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  • richardmitnick 2:39 pm on April 21, 2017 Permalink | Reply
    Tags: Antarctic bedrock, , Geology, The Antarctic Sun, US Antarctic Program   

    From The Antarctic Sun: “Ancient Ice Levels” Very cool. 

    USAP

    The Antarctic Sun

    April 20, 2017
    Michael Lucibella

    Scientists drill into Antarctic bedrock to see if the Icy Continent was once a bit less icy

    1
    The scientists and drillers set up camp at the foot of Mount Tidd in the Pirrit Hills. Photo Credit: John Stone

    Today, a massive sheet of ice covers nearly all of West Antarctica, but it likely hasn’t always been that way.

    2
    After positioning the drill platform, engines and hydraulic controls, IDDO drillers Mike Jayred (right) and Tanner Kuhl (center) look on as Clayton Armstrong raises the drill mast. Photo Credit: John Stone

    Over the past few hundred thousand years, researchers think that the ice sheets have waxed and waned, varying in size as the region’s climate changed. As they fluctuated, the ice sheets would have captured so much frozen water that sea levels around the world would have risen and dropped accordingly.

    The fate of the Antarctic ice sheets affects all parts of the planet. For scientists modelling future climate, the role the ice sheets play is one of the great unknowns, but it would certainly be significant. They estimate that if the entire West Antarctic Ice Sheet were to collapse, for example, it could raise global sea level by up to 15 feet on average.

    Counterintuitively, because of the interactions between the ice sheet and the Earth’s crust, the Northern Hemisphere would experience the biggest sea level rise from melting Antarctic ice.

    To gather hard geologic evidence of how dynamic the ice cover has been in the past, and may be in the future, John Stone of the University of Washington and his team traveled to a remote region of the continent this past season.

    “The aim of this project is to determine whether the ice sheet in West Antarctica has been thinner in the past,” Stone said. “Whether it has collapsed and contracted to a much smaller version of its present self.”

    3
    Once the drill was erected, the team built a tent around it to shelter drilling operations from snow and winds. Photo Credit: John Stone

    They flew deep into the barren landscape to drill down and collect a bedrock sample buried under more than 100 meters of ice. By analyzing its atomic properties, they’re able to test to see whether there was a time when the ice sheets of West Antarctica were once just a shadow of what they are today. The research was supported by the National Science Foundation, which manages the U.S. Antarctic Program.

    “There’s a good deal of evidence from sea level change that ice sheets globally were smaller during the last interglacial 125,000 years ago,” Stone said. “So it’s widely presumed that West Antarctica participated in that deglaciation that led to higher sea levels.”

    The researchers needed to get at the underlying bedrock beneath the ice that covers most of the continent today. They’re looking for evidence that the rocks once laid out on the surface, free of ice and totally exposed to cosmic rays. While it’s common for glacial researchers to analyze rocks on the surface to see how long they’ve been exposed, taking rock cores from beneath the ice is new.

    “The cosmic radiation interacts with… and induces nuclear reactions inside the minerals of rocks, and changes atoms from one chemical isotope to another,” Stone said. “When rocks become exposed to cosmic rays they begin to build up quantities of isotopes like beryllium-10, aluminum-26, chlorine-36, helium-3 and neon-21, which are otherwise very rare isotopes.”

    Many of these atomic variants are radioisotopes that are unstable and break down into other stable isotopes through radioactive decay. These radioisotopes build up as long as the rocks are exposed, but when these rocks are buried underneath multiple feet of cosmic-ray blocking ice, the radioisotopes break down at predictable rates.

    4
    IDDO driller Mike Jayred (left) prepares to add a rod to the drill string while coring the pilot hole at the first site. Photo Credit: John Stone

    Different isotopes have different rates of decay, or “half-lives,” which range from a few microseconds, to billions of years. Stone and his team focused on isotopes that have half-lives in the thousands and millions of years. By looking at the ratios of these different isotopes, the researchers can discern when the last time this rock had been exposed, and from that, the history of the ice sheet over the last few hundred thousand years.

    “We will measure a whole family of isotopes which have different radioactive half-lives,” Stone said. “By comparing the concentrations of those isotopes, we’ll be able to tell whether the exposure was a long time in the past, or whether it happened fairly recently.”

    In order to get to the rock still covered in ice, the team worked with a drill designed by the U.S. Ice Drilling Program for subglacial bedrock drilling known as the Agile Sub-Ice Geologic drill, or the ASIG drill. It’s adapted from a commercially available drill used for mineral exploration, but with a number of modifications to make it better at drilling through ice rather than rock.

    The team originally hoped to take two cores during their field season. Unfortunately, just feet away from finishing their first hole, there was a problem and it had to be abandoned.

    “That was a big disappointment, especially because it was the first of the two holes,” Stone said.

    What exactly happened is still unclear, but after several days of troubleshooting, they made the decision to give up on their first attempt. Despite the setback, they focused on making sure their second attempt was successful.

    5
    Geologists Perry Spector (foreground) and Trevor Hillebrand prepare to collect a rock sample from glacial deposits on Mt Tidd. In addition to the drill cores, scientists collected rock samples to study the history of the ice sheet above the current ice surface. Photo Credit: John Stone

    “We were able to get some auger bits flown out to us which simplified the business of getting a pilot hole drilled quickly, and with that done we were able to get a second hole started very efficiently,” Stone said. “The drill functioned exactly as it was meant to function for the second hole. It was really a very impressive performance actually.”

