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  • richardmitnick 2:42 pm on August 24, 2014 Permalink | Reply
    Tags: , Geology, ,   

    From The New York Times: “Methane Is Discovered Seeping From Seafloor Off East Coast, Scientists Say” 

    New York Times

    The New York Times

    AUG. 24, 2014
    HENRY FOUNTAIN

    Scientists have discovered methane gas bubbling from the seafloor in an unexpected place: off the East Coast of the United States where the continental shelf meets the deeper Atlantic Ocean.

    seeps
    Methane bubbles flow in small streams out of the sediment on an area of seafloor offshore Virginia north of Washington Canyon.

    The methane is emanating from at least 570 locations, called seeps, from near Cape Hatteras, N.C., to the Georges Bank southeast of Nantucket, Mass. While the seepage is widespread, the researchers estimated that the amount of gas was tiny compared with the amount released from all sources each year.

    In a paper published online Sunday in the journal Nature Geoscience, the scientists, including Adam Skarke of Mississippi State University and Carolyn Ruppel of the United States Geological Survey, reported evidence that the seepage had been going on for at least 1,000 years.

    They said the depths of the seeps suggested that in most cases the gas did not reach the atmosphere but rather dissolved in the ocean, where it could affect the acidity of the water, at least locally.

    But methane is a potent, if relatively short-lived, greenhouse gas, so the discovery should aid the study of an issue of concern to climate scientists: the potential for the release of huge stores of methane on land and under the seas as warming of the atmosphere and oceans continues.

    “It highlights a really key area where we can test some of the more radical hypotheses about climate change,” said John Kessler, a professor at the University of Rochester who was not involved in the research.

    Methane seeps occur in many places, but usually in areas that are tectonically active, like off the West Coast of the United States, or connect to deep petroleum basins, as in the Gulf of Mexico. The Atlantic margin, as the region where the shelf meets the deeper oceanic crust is known, is tectonically quiet, and most of the seeps are not thought to be linked to oil and gas deposits.

    “This is a large amount of methane seepage in an area we didn’t expect,” Dr. Skarke said. “That raises new questions for us.”

    Dr. Ruppel said that at about 40 of the seeps — those in water depths exceeding 3,300 feet — the methane may be migrating up through the sediments from deeper reservoirs of the gas. Further studies would be needed to confirm this, she said.

    If the gas is found to be originating from reservoirs, then oil companies could potentially be interested in determining whether the reservoirs can be tapped.

    But Dr. Ruppel said most of the seeps had been found in depths of about 800 to 2,000 feet, where the methane, which is produced by microbes, is most likely trapped in sediments near the seafloor , within cagelike molecules of ice called hydrates. Natural variability in water temperatures, caused by ocean circulation and other factors, may be warming these hydrates just enough to release the gas.

    Hydrates at such relatively shallow depths “are exquisitely sensitive to small changes in temperature,” she said. “You don’t have to change things very much to get the methane to come out.”

    Dr. Kessler, author of an article reviewing the findings in the same journal, said that because the Atlantic margin was unaffected by tectonic activity or other factors, it should prove to be a convenient location to conduct long-term studies of links between climate change and methane releases.

    “How will those release rates accelerate as bottom temperature warms, or how will they decelerate if there are some cooling events?” Dr. Kessler said. “We don’t really have all of the answers. But this is a great place to try to find them.”

    See the full article here.

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  • richardmitnick 2:20 pm on August 24, 2014 Permalink | Reply
    Tags: Earthquake, Geology   

    From The Star Tribune- Earthquake San Fransisco: “6.0-magnitude earthquake in Northern California causes injuries, damaging fires, power outages” 

    star Tribune

    August 24, 2014
    ELLEN KNICKMEYER

    NAPA, Calif. — The largest earthquake to hit the San Francisco Bay Area in 25 years sent scores of people to hospitals, ignited fires, damaged multiple historic buildings and knocked out power to tens of thousands in California’s wine country on Sunday.
    quake

    quake 2

    quake 3

    The 6.0-magnitude earthquake that struck at 3:20 a.m. about 6 miles from the city of Napa ruptured water mains and gas lines, left two adults and a child critically injured, upended bottles and casks at some of Napa Valley’s famed wineries and sent residents running out of their homes in the darkness.

    Dazed residents too fearful of aftershocks to go back to bed wandered at dawn through Napa’s historic downtown, where the quake had shorn a 10-foot chunk of bricks and concrete from the corner of an old county courthouse. Bolder-sized pieces of rubble littered the lawn and street in front of the building and the hole left behind allowed a view of the offices inside.

    College student Eduardo Rivera, 20, said the home he shares with six relatives shook so violently that he kept getting knocked back into his bed as he tried to flee.

    “When I woke up, my mom was screaming, and the sound from the earthquake was greater than my mom’s screams,” Rivera said.

    While inspecting the shattered glass at her husband’s storefront office in downtown Napa, Chris Malloy, 45, described calling for her two children in the dark as the quake rumbled under the family’s home, throwing heavy pieces of furniture 3 or 4 feet and breaking them.

    “It was shaking and I was crawling on my hands and knees in the dark, looking for them,” she said, wearing flip flops on feet left bloodied from crawling through broken glass.

    President Barack Obama was briefed on the earthquake, the White House said. Federal officials also have been in touch with state and local emergency responders. Gov. Jerry Brown declared a state of emergency for southern Napa County, directing state agencies to respond with equipment and personnel.

