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NOVA scienceNOW: Mass Extinction

Program Overview

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.

Teacher's Guide
NOVA scienceNOW: Mass Extinction

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