering figure in isotope cosmochemistry who died in June, combined many isotope analyses of rocks from different Apollo missions on a single plot, revealing a straight line called an “isochron” that corresponds to time. “When we plotted our data along with everybody else’s, there was a distinct trend that shows you that around 3.9 billion years ago, something massive imprinted on all the rocks on the moon,” Tera said.

    Wasserburg dubbed the event the “lunar cataclysm.” [Science Direct]. Now more often called the “late heavy bombardment,” it was a torrent of asteroids and comets that seems to have battered the moon 3.9 billion years ago, a full 600 million years after its formation, melting and chemically resetting the rocks on its surface. The late heavy bombardment surely would have rained down even more heavily on Earth, considering the planet’s greater size and gravitational pull. Having discovered such a momentous event in solar system history, Wasserburg left his younger, more reserved colleagues behind and “celebrated in Pasadena in some bar,” Tera said.

    As of 1974, no rocks had been found on Earth from the time of the late heavy bombardment. In fact, Earth’s oldest rocks appeared to top out at 3.8 billion years. “That number jumps out at you,” said Bill Bottke, a planetary scientist at the Southwest Research Institute in Boulder, Colorado. It suggests, Bottke said, that the late heavy bombardment might have melted whatever planetary crust existed 3.9 billion years ago, once again destroying the existing geologic record, after which the new crust took 100 million years to harden.

    In 2005, a group of researchers working in Nice, France, conceived of a mechanism to explain the late heavy bombardment — and several other mysteries about the solar system, including the curious configurations of Jupiter, Saturn, Uranus and Neptune, and the sparseness of the asteroid and Kuiper belts. Their “Nice model” [Nature] posits that the gas and ice giants suddenly destabilized in their orbits sometime after formation, causing them to migrate. Simulations by Bottke and others indicate that the planets’ migrations would have sent asteroids and comets scattering, initiating something very much like the late heavy bombardment. Comets that were slung inward from the Kuiper belt during this shake-up might even have delivered water to Earth’s surface, explaining the presence of its oceans.

    With this convergence of ideas, the late heavy bombardment became widely accepted as a major step on the timeline of the early solar system. But it was bad news for earth scientists, suggesting that Earth’s geochemical record began not at the beginning, 4.57 billion years ago, or even at the moon’s beginning, 4.51 billion years ago, but 3.8 billion years ago, and that most or all clues about earlier times were forever lost.

    Extending the Rock Record

    More recently, the late heavy bombardment theory and many other long-standing assumptions about the early history of Earth and the solar system have come into question, and Earth’s dark age has started to come into the light. According to Carlson, “the evidence for this 3.9 [billion-years-ago] event is getting less clear with time.” For instance, when meteorites are analyzed for signs of shock, “they show a lot of impact events at 4.2, 4.4 billion,” he said. “This 3.9 billion event doesn’t show up really strong in the meteorite record.” He and other skeptics of the late heavy bombardment argue that the Apollo samples might have been biased. All the missions landed on the near side of the moon, many in close proximity to the Imbrium basin (the moon’s biggest shadow, as seen from Earth), which formed from a collision 3.9 billion years ago. Perhaps all the Apollo rocks were affected by that one event, which might have dispersed the melt from the impact over a broad swath of the lunar surface. This would suggest a cataclysm that never occurred.

    8
    Lucy Reading-Ikkanda for Quanta Magazine

    Furthermore, the oldest known crust on Earth is no longer 3.8 billion years old. Rocks have been found in two parts of Canada dating to 4 billion and an alleged 4.28 billion years ago, refuting the idea that the late heavy bombardment fully melted Earth’s mantle and crust 3.9 billion years ago. At least some earlier crust survived.

    In 2008, Carlson and collaborators reported the evidence of 4.28 billion-year-old rocks in the Nuvvuagittuq greenstone belt in Canada. When Tim Elliott, a geochemist at the University of Bristol, read about the Nuvvuagittuq findings, he was intrigued to see that Carlson had used a dating method also used in earlier work by French researchers that relied on a short-lived radioactive isotope system called samarium-neodymium. Elliott decided to look for traces of an even shorter-lived system — hafnium-tungsten — in ancient rocks, which would point back to even earlier times in Earth’s history.

    The dating method works as follows: Hafnium-182, the “parent” isotope, has a 50 percent chance of decaying into tungsten-182, its “daughter,” every 9 million years (this is the parent’s “half-life”). The halving quickly reduces the parent to almost nothing; by 50 million years after the supernova that sparked the sun, virtually all the hafnium-182 would have become tungsten-182.