    Napa Fire Department Operations Chief John Callanan said the city has exhausted its own resources trying to extinguish six fires, some in places with broken water mains; transporting injured residents; searching homes for anyone who might be trapped; and answering calls about gas leaks and downed power lines.

    Two of the fires happened at mobile home parks, including one where four homes were destroyed and two others damaged, Callanan said.

    The earthquake sent at least 87 people to Queen of the Valley Medical Center in Napa, where officials set up a triage tent to handle the influx. Most patients had cuts, bumps, bruises, said Vanessa DeGier, hospital spokeswoman said. She says the facility has treated a hip fracture and heart attack, but it’s unclear if it was related to the quake.

    The child in critical condition was struck by part of a fireplace and had to be airlifted to a specialty hospital for a neurological evaluation, Callanan said.

    The earthquake is the largest to shake the Bay Area since the 6.9-magnitude Loma Prieta quake in 1989, the USGS said. That temblor struck the area on Oct. 17, 1989, during a World Series game between the San Francisco Giants and the Oakland Athletics, collapsing part of the Bay Bridge roadway and killing more than 60 people, most when an Oakland freeway fell.

    Sunday’s quake was felt widely throughout the region. People reported feeling it more than 200 miles south of Napa and as far east as the Nevada border. Amtrak suspended its train service through the Bay Area so tracks could be inspected.

    In Napa, at least three historic buildings were damaged, including the county courthouse, and at least two downtown commercial buildings have been severely damaged. A Red Cross evacuation center was set up at a high school, and crews were assessing damage to homes, bridges and roadways.

    “There’s collapses, fires,” said Napa Fire Capt. Doug Bridewell, standing in front of large pieces of masonry that broke loose from a turn of the century office building where a fire had just been extinguished. “That’s the worst shaking I’ve ever been in.”

    Bridewell said he had to climb over fallen furniture in his own home to check on his family before reporting to duty.

    The shaking emptied cabinets in homes and store shelves, set off car alarms and had residents of neighboring Sonoma County running out of their houses and talking about damage inside their homes.

    Pacific Gas and Electric spokesman J.D. Guidi said close to 30,000 lost power right after the quake hit, but the number was down just under 19,000, most of them in Napa. He says crews are working to make repairs, but it’s unclear when electricity would be restored.

    The depth of the earthquake was just less than 7 miles, and numerous small aftershocks have occurred, the USGS said.

    “A quake of that size in a populated area is of course widely felt throughout that region,” said Randy Baldwin, a geophysicist with the U.S. Geological Survey in Golden, Colorado.

    California Highway Patrol Officer Kevin Bartlett said cracks and damage to pavement closed the westbound Interstate 80 connector to westbound State Route 37 in Vallejo and westbound State Route 37 at the Sonoma off ramp. He says there haven’t been reports of injuries or people stranded in their cars, but there are numerous flat tires from motorists driving over damaged roads.

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  • richardmitnick 6:52 pm on August 23, 2014 Permalink | Reply
    Tags: , , Geology, Volcanos   

    From BBC: “Iceland volcano: Eruption under ice-cap sparks red alert” 

    BBC

    23 August 2014

    Iceland has issued a red alert to aviation after indications of a possible eruption under the country’s biggest glacier, the Vattnajokull.

    icecap
    Vatnajökull, Iceland Ice cap

    The Icelandic Met Office warned that a small eruption had taken place under the Dyngjujokull ice cap.

    cap
    Dyngjujokull ice cap

    Seismic activity is continuing at the Bardarbunga volcano, about 30km away.

    volcano
    Map of Iceland showing the location of Bárðarbunga.

    Airspace over the site has been closed, but all Icelandic airports currently remain open, authorities say. A Europe-wide alert has also been upgraded.

    European air safety agency Eurocontrol said it would produce a forecast of likely ash behaviour every six hours.

    Iceland’s Eyjafjallajokull volcano erupted in 2010, producing ash that severely disrupted air travel.

    vol
    Eyjafjallajokull on map of Iceland

    The red alert is the highest warning on the country’s five-point scale.
    Flooding threat

    The Icelandic Met Office said a team of scientists was flying across the region on Saturday afternoon to monitor seismic activity.

    “The eruption is considered a minor event at this point,” police said in a statement.

    “Because of pressure from the glacier cap, it is uncertain whether the eruption will stay sub-glacial or not.”

    sign
    Warning sign on the road to the Bardarbunga volcano (20 August) On Wednesday several hundred people were evacuated from the volcano area

    eruption
    Eyjafjallajokull eruption (18 April 2010) The eruption of Eyjafjallajokull in April 2010 caused the largest closure of European airspace since World War Two, with losses estimated at between 1.5bn and 2.5bn euros (£1.3-2.2bn).

    The Met Office later issued an update saying that tremor levels had decreased during the afternoon but that earthquake activity was continuing.

    Virgin Atlantic said it had rerouted a flight from London to San Francisco away from the volcano as a precautionary measure.

    It said its other flights “continue to operate as normal”.

    British Airways said it was keeping the situation “under close observation”, but that its flights were continuing to operate normally for now.

    The UK Civil Aviation Authority (CAA) said there would be no impact on flights unless there was an actual eruption.

    Bardarbunga and Dyngjujokull are part of a large volcano system hidden beneath the 500-metre (0.31-mile) thick Vatnajokull glacier in central Iceland.

    Authorities have previously warned that any eruption could result in flooding north of the glacier.

    On Wednesday, authorities evacuated several hundred people from the area over fears of an eruption.

