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Imigo Jones · 06-17-2008, 06:49 AM

Nova
"Mystery of the Megavolcano"

A look at a "supervolcano" that erupted some 74,000 years ago in Sumatra and may have precipitated a global deep freeze. Scientists examine evidence in Greenland's ice cap, from beneath the ocean floor, and in ash recovered from across southern Asia. [This quoted from local PBS listings; following material all from Nova "Mystery of the Megavolcano" site, various pages, except for comments in brackets, some font changes, etc. One oil painting. Some smileys.

]

Sixty-two-mile-long Lake Toba, seen in the center of this satellite image, was created by the largest explosive volcanic eruption of the past 100,000 years.

A Supersized Volcano
Beginning in 1949, when Dutch geologist Rein van Bemmelen discovered massive deposits of volcanic rock along the perimeter of Lake Toba on the Indonesian island of Sumatra, scientists knew they were onto something big. The thousand-square-mile area around the lake, it appeared, was a gargantuan caldera once filled not with water but with steaming volcanic ash and pumice. As volcanologists pieced together evidence of the cataclysmic event that took place there 74,000 years ago, as well as two earlier eruptions, Toba seemed so immense it was deemed a "supervolcano." In this interactive [link to slide show on page], see a portrait of the eruption of 74,000 years ago and how it dwarfs even the most disastrous "regular-sized" eruptions of our own era. . . .

To qualify as a supervolcano, a volcano must produce at least 240 cubic miles of magma, or partly molten rock, in a single eruption—about the same volume of water the Mississippi River dumps into the Gulf of Mexico during a single year. . . .

Imagine this view of the devastation caused by the 1991 eruption of Mt. Pinatubo covering a whole state or region rather than just the surrounding area, and you get an idea of what a supereruption could unleash.

Flash slide show: Highlights
Magma released, cubic miles of material
Mt. St. Helens, 1980, 0.12 cu mi
Pinatubo, Philippines, 1991, 1.2
Krakatau, 1883, 2.9
Tambora, 1815, 12
Toba, 72K B.C., 672
Over the course of one or two weeks, Toba erupted about 5,600 times the amount of magma released by Mt. St. Helens in 1980. [But see boldface after map.] . . .

The most recent [supervolcano] (Taupo, in New Zealand) occurred 26,500 years ago. One from 74,000 years ago (Toba, in Indonesia) left behind a caldera, or giant crater, about the size of Rhode Island. The biggest one yet identified (La Garita, in Colorado) coughed out 1,200 cubic miles of volcanic materials. On this map [links on page to interactive world map; click numbers 1-12 for descriptions of known supervolcano sites], sample a selection of the aptly named, though thankfully extremely rare, natural cataclysms known as "supereruptions." . . .

A supereruption would not only take out the summit but the entire mountain and much else besides. The caldera that underlies Yellowstone National Park—"caldera" essentially means humongous crater—is over 50 miles long and nearly 30 miles wide. You could fit four Manhattans placed end to end inside. The amount of magma, or molten rock, thrown out by its most recent supereruption 640,000 years ago was a staggering 240 cubic miles, with an ash volume two to three times that.

The intensity of such convulsions matches the magnitude. In A.D. 79, Vesuvius belched out an astounding 100,000 cubic yards of magma per second over a 24-hour period. Yet this is chicken feed compared to supereruptions, which can emit volcanic debris at up to 100 million cubic yards per second. . . .

Cotopaxi, Frederic Edwin Church, 1862
Original 85 inches long; interactive Artchive page zooms to about 24 inches.

All that erupted material wouldn't just fall nearby or waft harmlessly away like Semeru's ash clouds, either. If something the size of that 640,000-year-old Yellowstone eruption occurred under New York City, it would not only obliterate all five boroughs but bury what was left as well as large portions of Long Island, New Jersey, and Connecticut under half a mile of pyroclastic flow deposits (see diagram at right). Pyroclastic flows comprise all the heavy stuff that collapses out of an ash cloud, and in supereruptions they can travel up to 60 miles away at speeds of 100 yards per second—again, unimaginable fury. . . .

The devastation would spread much farther than the surrounding region. A stone monument atop Semeru memorialized several people who had died there after breathing volcanic fumes. But a supereruption would kill millions. "If you're close enough to the eruption—and in a supereruption that can mean thousands of miles away—if you breathe in the ash in an unprotected way, you're breathing in tiny glass needles,"

says geologist Michael Rampino of New York University. "They cause the blood vessels in your lungs to pop. Water in your lungs combines with this volcanic ash, and essentially you drown in a kind of soup or cement of wet volcanic ash."

