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Scientists Identify Cause of Japan's Devastating 2011 Tsunami - 0 views

  • In March 2011, a devastating tsunami struck Japan's Tohoku region
  • Now, researchers have uncovered the cause of this tsunami, shedding light on what displaced the seafloor off the northeastern coast of Japan
  • Learning more about the 2011 tsunami and its causes is an important step for monitoring future events.
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  • could help researchers provide earlier warnings
  • During their study
  • scientists underwent a 50-day expedition on the Japanese drilling vessel Chikyu
  • They then drilled three holes in the Japan Trench area in order to study the rupture zone of the 2011 earthquake
  • a fault in the ocean floor where two of Earth's major tectonic plates meet deep beneath the surface of the Pacific Ocean.
  • The conventional view among geologists
  • has been that deep beneath the seafloor, where rocks are strong, movements of the plates can generate a lot of elastic rebound
  • Closer to the surface of the seafloor, where rocks are softer and less compressed, this rebound effect was thought to taper off
  • In fact
  • the largest displacement of plates before the 2011 tsunami occurred in 1960 off the coast of Chile
  • That's when a powerful earthquake displaced seafloor plates by an average of 20 meters
  • The Tohoku earthquake, in contrast, displaced its own plates by 30 to 50 meters.
  • So what caused this unexpectedly violent slip
  • the fault itself is very thin--less than five meters thick in the area sampled.
  • makes it the thinnest plate boundary on Earth.
  • In addition, clay deposits that fill the narrow fault are made of extremely fine sediment, which makes it extremely slippery
  • these findings don't just show researchers a bit more about the past; they also have implications for the future
  • Other subduction zones in the northwest Pacific where this type of clay is present--from Russia's Kamchatka peninsula to the Aleutian Islands--may also be capable of generating similar, huge earthquakes
Mars Base

Sumatra quake was part of crustal plate breakup: Study shows huge jolt measured 8.7, ri... - 0 views

  • Seismologists have known for years that the Indo-Australian plate of Earth's crust is slowly breaking apart
  • quake was caused by at least four undersea fault ruptures
  • within a 2-minute, 40-second period
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  • This is part of the messy business of breaking up a plate. … This is a geologic process
  • will take millions of years to form a new plate boundary
  • likely, it will take thousands of similar large quakes for that to happen."
  • All four faults
  • were strike-slip faults, meaning ground on one side of the fault moves horizontally past ground on the other side
  • great quake of last April 11 "is possibly the largest strike-slip earthquake ever seismically recorded
  • although a similar size quake in Tibet in 1950 was of an unknown type
  • 2012 quakes likely were triggered, at least in part, by changes in crustal stresses caused by the magnitude-9.1 Sumatra-Andaman earthquake of Dec. 26, 2004
  • the 8.7 and 8.2 quakes were generated by horizontal movements
  • not by vertical motion
  • explains why they didn't generate major tsunamis
  • 8.7 quake caused small tsunamis, the largest of which measured about 12 inches in height at Meulaboh, Indonesia
  • Indo-Australian plate is breaking into two or perhaps three pieces
  • happening because it is colliding with Asia in the northwest, which slows down the western part of the plate, while the eastern part of the plate continues moving more easily by diving or "subducting" under the island of Sumatra to the northeast
  • subduction zone off Sumatra caused the catastrophic 2004 magnitude-9.1 quake and tsunami
  • ruptured along a roughly 90-mile length
  • seafloor on one side of the fault slipped about 100 feet past the seafloor on the fault's other side
  • second fault, which slipped about 25 feet, began to rupture 40 seconds after
  • extended an estimated 60 miles to 120 miles north-northeast to south-southwest – perpendicular to the first fault and crossing it.
  • third fault was parallel to the first fault and about 90 to the miles southwest
  • started breaking 70 seconds after the quake began
  • along a length of about 90 miles
  • slipped about 70 feet
  • The fourth fault paralleled the first and third faults
  • began to rupture 145 seconds after the quake began
  • fault rupture was roughly 30 miles to 60 miles long.
  • fault slipped about 20 feet past ground on the other side
Mars Base

