 |
|
Geologists discover signs of volcanoes blowing their tops in the deep ocean
June 26, 2008Evidence of violent eruptions on Gakkel Ridge in the Arctic defies assumptions about seafloor pressure and volcanism
A research team led by the Woods Hole Oceanographic Institution (WHOI) has uncovered evidence of explosive volcanic eruptions deep beneath the ice-covered surface of the Arctic Ocean. Such violent eruptions of splintered, fragmented rock-known as pyroclastic deposits-were not thought possible at great ocean depths because of the intense weight and pressure of water and because of the composition of seafloor magma and rock.
Researchers found jagged, glassy rock fragments spread out over a 10 square kilometer (4 square mile) area around a series of small volcanic craters about 4,000 meters (2.5 miles) below the sea surface. The volcanoes lie along the Gakkel Ridge, a remote and mostly unexplored section of the mid-ocean ridge system that runs through the Arctic Ocean.
"These are the first pyroclastic deposits we've ever found in such deep water, at oppressive pressures that inhibit the formation of steam, and many people thought this was not possible," said WHOI geophysicist Rob Reves-Sohn, lead author and chief scientist for the Arctic Gakkel Vents Expedition (AGAVE) of July 2007. "This means that a tremendous blast of CO2 was released into the water column during the explosive eruption."
The paper, which was co-authored by 22 investigators from nine institutions in four countries, was published in the June 26 issue of the journal Nature.
Seafloor volcanoes usually emit lobes and sheets of lava during an eruption, rather than explosive plumes of gas, steam, and rock that are ejected from land-based volcanoes. Because of the hydrostatic pressure of seawater, ocean eruptions are more likely to resemble those of Kilauea than Mount Saint Helens or Mount Pinatubo.
Making just the third expedition ever launched to the Gakkel Ridge-and the first to visually examine the seafloor--researchers used a combination of survey instruments, cameras, and a seafloor sampling platform to collect samples of rock and sediment, as well as dozens of hours of high-definition video. They saw rough shards and bits of basalt blanketing the seafloor and spread out in all directions from the volcanic craters they discovered and named Loke, Oden, and Thor.
They also found deposits on top of relatively new lavas and high-standing features-such as Duque's Hill and Jessica's Hill--indications that the rock debris had fallen or precipitated out of the water, rather than being moved as part of a lava flow that erupted from the volcanoes.
Closer analysis has shown that the some of the tiny fragments are angular bits of quenched glass known to volcanologists as limu o Pele, or "Pele's seaweed." These fragments are formed when lava is stretched thin around expanding gas bubbles during an explosion. Reves-Sohn and colleagues also found larger blocks of rock-known as talus-that could have been ejected by explosive blasts from the seafloor.
Much of Earth's surface is made up of oceanic crust formed by volcanism along seafloor mid-ocean ridges. These volcanic processes are tied to the rising of magma from Earth's mantle and the spreading of Earth's tectonic plates. Submerged under several kilometers of cold water, the volcanism of mid-ocean ridges tends to be relatively subdued compared to land-based eruptions.
To date, there have been scattered signs of pyroclastic volcanism in the sea, mostly in shallower water depths. Samples of sediment and rock collected on other expeditions have hinted at the possibilities at depths down to 3,000 meters, but the likelihood of explosive eruptions at greater depths seemed slim.
One reason is the tremendous pressure exerted by the weight of seawater, known as hydrostatic pressure. More importantly, it is very difficult to build up the amount of steam and carbon dioxide gas in the magma that would be required to explode a mass of rock up into the water column. (Far less energy is needed to do so in air.) In fact, the buildup of CO2 in magma in the sea crust would have to be ten times higher than anyone has ever observed in seafloor samples.
The findings from the Gakkel Ridge expedition appear to show that deep-sea pyroclastic eruptions can and do happen. "The circulation and plumbing of the Gakkel Ridge might be different," said Reves-Sohn. "There must be a lot more volatiles in the system than we thought." The research team hypothesizes that excess gas may be building up like foam or froth near the ceiling of the magma chambers beneath the crust, waiting to pop like champagne beneath a cork.
"Are pyroclastic eruptions more common than we thought, or is there something special about the conditions along the Gakkel Ridge?" said Reves-Sohn. "That is our next question."
Woods Hole Oceanographic Institution
"These are the first pyroclastic deposits we've ever found in such deep water, at oppressive pressures that inhibit the formation of steam, and many people thought this was not possible," said WHOI geophysicist Rob Reves-Sohn, lead author and chief scientist for the Arctic Gakkel Vents Expedition (AGAVE) of July 2007. "This means that a tremendous blast of CO2 was released into the water column during the explosive eruption."
The paper, which was co-authored by 22 investigators from nine institutions in four countries, was published in the June 26 issue of the journal Nature.
Seafloor volcanoes usually emit lobes and sheets of lava during an eruption, rather than explosive plumes of gas, steam, and rock that are ejected from land-based volcanoes. Because of the hydrostatic pressure of seawater, ocean eruptions are more likely to resemble those of Kilauea than Mount Saint Helens or Mount Pinatubo.