    Six days later, after cutting through 150 meters of ice, the researchers bored into the bedrock and extracted an eight-meter rock core.

    “These long profiles give you an idea of how far into rock cosmic rays penetrate,” Stone said. “Five or six feet, maybe a little further is the typical length of the profile where you’ll see the abundance of cosmic ray produced isotopes.”

    Picking the right spot was key for recovering the right kind of rock. The Pirrit Hills are an isolated collection of mountain peaks projecting out of the massive ice sheet in the middle of West Antarctica.

    “The Pirrit Hills are a beautiful place,” Stone said. “They’re actually quite substantial mountains, they’re called the Pirrit Hills but the three big peaks are sort of granite towers that are up to 800 or 900 meters above the ice sheet at that point.”

    These mountaintops, known as nunataks when only their peaks protrude out of the ice, are the ideal location in the region in part because they’re made of granite, the best material for isolating these radioisotope ratios.

    “Our knowledge of the subglacial geology and where different rock types are is not excellent over Antarctica,” said Perry Spector, also at the University of Washington. “So the fact that we’re right next to a mountain, a nunatak of granite, means that if we go just a little bit off board of there and drill down, we’re almost guaranteed to hit granite.”

    6
    Clayton Armstrong lowers a core tube into the ASIG drill string prior to drilling the final section of bedrock core as drilling engineer Tanner Kuhl looks on. Photo Credit: John Stone

    The team had visited these peaks before. In 2013 and 2014 they traveled to the Pirrit Hills and two other nunataks in the region, to determine where would be best to drill, and to collect samples up the slopes of the exposed mountaintops.

    “We have samples that currently go from hundreds of meters above the ice, all the way down ridges in the Pirrit Hills, finally at the ice level we have several samples, and our drill core will be the next two samples down the profile,” Stone said.

    Collectively, these samples will give researchers a comprehensive picture of the ice sheet over thousands of years.

    “The ones below the ice sheet can tell us information about if and when the ice has been thinner there, but the ones above the modern ice level can tell you information about if and when the ice was thicker in the past,” Spector said. “You can get information about both times when the West Antarctic ice sheet was thicker and more extensive than it is now, as well as information about if and when it was thinner and less extensive.”

    The Pirrit Hills are also in a key location on the ice sheet itself, a spot that acts like a bellwether, which can reveal much about the West Antarctic Ice Sheet as a whole.

    “Part of the site selection was to find a place where ice thinning would be sensitive to a large scale change in the ice sheet,” Stone said. “Ice sheet model calculations suggest that you’d be looking at substantial deglaciation of West Antarctica in order to uncover that rock.”

    7
    The scientists and drillers recovered 8 meters, or about 26 feet, of bedrock granite. Each section fit perfectly with the sections above and below it, ensuring a complete, uninterrupted record of cosmogonic isotopes. Photo Credit: John Stone

    The researchers are looking to the past to better understand what happens to the massive ice sheets in West Antarctica as climates warm in the modern day.

    “We think of it very much as a test of the sensitivity of ice sheets to climate change,” Stone said. “If we can establish which climates endanger the West Antarctic Ice Sheet then I think we can really make confident statements about future climates and the likely response of the Antarctic ice sheet to that. We sort of see it as looking at the vulnerability of the ice sheet to future climate change.”

    Understanding how the ice sheet behaved in past warm periods takes on extra importance as researchers are now trying to predict what might happen around the world as the current climate warms. As ice sheets melt, that water will flow into oceans and cause sea levels around the world to rise. Understanding how much the West Antarctic Ice Sheet is likely to melt will go a long way towards predicting how much extra water may end up in the oceans.

    Even though the West Antarctic Ice Sheet is on the far side of the planet, it would have a big impact in North America should it collapse. Counterintuitively, the Northern Hemisphere would experience the biggest sea level rise from melting Antarctic ice.

    “[The] deglaciation of Antarctica, rather than Greenland, actually has bigger effects in North America than the same amount of ice being released from Greenland,” Stone said.

    The huge weight of such a massive ice sheet actually deforms the Earth’s crust, flattening it out slightly. Should that ice melt and flow into the oceans, the planet’s surface would rebound and rise up, displacing that water towards the Northern Hemisphere.

    After spending about two months at the site, the team returned with the rock core that they’re now starting to process and analyze.

    “We’ve already started to cut sections from the core,” Stone said.

    They still need to carefully separate the pure mineral samples they want to analyze for the cosmic-ray produced isotopes within.

    “We’ve got measurements planned for four or possibly five cosmic ray produced isotopes in this rock,” Stone said. “They all have different half-lives, so by comparing them we will be able to get information about not only whether the rock was exposed but when.”

    NSF-funded research in this story: John Stone, University of Washington

    See the full articled here .

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  • richardmitnick 8:24 am on April 19, 2017 Permalink | Reply
    Tags: , Climate Change Reroutes a Yukon River in a Geological Instant, , Geology, , Kaskawulsh Glacier, , Slims River Valley   

    From NYT: “Climate Change Reroutes a Yukon River in a Geological Instant” 

    New York Times

    The New York Times

    APRIL 17, 2017
    JOHN SCHWARTZ

    1
    An aerial view of the ice canyon that now carries meltwater from the Kaskawulsh Glacier, on the right, away from the Slims River. “River piracy” refers to one river capturing and diverting the flow of another. Credit Dan Shugar/University of Washington-Tacoma

    In the blink of a geological eye, climate change has helped reverse the flow of water melting from a glacier in Canada’s Yukon, a hijacking that scientists call “river piracy.”

