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  • richardmitnick 4:19 pm on October 21, 2014 Permalink | Reply
    Tags: , , Geology, USGS   

    From livescience: “Earthquake Forecast: 4 California Faults Are Ready to Rupture” 

    Livescience

    October 13, 2014
    Becky Oskin

    With several faults slicing through the San Francisco Bay Area, forecasting the next deadly earthquake becomes a question of when and where, not if.

    Now researchers propose that four faults have built up enough seismic strain (stored energy) to unleash destructive earthquakes, according to a study published today (Oct. 13) in the Bulletin of the Seismological Society of America.

    The quartet includes the Hayward Fault, the Rodgers Creek Fault, the Green Valley Fault and the Calaveras Fault. While all are smaller pieces of California’s San Andreas Fault system, which is more than 800 miles (1,300 kilometers) long, the four faults are a serious threat because they directly underlie cities. [Photo Journal: The Gorgeous San Andreas Fault]

    fault
    San Francisco Bay Area earthquake faults are drawn in red.

    saf
    Description: USGS diagram of San Andreas Fault
    Date: 14 March 2006

    “The Hayward Fault is just right in the heart of where people live, and the most buildings and the most infrastructure,” said Jim Lienkaemper, lead study author and a research geophysicist at the U.S. Geological Survey’s Earthquake Science Center in Menlo Park, California. “But it’s not just one fault, it’s the whole shopping basket. If you are in the middle of the Bay Area, you are near a whole lot of faults, and I’m concerned about all of them.”

    Lienkaemper and his colleagues gauged the potential for destructive earthquakes by monitoring tiny surface shifts along California faults. Certain faults are in constant motion, creeping steadily by less than 0.4 inches (1 centimeter) each year. These slow movements add up over time, cracking sidewalk curbs and buildings. They also serve as clues to what’s happening deep below ground, where earthquakes strike.

    “If you figure out where faults are creeping, it tells you where they’re locked and how much they’re locked,” Lienkaemper told Live Science.

    Fault creep varies, with some faults sliding at a snail’s pace and others barely budging. Models suggest that the diversity comes from locked zones that are 3 to 6 miles (5 to 10 km) below the surface, where the fault is stuck instead of sliding. For example, the relatively fast-creeping southern Hayward Fault is only about 40 percent locked, on average, while the slow-creeping Rodgers Creek Fault is 89 percent locked, the study reports. When these locked areas build up a critical amount of strain, they break apart in an earthquake.
    earthquakes

    sfa
    Map of Bay Area earthquake faults and creep measurement sites.
    Credit: USGS

    Lienkaemper and his co-author estimated a fault’s future earthquake potential by combining creep measurements with mathematical fault models and other regional data, such as the time since the last earthquake.

    The Hayward Fault has banked enough energy for a magnitude-6.8 earthquake, according to the study. The Rodgers Creek Fault could trigger a magnitude-7.1 earthquake, and the Green Valley Fault also has the potential to unleash a magnitude-7.1 shaker. The Northern Calaveras Fault is set for a magnitude-6.8 temblor.

    Of all Bay Area faults, the Hayward Fault is most likely to spawn a damaging earthquake in the next 30 years, scientists think. Its 1868 earthquake was called the Big One until the great 1906 San Francisco quake came along. The Hayward Fault has ruptured about every 140 years for its previous five large earthquakes. The probability of a magnitude-6.7 earthquake on the Hayward Fault is 30 percent in the next 30 years.

    Though 146 years have now passed since the last Hayward earthquake, that doesn’t mean the fault is overdue for another quake, Lienkaemper said. “The average is 160 years, but the uncertainty is plus or minus 100 years, which is almost as big as the time [interval] itself.” The 160-year average comes from an analysis of data collected from trenches dug across the fault that revealed evidence of earthquakes over thousands of years.

    The Rodgers Creek and Green Valley Faults are also closing in on their average repeat times between earthquakes.

    See the full article here.

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  • richardmitnick 3:51 pm on October 16, 2014 Permalink | Reply
    Tags: , Geology,   

    From UC Berkeley: “Earth’s magnetic field could flip within a human lifetime” 

    UC Berkeley

    UC Berkeley

    October 14, 2014
    Robert Sanders

    Imagine the world waking up one morning to discover that all compasses pointed south instead of north.

