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Chemistry LibreTexts

Mass Extinctions

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  • 65 million years ago, 60 to 80% of all life on this planet died. This is not the first time Earth has experienced mass extinctions. The fossil record shows a pattern of extinctions occurring roughly ever 26 million years. Scientists tend to agree that there have been 5 or 6 mass extinctions.

    What could account for these mass extinctions? The list of suggested explanations is long, but most include

    • geologic events (volcanoes)
    • cosmic events (asteroids or comets)
    • climatic events (hot versus cold)
    • pathogenic events (diseases)

    Currently the majority of evidence supports the idea that the Earth was struck by a large meteor 10-20km in diameter forming the Chicxulub Crater on the Yucatan peninsula in Mexico. Some scientists disagree and suggest that massive volcanic eruptions could have precipitated the catastrophe.



    Think Questions

    1. Is there a pattern to when the mass extinctions occur?


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    2. Could we be in a mass extinction event now?