The geologic time scale is organized into four major divisions. List these divisions and describe how they are determined.

The geologic time scale is divided into eons, eras, periods, epochs and ages with eons being the longest time divisions and ages the shortest. The history of the earth is broken up into a hierarchical set of divisions for describing geologic time. As increasingly smaller units of time, the generally accepted divisions are eon, era, period, epoch, age.

Explanation:

then that particular organisms become extinct.

sodium i think the chemical element of atomic number 11, a soft silver-white reactive metal of the alkali metal group.