during the Pliocene
Pliocene began with the catastrophic origin of the Mediterranean Sea.
The Mediterranean Basin had been dry since the Miocene,
replaced by grasslands. However, at the beginning
of the Pliocene it was reflooded when a tectonic barrier near the
Straits of Gibraltar was breached, allowing water from the Atlantic
Ocean to pour into the basin, probably catastrophically. North and
South America were connected 3.4 million years ago by the formation
of the Panamanian Isthmus, due to the eastward movement of the Caribbean
plate. This closed the Balboa Portal between the Atlantic and Pacific
Oceans, creating significant changes in the marine environment by
separating these two oceans.
The continents were in nearly their present-day positions by the Pliocene.
The Indian plate continued to move northward under the Asian plate,
further elevating the Himalaya Mountains. Other areas of mountain-building
around the old Tethys Ocean involved the Caucasus
region in Asia, which also generated large orographic
changes in climate due to the rain-shadow effect. In North America,
the Cascades, Rockies, and Appalachian Mountains experienced continued
or renewed uplift, along with the Colorado Plateau. The Sierra Nevada
and Alaskan Ranges were forming as well. Mountain-building was also
taking place in Europe, including the Alps. All these orogenies
affected global climate and worked with astronomically controlled
climate cycles to create cooler and more unstable conditions relative
to the Miocene.
Life in the Pliocene |
Tectonics during the Pliocene
Climate Cycles during the Pliocene
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