The K/T Boundary

The divisions on the geological time tables are based on a significant geological and/or biological change (see below).

A geological time table showing the 6 occurences of major mass extinction (marked in black)

Sixty-five million years ago: 50% of all families, 75% of all genera, 85% of all species, 99.99% of all individuals became extinct.

This time is known as the K/T boundary or where the Cretaceous (K) ends and the Tertiary (T) begins. At this time all the dinosaurs became extinct. One of the most sought after answers in science and among the general public has been the question "what killed the dinosaurs?" in other words, what was the K/T event? Since the 1980s a tremendous amount of evidence has been compiled that supports an asteroid impact as the cause of the event at the K/T boundary.

This page focuses on the environmental and biological implications of an asteroid impact with reference to K/T boundary.

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What Was The K/T Event?