    That’s why the tungsten isotope ratio in rocks like Matt Jackson’s olivine samples can be so revealing: Any variation in the concentration of the daughter isotope, tungsten-182, measured relative to tungsten-184 must reflect processes that affected the parent, hafnium-182, when it was around — processes that occurred during the first 50 million years of solar system history. Elliott knew that this kind of geochemical information was previously believed to have been destroyed by early Earth melts and billions of years of subsequent mantle convection. But what if it wasn’t?

    Elliott contacted Stephen Moorbath, then an emeritus professor of geology at the University of Oxford and “one of the grandfather figures in finding the oldest rocks,” Elliott said. Moorbath “was keen, so I took the train up.” Moorbath led Elliott down to the basement of Oxford’s earth science building, where, as in many such buildings, a large collection of rocks shares the space with the boiler and stacks of chairs. Moorbath dug out specimens from the Isua complex in Greenland, an ancient bit of crust that he had pegged, in the 1970s, at 3.8 billion years old.

    Elliott and his student Matthias Willbold powdered and processed the Isua samples and used painstaking chemical methods to extract the tungsten. They then measured the tungsten isotope ratio using state-of-the-art mass spectrometers. In a 2011 Nature paper, Elliott, Willbold and Moorbath, who died in October, reported that the 3.8 billion-year-old Isua rocks contained 15 parts per million more tungsten-182 than the world average — the first ever detection of a “positive” tungsten anomaly on the face of the Earth.

    The paper scooped Richard Walker of Maryland and his colleagues, who months later reported [Science] a positive tungsten anomaly in 2.8 billion-year-old komatiites from Kostomuksha, Russia.

    Although the Isua and Kostomuksha rocks formed on Earth’s surface long after the extinction of hafnium-182, they apparently derive from materials with much older chemical signatures. Walker and colleagues argue that the Kostomuksha rocks must have drawn from hafnium-rich “primordial reservoirs” in the interior that failed to homogenize during Earth’s early mantle melts. The preservation of these reservoirs, which must trace to the first 50 million years and must somehow have survived even the moon-forming impact, “indicates that the mantle may have never been well mixed,” Walker and his co-authors wrote. That raises the possibility of finding many more remnants of Earth’s early history.

    9
    The 60 million-year-old flood basalts of Baffin Bay, Greenland, sampled by the geochemist Hanika Rizo (center) and colleagues, contain isotope traces that originated more than 4.5 billion years ago. Don Francis (left); courtesy of Hanika Rizo (center and right).

    The researchers say they will be able to use tungsten anomalies and other isotope signatures in surface material as tracers of the ancient interior, extrapolating downward and backward into the past to map proto-Earth and reveal how its features took shape. “You’ve got the precision to look and actually see the sequence of events occurring during planetary formation and differentiation,” Carlson said. “You’ve got the ability to interrogate the first tens of millions of years of Earth’s history, unambiguously.”

    Anomalies have continued to show up in rocks of various ages and provenances. In May, Hanika Rizo of the University of Quebec in Montreal, along with Walker, Jackson and collaborators, reported in Science the first positive tungsten anomaly in modern rocks — 62 million-year-old samples from Baffin Bay, Greenland. Rizo hypothesizes that these rocks were brought up by a plume that draws from one of the “blobs” deep down near Earth’s core. If the blobs are indeed rich in tungsten-182, then they are not tectonic-plate graveyards as many geophysicists suspect, but instead date to the planet’s infancy. Rizo speculates that they are chunks of the planetesimals that collided to form Earth, and that the chunks somehow stayed intact in the process. “If you have many collisions,” she said, “then you have the potential to create this patchy mantle.” Early Earth’s interior, in that case, looked nothing like the primordial magma ocean pictured in textbooks.

    More evidence for the patchiness of the interior has surfaced. At the American Geophysical Union meeting earlier this month, Walker’s group reported [2016 AGU Fall Meeting] a negative tungsten anomaly — that is, a deficit of tungsten-182 relative to tungsten-184 — in basalts from Hawaii and Samoa. This and other isotope concentrations in the rocks suggest the hypothetical plumes that produced them might draw from a primordial pocket of metals, including tungsten-184. Perhaps these metals failed to get sucked into the core during planet differentiation.

    10
    Tim Elliott collecting samples of ancient crust rock in Yilgarn Craton in Western Australia. Tony Kemp

    Meanwhile, Elliott explains the positive tungsten anomalies in ancient crust rocks like his 3.8 billion-year-old Isua samples by hypothesizing that these rocks might have hardened on the surface before the final half-percent of Earth’s mass — delivered to the planet in a long tail of minor impacts — mixed into them. These late impacts, known as the “late veneer,” would have added metals like gold, platinum and tungsten (mostly tungsten-184) to Earth’s mantle, reducing the relative concentration of tungsten-182. Rocks that got to the surface early might therefore have ended up with positive tungsten anomalies.