    It’s not as bizarre as it sounds. Earth’s magnetic field has flipped – though not overnight – many times throughout the planet’s history. Its dipole magnetic field, like that of a bar magnet, remains about the same intensity for thousands to millions of years, but for incompletely known reasons it occasionally weakens and, presumably over a few thousand years, reverses direction.

    team
    Left to right, Biaggio Giaccio, Gianluca Sotilli, Courtney Sprain and Sebastien Nomade sitting next to an outcrop in the Sulmona basin of the Apennine Mountains that contains the Matuyama-Brunhes magnetic reversal. A layer of volcanic ash interbedded with the lake sediments can be seen above their heads. Sotilli and Sprain are pointing to the sediment layer in which the magnetic reversal occurred. (Photo by Paul Renne)

    Now, a new study by a team of scientists from Italy, France, Columbia University and the University of California, Berkeley, demonstrates that the last magnetic reversal 786,000 years ago actually happened very quickly, in less than 100 years – roughly a human lifetime.

    “It’s amazing how rapidly we see that reversal,” said UC Berkeley graduate student Courtney Sprain. “The paleomagnetic data are very well done. This is one of the best records we have so far of what happens during a reversal and how quickly these reversals can happen.”

    Sprain and Paul Renne, director of the Berkeley Geochronology Center and a UC Berkeley professor-in- residence of earth and planetary science, are coauthors of the study, which will be published in the November issue of Geophysical Journal International and is now available online.

    Flip could affect electrical grid, cancer rates

    The discovery comes as new evidence indicates that the intensity of Earth’s magnetic field is decreasing 10 times faster than normal, leading some geophysicists to predict a reversal within a few thousand years.

    Though a magnetic reversal is a major planet-wide event driven by convection in Earth’s iron core, there are no documented catastrophes associated with past reversals, despite much searching in the geologic and biologic record. Today, however, such a reversal could potentially wreak havoc with our electrical grid, generating currents that might take it down.

    And since Earth’s magnetic field protects life from energetic particles from the sun and cosmic rays, both of which can cause genetic mutations, a weakening or temporary loss of the field before a permanent reversal could increase cancer rates. The danger to life would be even greater if flips were preceded by long periods of unstable magnetic behavior.

    “We should be thinking more about what the biologic effects would be,” Renne said.

    Dating ash deposits from windward volcanoes

    The new finding is based on measurements of the magnetic field alignment in layers of ancient lake sediments now exposed in the Sulmona basin of the Apennine Mountains east of Rome, Italy. The lake sediments are interbedded with ash layers erupted from the Roman volcanic province, a large area of volcanoes upwind of the former lake that includes periodically erupting volcanoes near Sabatini, Vesuvius and the Alban Hills.

    two
    Leonardo Sagnotti, standing, and coauthor Giancarlo Scardia collecting a sample for paleomagnetic analysis.

    Italian researchers led by Leonardo Sagnotti of Rome’s National Institute of Geophysics and Volcanology measured the magnetic field directions frozen into the sediments as they accumulated at the bottom of the ancient lake.

    Sprain and Renne used argon-argon dating, a method widely used to determine the ages of rocks, whether they’re thousands or billions of years old, to determine the age of ash layers above and below the sediment layer recording the last reversal. These dates were confirmed by their colleague and former UC Berkeley postdoctoral fellow Sebastien Nomade of the Laboratory of Environmental and Climate Sciences in Gif-Sur-Yvette, France.

    Because the lake sediments were deposited at a high and steady rate over a 10,000-year period, the team was able to interpolate the date of the layer showing the magnetic reversal, called the Matuyama-Brunhes transition, at approximately 786,000 years ago. This date is far more precise than that from previous studies, which placed the reversal between 770,000 and 795,000 years ago.

    “What’s incredible is that you go from reverse polarity to a field that is normal with essentially nothing in between, which means it had to have happened very quickly, probably in less than 100 years,” said Renne. “We don’t know whether the next reversal will occur as suddenly as this one did, but we also don’t know that it won’t.”

    Unstable magnetic field preceded 180-degree flip

    Whether or not the new finding spells trouble for modern civilization, it likely will help researchers understand how and why Earth’s magnetic field episodically reverses polarity, Renne said.
    the polar wanderingsThe ‘north pole’ — that is, the direction of magnetic north — was reversed a million years ago. This map shows how, starting about 789,000 years ago, the north pole wandered around Antarctica for several thousand years before flipping 786,000 years ago to the orientation we know today, with the pole somewhere in the Arctic.

