Mass Extinctions

Since life has been on Earth and left a clear record with its fossils in the rocks, we can see that there have been several widespread extinctions of life all round the Earth.

Graph modified after Verisimilus

The graph shows the percentage of marine animals becoming extinct. The five major events are:

Ordovician-Silurian, Late Devonian, Permo-Triassic, Triassic-Jurassic and Cretaceous-Paleogene. There were many other extinctions events, including two in the Cambrian (Cm on the diagram).

One theory is that these are caused by huge meteorite impacts. These may be asteroids, comets or they may have come from outside the solar system. The energy they release is huge. It is far more than all our nuclear weapons exploding at the same time!

There was a mass extinction at around 250 mya. After that the dinosaurs began to dominate the Earth.

There was another one, the last of these mass extinctions, about sixty mya when the dinosaurs died out.

So if the sixty million year theory is correct we might be due for another impact any day now!