    Other evidence complicates this hypothesis, however — namely, the concentrations of gold and platinum in the Isua rocks match world averages, suggesting at least some late veneer material did mix into them. So far, there’s no coherent framework that accounts for all the data. But this is the “discovery phase,” Carlson said, rather than a time for grand conclusions. As geochemists gradually map the plumes and primordial reservoirs throughout Earth from core to crust, hypotheses will be tested and a narrative about Earth’s formation will gradually crystallize.

    Elliott is working to test his late-veneer hypothesis. Temporarily trading his mass spectrometer for a sledgehammer, he collected a series of crust rocks in Australia that range from 3 billion to 3.75 billion years old. By tracking the tungsten isotope ratio through the ages, he hopes to pinpoint the time when the mantle that produced the crust became fully mixed with late-veneer material.

    “These things never work out that simply,” Elliott said. “But you always start out with the simplest idea and see how it goes.”

    See the full article here .

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    Formerly known as Simons Science News, Quanta Magazine is an editorially independent online publication launched by the Simons Foundation to enhance public understanding of science. Why Quanta? Albert Einstein called photons “quanta of light.” Our goal is to “illuminate science.” At Quanta Magazine, scientific accuracy is every bit as important as telling a good story. All of our articles are meticulously researched, reported, edited, copy-edited and fact-checked.

     
  • richardmitnick 6:04 am on December 6, 2016 Permalink | Reply
    Tags: Geology, Inorganic geochemistry, Molecular environmental science, , ,   

    From Stanford: “Eureka moment leads to new method of studying environmental toxins” 

    Stanford University Name
    Stanford University

    March 31, 2016 [Stanford just saw fit to put this in social media.]
    Ker Than

    1
    View of the TVA Kingston Fossil Plant fly ash spill. Work using X-ray beams is clarifying how pollutants bind or release from solid surfaces and move into groundwater. Photo: Brian Stansberry via Wikimedia Commons

    A technique for probing the surface of particles revealed how toxins move from the soil to groundwater.

    In 1986, Gordon Brown used SLAC’s Stanford Synchrotron Radiation Lightsource (SSRL) to visualize something no one had ever seen before: the exact way that atoms bond to a solid surface.

    SLAC/SSRL
    SLAC/SSRL

    The work stemmed from a eureka moment that Brown had during the doctoral defense of graduate student Kim Hayes but has since grown into one of the seminal works in inorganic geochemistry, and even spawned a new field of study — molecular environmental science.

    Knowing how charged ions interact with solid surfaces is crucial for understanding how toxic metal ions such as lead, arsenic and mercury or radioactive elements such as uranium may be released from particles in soils and sediments and into groundwater or vice versa. Using the techniques Brown’s team helped pioneer, scientists today can paint exquisitely detailed pictures of how metal ions bind to different solid surfaces, including those on nanoparticles.

    “You can determine what other atoms are around the pollutant ions of interest, the inter-atomic distances separating them and the number and types of chemical bonds that keep them bound to the surface,” says Brown, a professor of geological sciences and of photon science. “This is crucial for understanding how easily they move from one place to another.”


    Access mp4 video here .

    Synchrotron-generated X-rays like those produced at SSRL are ideal for this type of investigation for a number of reasons, says John Bargar, a senior scientist at SLAC and Brown’s former PhD student. For one thing, synchrotron X-rays are highly focused, much like laser beams. “All of the photons produced are condensed into either a pencil beam or a narrow fan,” Bargar says. “That means you can use nearly all of the photons that you’re making with very little waste.”

    Another advantage of synchrotron X-rays, Brown says, is that their extremely high intensity makes it possible to detect and study pollutant ions at the very low concentration levels typically found in many polluted environmental samples.

    Moreover, synchrotron X-rays are polarized, meaning their waves vibrate primarily in a single plane. By modifying the direction of polarization, scientists can create very powerful probes for studying chemical bonds in molecules.

    “A metal ion sitting inside a larger molecule is surrounded by many bonds. Oftentimes, we don’t want to interrogate all of those bonds at once,” Bargar says. “With polarized X-rays, we can selectively interrogate the bonds in a specific orientation.”

    Recently, Brown and Bargar have collaborated to study how organic matter and live microbial organisms affect the binding affinities of different environmental pollutants to solid surfaces. Bargar and Brown are also investigating ways to harness bacterial aggregations called biofilms to neutralize the effects of environmental pollutants. In addition, they are also using synchrotron X-rays at SSRL to look for more efficient ways of safely extracting oil and gas from tight shales via hydraulic fracturing, a process that is transforming the energy landscape of the United States.