    This engaging term refers to one river capturing and diverting the flow of another. It occurred last spring at the Kaskawulsh Glacier, one of Canada’s largest, with a suddenness that startled scientists.

    A process that would ordinarily take thousands of years — or more — happened in just a few months in 2016.

    Much of the meltwater from the glacier normally flows to the north into the Bering Sea via the Slims and Yukon Rivers. A rapidly retreating and thinning glacier — accelerated by global warming — caused the water to redirect to the south, and into the Pacific Ocean.

    Last year’s unusually warm spring produced melting waters that cut a canyon through the ice, diverting more water into the Alsek River, which flows to the south and on into Pacific, robbing the headwaters to the north.

    2
    Jim Best, a researcher, measuring water levels on the lower-flowing Slims River in early September. Credit Dan Shugar/University of Washington-Tacoma

    The scientists concluded that the river theft “is likely to be permanent.”

    Daniel Shugar, an assistant professor of geoscience at the University of Washington-Tacoma, and colleagues described the phenomenon in a paper published on Monday in the journal Nature Geoscience.

    River piracy has been identified since the 19th century by geologists, and has generally been associated with events such as tectonic shifts and erosion occurring thousands or even millions of years ago. Those earlier episodes of glacial retreat left evidence of numerous abandoned river valleys, identified through the geological record.

    In finding what appears to be the first example of river piracy observed in modern times, Professor Shugar and colleagues used more recent technology, including drones, to survey the landscape and monitor the changes in the water coursing away from the Kaskawulsh Glacier.

    2
    Kaskawulsh glacier junction from air
    29 August 2014
    Author Gstest

    The phenomenon is unlikely to occur so dramatically elsewhere, Professor Shugar said in a telephone interview, because the glacier itself was forming a high point in the landscape and serving as a drainage divide for water to flow one way or another. As climate change causes more glaciers to melt, however, he said “we may see differences in the river networks and where rivers decide to go.”

    Changes in the flow of rivers can have enormous consequences for the landscape and ecosystems of the affected areas, as well as water supplies. When the shift abruptly reduced water levels in Kluane Lake, the Canadian Broadcasting Corporation reported, it left docks for lakeside vacation cabins — which can be reached only by water — high and dry.

    The riverbed of the Slims River basin, now nearly dry, experienced frequent and extensive afternoon dust storms through the spring and summer of last year, the paper stated.

    3
    The ice-walled canyon at the terminus of the Kaskawulsh Glacier, with recently collapsed ice blocks. This canyon now carries almost all meltwater from the toe of the glacier down the Kaskawulsh Valley and toward the Gulf of Alaska. Credit Jim Best/University of Illinois

    The impacts of climate change, like sea level rise or the shrinkage of a major glacier, are generally measured over decades, not months as in this case. “It’s not something you could see if you were just standing on the beach for a couple of months,” Professor Shugar said.

    The researchers concluded that the rerouted flow from the glacier shows that “radical reorganizations of drainage can occur in a geologic instant, although they may also be driven by longer-term climate change.” Or, as a writer for the CBC put it in a story about the phenomenon last year, “It’s a reminder that glacier-caused change is not always glacial-paced.”

    4
    Looking up the Slims River Valley, from the south end of Kluane Lake. The river used to flow down the valley from the Kaskawulsh glacier. (Sue Thomas)

    The underlying message of the new research is clear, said Dr. Shugar in a telephone interview. “We may be surprised by what climate change has in store for us — and some of the effects might be much more rapid than we are expecting.”

    The Nature Geoscience paper is accompanied by an essay from Rachel M. Headley, an assistant professor of geoscience and glacier expert at the University of Wisconsin-Parkside.

    “That the authors were able to capture this type of event almost as it was happening is significant in and of itself,” she said in an interview via email. As for the deeper significance of the incident, she said, “While one remote glacial river changing its course in the Yukon might not seem like a particularly big deal, glacier melt is a source of water for many people, and the sediments and nutrients that glacier rivers carry can influence onshore and offshore ecological environments, as well as agriculture.”

    Her article in Nature Geoscience concludes that this “unique impact of climate change” could have broad consequences. “As the world warms and more glaciers melt, populations dependent upon glacial meltwater should pay special attention to these processes.”

    Another glacier expert not involved in the research, Brian Menounos of the University of Northern British Columbia, said that while glaciers have waxed and waned as a result of natural forces over the eons, the new paper and his own research underscore the fact that the recent large-scale retreat of glaciers shows humans and the greenhouse gases they produce are reshaping the planet. “Clearly, we’re implicated in many of those changes,” he said.

    See the full article here .

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  • richardmitnick 12:44 pm on April 17, 2017 Permalink | Reply
    Tags: , Geology, Mis-Atlantic Ridge, Plate techtonics,   

    From Universe Today: “What is the Mid-Atlantic Ridge?” 

    universe-today

    Universe Today

    17 Apr , 2017
    Matt Williams

    1
    The age of the oceanic crust – red is most recent, and blue is the oldest – which corresponds to the location of mid-ocean ridges. Credit: NCEI/NOAA

    If you took geology in high school, then chances you remember learning something about how the Earth’s crust = the outermost layer of Earth – is arranged into a series of tectonic plates. These plates float on top of the Earth’s mantle, the semi-viscous layer that surrounds the core, and are in constant motion because of convection in the mantle. Where two plates meet, you have what it is known as a boundary.

