Ans.
The geological time scale (GTS) is defined as a system of chronological dating, used to relate geological strata to time. Scientists use major events, such as catastrophic events in the history of the earth to divide the GTS.
For example, the partition between Permian and Triassic periods is denoted by a global extinction that led to elimination of many plants and animals of the earth.
Thus, the correct answer is option). 'evidence for catastrophic events in Earth's history.'