The Eocene began as a time of global warming, with temperatures across the planet soaring. Forests thrived and trees grew even in polar regions. Eventually, the Eocene became cooler and drier. As India continued to drift northwards, pushing against the Eurasian continent, the mass of rocks thrust up between them formed the Himalayas. At this time Africa was an island, not yet joined to the Middle East and Europe, but its own journey north was to trigger the formation of the Alps. Many species of grass evolved in the Eocene epoch, but were very limited in extent - today's grassy plains were still far in the future.
Began: 54.8 million years ago
Ended: 33.7 million years ago
Reconstruction of the Earth in the Eocene epoch, 54.8 million - 33.7 million years ago. Credit: Dr Ron Blakey, NAU Geology.
During this period the following extinction level events are thought to have occurred.
The Eocene (symbol Eo ) epoch, lasting from 56 to 33.9 million years ago, 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 Palaeocene Epoch to the beginning of the Oligocene Epoch. The start of the Eocene is marked by a brief period in which the concentration of the carbon isotope 13C in the atmosphere was exceptionally low in comparison with the more common isotope 12C. The end is set at a major extinction event called the Grande Coupure (the "Great Break" in continuity) or the Eocene–Oligocene extinction event, which may be related to the impact of one or more large bolides in Siberia and in what is now Chesapeake Bay. As with other geologic periods, the strata that define the start and end of the epoch are well identified, though their exact dates are slightly uncertain.
The name Eocene comes from the Greek ἠώς (eos, dawn) and καινός (kainos, new) and refers to the "dawn" of modern ('new') fauna that appeared during the epoch.
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