    These can be “divergent” or “convergent”, depending on whether the plates are moving apart or coming together. Where they diverge, hot magma can rise from below, creating features like long ridges or mountain chains. Interestingly enough, this is how one of the world’s largest geological features was formed. It called the Mid-Atlantic Ridge, which run from north to south along the ocean floor in the Atlantic.

    Description:

    The Mid-Atlantic Ridge (MAR) is known as a mid-ocean ridge, an underwater mountain system formed by plate tectonics. It is the result of a convergent plate boundary that runs from 87° N – about 333 km (207 mi) south of the North Pole – to 54 °S, just north of the coast of Antarctica.

    2
    The different types of Tectonic Plate Boundaries, ranging from convergent and transform to divergent. Credit: USGS/Jose F. Vigil

    3
    Small image showing the location of the Mid-Atlantic ridge. Wikipedia

    Like other ocean ridge systems, the MAR developed as a consequence of the divergent motion between the Eurasian and North American, and African and South American Plates. In the North Atlantic, it separates the Eurasian and North American Plates; whereas in the South Atlantic, it separates the African and South American Plates.

    The MAR is approximately 16,000 km (10,000 mi) long and between 1,000 and is 1,500 km (620 and 932 mi) wide. The peaks of the ridge stand about 3 km (1.86 mi) in height above the ocean floor, and sometimes reach above sea level, forming islands and island groups. The MAR is also part of the longest mountain chain in the world, extending continuously across the oceans floors for a total distance of 40,389 km (25,097 mi).

    The MAR also has a deep rift valley at is crest which marks the location where the two plates are moving apart. This rift valley runs along the axis of the ridge for nearly its entire length, measuring some 80 to 120 km (50 to 75 miles) wide. The rift marks the actual boundary between adjacent tectonic plates, and is where magma from the mantle reaches the seafloor.

    Where this magma is able to reach the surface, the result is basaltic volcanoes and islands. Where it is still submerged, it produces “pillow lava”. As the plates move further apart, new ocean lithosphere is formed at the ridge and the ocean basin gets wider. This process, known as “sea floor spreading”, is happening at an average rate of about 2.5 cm per year (1 inch).

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

    In other words, North America and Europe are moving away from each other at a very slow rate. This process also means that the basaltic rock that makes up the ridge is younger than the surrounding crust.
    Notable Features:

    As noted, the ridge (while mainly underwater) does have islands and island groups that were created by volcanic activity. In the Northern Hemisphere, these include Jan Mayen Island and Iceland (Norway), and the Azores (Portugal). In the Southern Hemisphere, MAR features include Ascension Island, St. Helena, Tristan da Cunha, Gough Island (all UK territories) and Bouvet Island (Norway).

    Near the equator, the Romanche Trench divides the North Atlantic Ridge from the South Atlantic Ridge. This narrow submarine trench has a maximum depth of 7,758 m (25,453 ft), one of the deepest locations of the Atlantic Ocean. This trench, however, is not regarded an official boundary between any of the tectonic plates.

    History of Exploration:

    The ridge was initially discovered in 1872 during the expedition of the HMS Challenger. In the course of investigating the Atlantic for the sake of laying the transatlantic telegraph cable, the crew discovered a large rise in the middle of the ocean floor. By 1925, its existence was confirmed thanks to the invention of sonar.

    5
    The super-continent Pangaea during the Permian period (300 – 250 million years ago). Credit: NAU Geology/Ron Blakey

    By the 1960s, scientists were able to map the Earth’s ocean floors, which revealed a seismically-active central valley, as well as a network of valleys and ridges. They also discovered that the ridge was part of a continuous system of mid-ocean ridges that extended across the entire ocean floor, connecting all the divergent boundaries around the planet.

    This discovery also led to new theories in terms of geology and planetary evolution. For instance, the theory of “seafloor spreading” was attributed to the discovery of the MAR, as was the acceptance of continental drift and plate tectonics. In addition, it also led to the theory that all the continents were once part of subcontinent known as “Pangaea”, which broke apart roughly 180 million years ago.

    Much like the “Pacific Ring of Fire“, the discovery of the Mid-Atlantic Ridge has helped inform our modern understanding of the world. Much like convergent boundaries, subduction zones and other geological forces, the process that created it is also responsible for the world as we know it today.

    7
    Pacific Ring of Fire. USGS

    Basically, it is responsible for the fact that the Americas have been drifting away from Africa and Eurasia for millions of years, the formation of Australia, and the collision between the India Subcontinent and Asia. Someday – millions of years from now – the process of seafloor spreading will cause the Americas and Asia to collide, thus forming a new super continent – “Amasia”.

    For more information, check out the Geological Society’s page on the Mid-Atlantic Ridge.

    See the full article here .

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  • richardmitnick 8:46 am on April 14, 2017 Permalink | Reply
    Tags: , Geology, What Led to the Largest Volcanic Eruption in Human History   

    From Eos: “What Led to the Largest Volcanic Eruption in Human History?” 

    AGU bloc

    AGU
    Eos news bloc

    Eos

    13 April 2017
    Sarah Witman

    1
    A lake (black) fills Toba’s caldera in Sumatra, Indonesia, as seen in this false-color image from NASA’s Landsat satellite. A supereruption 74,000 years ago is thought to be the largest eruption ever to have been experienced by humans. Credit: NASA

    In the northern part of the Indonesian island of Sumatra lies the Toba caldera, a massive crater formed by what scientists think is the largest volcanic eruption ever experienced by humanity. The eruption, called the Youngest Toba Tuff supereruption, took place about 74,000 years ago.

