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

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


    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

    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.

    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.”

    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.

    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.

    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.”

    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.”

    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 10:07 am on April 20, 2017 Permalink | Reply
    Tags: , , , , Earth Observation, Everywhere!, Hydrogen,   

    From U Arizona: “Hydrogen, Hydrogen, Everywhere!” 

    U Arizona bloc

    University of Arizona

    April 18, 2017
    Daniel Stolte

    What our Milky Way might look like to alien astronomers: This image of NGC 2683, a spiral galaxy also known as the “UFO Galaxy” due to its shape, was taken by the Hubble Space Telescope. Since trying to find out what the Milky Way looks like is a bit like trying to picture an unfamiliar house while being confined to a room inside, studies like this one help us gain a better idea of our cosmic home. (Image: NASA/ESA/Hubble)

    UA astronomers Huanian Zhang and Dennis Zaritsky are lifting the veil of our galactic home by providing the first detections of diffuse hydrogen wafting about in a vast halo surrounding the Milky Way.


    The spectra used in this study cover large portions of the sky, depicted here as a map wrapping around the observer. The colors code for spectral emissions from diffuse hydrogen gas in the Milky Way’s halo: While the degrees of brightness vary, they are remarkably uniform across the sky, indicating a rather uniform distribution of hydrogen as would be expected in a galactic halo. (Image: H. Zhang and D. Zaritsky)

    Sometimes it takes a lot of trees to see the forest. In the case of the latest discovery made by astronomers at the University of Arizona, exactly 732,225. Except that in this case, the “forest” is a veil of diffuse hydrogen gas enshrouding the Milky Way, and each “tree” is another galaxy observed with the 2.5-meter telescope of the Sloan Digital Sky Survey.

    SDSS Telescope at Apache Point Observatory, NM, USA

    After combining this staggering number of spectra — recorded patterns of wavelengths revealing clues about the nature of a cosmic target — UA astronomers Huanian Zhang and Dennis Zaritsky report the first detections of diffuse hydrogen wafting about in a vast halo surrounding the Milky Way. Such a halo had been postulated based on what astronomers knew about other galaxies, but never directly observed.

    Astronomers have long known that the most prominent features of a typical spiral galaxy such as our Milky Way — a central bulge surrounded by a disk and spiral arms — account only for the lesser part of its mass.

    Milky Way NASA/JPL-Caltech /ESO R. Hurt

    The bulk of the missing mass is suspected to lie in so-called dark matter, a postulated but not yet directly observed form of matter believed to account for the majority of matter in the universe. Dark matter emits no electromagnetic radiation of any kind, nor does it interact with “normal” matter (which astronomers call baryonic matter), and is therefore invisible and undetectable through direct imaging.

    The dark matter of a typical galaxy is thought to reside in a more or less spherical halo that extends 10 to 30 times farther out than the distance between the center of our galaxy and the sun, according to Zaritsky, a professor in the UA’s Department of Astronomy and deputy director of the UA’s Steward Observatory.

    U Arizona Steward Observatory at Kitt Peak, AZ, USA

    “We infer its existence through dynamical simulations of galaxies,” Zaritsky explains. “And because the ratio of normal matter to dark matter is now very well known, for example from measuring the cosmic microwave background, we have a pretty good idea of how much baryonic matter should be in the halo. But when we add all the things we can see with our instruments, we get only about half of what we expect, so there has to be a lot of baryonic matter waiting to be detected.”

    By combining such a large number of spectra, Zaritsky and Zhang, a postdoctoral fellow in the Department of Astronomy/Steward Observatory, covered a large portion of space surrounding the Milky Way and found that diffuse hydrogen gas engulfs the entire galaxy, which would account for a large part of the galaxy’s baryonic mass.

    “It’s like peering through a veil,” Zaritsky said. “We see diffuse hydrogen in every direction we look.”

    He pointed out that this is not the first time gas has been detected in halos around galaxies, but in those instances, the hydrogen is in a different physical state.

    “There are cloudlets of hydrogen in the galaxy halo, which we have known about for a long time, called high-velocity clouds,” Zaritsky said. “Those have been detected through radio observations, and they’re really clouds — you see an edge, and they’re moving. But the total mass of those is small, so they couldn’t be the dominant form of hydrogen in the halo.”