    The magnetic record the Italian-led team obtained shows that the sudden 180-degree flip of the field was preceded by a period of instability that spanned more than 6,000 years. The instability included two intervals of low magnetic field strength that lasted about 2,000 years each. Rapid changes in field orientations may have occurred within the first interval of low strength. The full magnetic polarity reversal – that is, the final and very rapid flip to what the field is today – happened toward the end of the most recent interval of low field strength.

    Renne is continuing his collaboration with the Italian-French team to correlate the lake record with past climate change.

    Renne and Sprain’s work at the Berkeley Geochronology Center was supported by the Ann and Gordon Getty Foundation.

    See the full article here.

    Founded in the wake of the gold rush by leaders of the newly established 31st state, the University of California’s flagship campus at Berkeley has become one of the preeminent universities in the world. Its early guiding lights, charged with providing education (both “practical” and “classical”) for the state’s people, gradually established a distinguished faculty (with 22 Nobel laureates to date), a stellar research library, and more than 350 academic programs.

    UC Berkeley Seal

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  • richardmitnick 3:43 pm on September 19, 2014 Permalink | Reply
    Tags: , , Geology,   

    From astrobio.net: “What set the Earth’s plates in motion?” 

    Astrobiology Magazine

    Astrobiology Magazine

    Sep 19, 2014
    Source: University of Sidney

    The mystery of what kick-started the motion of our earth’s massive tectonic plates across its surface has been explained by researchers at the University of Sydney.

    “Earth is the only planet in our solar system where the process of plate tectonics occurs,” said Professor Patrice Rey, from the University of Sydney’s School of Geosciences.

    “The geological record suggests that until three billion years ago the earth’s crust was immobile so what sparked this unique phenomenon has fascinated geoscientists for decades. We suggest it was triggered by the spreading of early continents then eventually became a self-sustaining process.”

    Professor Rey is lead author of an article on the findings published in Nature on Wednesday, 17 September.

    The other authors on the paper are Nicolas Flament, also from the School of Geosciences and Nicolas Coltice, from the University of Lyon.

    split
    The image shows a snapshot from the film after 45 million years of spreading. The pink is the region where the mantle underneath the early continent has melted, facilitating its spreading, and the initiation of the plate tectonic process. Credit: Patrice Rey, Nicolas Flament and Nicolas Coltice.

    The image shows a snapshot after 45 million years of spreading. The pink is the region where the mantle underneath the early continent has melted, facilitating its spreading, and the initiation of the plate tectonic process. Credit: Patrice Rey, Nicolas Flament and Nicolas Coltice.

    There are eight major tectonic plates that move above the earth’s mantle at rates up to 150 millimetres every year.

    In simple terms the process involves plates being dragged into the mantle at certain points and moving away from each other at others, in what has been dubbed ‘the conveyor belt’.

    Plate tectonics depends on the inverse relationship between density of rocks and temperature.

    At mid-oceanic ridges, rocks are hot and their density is low, making them buoyant or more able to float. As they move away from those ridges they cool down and their density increases until, where they become denser than the underlying hot mantle, they sink and are ‘dragged’ under.

    ridge
    Mid-ocean ridge

    But three to four billion years ago, the earth’s interior was hotter, volcanic activity was more prominent and tectonic plates did not become cold and dense enough to spontaneously sank.

    “So the driving engine for plate tectonics didn’t exist,” said Professor Rey said.

    “Instead, thick and buoyant early continents erupted in the middle of immobile plates. Our modelling shows that these early continents could have placed major stress on the surrounding plates. Because they were buoyant they spread horizontally, forcing adjacent plates to be pushed under at their edges.”

    “This spreading of the early continents could have produced intermittent episodes of plate tectonics until, as the earth’s interior cooled and its crust and plate mantle became heavier, plate tectonics became a self-sustaining process which has never ceased and has shaped the face of our modern planet.”

    The new model also makes a number of predictions explaining features that have long puzzled the geoscience community.

    See the full article here.

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  • richardmitnick 2:26 pm on September 17, 2014 Permalink | Reply
    Tags: , , Geology   

    from astrobio.net: “Early Earth less hellish than previously thought” 

    Astrobiology Magazine

    Astrobiology Magazine
    Source: Vanderbilt University

    Sep. 15, 2014
    David Salisbury

    Conditions on Earth for the first 500 million years after it formed may have been surprisingly similar to the present day, complete with oceans, continents and active crustal plates.