    By dating zircon, a diamond-like gemstone, and other minerals in the area such as quartz, Reid and Vazquez have pieced together clues about the activity of magma below the surface prior to the supereruption.

    Zircon is the oldest dated mineral on Earth. With a hardness rating of 7.5, it is resistant to chemical and mechanical weathering and can withstand metamorphism (structural changes due to heat, pressure, and other natural processes). All of these factors make it an ideal mineral for geological dating, especially for magma. Because zircon does not gain or lose uranium or lead even at magmatic temperatures, zircon typically contains high uranium and low lead levels, and scientists may use the ratio of these two elements in the zircon to determine the age of the sample.

    The way in which zircon crystals in the Youngest Toba Tuff magma appear to have nucleated and grown over time, the researchers found, provides evidence of intermittent changes in the composition of the underground body of magma that eventually erupted. Certain characteristics of the zircon also indicate repeated episodes of magma recharge—fresh influxes of magma that often trigger eruptions—occurring tens of thousands to hundreds of thousands of years before the supereruption.

    The team’s findings are significant for modern-day humans, given that aerosols and ash that erupted from Youngest Toba Tuff are thought to have entered the atmosphere, causing global cooling and the near extinction of the human race. A supereruption of equal or greater magnitude today could therefore have similarly drastic consequences. By better understanding the conditions that led up to the Youngest Toba Tuff supereruption, scientists can help paint a clearer picture of the future.

    Science paper
    http://onlinelibrary.wiley.com/doi/10.1002/2016GC006641/abstract;jsessionid=C04D6BAFE7F708964146B4B1B210F807.f03t03

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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 10:28 am on April 13, 2017 Permalink | Reply
    Tags: , Geology, LiDAR, Technology to improve rockfall analysis on cliffs could save money lives,   

    From U Washington: “Technology to improve rockfall analysis on cliffs could save money, lives” 

    U Washington

    University of Washington

    April 11, 2017
    Jennifer Langston

    1
    This LiDAR image of a rock slope on Alaska’s Glenn Highway shows the “kinetic energy” of the slope, with red indicating a higher hazard from rockfalls.Matthew O’Banion/Oregon State University

    Pacific Northwest engineers have developed a new, automated technology to analyze the potential for rockfalls from cliffs onto roads and areas below, which should speed and improve this type of risk evaluation, help protect public safety and ultimately save money and lives.

    Called a “rockfall activity index,” the system is based on the powerful abilities of light detection and ranging, or LIDAR technology. It should expedite and add precision to what’s now a somewhat subjective, time-consuming process to determine just how dangerous a cliff is to the people, vehicles, roads or structures below it.

    This is a multimillion-dollar global problem, experts say, of significant concern to transportation planners.

    It’s a particular concern in the Pacific Northwest with its many mountain ranges, heavy precipitation, erosion of steep cliffs and unstable slopes, and thousands of roads that thread their way through that terrain. The evaluation system now most widely used around the world, in fact, was developed by the Oregon Department of Transportation more than 25 years ago.

    The new technology should improve on that approach, according to researchers who developed it from the University of Washington, Oregon State University and the University of Alaska Fairbanks. Findings were just published in Engineering Geology.

    “Transportation agencies and infrastructure providers are increasingly seeking ways to improve the reliability and safety of their systems, while at the same time reducing costs,” said Joe Wartman, associate professor of civil and environmental engineering at the University of Washington, and corresponding author of the study.

    “As a low-cost, high-resolution landslide hazard assessment system, our rockfall activity index methodology makes a significant step toward improving both protection and efficiency.”

    The new approach could replace the need to personally analyze small portions of a cliff at a time, looking for cracks and hazards, with analysts sometimes even rappelling down it to assess risks. LIDAR analysis can map large areas in a short period, and allow data to be analyzed by a computer.

    “Rockfalls are a huge road maintenance issue,” said co-author Michael Olsen, an associate professor of geomatics at Oregon State University.

    “Pacific Northwest and Alaskan highways, in particular, are facing serious concerns for these hazards. A lot of our highways in mountainous regions were built in the 1950s and 60s, and the cliffs above them have been facing decades of erosion that in many places cause at least small rockfalls almost daily. At the same time traffic is getting heavier, along with increasing danger to the public and even people who monitor the problem.”

    The study, based on some examples in southern Alaska, showed the new system could evaluate rockfalls in ways that very closely matched the dangers actually experienced. It produces data on the “energy release” to be expected from a given cliff, per year, that can be used to identify the cliffs and roads at highest risk and prioritize available mitigation budgets to most cost-effectively protect public safety.

    Tens of millions of dollars are spent each year in the U.S. on rock slope maintenance and mitigation.

    “This should improve and speed assessments, reduce the risks to people doing them, and hopefully identify the most serious problems before we have a catastrophic failure,” Olsen said.

    The technology is now complete and ready for use, researchers said, although they are continuing to develop its potential, possibly with the use of flying drones to expand the data that can be obtained.

    This research was supported by the UW-based Pacific Northwest Transportation Consortium, the National Science Foundation and the Alaska Department of Transportation and Public Facilities. Co-authors are Lisa Dunham, a UW graduate in civil and environmental engineering now at McMillen Jacobs Associates in Seattle; graduate assistant Matthew O’Banion at OSU; and Keith Cunningham, research assistant professor of remote sensing at the University of Alaska Fairbanks.

    For more information, contact Joe Wartman at wartman@uw.edu or 206-685-4806.