06-17-2008, 06:49 AM	#40
Imigo Jones Tornado Ali Join Date: Apr 2008 Location: Used to be woods in town on prairie; now Emerald City Posts: 82	Tonight on "Nova" Nova "Mystery of the Megavolcano" A look at a "supervolcano" that erupted some 74,000 years ago in Sumatra and may have precipitated a global deep freeze. Scientists examine evidence in Greenland's ice cap, from beneath the ocean floor, and in ash recovered from across southern Asia. [This quoted from local PBS listings; following material all from Nova "Mystery of the Megavolcano" site, various pages, except for comments in brackets, some font changes, etc. One oil painting. Some smileys. ] Sixty-two-mile-long Lake Toba, seen in the center of this satellite image, was created by the largest explosive volcanic eruption of the past 100,000 years. A Supersized Volcano Beginning in 1949, when Dutch geologist Rein van Bemmelen discovered massive deposits of volcanic rock along the perimeter of Lake Toba on the Indonesian island of Sumatra, scientists knew they were onto something big. The thousand-square-mile area around the lake, it appeared, was a gargantuan caldera once filled not with water but with steaming volcanic ash and pumice. As volcanologists pieced together evidence of the cataclysmic event that took place there 74,000 years ago, as well as two earlier eruptions, Toba seemed so immense it was deemed a "supervolcano." In this interactive [link to slide show on page], see a portrait of the eruption of 74,000 years ago and how it dwarfs even the most disastrous "regular-sized" eruptions of our own era. . . . To qualify as a supervolcano, a volcano must produce at least 240 cubic miles of magma, or partly molten rock, in a single eruption—about the same volume of water the Mississippi River dumps into the Gulf of Mexico during a single year. . . . Imagine this view of the devastation caused by the 1991 eruption of Mt. Pinatubo covering a whole state or region rather than just the surrounding area, and you get an idea of what a supereruption could unleash. Flash slide show: Highlights Magma released, cubic miles of material Mt. St. Helens, 1980, 0.12 cu mi Pinatubo, Philippines, 1991, 1.2 Krakatau, 1883, 2.9 Tambora, 1815, 12 Toba, 72K B.C., 672 Over the course of one or two weeks, Toba erupted about 5,600 times the amount of magma released by Mt. St. Helens in 1980. [But see boldface after map.] . . . The most recent [supervolcano] (Taupo, in New Zealand) occurred 26,500 years ago. One from 74,000 years ago (Toba, in Indonesia) left behind a caldera, or giant crater, about the size of Rhode Island. The biggest one yet identified (La Garita, in Colorado) coughed out 1,200 cubic miles of volcanic materials. On this map [links on page to interactive world map; click numbers 1-12 for descriptions of known supervolcano sites], sample a selection of the aptly named, though thankfully extremely rare, natural cataclysms known as "supereruptions." . . . A supereruption would not only take out the summit but the entire mountain and much else besides. The caldera that underlies Yellowstone National Park—"caldera" essentially means humongous crater—is over 50 miles long and nearly 30 miles wide. You could fit four Manhattans placed end to end inside. The amount of magma, or molten rock, thrown out by its most recent supereruption 640,000 years ago was a staggering 240 cubic miles, with an ash volume two to three times that. The intensity of such convulsions matches the magnitude. In A.D. 79, Vesuvius belched out an astounding 100,000 cubic yards of magma per second over a 24-hour period. Yet this is chicken feed compared to supereruptions, which can emit volcanic debris at up to 100 million cubic yards per second. . . . Cotopaxi, Frederic Edwin Church, 1862 Original 85 inches long; interactive Artchive page zooms to about 24 inches. All that erupted material wouldn't just fall nearby or waft harmlessly away like Semeru's ash clouds, either. If something the size of that 640,000-year-old Yellowstone eruption occurred under New York City, it would not only obliterate all five boroughs but bury what was left as well as large portions of Long Island, New Jersey, and Connecticut under half a mile of pyroclastic flow deposits (see diagram at right). Pyroclastic flows comprise all the heavy stuff that collapses out of an ash cloud, and in supereruptions they can travel up to 60 miles away at speeds of 100 yards per second—again, unimaginable fury. . . . The devastation would spread much farther than the surrounding region. A stone monument atop Semeru memorialized several people who had died there after breathing volcanic fumes. But a supereruption would kill millions. "If you're close enough to the eruption—and in a supereruption that can mean thousands of miles away—if you breathe in the ash in an unprotected way, you're breathing in tiny glass needles," says geologist Michael Rampino of New York University. "They cause the blood vessels in your lungs to pop. Water in your lungs combines with this volcanic ash, and essentially you drown in a kind of soup or cement of wet volcanic ash."