    This alternate view of Earth’s first geologic eon, called the Hadean, has gained substantial new support from the first detailed comparison of zircon crystals that formed more than 4 billion years ago with those formed contemporaneously in Iceland, which has been proposed as a possible geological analog for early Earth.

    The study was conducted by a team of geologists directed by Calvin Miller, the William R. Kenan Jr. Professor of Earth and Environmental Sciences at Vanderbilt University, and published online this weekend by the journal Earth and Planetary Science Letters in a paper titled, Iceland is not a magmatic analog for the Hadean: Evidence from the zircon record.

    From the early 20th century up through the 1980’s, geologists generally agreed that conditions during the Hadean period were utterly hostile to life. Inability to find rock formations from the period led them to conclude that early Earth was hellishly hot, either entirely molten or subject to such intense asteroid bombardment that any rocks that formed were rapidly remelted. As a result, they pictured the surface of the Earth as covered by a giant “magma ocean.”

    cm
    Calvin Miller at the Kerlingarfjoll volcano in central Iceland. Some geologists have proposed that the early Earth may have resembled regions like this. (Tamara Carley / Vanderbilt)

    This perception began to change about 30 years ago when geologists discovered zircon crystals (a mineral typically associated with granite) with ages exceeding 4 billion years old preserved in younger sandstones. These ancient zircons opened the door for exploration of the Earth’s earliest crust. In addition to the radiometric dating techniques that revealed the ages of these ancient zircons, geologists used other analytical techniques to extract information about the environment in which the crystals formed, including the temperature and whether water was present.

    Since then zircon studies have revealed that the Hadean Earth was not the uniformly hellish place previously imagined, but during some periods possessed an established crust cool enough so that surface water could form – possibly on the scale of oceans.

    Accepting that the early Earth had a solid crust and liquid water (at least at times), scientists have continued to debate the nature of that crust and the processes that were active at that time: How similar was the Hadean Earth to what we see today?

    Two schools of thought have emerged: One argues that Hadean Earth was surprisingly similar to the present day. The other maintains that, although it was less hostile than formerly believed, early Earth was nonetheless a foreign-seeming and formidable place, similar to the hottest, most extreme, geologic environments of today. A popular analog is Iceland, where substantial amounts of crust are forming from basaltic magma that is much hotter than the magmas that built most of Earth’s current continental crust.

    “We reasoned that the only concrete evidence for what the Hadean was like came from the only known survivors: zircon crystals – and yet no one had investigated Icelandic zircon to compare their telltale compositions to those that are more than 4 billion years old, or with zircon from other modern environments,” said Miller.

    z
    Images of a collection of Icelandic zircons taken with a scanning electron microscope. They range in size from a tenth of a millimeter to a few thousands of a millimeter. (Tamara Carley / Vanderbilt)

    In 2009, Vanderbilt doctoral student Tamara Carley, who has just accepted the position of assistant professor at Layfayette College, began collecting samples from volcanoes and sands derived from erosion of Icelandic volcanoes. She separated thousands of zircon crystals from the samples, which cover the island’s regional diversity and represent its 18 million year history.

    Working with Miller and doctoral student Abraham Padilla at Vanderbilt, Joe Wooden at Stanford University, Axel Schmitt and Rita Economos from UCLA, Ilya Bindeman at the University of Oregon and Brennan Jordan at the University of South Dakota, Carley analyzed about 1,000 zircon crystals for their age and elemental and isotopic compositions. She then searched the literature for all comparable analyses of Hadean zircon and for representative analyses of zircon from other modern environments.

    “We discovered that Icelandic zircons are quite distinctive from crystals formed in other locations on modern Earth. We also found that they formed in magmas that are remarkably different from those in which the Hadean zircons grew,” said Carley.

    Most importantly, their analysis found that Icelandic zircons grew from much hotter magmas than Hadean zircons. Although surface water played an important role in the generation of both Icelandic and Hadean crystals, in the Icelandic case the water was extremely hot when it interacted with the source rocks while the Hadean water-rock interactions were at significantly lower temperatures.

    “Our conclusion is counterintuitive,” said Miller. “Hadean zircons grew from magmas rather similar to those formed in modern subduction zones, but apparently even ‘cooler’ and ‘wetter’ than those being produced today.

    he study was supported by National Science Foundation grants EAR-1220523, EAR- CAREER-0844772 and DGE-0909667, and research grants from the National Geographic Society and the Keck Geology Consortium.

    See the full article here.

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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: , 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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