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

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

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    AGU
    Eos news bloc

    Eos

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

    4.11.17
    Veronique Dehant
    Richard Gross

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

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

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

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

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

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

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

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

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

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

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

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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 3:01 pm on April 7, 2017 Permalink | Reply
    Tags: 'Nesting doll' minerals offer clues to Earth’s mantle dynamics, , , , Geology, Majorite mineral   

    From Carnegie: “‘Nesting doll’ minerals offer clues to Earth’s mantle dynamics” 

    Carnegie Institution for Science
    Carnegie Institution for Science

    1
    The fragment of the metamorphic rock eclogite in which the garnet that encased the ferric-iron-rich majorite sample was found in Northern China. Credit: Yingwei Fei.

    April 07, 2017
    No writer credit found
    Reference to Person:
    Yingwei Fei

    Recovered minerals that originated in the deep mantle can give scientists a rare glimpse into the dynamic processes occurring deep inside of the Earth and into the history of the planet’s mantle layer. A team led by Yingwei Fei, a Carnegie experimental petrologist, and Cheng Xu, a field geologist from Peking University, has discovered that a rare sample of the mineral majorite originated at least 235 miles below Earth’s surface. Their findings are published by Science Advances.

    Majorite is a type of garnet formed only at depths greater than 100 miles. Fascinatingly, the majorite sample Fei’s team found in Northern China was encased inside a regular garnet—like mineralogical nesting dolls. It was brought to surface in the North China Craton, one of the oldest cratonic blocks in the world. What’s more, the majorite was rich in ferric iron, an oxidized form of iron, which is highly unusual for the mineral.

    All of these uncommon factors prompted the team to investigate the majorite’s origins.

    They used several different kinds of analytical techniques to determine the chemistry and structural characteristics of this majorite formed deep inside the Earth. In order to determine the exact depth of its origin, Carnegie’s postdoc Renbiao Tao conducted high-pressure experiments that mimicked the formation conditions of natural majorite. The team pinpointed its origin to a depth of nearly 250 miles (400 kilometers), at the bottom of the soft part of the upper mantle, called the asthenosphere, which drives plate tectonics.

    It is extremely unusual that a high-pressure majorite could survive transportation from such a depth. Adding to the strange circumstances is the fact that it was later encased by a garnet that formed at a much shallower depth of about 125 miles (200 kilometers). The nesting-doll sample’s existence required two separate geological events to explain, and these events created a time capsule that the researchers could use to better understand the Earth’s deep history.

    “This two-stage formation process offers us important clues about the mantle’s evolutionary stage at the time when the majorite was first formed,” Fei explained.

    The sample’s location and depth of origin indicate that it is a relic from the end of an era of supercontinent assembly that took place about 1.8 billion years ago. Called Columbia, the supercontinent’s formation built mountain ranges that persist today.

    “More research is needed to understand how the majorite became so oxidized, or rich in ferric iron, and what this information can tell us about mantle chemistry. We are going back to the site this summer to dig deeper trenches and hope to find fresh rocks that contain more clues to the deep mantle,” Fei added.

    This research was supported by the National Natural Science Foundation of China, the Carnegie Institution for Science, and the U.S. National Science Foundation.

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    Carnegie Institution of Washington Bldg

    Andrew Carnegie established a unique organization dedicated to scientific discovery “to encourage, in the broadest and most liberal manner, investigation, research, and discovery and the application of knowledge to the improvement of mankind…” The philosophy was and is to devote the institution’s resources to “exceptional” individuals so that they can explore the most intriguing scientific questions in an atmosphere of complete freedom. Carnegie and his trustees realized that flexibility and freedom were essential to the institution’s success and that tradition is the foundation of the institution today as it supports research in the Earth, space, and life sciences.

    6.5 meter Magellan Telescopes located at Carnegie’s Las Campanas Observatory, Chile.
    6.5 meter Magellan Telescopes located at Carnegie’s Las Campanas Observatory, Chile

     
  • richardmitnick 5:41 am on March 30, 2017 Permalink | Reply
    Tags: Ancient Earth leaves a fading signature, , , , Geology   

    From COSMOS: “Ancient Earth leaves a fading signature” 

    Cosmos Magazine bloc

    COSMOS

    17 March 2017
    Richard A Lovett

    1
    Granite such as this along the eastern shores of the Hudson Bay reveal remnants of the Earth’s crust. Rick Carlson

    Scientists studying ancient rocks in northeastern Canada have found them to be composed of remnants of even older rocks, dating back to within a few hundred million years of the formation of the Earth.

    These remnants suggest that tectonic processes in the planet’s first 1.5 billion years may have been very different to what we know today. The find is important in part because on most of the planet’s surface, geological processes have long ago erased visible traces of the Earth’s primitive crust.

    There are a few places with rocks believed to be at least four billion years old, and in Western Australia, geologists have found crystals, called zircons, that might have formed 4.4 billion years ago, only 150 million years or so after the Earth’s formation.

    But in general, says Richard Carlson, a geochemist from Carnegie Institution for Science in Washington DC, “finding really old rock has been almost impossible.” Not that Carlton and his colleague, Jonathan O’Neil of the University of Ottawa, Canada, actually found a new trove of super-ancient rocks.

    Instead, in a study published in Science, they looked for isotopic traces of earlier rocks in ones not quite so ancient. The rocks in question are granites lying east of Canada’s Hudson Bay.

