Planet Earth has experienced five major mass extinctions in its 4.5 billion-year history. The largest, the Permian, wiped out 96 percent of species as well as Earth's forests and coral reefs. The most well-known extinction, the Cretaceous-Tertiary, claimed about 80 percent of animal species, including the dinosaurs.

Sources: “Big Five mass extinction events,” BBC Nature, 2017, https://tinyurl.com/cw2x786; Michael J. Benton, “Mass Extinctions,” New Scientist, March 5, 2011, https://tinyurl.com/mgl9bfh

Data for the graphic are as follows:

Extinction Event Time Period Event Description
Ordovician-Silurian 440 million years ago When most plants and animals, including jawless fish, lived in tropical waters, extreme cooling and falling sea levels killed about 85 percent of species.
Late Devonian 365 million years ago When most species still lived in the sea, oceanic “dead zones” likely caused by deoxygenation killed three-quarters of species.
Permian 250 million years ago The so-called Great Dying destroyed about 96 percent of species, likely due to climate warming caused by volcanic eruptions. Scientists believe Earth's ecosystems needed 10 million to 15 million years to recover.
Triassic-Jurassic 200 million years ago About three-fourths of species died from uncertain causes, possibly climate warming caused by volcanic eruptions, clearing the way for dinosaurs to dominate Earth.
Cretaceous-Tertiary 65 million years ago Climate change caused by volcanic eruptions and/or an asteroid strike killed off the dinosaurs. Most mammals, which were then small, survived and eventually came to dominate the planet as they grew in size, number and complexity.

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