Making just the third expedition ever launched to the Gakkel Ridge-and the first to visually examine the seafloor--researchers used a combination of survey instruments, cameras, and a seafloor sampling platform to collect samples of rock and sediment, as well as dozens of hours of high-definition video. They saw rough shards and bits of basalt blanketing the seafloor and spread out in all directions from the volcanic craters they discovered and named Loke, Oden, and Thor.
They also found deposits on top of relatively new lavas and high-standing features-such as Duque's Hill and Jessica's Hill--indications that the rock debris had fallen or precipitated out of the water, rather than being moved as part of a lava flow that erupted from the volcanoes.
Closer analysis has shown that the some of the tiny fragments are angular bits of quenched glass known to volcanologists as limu o Pele, or "Pele's seaweed." These fragments are formed when lava is stretched thin around expanding gas bubbles during an explosion. Reves-Sohn and colleagues also found larger blocks of rock-known as talus-that could have been ejected by explosive blasts from the seafloor.
Much of Earth's surface is made up of oceanic crust formed by volcanism along seafloor mid-ocean ridges. These volcanic processes are tied to the rising of magma from Earth's mantle and the spreading of Earth's tectonic plates. Submerged under several kilometers of cold water, the volcanism of mid-ocean ridges tends to be relatively subdued compared to land-based eruptions.
To date, there have been scattered signs of pyroclastic volcanism in the sea, mostly in shallower water depths. Samples of sediment and rock collected on other expeditions have hinted at the possibilities at depths down to 3,000 meters, but the likelihood of explosive eruptions at greater depths seemed slim.
One reason is the tremendous pressure exerted by the weight of seawater, known as hydrostatic pressure. More importantly, it is very difficult to build up the amount of steam and carbon dioxide gas in the magma that would be required to explode a mass of rock up into the water column. (Far less energy is needed to do so in air.) In fact, the buildup of CO2 in magma in the sea crust would have to be ten times higher than anyone has ever observed in seafloor samples.
The findings from the Gakkel Ridge expedition appear to show that deep-sea pyroclastic eruptions can and do happen. "The circulation and plumbing of the Gakkel Ridge might be different," said Reves-Sohn. "There must be a lot more volatiles in the system than we thought." The research team hypothesizes that excess gas may be building up like foam or froth near the ceiling of the magma chambers beneath the crust, waiting to pop like champagne beneath a cork.
"Are pyroclastic eruptions more common than we thought, or is there something special about the conditions along the Gakkel Ridge?" said Reves-Sohn. "That is our next question."
Woods Hole Oceanographic Institution
Volcanic Eruption Current Events and Volcanic Eruption News RSSScientists measure the rate of ascent of volcanic magma
Plinian volcanic eruptions are notoriously destructive. These very powerful eruptions often occur after long periods of quiescence and are preceded by relatively short periods of seismic restiveness.
Coal-mining hazard resembles explosive volcanic eruption, study shows
Worldwide, thousands of workers die every year from mining accidents, and instantaneous coal outbursts in underground mines are among the major killers. But although scientists have been investigating coal outbursts for more than 150 years, the precise mechanism is still unknown.
'Rosetta Stone' of supervolcanoes discovered in Italian Alps
Scientists have found the "Rosetta Stone" of supervolcanoes, those giant pockmarks in the Earth's surface produced by rare and massive explosive eruptions that rank among nature's most violent events. The eruptions produce devastation on a regional scale - and possibly trigger climatic and environmental effects at a global scale.
Texas A&M-Galveston professor discovers new species of marine life
Two tiny worms much smaller than a rice grain and a strange crustacean that has no eyes and poisonous fangs are among several new species of marine life discovered in an underwater cave by a Texas A&M University at Galveston researcher, who has had one of the new species named after him.
NASA and NOAA'S GOES-14 satellite takes first full disk image
The latest Geostationary Operational Environmental Satellite, GOES-14, provided its first visible full disk image of Earth on July 27, at 2:00 p.m. EDT. The prime instrument on GOES, called the Imager, is taking images of Earth with a 1 kilometer (km) or 0.62 mile resolution from an altitude of 36,000 km (22,240 miles) above Earth's surface, equivalent to taking a picture of a dime from a distance of seven football fields.
World's largest aerosol sensing network has leafy origins
Twenty years ago, Brent Holben was part of a NASA team studying vegetation from space. In an unlikely career twist, his research morphed into the study of a critical, if overlooked, subplot in the story of climate change.
Giant eruption reveals 'dead' star
An enormous eruption has found its way to Earth after travelling for many thousands of years across space. Studying this blast with ESA's XMM-Newton and Integral space observatories, astronomers have discovered a dead star belonging to a rare group: the magnetars.
CU-Boulder study shows Maya intensively cultivated manioc 1,400 years ago
A University of Colorado at Boulder team has uncovered an ancient and previously unknown Maya agricultural system -- a large manioc field intensively cultivated as a staple crop that was buried and exquisitely preserved under a blanket of ash by a volcanic eruption in present-day El Salvador 1,400 years ago.