    The region, located more than 300km (190 miles) from the capital Reykjavik, has no permanent residents but sits within a national park popular with tourists.

    The move came after geologists reported that about 300 earthquakes had been detected in the area since midnight on Tuesday.

    Criticism following the strictly enforced shutdown resulted in the CAA relaxing its rules to allow planes to fly in areas with a low density of volcanic ash.

    See the full article here.

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  • richardmitnick 8:49 am on August 12, 2014 Permalink | Reply
    Tags: Dinosaurs, Geology,   

    From M.I.T.: “Rise of the dinosaurs” 


    MIT News

    August 12, 2014
    Jennifer Chu | MIT News Office

    The Jurassic and Cretaceous periods were the golden age of dinosaurs, during which the prehistoric giants roamed the Earth for nearly 135 million years. Paleontologists have unearthed numerous fossils from these periods, suggesting that dinosaurs were abundant throughout the world. But where and when dinosaurs first came into existence has been difficult to ascertain.

    face
    Collage: Jose-Luis Olivares/MIT (original background photograph courtesy of Malka Machlus from Lamont-Doherty Earth Observatory of Columbia University)

    Fossils discovered in Argentina suggest that the first dinosaurs may have appeared in South America during the Late Triassic, about 230 million years ago — a period when today’s continents were fused in a single landmass called Pangaea. Previously discovered fossils in North America have prompted speculation that dinosaurs didn’t appear there until about 212 million years ago — significantly later than in South America. Scientists have devised multiple theories to explain dinosaurs’ delayed appearance in North America, citing environmental factors or a vast desert barrier.

    pangaea
    depiction of Pangaea

    But scientists at MIT now have a bone to pick with such theories: They precisely dated the rocks in which the earliest dinosaur fossils were discovered in the southwestern United States, and found that dinosaurs appeared there as early as 223 million years ago. What’s more, they demonstrated that these earliest dinosaurs coexisted with close nondinosaur relatives, as well as significantly more evolved dinosaurs, for more than 12 million years. To add to the mystery, they identified a 16-million-year gap, older than the dinosaur-bearing rocks, where there is either no trace of any vertebrates, including dinosaurs, in the rock record, or the corresponding rocks have eroded.

    “Right below that horizon where we find the earliest dinosaurs, there is a long gap in the fossil and rock records across the sedimentary basin,” says Jahan Ramezani, a research scientist in MIT’s Department of Earth, Atmospheric and Planetary Sciences. “If the record is not there, it doesn’t mean the dinosaurs didn’t exist. It means that either no fossils were preserved, or we haven’t found them. That tells us the theory that dinosaurs simply started in South America and spread all over the world has no firm basis.”

    Ramezani details the results of his geochronological analysis in the American Journal of Science. The study’s co-authors are Sam Bowring, the Robert R. Shrock Professor of Geology at MIT, and David Fastovsky, professor of geosciences at the University of Rhode Island.

    The isotope chronometer

    The most complete record of early dinosaur evolution can be found in Argentina, where layers of sedimentary rock preserve a distinct evolutionary progression: During the Late Triassic period, preceding the Jurassic, dinosaur “precursors” first appeared, followed by animals that began to exhibit dinosaur-like characteristics, and then advanced, or fully evolved, dinosaurs. Each animal group is found in a distinct rock formation, with very little overlap, revealing a general evolutionary history.

    In comparison, the dinosaur record in North America is a bit muddier. The most abundant fossils from the Late Triassic period have been discovered in layers of rock called the Chinle Formation, which occupies portions of Arizona, New Mexico, Utah, and Colorado, and is best exposed in Petrified Forest National Park. Scientists had previously dated isolated beds of this formation, and determined the earliest dinosaur-like animals, discovered in New Mexico, appeared by 212 million years ago.

    chinle
    Chinle Badlands, Grand Staircase-Escalante National Monument, Utah, US.

    pet
    The Tepees in Petrified Forest National Park in northeastern Arizona, United States. View is toward the northwest from the main park road. According to a National Park Service (NPS) document, rock strata exposed in the Tepees area of the park belong to the Blue Mesa Member of the Chinle Formation and are about 220 to 225 million years old. The colorful bands of mudstone and sandstone were laid down during the Triassic, when the area was part of a huge tropical floodplain

    Ramezani and Bowring sought to more precisely date the entire formation, including levels in which the earliest dinosaur fossils have been found. The team took samples from exposed layers of sedimentary rock that were derived, in large part, from volcanic debris in various sections of the Chinle Formation. In the lab, the researchers pulverized the rocks and isolated individual microscopic grains of zircon — a uranium-bearing mineral that forms in magma shortly prior to volcanic eruptions. From the moment zircon crystallizes, the decay of uranium to lead begins in the mineral and, as Ramezani explains it, “the chronometer starts.” Researchers can measure the ratio of uranium to lead isotopes to determine the age of the zircon, and, inferentially, the rock in which it was found.

    mesa
    The Blue Mesa locality of the Petrified Forest National Park in Arizona contains the Late Triassic continental sedimentary rocks of the Chinle Formation. Near Blue Mesa, the oldest documented dinosaur remains in the Chinle Formation have been found. Courtesy of Malka Machlus from Lamont-Doherty Earth Observatory of Columbia University

    A unique but incomplete record

    The team analyzed individual grains of zircon, and created a precise map of ages for each sedimentary interval of the Chinle Formation. Ramezani found, based on rock ages, that the fossils found in New Mexico are, in fact, not the earliest dinosaurs in North America. Instead, it appears that fossils found in Arizona are older, discovered in rocks as old as 223 million years.

