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Will the cross section of a mammoth's tusk provide clues to why the mammoths became extinct?
© AMNH, Ross MacPhee |
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Water level also affects the oxygen distribution and salinity of oceans, and scientists think that these chemical fluctuations could also have affected extinction rates.
#3 - Asteroid Impact
In 1980, physicist Luis Alvarez suggested that the most famous extinction, the one that wiped out the dinosaurs at the end of the Cretaceous period, was caused by a giant asteroid crashing into earth. For evidence, Alvarez pointed to unusually large amounts of a rare element called iridium in the rocks that marked the boundary between the Cretaceous and the Tertiary period.
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