Land Bridge Caused Wild Temperature Swings - ScienceNOW - 0 views

  • When the Bering Strait (box, lower left) was closed at the height of the last ice age, any sudden influx of fresh water to the North Atlantic couldn't flow through the Arctic Ocean to the North Pacific, making episodes of abrupt climate change much more likely.
  • Much of the last ice age was characterized by violent climate swings
  • beginning about 80,000 years ago, average temperatures in and around the North Atlantic rose or fell by 10°C or more in the course of a decade or two—a pattern that lasted for 70,000 years
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  • a new study also points to a more earthbound culprit: the presence of a land bridge connecting Asia to North America.
  • debated whether the climate swings were driven by sharp variations in solar activity or simply by unstable climatic processes
  • Earth's climate has been relatively stable since the end of the last ice age
  • temperatures were fairly stable, too, after the ice age began in earnest about 100,000 years ago
  • 20,000 years later, things became unhinged
  • global sea level dropped to about 50 meters lower than it is today
  • As the ice sheets that covered North America and northern Eurasia snatched up more and more of Earth's water
  • exposed a broad strip of land that connected what is today Alaska and Siberia
  • Ancient animals used the land bridge, which measured as much as 1500 kilometers wide in spots, to roam back and forth between Asia and North America
  • also huge consequences for Earth's climate
  • two sets of climate simulations
  • one in which the Bering Strait was open
  • one in which it was blocked
  • each set of simulations, the researchers gradually added large amounts of fresh water to the North Atlantic between the latitudes of 20° and 50
  • researchers propose, this swath, which spans the latitudes from southern Cuba to southern England, would have received large amounts of meltwater from Northern Hemisphere ice sheets during warm spells that occasionally punctuated the ice age
  • Today, the surface waters in this swath affect the temperature and salinity of water even farther north in the Atlantic
  • a region where surface waters cool, sink to the seafloor, and then flow southward—a critical link of the worldwide conveyor belt of ocean circulatio
  • Gulf Stream, which brings climate-warming waters from the equator to the North Atlantic, comes to a halt.
  • If waters of the far North Atlantic don't sink, says Hu, much of the large-scale ocean circulation worldwide temporarily collapses
  • surface waters became so fresh that they never got denser than the underlying salty water, and therefore never sank
  • shutting down ocean circulation and plunging areas around the North Atlantic, including Greenland, into a cold spell
  • researchers noted a critical difference between the sets of simulations: When the Bering Strait was closed, it took as many as 1400 years for ocean circulation to recover; when the strait was open, the circulation rarely took more than 400 years to recuperate
  • sign that ocean circulation is stable when the strait is open
  • Whenever the ocean circulation shut down in the simulations, temperatures in Greenland suddenly dropped by 12°C—a decrease similar in magnitude to many abrupt cold snaps chronicled in the Greenland ice core records
Mars Base

News in Brief: World's largest volcano lurks beneath Pacific Ocean | Earth | Science News - 0 views

  • The most massive volcano in the world, with a footprint the size of New Mexico, crouches in the dark depths of the western Pacific Ocean
  • hollowed peak lying beneath 2 kilometers of water
  • a basaltic mound, may rival the largest known volcano in the solar system: Mars’ Olympus Mons
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  • A team led by oceanographer
  • bounced sound waves off the deep-sea mountain to measure its size
  • Tamu Massif forms a broad, rounded dome rising 4 kilometers from the seafloor and stretching 450 by 650 kilometers across
  • Core samples that the researchers extracted from the volcano’s slopes showed that, during its prime 145 million years ago, the ancient mound spewed lava sheets 23 meters thick.
Mars Base

