Monday, May 17, 2010

What happened during the long period of glaciation called the Pleistocene?

The Pleistocene is the epoch from 2.588 million to 12,000 years BP (before the present) covering the world's recent period of repeated glaciations.

The name pleistocene is derived from the Greek πλεῖστος (pleistos "most") and καινός (kainos "new").

Pleistocene climate was marked by repeated glacial cycles where continental glaciers pushed to the 40th parallel (Shreveport is at the 32nd parallel) in some places. It is estimated that, at maximum glacial extent, 30% of the Earth's surface was covered by ice.

The sum of transient factors acting at the Earth's surface is cyclical: climate, ocean currents and other movements, wind currents, temperature, etc. The waveform response comes from the underlying cyclical motions of the planet, which eventually drag all the transients into harmony with them. The repeated glaciations of the Pleistocene were caused by the same factors.

The similarity of our present interglacial interval (known as the Holocene, Postglacial, or the Present Interglacial) to that of an earlier one about 400,000 years ago suggests that the next glacial will begin in about 20,000 years.

A major extinction event of large mammals (megafauna), which included mammoths, mastodons, saber-toothed cats, glyptodons, ground sloths, Irish elk and cave bears began late in the Pleistocene and continued into the Holocene.

Neanderthals also became extinct during this period.

At the end of the last ice age, cold-blooded animals, smaller mammals like wood mice, migratory birds, and swifter animals like whitetail deer had replaced the megafauna and migrated north.

Scientific evidence[11] indicates that humans evolved into their present form during the Pleistocene.[12]