    In this North American mix, the early relatives of dinosaurs apparently coexisted with more evolved dinosaurs for more than 12 million years, according to Ramezani’s analysis.

    “In South America, there is very little overlap,” Ramezani says. “But in North America, we see this unique interval when these groups were coexisting. You could think of it as Neanderthals coexisting with modern humans.”

    While fascinating to think about, Ramezani says this period does not shed much light on when the very first dinosaurs appeared in North America.

    “The fact that our record starts with advanced forms tells us there was a prior history,” Ramezani says. “It’s not just that advanced dinosaurs suddenly appeared 223 million years ago. There must have been prior evolution in North America — we just haven’t identified any earlier dinosaurs yet.”

    He says the answer to when dinosaurs first appeared in North America may lie in a 16-million-year gap, in the lower Chinle Formation and beneath it, which bears no fossils, dinosaurian or otherwise. The absence of any fossils is unremarkable; Ramezani notes that fossil preservation is “an exceptional process, requiring exceptional circumstances.” Dinosaurs may well have first appeared during this period; if they left any fossil evidence, it may have since been erased.

    “Every study like this is a step forward, to try to reconstruct the past,” Ramezani says. “Dinosaurs really rose to the top of the pyramid. What made them so successful, and what were the evolutionary advantages they developed so as to dominate terrestrial ecosystems? It all goes back to their beginning, to the Late Triassic when they just started to appear.”

    The new dates provide a framework against which other theories of dinosaur evolution may be tested, says Raymond Rogers, a professor of geology at Macalester College in Saint Paul, Minn., who was not involved in this work.

    “This is the kind of careful work that needs to be done before evolutionary hypotheses that relate to the origination and diversification of the dinosaurs can be addressed,” Rogers says. “This gap in the Chinle fossil record makes comparing the North American and South American dinosaur records problematic. Existing hypotheses that relate to the timing of dinosaur evolution in North and South America arguably need to be reconsidered in light of this new study.”

    This research was supported by funding from the National Science Foundation.

    See the full article here.

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  • richardmitnick 2:53 pm on August 5, 2014 Permalink | Reply
    Tags: , Geology,   

    From Stanford University: “Powerful tool could unlock secrets of Earth’s interior ocean” 

    Stanford University Name
    Stanford University

    July 28, 2014
    Ker Than

    A new way of determining the hydrogen content in mantle rocks could lead to improved estimates of Earth’s interior water and a better understanding of our planet’s early evolution.

    rock
    Graduate student Suzanne Birner and former postdoctoral researcher Lars Hansen collect structural data in the Josephine Peridotite in Oregon. Megan D’Errico

    A new technique for determining the hydrogen content of mantle rocks could lead to more precise estimates of how much water is contained in Earth’s deep interior and an improved understanding of our planet’s early evolution.

    The rocks that make up the planet’s mantle, which extends from about 20 to 1,800 miles beneath the Earth’s surface, harbor hydrogen atoms within their crystal structures. Scientists estimate that if all of that hydrogen were converted to water–by combining with the oxygen that is naturally found in the planet’s interior–it would equal between half to four times as much water as is found in all of the Earth’s oceans combined. “Scientists used to think that there was not a lot of water inside the Earth because mantle minerals weren’t thought to be able to contain much water,” said Jessica Warren, an assistant professor in the department of Geological and Environmental Sciences at Stanford University.

    In the late 1980s, however, scientists realized that minerals that were considered anhydrous, or lacking in water, actually can contain hydrogen atoms, but only at concentrations of a several parts per million. “That sounds miniscule, but if you multiply that by the volume of the mantle, it’s a very significant amount of water,” Warren said.

    The amount of water contained in mantle rocks is known to influence geological processes such as volcanic eruptions. “The amount of water present within the Earth controls how explosive a volcanic eruption will be,” Warren said, “because during an eruption, there is a rapid pressure change and water dissolved in the magma is released as gas.”

    Many scientists also suspect that mantle water directly influences the shift of the continents over geologic timescales. “The amount of water in the mantle controls its viscosity, or resistance to flow, and some scientists have argued that without water inside the Earth, you would not have plate tectonics,” Warren said.

    A better understanding of how much water is locked away inside Earth could also help constrain models of our planet’s early evolution. “One long-standing question is how much water did our planet contain when it formed?” Warren said. “If we don’t know how much water is within the Earth today, it’s hard to project back to the past and model the early Earth and understand its formation.”

    One reason that the estimates for how much water is inside the Earth vary so widely is that the mineral that scientists have traditionally used to estimate mantle water concentrations, called olivine, loses water over time. “Hydrogen diffuses out of olivine very quickly,” Warren explained. “Just the process of being transported from the mantle to the Earth’s surface results in water loss, so it’s difficult to estimate how much water an olivine sample once held.”

    In a recent study, Warren and Erik Hauri, a geochemist at the Carnegie Institution of Washington, propose using pyroxene–the second-most abundant mantle mineral after olivine–as a proxy for estimating mantle water.

    The pair analyzed several samples of peridotite, a rock that contains both olivine and different types of pyroxenes, which were collected from the seafloors of the Arctic and Indian Oceans and from a unique field site in Oregon. “When tectonic plates collide together, a slice of very deep material can get pushed up onto the crust,” Warren said. “At the field site in Oregon, we can actually walk around on what used to be the mantle.”