Bone bed tells of life along California's ancient coastline
In the famed Sharktooth Hill Bone Bed near Bakersfield, Calif., shark teeth as big as a hand and weighing a pound each, intermixed with copious bones from extinct seals and whales, seem to tell of a 15-million-year-old killing ground.
Ancient volcanic eruptions caused global mass extinction
A previously unknown giant volcanic eruption that led to global mass extinction 260million years ago has been uncovered by scientists at the University of Leeds.
More Volcanic Eruption Current Events and Volcanic Eruption News Articles
 |
La Catastrophe: The Eruption of Mount Pelee, the Worst Volcanic Disaster of the 20th Century by Alwyn Scarth (Author) On May 8, 1902, on the Caribbean island of Martinique, the volcano Mount Pelee loosed the most terrifying and lethal eruption of the twentieth century. In minutes, it killed 27,000 people and leveled the city of Saint-Pierre. In La Catastrophe, Alwyn Scarth provides a gripping day-by-day and hour-by-hour account of this devastating eruption, based primarily on chilling eyewitness accounts. Scarth recounts how, for many days before the great eruption, a series of smaller eruptions spewed dust and ash. Then came the eruption. A blinding flash lit up the sky. A tremendous cannonade roared out that was heard in Venezuela. Then a scorching blast of superheated gas and ash shot straight down towards Saint-Pierre, racing down at hundreds of miles an hour. This infernal avalanche of dark,... |
 |
Volcano Java Eruption Volcanic French Print 1931 by old-print A Page As Shown Taken From The ILlustration Newspaper Of 1931. A Weekly Newspaper Published In Paris. It Was Founded By Edouard Charton; The First Issue Was Published On March 4Th 1843.Size Of Each Page Is Approx 15 X 11 Inches (380X280)All Are Genuine Prints And Not Reproductions. Please Check Image Carefully For The Condition Of These Prints. |
 |
On Tour... CIRCUMETNEA RAILROAD SICILIA Mount Etna's "Volcanic" Train Directed By: TravelVideoStore.com Also With: TravelVideoStore.com (Producer) |
 |
Sonic Design: Volcanic Eruptions In Slow Motion Carlo Mombelli & the Prisoners of Strange (Primary Contributor) |
 |
History - Mega Disasters : Yellowstone Eruption Also With: Creative Differences (Producer) The world's largest, most active volcano system exists in the western US. 6,000 years ago, the Yellowstone Volcano erupted. Lava and pyroclastic flows covered 3,000-square miles with ash 3-feet thick. Fossils discovered as far away as Nebraska were foundto have died from inhaling the Yellowstone debris. If--or perhaps we should say when--it erupts again, the Yellowstone "Mega-Volcano" will create a global cataclysm beyond human comprehension. Everything within 150 miles--including the cities of Cody, Wyoming and Bozeman, Montana--will be hit by an 800-degree blast of heat and 200 miles-per-hour winds. Thousands will be killed. That's just the local effects. Half the US will be buried beneath a blanket of volcanic ash. Crops in the Midwest--the world's breadbasket--will be destroyed. And... |
 |
Volcanic Eruption Kit by Eastcolight This classic experiment lets kids have a blast simulating real volcanic eruptions! This kit also includes educational volcanic facts. Completely safe. |
 |
Tiki Art Now!: A Volcanic Eruption Of Art by Otto Von Stroheim (Author), Robert Williams (Author) Tiki Style is a recognized part of American Folk Art with a longstanding history and mass appeal. Here are some of today's most exciting American Tiki artists and international artists working in the Tiki Style, including: Shag, Marco Almera, Bosko, Sunny Buick, Dave Burke, Kalynn Campbell, Dirty Donny, Crazy Al Evans, Richie Fahey, Rod Filbrandt, Mary Fleener, Bruce Gossett, Christine Karas, Joe Leonard, Sharon Leong, Mr. Lucky, Munktiki, Mitch O'Connell, Lisa Petrucci, The Pizz, Isabel Samaras, Von Franco, and more. |
 |
Anjer Coast Java Volcanic Eruption 1883 Mountains Art by old-print XXXXXXXX |
|
Krakatau 1883, The Volcanic Eruption and Its Effects by Tom Simkin (Author), Richard S. Fiske (Author) | |
 |
Summer 2002 Eruption Update: A Firsthand Account of the Current Eruption of Kilauea Volcano Also With: John Kjargaard (Primary Contributor), Jenda Johnson (Primary Contributor), Dr. Ken Hon (Primary Contributor), Dr. Cheryl Gansecki (Primary Contributor) During an eruption anything can happen. Anywhere. Without warning. Nothing can be taken for granted. Your every action depends on your experience and how you read the situation. Here all your senses are on alert. You must be acutely aware of changes. Changes in the everpresent roar, changes in wind direction, changes in fountain height and shape, changes in the heat. The heat is everywhere. It sears your skin, Scorches your clothes, and tries to set your feet on fire. In your mind you keep asking: Can I still get out the way I got in? What do I do, where do I run... if it breaks out behind me, if the wind shifts, if the forest ignites. Panic, and you've had it. It's intense, whether It's your first or fortieth trip. The experience is always hard to describe, for there is little in our... |
| © 2009 BrightSurf.com |