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NOVA scienceNOW: Mass Extinction
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Program Overview
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Researchers believe they have an idea of what caused the greatest
extinction of life ever. The die-off occurred 248 million years ago
at the end of the Paleozoic Era's Permian period, which lasted from
290 to 248 million years ago. The Permian extinction may have been
the result of global warming. In fact, some scientists think that
environmental events, such as ice ages and extreme warming, might
explain several of Earth's five mass extinctions, all of which
occurred in the past 600 million years.
This NOVA scienceNOW segment:
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introduces Earth's greatest mass extinction. It occurred 248
million years ago at the end of the Permian period and wiped out
95 percent of all ocean- and land-dwelling life, recasting the
nature of life on Earth.
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describes an ancient group of volcanoes, the Siberian Traps,
which oozed lava for one million years, smothering an area the
size of the continental United States with lava one mile deep
and sending vast quantities of carbon dioxide into the
atmosphere.
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suggests a likely chain of events leading to the Permian
extinction: volcanoes released carbon dioxide and triggered
global warming. The ocean temperatures increased significantly,
causing dissolved oxygen levels to plummet. Anaerobic conditions
in the oceans promoted the growth of bacteria that produced
hydrogen sulfide, a toxic gas. Large amounts of hydrogen sulfide
accumulated in the oceans and atmosphere, killing most plants
and animals.
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presents the evidence for this theory: a sudden loss of plant
and animal life shown in the fossil record, and 250
million-year-old rocks that contain hydrogen sulfide.
Taping Rights: Can be used up to one year after the program
is taped off the air.
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