Eocene
Overview
The Eocene epoch is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Paleocene Epoch to the beginning of the Oligocene Epoch. The start of the Eocene is marked by a brief period of intense warming known as the Paleocene-Eocene Thermal Maximum (PETM), during which temperatures rose rapidly and dramatically.
Paleogeography and Climate
During the Eocene, the continents continued to drift toward their present positions. At the beginning of the period, Australia and Antarctica were still connected, and India was just beginning its collision with Asia, an event that led to the formation of the Himalayas. The Tethys Sea was shrinking as Africa moved north towards Europe, and South America was moving away from Antarctica.
The Eocene's climate was warm and humid, with subtropical forests spreading from the poles to the equator. This warm climate was maintained by high levels of greenhouse gases, possibly caused by volcanic activity. The Azolla event, a massive bloom of freshwater ferns in the Arctic Ocean, occurred during the middle Eocene, which helped to reduce carbon dioxide levels and may have contributed to the cooling at the end of the period.
Flora and Fauna
The warm climate of the Eocene was ideal for plant growth. The period saw the first appearance of several important plant families, including the palms and the eucalyptus. The forests of the Eocene were dense and lush, with a diverse mix of conifers, broadleaf trees, and ferns.
The Eocene was also a time of significant evolution and diversification for mammals. Many modern mammal orders, including primates, cetaceans, and artiodactyls, first appeared in the Eocene. The period also saw the first appearance of many modern bird families, including the first large, flightless birds. The seas of the Eocene were home to a variety of marine life, including sharks, rays, and early forms of whales.
End of the Eocene
The end of the Eocene is marked by a significant cooling event, the Eocene-Oligocene extinction event, which led to the extinction of many species and the rise of others. This event is often attributed to a decrease in atmospheric carbon dioxide, which led to global cooling and the formation of Antarctic ice sheets.