    Since observing our own galaxy is a bit like trying to see what an unfamiliar house looks like while being confined to a room inside, astronomers rely on computer simulations and observations of other galaxies to get an idea of what the Milky Way might look like to an alien observer millions of light-years away.

    For their study, published in the journal Nature Astronomy, the researchers sifted through the public databases of the Sloan Digital Sky Survey and looked for spectra taken by other scientists of galaxies outside our Milky Way in a narrow spectral line called hydrogen alpha. Seeing this line in a spectrum tells of the presence of a particular state of hydrogen that is different from the vast majority of hydrogen found in the universe.

    Unlike on Earth, where hydrogen occurs as a gas consisting of molecules of two hydrogen atoms bound together, hydrogen exists as single atoms in outer space, and those can be positively or negatively charged, or neutral. Neutral hydrogen constitutes a small minority compared to its ionized (positive) form, which constitutes more than 99.99 percent of the gas spanning the intergalactic gulfs of the universe.

    Unless neutral hydrogen atoms are being energized by something, they are extremely difficult to detect and therefore remain invisible to most observational approaches, which is why their presence in the Milky Way’s halo had eluded astronomers until now. Even in other galaxies, halos are difficult to pin down.

    “You don’t just see a pretty picture of a halo around a galaxy,” Zaritsky said. “We infer the presence of galactic halos from numerical simulations of galaxies and from what we know about how they form and interact.”

    Zaritsky explained that based on those simulations, scientists would have predicted the presence of large amounts of hydrogen gas stretching far out from the center of the Milky Way, but remaining associated with the galaxy, and the data collected in this study confirm the presence of just that.

    “The gas we detected is not doing anything very noticeable,” he said. “It is not spinning so rapidly as to indicate that it’s in the process of being flung out of the galaxy, and it does not appear to be falling inwards toward the galactic center, either.”

    One of the challenges in this study was to know whether the observed hydrogen was indeed in a halo outside the Milky Way, and not just part of the galactic disk itself, Zaritsky said.

    “When you see things everywhere, they could be very close to us, or they could be very far away,” he said. “You don’t know.”

    The answer to this question, too, was in the “trees,” the more than 700,000 spectral analyses scattered across the galaxy. If the hydrogen gas were confined to the disk of the galaxy, our solar system would be expected to “float” inside of it like a ship in a slowly churning maelstrom, orbiting the galactic center. And just like the ship drifting with the current, very little relative movement would be expected between our solar system and the ocean of hydrogen. If, on the other hand, it surrounded the spinning galaxy in a more or less stationary halo, the researchers expected that wherever they looked, they should find a predictable pattern of relative motion with respect to our solar system.

    “Indeed, in one direction, we see the gas coming toward us, and the opposite direction, we see it moving away from us,” Zaritsky said. “This tells us that the gas is not in the disk of our galaxy, but has to be out in the halo.”

    Next, the researchers want to look at even more spectra to better constrain the distribution around the sky and the motions of the gas in the halo. They also plan to search for other spectral lines, which may help better understand the physical state such as temperature and density of the gas.

    See the full article here .

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    U Arizona campus

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

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

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

  • richardmitnick 8:24 am on April 19, 2017 Permalink | Reply
    Tags: , Climate Change Reroutes a Yukon River in a Geological Instant, Earth Observation, , , 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

    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.

    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.

    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.

    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.”

    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: Earth Observation, , Mis-Atlantic Ridge, Plate techtonics,   

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


    Universe Today

    17 Apr , 2017
    Matt Williams

    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.


    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.

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

    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.

    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.

    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 9:19 am on April 13, 2017 Permalink | Reply
    Tags: , Earth Observation,   

    From U Arizona: “Biosphere 2 as You’ve Never Seen It Before” 

    U Arizona bloc

    University of Arizona

    April 12, 2017
    Robin Tricoles

    U Arizona Biosphere 2

    UA researcher Tyeen Taylor goes high into Biosphere 2 in his study of plant volatiles, the molecular compounds that are small enough to become a gas. (Photo: Bob Demers/UANews)

    Inside the iconic structure far from the UA’s main campus, climate change researcher Tyeen Taylor uses the simulation rainforest to study botanical volatiles, looking for clues to how those plants manage high temperatures and drought.

    Tyeen Taylor moves catlike along a narrow path fashioned from wooden planks. The path, tucked inside a simulation Brazilian rainforest, is man-made. The air is warm and thick. The scent of damp earth and assorted greenery predominates.

