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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:
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. 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. 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. 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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