    By comparing pyroxenes in the field rocks with samples that had been synthesized in the lab, Warren and Hauri concluded that pyroxene retains water better than olivine. The pair suggests that pyroxenes could be a “powerful tool” for estimating the concentration and location of water bound in minerals in the upper mantle. “Our results suggest that pyroxene does not have olivine’s water-loss problem,” Warren said.

    It may be a while, however, before scientists can use pyroxenes to settle the question of just how much water is contained in the Earth’s mantle. “It’s a complicated calculation,” Warren said, “and we are still a long way off from actually being able to perform that estimate.”

    The pair’s research was published earlier this year of the Journal of Geophysical Research: Solid Earth and was recently featured in Eos, a publication of the American Geophysical Union.

    See the full article here.

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

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  • richardmitnick 2:02 pm on July 30, 2014 Permalink | Reply
    Tags: , , Geology,   

    From SPACE.com: “Early Earth: A Battered, Hellish World with Water Oases for Life “ 

    space-dot-com logo

    July 30, 2014
    Charles Q. Choi

    Asteroids and comets that repeatedly smashed into the early Earth covered the planet’s surface with molten rock during its earliest days, but still may have left oases of water that could have supported the evolution of life, scientists say.

    The new study reveals that during the planet’s infancy, the surface of the Earth was a hellish environment, but perhaps not as hellish as often thought, scientists added.

    Earth formed about 4.5 billion years ago. The first 500 million years of its life are known as the Hadean Eon. Although this time amounts to more than 10 percent of Earth’s history, little is known about it, since few rocks are known that are older than 3.8 billion years old.

    early earth
    depiction of possible early planet Earth

    Earth’s violent youth

    For much of the Hadean, Earth and its sister worlds in the inner solar system were pummeled with an extraordinary number of cosmic impacts.

    “It was thought that because of these asteroids and comets flying around colliding with Earth, conditions on early Earth may have been hellish,” said lead study author Simone Marchi, a planetary scientist at the Southwest Research Institute in Boulder, Colorado. This imagined hellishness gave the eon its name — Hadean comes from Hades, the lord of the underworld in Greek mythology.

    However, in the past dozen years or so, a radically different picture of the Hadean began to emerge. Analysis of minerals trapped within microscopic zircon crystals dating from this eon “suggested there was liquid water on the surface of the Earth back then, clashing with the previous picture that the Hadean was hellish,” Marchi said. This could explain why the evidence of the earliest life on Earth appears during the Hadean — maybe the planet was less inhospitable during that eon than previously thought.

    Cosmic bombardment history

    The exact timing and magnitude of the impacts that smashed Earth during the Hadean are unknown. To get an idea of the effects of this bombardment, Marchi and his colleagues looked at the moon, whose heavily cratered surface helped model the battering that its close neighbor Earth must have experienced back then.

    “We also looked at highly siderophile elements (elements that bind tightly to iron), such as gold, delivered to Earth as a result of these early collisions, and the amounts of these elements tells us the total mass accreted by Earth as the result of these collisions,” Marchi said. Prior research suggests these impacts probably contributed less than 0.5 percent of the Earth’s present-day mass.

    The researchers discovered that “the surface of the Earth during the Hadean was heavily affected by very large collisions, by impactors larger than 100 kilometers (60 miles) or so — really, really big impactors,” Marchi said. “When Earth has a collision with an object that big, that melts a large volume of the Earth’s crust and mantle, covering a large fraction of the surface,” Marchi added.

    These findings suggest that Earth’s surface was buried over and over again by large volumes of molten rock — enough to cover the surface of the Earth several times. This helps explain why so few rocks survive from the Hadean, the researchers said.

    However, although these findings might suggest that the Hadean was a hellish eon, the researchers found that “there were time gaps between these large collisions,” Marchi said. “Generally speaking, there may have been something on the order of 20 or 30 impactors larger than 200 km (120 miles) across during the 500 million years of the Hadean, so the time between such impactors was relatively long,” Marchi said.

    Any water vaporized near these impacts “would rain down again,” Marchi said, and “there may have been quiet tranquil times between collisions — there could have been liquid water on the surface.”

    The researchers suggested that life emerging during the Hadean was probably resistant to the high temperatures of the time. Marchi and his colleagues detailed their findings in the July 31 issue of the journal Nature.

    See the full article, with video, here.


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  • richardmitnick 2:43 pm on July 28, 2014 Permalink | Reply
    Tags: , , , Geology,   

    From SPACE.com: “Microbe’s Innovation May Have Started Largest Extinction Event on Earth” 

    space-dot-com logo

    SPACE.com

    July 27, 2014
    Michael Schirber, Astrobiology Magazine

    The environment can produce sudden shocks to the life of our planet through impacting space rocks, erupting volcanoes and other events.

    But sometimes life itself turns the tables and strikes a swift blow back to the environment. New research suggests that the biggest extinction event on record may have been initiated by a small, but significant change to a tiny microbe .

    The end-Permian (or PT) extinction event occurred 252 million years ago. It is often called the Great Dying because around 90 percent of marine species disappeared in one fell swoop. Similar numbers died on land as well, producing a stark contrast between Permian rock layers beneath (or before) the extinction and the Triassic layers above. Extinctions are common throughout time, but for this one, the fossil record truly skipped a beat.

    permian
    A photo of the Permian Triassic (PT) boundary at Meishan, China.
    Credit: Shuzhong Shen

    graph2
    Plot of extinction intensity (percentage of genera that are present in each interval of time but do not exist in the following interval) vs time in the past for marine genera.[1] Geological periods are annotated (by abbreviation and colour) above. The Permian–Triassic extinction event is the most significant event for marine genera, with just over 50% (according to this source) failing to survive.

