Smithsonian National Museum of Natural History Geologic Time The Story of a Changing Earth
Presented by the Department of Paleobiology.
The Eocene
Eocene Overview
Terrestrial Life during the Eocene
Marine Life in the Eocene
Shifting Continents and Changing Climates
A fossil weevil from the Green River
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Dawn horse
Pseudocrypturus cereamaxis
Extinct whale
Snail shell
Fern leaf
Palm leaf
March fly

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Shifting Continents and Changing Climates
Sea levels rose again during the Eocene, flooding the coastal plains of Africa, Siberia, and Australia. Uplift of the Rockies ceased toward the end of the Eocene, but mountain-building continued in Scotland. The Atlantic Ocean continued widening, and by the middle Eocene an Arctic channel ran to the North Atlantic and separated North America from Europe. Faunal interchanges continued between Eurasia and North America across the Bering land bridge. By the late Eocene, the collision of the Indian subcontinent with Asia was causing deformation and mountain-building that would eventually become the Himalayas. At the end of the Eocene a deep-water connection developed between the Pacific and the South Atlantic as South America separated fully from Antarctica.

A brief warming event occurred at the start of the Eocene, as methane was released from ocean-floor sediments. Over a few tens of thousands of years global temperatures rose as a result of the methane release, then cooled again in the succeeding 100,000-200,000 years. Even after this geologically brief interval of very warm climate, subtropical climates existed up to relatively high northern latitudes. These areas had much greater rainfall than today, and less seasonal change in temperature. Carbonate reefs existed in the Bahamas and from Florida to North Carolina. From the middle Eocene onward the climate cooled and became drier. At the end of the epoch circumpolar current formed in the Southern Ocean because of the northward movement of South America. The circumpolar current helped to isolate Antarctica and probably was an important factor in the early development of the South Polar Ice Cap. The cooling of Antarctica in turn meant that cold water began to flow north along the ocean bottoms from high southern latitudes. These changes in ocean circulation brought an end to the long greenhouse climate that had existed since the Mesozoic.


Eocene Overview | Terrestrial Life during the Eocene | Marine Life in the Eocene
Shifting Continents and Changing Climates

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