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Eon

All time on earth is first divided into two Eons, the Cyptozoic and the Phanerozoic. These terms identify the time before fossil evidence for life and the time of fossil evidence for life.

Cryptozoic means "hidden" life and dates from 4 billion years ago to around 600 million years ago.

The Phanerozoic Eon means "visible" life and begins about 600 million years ago when we start to see fossils in the geological record. The Phanerozoic continues to the present

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Eras

Three geological eras. The paleozoic, Mesozoic and Cenozoic. These eras document life on earth as it moves from a dedicated aquatic environment to a life existing on land.

PALEO means old and ZOIC means life. The paleozoic is the oldest of the three eras; it dates from about 600 million years ago to around 245 million years ago. It is the time of Amphibians and life in water.

MESOZOIC means middle life. The Mesozoic is the time of reptiles and dates from 245 mya. to 66 mya ago. This is the time of life on earth living both on land and water. This is the time of transition from living in water to living on land.

CENOZOIC means recent life. The era begins aprox 66 mya and continues onto the present. This is the era we can identify and begin to trace our distant ancestry. It is the time of the mammals.

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Periods

Geologists have sub divided the cenozoic Era into two broad geological periods, the tertiary and quanternary.
-The tertiary period has two smaller subdivisions; the Miocene and pliocene Epoch

We currently live in the Quaternary period which begins approximately 2 million years ago.

The Quaternary is the geological time that documents the development of humanity and it consists of TWO epochs, The pleistocene and Holocene.

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Epochs

The pleistocene Epoch is commonly referred to as the maternity ward for humanity. Some say we humans are in fact a product of the pliestocene.
-The pleistocene Epoch begins aprox 2 mya. ago and ends with the last of the great glacial events about 10 thousand years ago.

Glaciations (or glacial cycles) are what characterize the Pleistocene.
-Scientists have identified at least 12 glacial cycles during Pleistocene. Each glacial cycle lasts 25 thousand years.
-These glacial events are usually discussed as a time of cold (stadials) or times of warm (interstadials)

We are now out of the Pleistocene and have entered our last geological time; This is the Holocene Epoch.

-Commonly referred to as the long summer, the Holocene represents a time of warmth that began about 13,000 years ago.

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stadial

short period of increased glaciation. Stadials can occur during either glacials or interglacials and are separate by interstadials.

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interstadials

short periods during the pleistocene when temperature increased and glaciers receded.

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Interglacials

Period during the Pleistocene when temperature alleviated. Interglacials lasted for thousands of years, and were preceded and followed by glacials.

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What period do Australopithecus place their origins?

5 million years ago, so to the Pliocene/Miocene boundary