    This living lab is part of the University of Arizona’s Biosphere 2, which this month is celebrating its 10th anniversary of UA research. And this is where Taylor conducts much of his study of climate change — specifically volatiles, the molecular compounds that are small enough to become a gas.

    “My work is about what you smell as you walk into the rainforest, which is plant volatiles,” says Taylor, a researcher at Biosphere 2. “I’m studying the volatiles that help plants deal with stress like the stress that comes from high temperatures and drought. With some plants’ leaves, if you crush them up, you smell all of this good-smelling stuff. Those are oils, and they’re stored as oils, but once you break them free, just like a perfume, the oil is gradually released into the air.”

    But other volatiles are produced on demand in response to environmental conditions that can shift at any given moment. Those are the ones Taylor is focused on. He explains that once the temperature of a leaf climbs, enzymes start modifying particular molecules inside the leaf, which turns those molecules into gas, which is then released.

    Although plants that inhabit rainforests exchange massive amounts of carbon dioxide and oxygen, it’s this process of volatile production, says Taylor, that mitigates damage and helps plants cope with climatic change — and, in turn, affects the world’s climate. For example, volatiles affect the length of time methane, a greenhouse gas, stays in the atmosphere, he says.

    “The volatiles also form aerosol particles after reacting with other chemicals in the atmosphere, and those aerosol particles are required for water to condense around,” Taylor says. “That’s what makes clouds, and the clouds, of course, make rain, and they reflect sunlight, which cools the planet.”

    Taylor, who grew up in Alaska, says his love for tropical forests started early, when he traveled as a child with his parents to Costa Rica on Christmas breaks. Now one of his favorite things to do when visiting tropical rainforests is to identify the plants by scent.

    “Oftentimes the leaves are so high up you can’t get a sample, but you can put a little cut in the trunk, and from the smell from that cut, you can work your way through the evolutionary structure of different plant groups because particular plant groups have particular types of volatiles,” Taylor says. “Once you calibrate your nose, you can get to the order and family and genus of a plant — maybe even the species, if it’s a peculiar enough smell.”

    While working on his doctorate at UA, Taylor built the first-ever instrument designed for the precise measurements of leaf-volatile emissions in the field. He is now attempting to merge the instrument with one that measures photosynthesis, so he can see these two processes simultaneiously.

    “I’ll be able to see how much carbon is entering the leaf in terms of carbon dioxide and how much of that carbon is leaving the leaf in terms of volatiles,” Taylor says.

    Taylor says carbon is like money in the bank for the leaf, and the leaf has to spend that money wisely. Too high a cost, and plant growth and leaf processes could be reduced, which could become an unsound evolutionary strategy for some species, he says.

    “I want to see what the carbon expense of these volatiles is because we know they help leaves deal with stress, but we also know not all species do it,” Taylor says. “The important question is why, and the answer may be that it costs too much carbon. If it turns out it doesn’t cost enough carbon to be a selective disadvantage, then there has to be another answer.

    “We know that different species will respond to climate change differently, but we want to know if some of them will be able to handle the warmer temperatures and droughts. By understanding the evolutionary controls on plant stress responses, we can better predict which species will be tolerant and which will not. If we know that, we’ll know a little more about the response of the rainforest and a little more about how the forest controls the climate.”

    See the full article here .

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    U Arizona campus

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

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

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

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

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

    Carnegie Institution for Science
    Carnegie Institution for Science

    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.

    See the full article here .

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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 10:39 am on April 6, 2017 Permalink | Reply
    Tags: , Brexit 1.0: scientists find evidence of Britain's separation from Europe, Earth Observation,   

    From ICL: “Brexit 1.0: scientists find evidence of Britain’s separation from Europe” 

    Imperial College London
    Imperial College London

    04 April 2017
    Colin Smith

    Researchers have found evidence of how ancient Britain separated from Europe, which happened in two stages, they report in Nature Communications.

    Artist’s impression of the ancient land bridge. Credit: Imperial College London/Chase Stone

    Nearly 450,000 years ago, when Earth was in the grip of an ice age, ice stretched right across the North Sea, from Britain to Scandinavia. The low sea levels meant that the entire English Channel was dry land, a frozen tundra landscape, crisscrossed by small rivers.

