Open main menu


subdivision of geological time; shorter than an eon and longer than a period


An era is made up of periods, and several eras make up an eon. The Phanerozoic eon started about 541 million years ago (mya). It is made up of the Paleozoic era (from the Greek for "oldest life"), the Mesozoic era ("middle life") and the Cainozoic era ("latest life").