Eocene

The Eocene epoch (56-34 mya) is a major division of the geologic timescale and the second epoch of the Palaeogene 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 the emergence of the first modern mammals. The end is set at a major extinction event that may be related to the impact of one or more large bolides in Siberia and in what is now Chesapeake Bay. Still, as with other other geologic periods, the strata that define the start and end of the epoch are well identified, but their exact dates are slightly uncertain.

Eocene paleogeography

During the Eocene, the continents continued to drift toward their present positions.

Related Topics:
Continent - Drift

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At the beginning of the period, Australia and Antarctica remained connected, and warm equatorial currents mixed with colder Antarctic waters, distributing the heat around the world and keeping global temperatures high. But when Australia split from the southern continent around 45 mya, the warm equatorial currents were deflected away from Antarctica, and an isolated cold water channel developed between the two continents. The Antarctic region cooled down, and the ocean surrounding Antarctica began to freeze, sending cold water and icefloes north, reinforcing the cooling.

Related Topics:
Australia - Equator

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The northern supercontinent of Laurasia began to break up, as Europe, Greenland and North America drifted apart.

Related Topics:
Supercontinent - Laurasia - Europe - Greenland - North America

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In western North America, mountain building started in the Eocene, and huge lakes formed in the high flat basins among uplifts.

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Europe saw the Tethys Sea finally vanish, while the uplift of the Alps isolated its final remnant, the Mediterranean, and created another shallow sea with island archipelagos to the north. Though the North Atlantic was opening, a land connection appears to have remained between North America and Europe as the faunas of the two regions are very similar.

Related Topics:
Tethys Sea - Alps - Mediterranean - Archipelago - Atlantic

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India continued its journey away from Africa, and began its collision with Asia, folding the Himalayas into existence.

Related Topics:
India - Africa - Asia - Himalaya

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• Detailed maps of Tertiary Western North America: Eocene
• Map of Eocene Earth