    Britain’s separation from mainland Europe is believed to be the result of spill over from a proglacial lake – a type of lake formed in front of an ice sheet – in the North Sea, but this has remained unproven. Now, researchers from Imperial College London and their colleagues from institutes in Europe show that the opening of the Dover Strait in the English Channel occurred in two episodes, where an initial lake spill over was followed by catastrophic flooding.

    Ten years ago, the researchers from Imperial College London revealed geophysical evidence of giant valleys on the seafloor in the central part of English Channel. They believed these valley networks were evidence of a megaflood gouging out the land, which they speculated may have been caused by a catastrophic breach in a chalk rock ridge joining Britain to France.

    The new study by the team, working with their colleagues in Europe, now shows for the first time the details of how this chalk ridge in the Dover Strait, between Dover and Calais, was breached. New geophysical data collected by colleagues from Belgium and France has been combined with seafloor data from the UK showing evidence of huge holes and a valley system located on the seafloor.

    The team show that the chalk ridge acted like a huge dam and behind it was a proglacial lake. This lake was first hypothesised by scientists more than 100 years ago and the authors of today’s study show how the lake overflowed in giant waterfalls, eroding the rock escarpment, weakening it and eventually causing it to fail and release huge volumes of water onto the valley floor below.

    The team believe that the huge holes that they analysed on the seafloor are plunge pools, created when water cascading over an escarpment hit the ground and eroded rock. The plunge pools in the Dover Strait are huge – up to several kilometres in diameter and around 100 metres deep and were drilled into solid rock. Around seven plunge pools run in a line from the ports of Calais to Dover. The researchers suggest these plunge pools are evidence of an overflow of water from the lake in the southern North Sea.

    The straight line of the plunge pools suggests they were cascading off one single rock ridge perhaps 32 kilometres long and 100 metres high– the land bridge between Europe and the UK.

    The researchers have also found evidence that a second event fully opened the Dover Strait. Later on, perhaps hundreds of thousands of years later, a new valley system, the Lobourg Channel, was carved by megaflood processes that crossed the Dover Strait. The researchers demonstrate that this valley system is connected to the giant valley network in the central English Channel. They suggest that a spill over of other, smaller lakes in front of the ice sheets in the North Sea may have been responsible for the later episode of flood erosion.

    Putting the puzzle together

    It has taken ten years, but by pulling all the pieces of the geological jigsaw puzzle together the team say they are more confident about what may have caused the megaflood in the English Channel thousands of years ago.

    Dr Jenny Collier, a co-author of the study from the Department of Earth Science and Engineering at Imperial College London, said: “Based on the evidence that we’ve seen, we believe the Dover Strait 450,000 years ago would have been a huge rock ridge made of chalk joining Britain to France, looking more like the frozen tundra in Siberia than the green environment we know today. It would have been a cold world dotted with waterfalls plunging over the iconic white chalk escarpment that we see today in the White Cliffs of Dover.

    “We still don’t know for sure why the proglacial lake spilt over. Perhaps part of the ice sheet broke off, collapsing into the lake, causing a surge that carved a path for the water to cascade off the chalk ridge. In terms of the catastrophic failure of the ridge, maybe an earth tremor, which is still characteristic of this region today, further weakened the ridge. This may have caused the chalk ridge to collapse, releasing the megaflood that we have found evidence for in our studies.”

    Engineers first found evidence of the plunge pools when they were carrying out geological surveys of the Dover Strait seafloor back in the 1960s. No one knew what caused them, but they were called the Fosse Dangeard. The loose gravel and sand infilling these plunge pools meant that the engineers had to move the route of the Channel Tunnel to avoid them. In 1985 a marine geologist named Professor Alec Smith, from Bedford College in London, first proposed that the holes were created by ancient waterfalls, but the lack of hard evidence meant that the assertions were largely forgotten. Now, the authors of today’s study say Smith’s original assertions were right.

    The scientists say if it wasn’t for a set of chance geological circumstances, Britain may have still remained connected to mainland Europe, jutting out into the sea similarly to Denmark.

    Professor Sanjeev Gupta, a co-author from the Department of Earth Science and Engineering at Imperial, added: “The breaching of this land bridge between Dover and Calais was undeniably one of the most important events in British history, helping to shape our island nation’s identity even today. When the ice age ended and sea levels rose, flooding the valley floor for good, Britain lost its physical connection to the mainland. Without this dramatic breaching Britain would still be a part of Europe. This is Brexit 1.0 – the Brexit nobody voted for.”

