Pliocene Epoch

The period in the geologic timescale that extends from 5.332 million to 2.588 million years before present:

Pliocene Epoch

During the Pliocene epoch climate became cooler and drier, and seasonal, similar to modern climates.

In 2002, astronomers discovered that roughly 2 million years ago, around the end of the Pliocene epoch, a group of bright O and B stars called the Scorpius-Centaurus OB association passed within 150 light-years of Earth and that one or more supernovae may have occurred in this group at that time. Such a close explosion could have damaged the Earth's ozone layer and caused the extinction of some ocean life (at its peak, a supernova of this size could have the same absolute magnitude as an entire galaxy of 200 billion stars).[Reference: Discovering the Universe, Comins & Kaufmann (2005), p. 359.]