The geologic time scale is subdivided on the basis of
A) the appearance of different radioactive isotopes in different strata.
B) levels of background extinction.
C) periods of mass extinction.
D) the appearance of different radioactive isotopes in different strata and levels of background extinction.
E) the appearance of different radioactive isotopes in different strata, levels of background extinction, and periods of mass extinction.

Question

Quizplus · Accepted Answer

The geologic time scale is primarily subdivided based on significant events in Earth's history, such as periods of mass extinction, which mark the boundaries between different eras and periods.

The Geologic Time Scale Is Subdivided on the Basis of