Name ______Assn ____
Volcanoes and Extinctions
“Forget “The Asteroid”: Could Supervolcanoes Have Killed the Dinosaurs?”
1.Where are the Deccan Traps?
2.How long ago did they have massive eruptions?
3.The volcanoes released sulfur dioxide. How might this have affected Earth's atmosphere?
4.The volcanoes erupted what type of magma?
Did this form a tall volcano or a broad plateau?
Given this, were these quiet or explosive eruptions?
5.How did researchers use magnetic fields to determine the dates of eruptions?
6.Until this research, what was the most accepted theory about what caused the dinosaur extinction?
“Toxic Gases Caused World’s Worst Extinction”
1.The Siberian Traps are thought to have helped caused the Permian extinction.
How long ago was this?______
What percentage of life was killed?______
How many years before or after the dinosaur extinction was this?
2.The eruptions put a great deal of carbon into the air. How might this have changed the world's climate?
3.When lava combined with salt deposits in the earth, what might have formed?
How might this have affected the planet?
Forget “The Asteroid”: Could Supervolcanoes Have Killed the Dinosaurs?
From Discover Magazine Blogs, Eliza Strickland, December 2008
An asteroid that crashed into the earth 65 million years ago may not have been the cause of the dinosaurs‘ extinction, a group of researchers are arguing. Instead, that impact may have been just a prelude to the main event, when a wave of volcanic eruptions spewed out massive clouds of sulfur dioxide, clouding the air and bringing showers of acid rain. The researchers are basing their theory on studies of an area in India called the Deccan Traps, which was convulsed with volcanic activity around 65 million years ago. At least four waves of massive eruptions spread successive sheets of thick basalt across the land for more than 500 miles, and they piled into a plateau more than 11,000 feet high over thousands of years [San Francisco Chronicle].
The new research on the Deccan Traps volcanoes, announced at the ongoing meeting of the American Geophysical Union, are the first major challenge to the asteroid theory that has dominated dinosaur extinction studies for three decades. That theory posits that a six-mile-wide asteroid slammed into Mexico’s Yucatan peninsula, creating the Chicxulub crater and cooling the climate so drastically that the majority of life forms went extinct in what’s known as the Cretaceous-Tertiary (or K-T) extinction. But geologist Gerta Keller and her colleagues argue that the impact occurred well before the massive die-offs began. By examining sediment layers, the team found that the crater impact appears to have occurred about 300,000 years before the K-T boundary, with virtually no effects to biota. “There is essentially no extinction associated with the impact,” Keller said [LiveScience].
Meanwhile, geophysicist Vincent Courtillot determined more exact dates for the Deccan Trap eruptions by studying the magnetic signatures of the Indian volcanic deposits that lined up with the Earth’s magnetic field as they cooled. Because the orientation of the magnetic field has changed over time, lava that cooled at different times will have different signatures. The more than 2-mile thick pile of Deccan Traps deposits has several major pulses that occurred over the course of several decades each, almost certainly less than a hundred years [Wired Science].
The researchers say they detected individual pulses of eruptions at 67.5 and 65 million years ago, with two more quickly following. After the first flow, “the species disappear; we have essentially very few left,” Keller said. The two subsequent flows prevented any recovery, and “by the fourth flow, the extinction is complete,” Keller said [LiveScience]. The researchers also argue that an asteroid impact wouldn’t kick up enough dust and sulfur dioxide to alter the climate around the planet, but says that these supervolcanoes may have spewed 10 billion to 150 billion tons of sulfur dioxide into the air with each pulse of eruptions.
However, the proponents of the asteroid impact theory aren’t going to quietly accept the junking of their thesis. “There was volcanism at the time. There’s always volcanism, but that impact is so significant that you can’t ignore it,” said Rick Firestone of Lawrence Berkeley National Laboratory who studies the link between impacts and extinctions. “The only question is, were there other things that happened as result of it” [Wired Science].
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Toxic Gases Caused World's Worst Extinction
Michael Reilly, Discovery News
Feb. 4, 2009 -- An ancient killer is hiding in the remote forests of Siberia. Scientists are starting to uncover the remnants of a supervolcano, that was walled off from western eyes during the Soviet era and that rained Hell on Earth 250 million years ago, killing 90 percent of all life.
Researchers have known about the volcano -- the Siberian Traps, for years. And they've speculated that the volcanic rocks, which cover an area about the size of Alaska, played a role in runaway global warming that led to the end -- Permian mass extinction, the worst dying the planet has ever seen.
Now a team of researchers led by Henrik Svenson of the University of Oslo in Norway have performed a series of experiments, showing the volcano employed an arsenal of deadly weapons during its 200,000-year-long assault on the biosphere.
Prime among them was carbon. Searing magmas from the volcano intruded into the Tunguska Basin in eastern Siberia, a region laden with thick deposits of coal, oil and gas. Heat from the molten rock baked the hydrocarbons, turning the area into the world's largest fossil fuel-burning plant. In all, the volcano may have belched as much as 100,000 gigatons of carbon into the air (all of humanity emits about eight gigatons of carbon annually).
That's more than enough to cause a global climate apocalypse. But the team also wanted to know what happened when lava infiltrated the area's abundant salt deposits. When heated in a laboratory to 275 degrees Centigrade (527 degrees Fahrenheit), the salts released a host of toxic gases, chief among them methyl chloride, an efficient ozone-killer.
"This is the first geologically realistic evidence that ozone collapse during the end-Permian could have actually happened," Svenson said.
But there is still a lot of uncertainty surrounding the findings, Linda Elkins-Tanton of the Massachusetts Institute of Technology said. "There is evidence of a large number of genetic mutations in the fossil record around this time," she said, which could be the result of an onslaught of ultraviolet radiation due to a weak ozone layer. "But the idea of ozone destroyers is pretty new. The question is whether or not the eruptions were powerful enough to inject gases into the stratosphere."
The answer may come from close examination of hundreds of pipe-like structures strewn throughout the Tunguska Basin. Often 300 meters (984 feet) in diameter, the pipes are believed to be ancient volcanic craters left over after the lethal mix of carbon and chlorine gases exploded into the atmosphere.