The Pliocene Epoch (from the Greek, meaning “more recent”) is a geological epoch that extends from 5.332 to 2.58 million years ago (mya). It is the most recent of three periods in which the Earth’s crust underwent large-scale changes in composition and temperature. The other two are the Miocene and Oligocene, which together make up the Neogene Period.
The Pliocene was marked by significant global warming; after being relatively cool during the Miocene, average global temperatures increased by roughly 3 °C during the Pliocene. This was accompanied by a sharp rise in sea level due to melting glaciers and ice sheets. The Pliocene also saw an expansion of grasslands and savannahs as well as a retreat of forests worldwide; this trend continued into the early Pleistocene. Additionally, mammals became more numerous and diversified during this time; some notable examples include early horses, mastodons, giant sloths, and saber-toothed cats.
The cause of these changes is still debated today, but they are thought to be related to tectonic activity as well as variations in atmospheric circulation patterns caused by alterations in Earth’s orbit around the sun (known as Milankovitch cycles). Whatever their exact cause, these shifts had profound effects on both marine and terrestrial ecosystems alike, paving the way for dramatic changes in climate and vegetation over the next several million years.