    “The X-ray beams synchrotrons are able to generate today are about 15 orders of magnitude brighter than what was available when I was a graduate student. This has led to a revolution in all areas of science and engineering,” Brown says. “I could collect the data for my entire PhD thesis in one morning at SSRL now.”

    See the full article here .

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    Leland and Jane Stanford founded the University to “promote the public welfare by exercising an influence on behalf of humanity and civilization.” Stanford opened its doors in 1891, and more than a century later, it remains dedicated to finding solutions to the great challenges of the day and to preparing our students for leadership in today’s complex world. Stanford, is an American private research university located in Stanford, California on an 8,180-acre (3,310 ha) campus near Palo Alto. Since 1952, more than 54 Stanford faculty, staff, and alumni have won the Nobel Prize, including 19 current faculty members

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  • richardmitnick 8:55 am on November 30, 2016 Permalink | Reply
    Tags: , , Geology, Ring of Fire, Scientists have found the largest exposed fault on Earth   

    From Science Alert: “Scientists have found the largest exposed fault on Earth” 

    ScienceAlert

    Science Alert

    29 NOV 2016
    BEC CREW

    1
    Pulau Banta island in the Banta Sea. Credit: Jialiang Gao/Wikimedia

    For the first time, researchers have confirmed the existence of the largest exposed fault on Earth, and it could explain how a 7.2-km-deep (4.5-mile) abyss formed in the Pacific Ocean.

    Discovered beneath the Banda Sea in eastern Indonesia, the massive fault plane runs right through the notorious Ring of Fire – an explosive region where roughly 90 percent of the world’s earthquakes and 75 percent of all active volcanoes occur.

    4
    SVG version of File:Pacific_Ring_of_Fire.png, recreated using WDB vector data using code mentioned in File:Worldmap_wdb_combined.svg. 11 February 2009. Gringer

    For almost a century, scientists have known about the Weber Deep – a massive chasm lurking near the Maluku Islands of Indonesia that forms the deepest point of Earth’s oceans not within a trench.

    But until now, no one could figure out how it formed.

    To investigate, geologists from the Australian National University (ANU) in Canberra and Royal Holloway University of London analysed maps of the sea floor taken from the Banda Sea region in the Pacific Ocean.

    They discovered that rocks sitting the bottom of the sea were cut by hundreds of straight parallel scars.

    Simulations of the sea floor suggested that a massive piece of crust bigger than Belgium was at some point ripped apart by a massive crack – or fault – in the oceanic plates to form a deep depression in the ocean floor.

    The activity appeared to have left behind the biggest exposed fault plane ever detected on Earth, which the researchers have tentatively called the Banda Detachment.

    When a fault forms in Earth’s crust, it forms two main features: a fault plane, which is the flat surface of a fault; and the fault line, which is the intersection of a fault plane with the ground surface.

    The team’s simulations showed that the Banda Detachment fault plane was exposed over an area of 60,000 square kilometres (23,166 square miles) when the sea floor cracked.

    “We had made a good argument for the existence of this fault we named the Banda Detachment, based on the bathymetry [underwater topography] data and on knowledge of the regional geology,” said one of the researchers, Gordon Lister from ANU.

    3
    Diagram showing the Banda Detachment fault beneath the Weber Deep basin. Credit: ANU

    But as far as the researchers were concerned, this massive fault didn’t exist until they saw evidence of it with their own eyes.

    When they sailed out in the Pacific Ocean in eastern Indonesia, they identified prominent landforms in the water that were formed by the Banda Detachment fault plane.

    “I was stunned to see the hypothesised fault plane, this time not on a computer screen, but poking above the waves,” says one of the team, Jonathan Pownall from ANU. “The discovery will help explain how one of Earth’s deepest sea areas became so deep.”

    The team says the fact that the Weber Deep abyss formed right where the Banda Detachment was exposed could help researchers figure out how it formed.

    “Our research found that a 7 km-deep abyss beneath the Banda Sea off eastern Indonesia was formed by extension along what might be Earth’s largest-identified exposed fault plane,” says Pownall.

    The discovery could also help geologists predict the movements of one of the most tectonically active regions in the world – the Pacific Ring of Fire, a 40,000-km (25,000-mile) stretch of ocean dotted with no less than 452 volcanoes, which is around 75 percent of the world’s total.

    “In a region of extreme tsunami risk, knowledge of major faults such as the Banda Detachment, which could make big earthquakes when they slip, is fundamental to being able to properly assess tectonic hazards,” says Pownall.

    The research has been published in Geology.

    See the full article here .

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