    The team still do not have an exact timeline of events. In the next step, the researchers would like to take core samples of the in-filled sediments in the plunge pools, which they will analyse to determine the timing of erosion and infill of the plunge pools, the environments represented by these sediments, and the source of the sediments. Developing a timeline of events would enable them to learn more about the distinctive evolution of Britain, compared to mainland Europe. However, this will be a real challenge for the team as getting sediment core samples in the Dover Strait means dealing with huge tidal changes and traversing the world’s busiest shipping lane.

    The study was carried out in conjunction with researchers from Royal Observatory Belgium; Ghent University, Belgium; CNRS, the University of Lille, and the University of Western Britanny in France; and Top-Hole Studies Ltd, UK.

    See the full article here .

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    Imperial College London

    Imperial College London is a science-based university with an international reputation for excellence in teaching and research. Consistently rated amongst the world’s best universities, Imperial is committed to developing the next generation of researchers, scientists and academics through collaboration across disciplines. Located in the heart of London, Imperial is a multidisciplinary space for education, research, translation and commercialisation, harnessing science and innovation to tackle global challenges.

  • richardmitnick 9:26 am on April 4, 2017 Permalink | Reply
    Tags: , Earth Observation, , Why Do Great Earthquakes Follow Other at Subduction Zones?   

    From Eos: “Why Do Great Earthquakes Follow Other at Subduction Zones? “ 

    AGU bloc

    Eos news bloc


    31 March 2017
    Terri Cook

    A decade of continuous GPS measurements in South America indicates that enhanced strain accumulation following a great earthquake can initiate failure along adjacent fault segments.

    People walk through the streets of Talca, Chile, past major damage from the earthquake on 12 March 2010. Credit: Joe Raedle/Getty Images

    Recently, seismologists have recognized that great subduction zone earthquakes, also known as megathrust earthquakes, tend to recur in “supercycles.” These cycles are characterized by the release of strain in a cluster of earthquakes within a few years of each other, followed by a lengthy period of quiescence ranging from several decades to several centuries, during which strain once again accumulates. Megathrust earthquakes have the potential to cause widespread damage and devastating tsunamis, yet the mechanisms that trigger two or more of these events within a few years to a decade are still not well understood, primarily because of a lack of long-term geodetic data.

    Now Melnick et al. [Geophysical Research Letters] have analyzed a decade’s worth of continuously measured GPS data spanning two great earthquakes, the 2010 Maule (M 8.8) and 2015 Illapel (M 8.3) events.

    2010 Maule (M 8.8)

    2015 Illapel (M 8.3)

    Both earthquakes occurred along the central Chilean margin where the Nazca plate is diving beneath the South American plate at a rate of 66 millimeters per year. The team used these data to estimate changes in surface deformation rates throughout the Andes Mountains and then compared the results with numerical simulations.

    The researchers’ findings indicate that surface velocities increased following the Maule earthquake, a change they attribute to the large-scale, elastic response of both the continental and oceanic plates to fault slip during and immediately after the earthquake. This response, the team argues, accelerated the rate of shortening across the megathrust and heightened the stress on adjacent fault segments. According to the researchers, the resulting period of stress accumulation constitutes a “superinterseismic” phase of the earthquake cycle that may have brought nearby fault segments closer to failure and ultimately triggered the 2015 event.

    This study demonstrates that cycles of megathrust earthquakes can be strongly influenced by the behavior of nearby seismic events. The results may help clarify the occurrence of clusters of other great earthquakes, including those that have occurred in Alaska, Cascadia, Sumatra, and Japan, as well as provide insight into the processes controlling the lag time between those events.

    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 7:43 am on April 4, 2017 Permalink | Reply
    Tags: , Earth Observation, , We Have Some God News on the California Drought. Take a Look   

    From NYT: “We Have Some God News on the California Drought. Take a Look.” 

    New York Times

    The New York Times


    MARCH 22, 2017

    The majestic beauty of California’s Sierra Nevada never fails to impress. But the mountain range, which stretches hundreds of miles, is much more than a stunning vista. It’s a linchpin that helps make living in an arid state possible.

    That’s because one of California’s most important water supplies is melted snow. Each spring and summer, the Sierra sends runoff down its slopes that recharges rivers and reservoirs, allowing crops to be irrigated and drinking glasses to be filled.

    Knowing with precision how much snow has accumulated is crucial for farmers and water managers.

