Question

8. How do scientists know when a mass extinction took place?
A
They find more fossils of plants
B.
They find fossils of animals that died suddenly.
C.
They find a sudden disappearance of many fossil species.
D.
They find evidence of changes in the Earth's atmosphere.

Answer 1

Answer:

C.

They find a sudden disappearance of many fossil species.

Explanation:

A mass extinction is usually defined as a loss of about three quarters of all species in existence across the entire Earth over a “short” geological period of time. Given the vast amount of time since life first evolved on the planet, “short” is defined as anything less than 2.8 million years.