    “The end-Permian is the greatest extinction event that we know of,” said Daniel Rothman, a geophysicist at the Massachusetts Institute of Technology. “The changes in the fossil record were obvious even to 19th Century geologists.”

    graph.
    A plot of data on mass extinctions in Earth’s history. The end-Permian extinction event is the large peak on the left at 250 million years ago.
    Credit: University of Chicago

    Understanding the cause of this biological devastation requires understanding the geochemical clues that go along with it. Chief among these clues is a sudden swing in the balance of carbon isotopes stored in rocks from that same time period.

    If geologists can find what disrupted the carbon, they’ll likely know what killed off so much of the Earth’s life forms. Several theories have tried to explain the carbon perturbation as, for example, massive volcanism, or a drop in sea level, but none of these environmental causes have fully matched the data.

    Rothman and his colleagues have identified a different culprit — one coming from biology rather than geology. They argue in the Proceedings of the National Academy of Sciences that the carbon disruption and, consequently, the end-Permian extinction were set off by a particular microorganism that evolved a new way to digest organic material into methane.

    With this genetic innovation, these methane-producers, or methanogens, ran rampant across the ocean, overturning the carbon cycle. The resulting changes in ocean chemistry would have driven many species to extinction.

    “This shows how unstable Earth’s systems are,” Rothman said. “A very small event in the microbial community can have an enormous impact on the environment.”
    Carbon exchange

    The basis of this new theory comes from a reassessment of the carbon data.

    For decades, geologists have been aware that the ratio of carbon isotopes (the light verses heavy forms of the element) changed abruptly in geological samples around the time of the end-Permian event. Specifically, the carbon stored in rocks tilted towards the lighter isotope by about 1 percent over a matter of 100,000 years.

    Rothman and his colleagues re-analyzed these isotope fluctuations, incorporating them into a model of dynamical exchange between different reservoirs of carbon material. The results showed that the level of carbon dioxide in the ocean rose faster than exponentially. The increase was slow at first, but picked up pace as time went on.

    Rothman and his collaborators argue that no geological source can adequately explain the dramatic growth of carbon dioxide. One popular theory has been that high levels of carbon dioxide were released by massive volcanic eruptions in Siberia, which lasted for a million years and covered a million square miles with lava.

    “It’s hard to get the arithmetic right with just volcanoes,” Rothman said.

    He and his fellow authors believe an additional input is needed – one coming from biology. A burst in biological activity could explain the exponential-like growth in the ocean’s carbon dioxide reserve.

    Success breeds success

    Exponential-like growth is not uncommon in biology. Certain invasive species, for example, experience population explosions once they enter a new ecosystem. Similar types of expansion can occur when an evolutionary development gives a particular species a leg up on its competition.

    The authors contend that some sort of biological innovation altered the distribution of carbon in the ocean. And they assume that the ocean was, in some sense, waiting for this innovation with a large reservoir of organic material (the detritus from dead organisms) in the ocean sediment.

    “Other research has shown that during the end Permian, these organic products had accumulated to very high levels, probably due to a slowdown of normal degradation,” said Greg Fournier, a co-author also from MIT.

    This organic sediment was like “a big pile of food” for an enterprising organism to exploit.

    Fournier had a clue as to what sort of organism this might be. From previous work he had done as a NASA Astrobiology Institute (NAI) postdoctoral fellow, he knew that a major innovation occurred around this time period in a type of methane-spewing archaea called Methanosarcina.

    This methanogen is currently found all over the place, Fournier says, with species inhabiting marine and freshwater sediments, soils, sewage, and even inside the guts of animals such as cattle, where they produce a lot of the methane released into the world.

    Part of Methanosarcina’s success is due to the fact that these organisms can process acetate, a common organic residue, faster than some of their methanogen cousins. Basically, the Methanosarcina are able to get more energy out of the conversion of acetate to methane.

    Fournier had earlier shown that Methanosarcina had acquired this ability from horizontal gene transfer. In some long-ago microbial tryst, an ancient methanogen (which produced methane as waste) swapped genes with an ancient cellulose-eating bacterium (which produced acetate as waste). This genetic “technology transfer” created an organism that could more efficiently metabolize acetate.

    To obtain a more precise date for when this microbial innovation happened, Fournier and his colleagues performed a rigorous genetic analysis.

    “We compared genomes from a variety of different methanogens and dated the evolution of this [new metabolic pathway] by using a calibrated ‘clock’ that counts the changes accumulated in genes over time,” Fournier said.

    The results placed the gene-swapping event at 240 million years ago, plus or minus 40 million years.

    “The molecular clock analysis simply confirms that, to the best of our ability to measure, the timing is consistent with [the end-Permian event],” Fournier said.

    If indeed the genetic innovation occurred in the late Permian, then it’s reasonable to assume that the Methanosarcina population began to multiply. Much of the methane produced by these organisms would have converted — through oxidation reactions or biological processing — into carbon dioxide, causing a rise in the carbon dioxide levels of the ocean.

    The conversion of methane into carbon dioxide would have had a secondary effect as well: it would have driven down the amount of oxygen in the ocean water. Because Methanosarcina is anaerobic, the reduction in oxygen would have helped them thrive even more, creating a positive feedback loop. This could explain the faster than exponential growth in carbon dioxide concentrations that the authors observed.