    That’s where a mapping project at NASA’s Jet Propulsion Laboratory known as the Airborne Snow Observatory comes in.


    Using measurements gathered by specialized instruments on a plane, scientists have been able to gain an unprecedented understanding of the amount of water present in the Sierra’s snow.

    This year, after California’s very wet winter, the totals have been remarkably big.

    Using the NASA data, we compared this year’s snowpack with that of 2015, when the state was in the grip of drought (which, at least officially, is still ongoing). In the interactive maps below, the white areas had a meter, or 3.3 feet, or more of snow on the ground in March.

    High in the mountains, this year’s snow blankets the ground in layers tens of feet deep in many places.

    At the lower elevations around the Hetch Hetchy reservoir, which collects most of the melting snow runoff in this area and supplies water to millions, there was almost no snow to speak of in 2015. This year, the snowpack reached down to within a few hundred feet of the reservoir’s edge.

    These maps show parts of the Tuolumne Basin, which in late February was blanketed by 1.2 million acre-feet of snow-water equivalent, or the amount of water that would result if the snow were instantly melted.

    That’s about 10 times the amount as the same time in 2015, said Thomas Painter, a snow hydrologist at the NASA Jet Propulsion Laboratory/California Institute of Technology, who leads the NASA program.

    He added, “And it keeps on coming.”

    The pattern has held for the central Sierra region as a whole:


    The airborne observatory has been detecting snow depths in the mountains ranging from a few feet at lower elevations to more than 70 feet in avalanche areas.

    “Some of the snowdrifts have faces of 25 to 40 feet,” said Jeffrey Payne, a water resources manager at the Friant Water Authority who has analyzed the NASA data. “So we’ve got some pretty serious snow.”

    Strong winds created huge snowdrifts near the western cliffs of the Minarets in the central Sierra Nevada. Photo by Jim Wilson/The New York Times

    Trees on a slope in the snow-covered eastern Sierra Nevada. Photo by Jim Wilson/The New York Times

    Ski resorts that typically close in the spring are so deeply blanketed that they have been making plans to extend their seasons.
    Officials at Squaw Valley, in the Lake Tahoe area, and Mammoth Mountain, below, in the eastern Sierra, said they anticipated staying open well into summer.

    Skiers at Mammoth Mountain. Photo by Jim Wilson/The New York Times

    A snow-covered ridge on the western slope of the central Sierras. Photo by Jim Wilson/The New York Times

    The snow observatory project, which began flights over the Sierra in 2013, is a groundbreaking initiative in California, where aging infrastructure, a warming climate and rapid population growth have made water management a high-stakes job.

    For decades, state officials have estimated snowpack levels by extrapolating from ground-based data gathered at points across the range.

    The margin of error, unsurprisingly, has been huge.

    “It’s like turning on your TV screen and four of the pixels turn on, and you can only use those four every single time you watch ‘Breaking Bad,’” Dr. Painter said.

    Every one to four weeks, the NASA crew circles above the Sierra Nevada in an airplane that fires laser pulses toward the ground. By measuring how fast the pulses bounce back, the scientists are able to create detailed topographical maps.

    Compare those with maps of the mountains when bare and factor in the snow’s density, and they can tell how much water is present.

    With the view from the sky, Dr. Painter said, “we turn on the whole screen, every pixel.”

    Thomas Painter on the steps of the plane NASA uses to gauge snow depth. Photo by Jim Wilson/The New York Times

    Dr. Painter with a device that uses laser beams to precisely measure topography.

    The observatory also measures the reflection of sunlight off the snow, which is critical to understanding how much energy the snow absorbs and how fast it could melt.

    Mr. Payne of the Friant Water Authority, which manages water for agricultural land in the San Joaquin Valley, said the new snow data was game-changing for farmers, who will be able to plan their crops with greater confidence.

    “We need to be smarter about how we approach water resource management,” Mr. Payne said. “And this new technology is sort of a beacon of hope.”

    For now, the observatory is taking measurements for most of the central Sierra Nevada. The hope is to get more buy-in from state officials and expand to the whole range, Dr. Painter said.

    It has been an increasingly easy sell.

    “It really has gotten to the point now where we don’t call on anyone,” Dr. Painter said. “We are simply responding to phone calls.”

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

    From COSMOS: “Ancient Earth leaves a fading signature” 

    Cosmos Magazine bloc


    17 March 2017
    Richard A Lovett

    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.”

    See the full article here .

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