    Scientists have long known that these formed about 2.7 billion years ago. Their chemical composition says they didn’t erupt directly from the mantle, but were instead formed from pre-existing basalts that were pulled below the surface, heated, and then recycled back to the surface to form the granites we see today.

    In the process, the physical remnants of the older rocks were destroyed, but their isotopic signatures remain. The isotope in question is neodymium-142, a rare-earth element used to make extremely powerful magnets.

    Neodymium-142 is one of five stable isotopes of neodymium, but it’s important because it is the decay product from the radioactive decay of an isotope of another rare-earth element, samarium-146.

    Samarium-146 has a half-life of 103 million years. That may sound like a lot in human terms, but in the context of the world’s most ancient rocks, it is actually fairly short, especially because within five or six half-lives it would have been “basically gone,” Carlson says.

    What this means is that by carefully measuring the relative quantities of various isotopes of neodymium, including neodymium-142, scientists can determine whether a rock includes ingredients that come from an older rock that formed before the earth ran out of samarium-146.

    “You can see it with a mass spectrometer, but you can’t see it with a microscope,” Carlton says.

    Using this method, he and O’Neil found that the basalts that were reprocessed to form the 2.7-billion-year-old granites must have formed at least 4.2 billion years ago.

    That’s an interesting find in and of itself, says Tim Johnson, from Curtin University in Perth, Australia, who was not part of the study team, because it provides “convincing evidence” that the Earth’s most ancient crust was indeed recycled into granites, such as those studied by Carlton and O’Neil, rocks that Johnson calls “the nuclei of the continents.”

    But it’s also important because it means that the basalts that formed Carlton’s and O’Neal’s 2.7-billion-year-old granites survived for 1.5 billion years before they were subducted and metamorphosed into them. That’s a long time, given the fact that today’s basalts only survive for a couple hundred million years before modern plate tectonics recycles them.

    One explanation might be that the basalts that formed the Canadian granites came from a gigantic block of rock that somehow resisted subduction for 1.5 billion years. Another is that tectonics on the early Earth moved very slowly, if at all, allowing basalts to remain on the surface of the earth for much longer than is possible in today’s tectonic regime.

    Johnson thinks it’s the latter. Other research, including his own, has been finding that plate tectonics may well not have been occurring on the early Earth.

    “In my view,” he says, “[this] is another nail in the coffin for the view that plate tectonics best explains the geodynamic evolution of the Earth in its first billion years.”

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  • richardmitnick 10:31 am on March 29, 2017 Permalink | Reply
    Tags: A Seismic Mapping Milestone, , , Geology, , ,   

    From ORNL: “A Seismic Mapping Milestone” 

    i1

    Oak Ridge National Laboratory

    March 28, 2017

    Jonathan Hines
    hinesjd@ornl.gov
    865.574.6944

    1
    This visualization is the first global tomographic model constructed based on adjoint tomography, an iterative full-waveform inversion technique. The model is a result of data from 253 earthquakes and 15 conjugate gradient iterations with transverse isotropy confined to the upper mantle. Credit: David Pugmire, ORNL

    When an earthquake strikes, the release of energy creates seismic waves that often wreak havoc for life at the surface. Those same waves, however, present an opportunity for scientists to peer into the subsurface by measuring vibrations passing through the Earth.

    Using advanced modeling and simulation, seismic data generated by earthquakes, and one of the world’s fastest supercomputers, a team led by Jeroen Tromp of Princeton University is creating a detailed 3-D picture of Earth’s interior. Currently, the team is focused on imaging the entire globe from the surface to the core–mantle boundary, a depth of 1,800 miles.

    These high-fidelity simulations add context to ongoing debates related to Earth’s geologic history and dynamics, bringing prominent features like tectonic plates, magma plumes, and hotspots into view. In September 2016, the team published a paper in Geophysical Journal International on its first-generation global model. Created using data from 253 earthquakes captured by seismograms scattered around the world, the team’s model is notable for its global scope and high scalability.

    “This is the first global seismic model where no approximations—other than the chosen numerical method—were used to simulate how seismic waves travel through the Earth and how they sense heterogeneities,” said Ebru Bozdag, a coprincipal investigator of the project and an assistant professor of geophysics at the University of Nice Sophia Antipolis. “That’s a milestone for the seismology community. For the first time, we showed people the value and feasibility of running these kinds of tools for global seismic imaging.”

    The project’s genesis can be traced to a seismic imaging theory first proposed in the 1980s. To fill in gaps within seismic data maps, the theory posited a method called adjoint tomography, an iterative full-waveform inversion technique. This technique leverages more information than competing methods, using forward waves that travel from the quake’s origin to the seismic receiver and adjoint waves, which are mathematically derived waves that travel from the receiver to the quake.

    The problem with testing this theory? “You need really big computers to do this,” Bozdag said, “because both forward and adjoint wave simulations are performed in 3-D numerically.”

    In 2012, just such a machine arrived in the form of the Titan supercomputer, a 27-petaflop Cray XK7 managed by the US Department of Energy’s (DOE’s) Oak Ridge Leadership Computing Facility (OLCF), a DOE Office of Science User Facility located at Oak Ridge National Laboratory.


    ORNL Cray XK7 Titan Supercomputer

    After trying out its method on smaller machines, Tromp’s team gained access to Titan in 2013. Working with OLCF staff, the team continues to push the limits of computational seismology to deeper depths.