    As previous scientists have argued, the high levels of carbon dioxide would have led to a more acidic ocean, which would have been especially deadly for shell-bearing lifeforms. And like a house of cards, many other species followed suit.

    A nickel’s worth

    One possible sticking point is that exponential-like growth often gets ahead of itself and becomes a victim of its own success. In biology, overgrown populations tend to run out of food or some other resource.

    In the case of methanogens, this limiting resource might have been the element nickel, which these organisms need to produce metabolic enzymes. The levels of nickel in the ocean are not typically very high.

    “If methanogens were to become active, they could be limited by nickel,” Rothman said.

    However, when the team checked nickel concentrations in late Permian geological samples, they found a spike that corresponded with the carbon isotope fluctuations. The source of this high nickel abundance was most likely the massive volcanic activity in Siberia, where the world’s largest nickel deposits are located. That spike in nickel allowed methanogens to take off.

    “It’s a nice confirmation because it closes a circle, so to speak, by bringing the story back to volcanism,” Rothman said.

    Who gets the blame finally?

    “It is a novel idea that will need a lot of testing to see if it has ‘legs’,” said geologist David Bottjer of the University of Southern California, who was not involved with this work.

    The arguments seem valid to him, but it will take some time for “the process of science to unwind as we see how this new idea stands up to earlier proposed mechanisms.”

    Rothman said they are currently studying whether the methanogens may have left some sort of biomarker, for example an organic compound, which could provide further support for the scenario.

    “[The authors] have done a really nice job linking the latest geo-chronologic age constraints on the duration of the extinction to the changes in the carbon cycle,” said paleontologist Douglas Erwin of the Smithsonian Institution.

    But Erwin thinks the emphasis on methanogens is misplaced.

    “Their suggestion that the PT [extinction] was instigated by a ‘specific microbial innovation’ suggests a misunderstanding of causality,” he said.

    To his thinking, volcanism is the ultimate cause, since it triggered the methanogen growth by creating favorable conditions.

    Rothman admits that’s one way to look at it, but he doesn’t think the volcanoes (and their release of nickel) were necessary for the explosive microbial growth. Instead, he calls the volcanism a “catalytic event” that helped propel the genetic innovation.

    “There is a random component to biological evolution,” said Fournier. “This gene transfer occurs by chance, but is only selected for and expands through a population when it conveys a specific advantage, which would be realized under those conditions [brought on by the volcanism].”

    Either way, it’s impressive how interdependent all these different elements appear to have been.

    “The clear implication is that life and the environment have co-evolved,” Rothman said.

    See the full article here.

    This article originated in Astrobiology Magazine

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  • richardmitnick 1:57 pm on January 24, 2014 Permalink | Reply
    Tags: , , Geology,   

    From Argonne APS: “Earth’s Core Reveals an Inner Weakness” 

    News from Argonne National Laboratory

    JANUARY 23, 2014
    Michael Schirber

    The word “core” conjures up an image of something strong. However, new experiments show that the iron found in the Earth’s core is relatively weak. This finding is based on x-ray spectroscopy and diffraction measurements performed at high pressure and utilizing several x-ray beamlines at two U.S. Department of Energy Office of Science light sources including the Advanced Photon Source at Argonne National Laboratory. The researchers in these studies extrapolated their results to core conditions and found that the strength of iron deep within the Earth is lower than previously thought. This weakness may explain how the crystal structure in the Earth’s core has transformed over geological time scales.

    graph
    The strength of several different metals, extrapolated to high pressure. (Courtesy of A.E. Gleason.)

    The extreme conditions of the Earth’s core are very difficult to reproduce in a laboratory. The pressure rises above 3 million atmospheres (atm, 320-370 gigapascals, or GPa), and the temperature is comparable to that on the surface of the Sun (over 5000° C). Seismologists have learned about the core by studying seismic waves that travel through the Earth’s interior.

    One surprising discovery is that core-traversing seismic waves travel 3% faster along the polar axis as compared to those moving through the equatorial plane. Researchers assume that this seismic-wave anisotropy is due to iron crystals aligning their lattice structures. Such alignment requires a certain amount of “flow” through the solid core, and this has yet to be explained.

    Deep inside the Earth, iron has a different structure than it does at the surface. For objects like horseshoes and tea kettles, the iron atoms are packed together in a pattern called body-centered cubic (bcc). However, when the pressure rises above 12 GPa, the iron atoms rearrange into a hexagonally close-packed (hcp) structure.

    In order to better understand hcp iron, researchers from <a href="Stanford University“>Stanford University and the SLAC National Accelerator Laboratory have made new strength measurements at high pressure, as described in Nature Geoscience. Strength, which is a material’s resistance to flow, is characterized by the pressure at which the material begins to deform. Previous studies of iron’s strength have typically applied pressure in a non-uniform (or non-hydrostatic) way.

    To reproduce the hydrostatic conditions of the Earth’s interior, the researchers here loaded their foil-shaped samples of iron into a gasket filled with a pressure-transmitting medium of neon or helium gas. This gasket was then placed in a diamond-anvil cell, where pressures as high as 200 GPa could be applied.