'Mother Lode' of Fossils Discovered in Canada - Scientific American - 0 views

  • A treasure trove of fossils chiseled out of a canyon in Canada's Kootenay National Park rivals the famous Burgess Shale, the best record of early life on Earth, scientists say.
  • The Burgess Shale refers to both a fossil find and a 505-million-year-old rock formation made of mud and clay
  • Burgess Shale fossil quarry, a UNESCO World Heritage site located in Yoho National Park, is in a glacier-carved cliff in the Canadian Rockies.
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  • The fossils were discovered in 1909. Since then, several other fossil sites have been found in the Burgess Shale, but none as rich as the original.
  • The fossils are extraordinary because they preserve soft parts of ancient animals in exceptional detail
  • soft parts are less likely to be imprinted in stone than harder parts, like bones
  • More than 200 animal species have been identified at the 1909 fossil site
  • The new site is also in the Burgess Shale formation, and seems to rival the 1909 original in fossil diversity and preservation
  • In just two weeks, the research team collected more than 3,000 fossils representing 55 species. Fifteen of these species are new to science.
  • there is a high possibility that we'll eventually find more species here than at the original Yoho National Park site, and potentially more than from anywhere else in the world
  • The new fossils were spotted in a mountain cliff, in Marble Canyon, about 26 miles (42 kilometers) southeast of the original Burgess Shale site
  • The newly discovered rocks are probably about 100,000 years younger than those at the first Burgess Shale site
  • Many of the fossils at the new site are better preserved than their quarry counterparts
  • The new fossils reveal the internal organs of several different arthropods, the most common type of animal in both the new and old Burgess Shale locations.
  • Retinas, corneas, neural tissue, guts and even a possible heart and liver were found.
  • the first time we're seeing these details
  • About half of the 55 species discovered at Marble Canyon so far are also found at the original Burgess Shale site
  • Some of the original site's rare species are more abundant in the canyon
  • Some species at Marble Canyon are also found in China's Chengjiang fossil beds, which are 10 million years older than the Burgess Shale
  • Until now, researchers thought these Cambrian animals went extinct by the time the Burgess Shale formed.
  • Their discovery in Canada means that many Cambrian life forms were more widespread and longer-lived than previously thought
Mars Base

Scientists Discover Untapped Freshwater Reserves Beneath the Oceans - 0 views

  • Australian scientists have identified vast freshwater reserves buried beneath the oceans
  • According to the latest report documented in the journal Nature
  • researchers have revealed the presence of nearly half a million cubic kilometres of low salinity water located beneath the seabed on the continental shelves
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  • Located off Australia, China, North America and South Africa, the newly discovered fresh water reserves can be used to supply water to coastal cities
  • this water resource is a hundred times greater than the amount we've extracted from the Earth's sub-surface in the past century since 1900
  • groundwater scientists were very well aware of the presence of the freshwater reserves beneath the seafloor, but have assumed it to occur during unusual and extraordinary situations
  • this latest study reveals that the fresh and brackish aquifers under the seabed are a common phenomena
  • formed hundreds to thousands of years ago when the sea level was lower than what it is currently
  • rainwater penetrated into the ground and filled up the water tables in regions that are currently under sea
  • Nearly 20,000 years ago, the sea levels rose, the ice caps began melting and the areas were covered by oceans
  • Most of the aquifers today are protected from seawater by blankets of clay and sediments that are piled on top
  • These aquifers are not different from those found below land. Their salinity is low due to which they can be easily converted into drinking water
  • researchers propose two ways to gain access to these freshwater reserves
  • either be by constructing a platform and drilling into the seabed, which is expensive
  • Or drill from the mainland that is at a closer distance from the aquifer
  • Freshwater under the seabed is much less salty than seawater
  • it can be converted to drinking water with less energy than seawater desalination
  • also leave us with a lot less hyper-saline water
  • freshwater offshore should remember is that the water reserves are non-renewable and should be used carefully
Mars Base

Paleontologists discover new fossil organism -- ScienceDaily - 0 views

  • Paleontologists have discovered a fossil of a newly discovered organism from the Ediacara Biota
  • Plexus ricei was a broadly curving tube that resided on the seafloor
  • Individuals range in size from 5 to 80 cm long and 5 to 20 mm wide
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  • disappeared from the fossil record around 540 million years ago, just around the time the Cambrian Explosion of evolutionary history
  • "Ediacaran fossils are extremely perplexing: they don't look like any animal that is alive today, and their interrelationships are very poorly understood," said Lucas V. Joel
Mars Base

New 'Walking' Shark Species Caught on Video | LiveScience - 0 views

  • A new species of "walking" shark has been discovered in a reef off a remote Indonesian island
  • These sharks don't always rely on "walking" to move about — often, they only appear to touch the seafloor as they swim using their pectoral and pelvic fins in a walklike gait
  • The shark grows up to 27 inches (70 centimeters) long and is harmless to humans
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  • Hemiscyllium halmahera, named after the eastern Indonesian island of Halmahera where it was found
  • Of all known
  • walking sharks, six of nine species hail from Indonesia
  • The animals lay eggs under coral ledges, after which the young sharks lead relatively sedentary lives until adulthood
  • These sharks do not cross areas of deep water and are found in isolated reefs
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