    Stitching Together Seismic Slices

    As quake-induced seismic waves travel, seismograms can detect variations in their speed. These changes provide clues about the composition, density, and temperature of the medium the wave is passing through. For example, waves move slower when passing through hot magma, such as mantle plumes and hotspots, than they do when passing through colder subduction zones, locations where one tectonic plate slides beneath another.

    Each seismogram represents a narrow slice of the planet’s interior. By stitching many seismograms together, researchers can produce a 3-D global image, capturing everything from magma plumes feeding the Ring of Fire, to Yellowstone’s hotspots, to subducted plates under New Zealand.

    This process, called seismic tomography, works in a manner similar to imaging techniques employed in medicine, where 2-D x-ray images taken from many perspectives are combined to create 3-D images of areas inside the body.

    In the past, seismic tomography techniques have been limited in the amount of seismic data they can use. Traditional methods forced researchers to make approximations in their wave simulations and restrict observational data to major seismic phases only. Adjoint tomography based on 3-D numerical simulations employed by Tromp’s team isn’t constrained in this way. “We can use the entire data—anything and everything,” Bozdag said.

    Digging Deeper

    To improve its global model further, Tromp’s team is experimenting with model parameters on Titan. For example, the team’s second-generation model will introduce anisotropic inversions, which are calculations that better capture the differing orientations and movement of rock in the mantle. This new information should give scientists a clearer picture of mantle flow, composition, and crust–mantle interactions.

    Additionally, team members Dimitri Komatitsch of Aix-Marseille University in France and Daniel Peter of King Abdullah University in Saudi Arabia are leading efforts to simulate higher-frequency seismic waves. This would allow the team to model finer details in the Earth’s mantle and even begin mapping the Earth’s core.

    To make this leap, Tromp’s team is preparing for Summit, the OLCF’s next-generation supercomputer.


    ORNL IBM Summit supercomputer depiction

    Set to arrive in 2018, Summit will provide at least five times the computing power of Titan. As part of the OLCF’s Center for Accelerated Application Readiness, Tromp’s team is working with OLCF staff to take advantage of Summit’s computing power upon arrival.

    “With Summit, we will be able to image the entire globe from crust all the way down to Earth’s center, including the core,” Bozdag said. “Our methods are expensive—we need a supercomputer to carry them out—but our results show that these expenses are justified, even necessary.”

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    ORNL is managed by UT-Battelle for the Department of Energy’s Office of Science. DOE’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time.

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  • richardmitnick 6:59 am on March 29, 2017 Permalink | Reply
    Tags: , Geology, Lunar and Planetary Science, Smithsonian Air&Space   

    From Smithsonian: “After the Asteroid Impact” 

    smithsonian
    Smithsonian.com

    Air & Space

    March 28, 2017
    Dirk Schulze-Makuch

    1
    Chicxulub, Mexico, as it looks today. Sixty-six million years ago, this was ground zero. (Wikimedia Commons)

    Last week at the Lunar and Planetary Science Meeting in Houston, a research team headed by Chris Lowery from the University of Texas Institute for Geophysics presented the first results of their work at the site of the asteroid impact that wiped out the dinosaurs at the end of the Cretaceous period 66 million years ago. The researchers have recovered nearly 1,000 meters of core material from Chicxulub Crater, located off the Yucatan Peninsula in the Gulf of Mexico. They’re looking to find out exactly what mechanism caused the mass extinction following the impact, and how life eventually came back in the crater.

    According to their findings, life at ground zero bounced back astonishingly quickly. Not all kinds of organisms returned at the same time, however. Microorganisms that can reproduce rather quickly, and that float or drift in great numbers in the upper meters of the sea, came back sooner. Many of these were small photosynthetic organisms that harvest sunlight. The early returners included various types of single-celled microorganisms called foraminifera, including one species with the tongue-twisting name Parvularugoglobigerina eugubina. In fact, this particular organism is seen in the fossil record only after the impact, and may have been one of the first new species of plankton to evolve, just 30,000 years after the asteroid hit.

    Organisms that live on or near the bottom of the sea had a much harder time recovering, and appear to have remained environmentally stressed for a long time. Foraminifera survived the impact in other parts of the world where conditions were less disastrous than at ground zero. Then they diversified and underwent evolutionary change rapidly. Eventually they re-settled the water column above Chicxulub Crater, and when that happened, it happened very quickly.

    This provides us with a general lesson for life on Earth. No matter how grave the conditions, or how severe the blow to life in one particular location, that place will be resettled as soon as environmental conditions become bearable again—if there are other places where life was able to hunker down and stay protected. Challenge life, and its evolutionary toolset kicks in to deal with the new environmental conditions. Microorganisms generally deal much better with dramatically changing conditions than larger animals, so it was “game over” for the dinosaurs. But there are exceptions based on lifestyle. Our mammal ancestors—small burrowing animals—were better protected from the cataclysmic fallout of the asteroid impact than the dinosaurs were, and so eventually carried the day.

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    Air & Space/Smithsonian magazine has been delighting aerospace enthusiasts with the best writing about their favorite subject since April 1986. The bimonthly magazine emphasizes the human stories behind the hardware and has established a track record of getting its readers into those places of the aerospace industry marked “authorized personnel only.”

    As an adjunct of the Smithsonian Institution’s National Air and Space Museum, Air&Space magazine matches the grand scope of the Museum, encompassing every era of aviation and space exploration, and publishes extensively about the Museum collection. With stories that range from the German airmen whose unlucky task it was to crew World War I zeppelins to the design of NASA’s next lunar lander, Air & Space seeks to surprise its audience with a wealth of detail about aviation and spaceflight.


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