    To study the material properties of hydrostatically compressed iron, the team first performed nuclear resonant inelastic x-ray scattering (NRIXS) experiments at two Advanced Photon Source x-ray beamlines: 3-ID-B (operated by the Argonne X-ray Science Division within the APS) and16-ID-D (operated by the High Pressure Collaborative Access Team, or HP-CAT). The spectrum of the scattered x-rays contained information about shear waves that travel through the iron like seismic waves. From their data analysis, the team derived the shear modulus — a measure of the rigidity of a material — and found it to be slightly lower than previous measurements of iron taken in non-hydrostatic environments.

    The team then performed radial x-ray diffraction (rXRD) experiments at the HP-CAT 16-BM-D beamline, as well as with another x-ray beamline at the Advanced Light Source at Lawrence Berkeley National Laboratory. These measurements showed a shift in iron diffraction lines due to a squeezing (or strain) of the lattice separation when the sample was under pressure.

    The researchers combined the observed strain and shear modulus values to obtain the strength of iron at high pressures. Surprisingly, the derived strength was 60% lower than previous estimates, making iron one of the weakest metals at high pressures (see the figure).

    The team estimated that iron’s strength is around 1 GPa at the pressure and temperature of the Earth’s core. This low value has implications for how the material in the core deforms, or “creeps,” over time. Previous models assumed that this creep was a very slow process, based mostly on diffusion of atoms. However, a lower strength for iron means that creep could occur through the movement of defects, or “dislocations,” in the crystal structure. This faster dislocation creep would imply that the observed seismic-wave anisotropy developed relatively early in the Earth’s history.

    To explore this idea further, the team plans to perform a new set of iron experiments at high temperature as well as high pressure.

    See the full article here.

    Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy’s Office of Science

    The Advanced Photon Source at Argonne National Laboratory is one of five national synchrotron radiation light sources supported by the U.S. Department of Energy’s Office of Science to carry out applied and basic research to understand, predict, and ultimately control matter and energy at the electronic, atomic, and molecular levels, provide the foundations for new energy technologies, and support DOE missions in energy, environment, and national security.

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  • richardmitnick 11:01 am on May 21, 2013 Permalink | Reply
    Tags: , Geology, ,   

    From SLAC: “Earth’s iron core is surprisingly weak, Stanford researchers say” 

    The researchers used a diamond anvil cell to squeeze iron at pressures as high as 3 million times that felt at sea level to recreate conditions at the center of Earth. The findings could refine theories of how the planet and its core evolved.

    May 16, 2013
    Louis Bergeron

    “The massive ball of iron sitting at the center of Earth is not quite as “rock-solid” as has been thought, say two Stanford mineral physicists. By conducting experiments that simulate the immense pressures deep in the planet’s interior, the researchers determined that iron in Earth’s inner core is only about 40 percent as strong as previous studies estimated.

    two
    Through laboratory experiments, postdoctoral researcher Arianna Gleason, left, and Wendy Mao, an assistant professor of geological and environmental sciences and of photon science, determined that the iron in Earth’s inner core is about 40 percent as strong as previously believed.

    This is the first time scientists have been able to experimentally measure the effect of such intense pressure – as high as 3 million times the pressure Earth’s atmosphere exerts at sea level – in a laboratory. A paper presenting the results of their study is available online in Nature Geoscience.

    Until now, almost all of what is known about Earth’s inner core came from studies tracking seismic waves as they travel from the surface of the planet through the interior. Those studies have shown that the travel time through the inner core isn’t the same in every direction, indicating that the inner core itself is not uniform. Over time and subjected to great pressure, the core has developed a sort of fabric as grains of iron elongate and align lengthwise in parallel formations.

    Gleason and Mao conducted their experiments using a diamond anvil cell – a device that can exert immense pressure on tiny samples clenched between two diamonds. They subjected minute amounts of pure iron to pressures between 200 and 300 gigapascals (equivalent to the pressure of 2 million to 3 million Earth atmospheres). Previous experimental studies were conducted in the range of only 10 gigapascals.

    Gleason and Mao expect their findings will help other researchers set more realistic variables for conducting their own experiments.”

    See the full article here.

    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.

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  • richardmitnick 2:59 pm on March 4, 2013 Permalink | Reply
    Tags: , , , , Geology   

    From Argonne Lab: “Doubling Estimates of Light Elements in the Earth’s Core” 

    Argonne National Laboratory

    MARCH 1, 2013
    Zhu Mao

    The inner core of the Earth is the remotest area on the globe, mostly impossible to study directly. It is an area of the planet that experiences both extremely high pressure ranging from 3,300,000 to 3,600,000 times atmospheric pressure, and extremely high temperatures somewhere from 5000 to 6000 K. One way to study this area is by recording how sound waves travel across the interior, matching these profiles to known information about how sound waves travel through candidate iron alloys, and attempting to discern which materials must be present. This method requires an understanding of how sound waves travel through the potential materials present in the core. A team of researchers utilized APS x-rays to develop a new model of how sound waves travel through iron and iron-silicon alloys, showing for the first time that increased temperatures will affect the sound wave profile, and that sound velocity and density correlate in a non-linear way. Their results suggest that the amount of light elements in the inner core could be two times more than estimated in previous studies without considering these effects.

    plots
    Velocity-density plots of the samples at high pressures and temperatures. The top panel shows the velocity-density plot for hcp-Fe at both 300 K and 700 K. The dashed lines shows the linear fit, while the solid line shows the power law fit, which matches the data more closely. The bottom panel shows the velocity-density relation of both hcp-Fe and the iron-silicon alloy at 300 K.

    earth core

    See the full article here.

    Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy’s Office of Science

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