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Geologic Geologic Time Scale Time Scale • Division of Eon Earth’s history The longest of all based on the subdivision based types of life on the abundance forms that lived of certain fossils only during certain periods.

Eras Era | Period • 2nd longest subdivision • Marked by worldwide changes in types of fossils.

Periods • Units of geologic me marked by the types of life exisng worldwide at the me.

Trilobites are seen in many epochs different geological periods - Smallest of geologic divisions as different species. - Characterized by different life forms. - Some differences vary from connent to content. Different species in different me period can be used as index fossils.

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FOUR Eras… Precambrian Era • The earliest and longest geologic era • PRE-CAMBRIAN – 88% of earth’s history lasng about 4.5 billion years. • Lile is known of organisms of this era. • Paleozoic (ancient life) *due to rock having been destroyed. – 544 million years ago…lasted 300 million yrs

• Mesozoic (middle life) – 245 million years ago…lasted 180 million yrs

• Cenozoic (recent life) – 65 million years ago…connues through present day

Ediacarans Cyanobacteria in the Precambrian Era Ancient jellyfish like creature appeared are the earliest life forms known to man. near the end of the Precambrian Ear.

The Appalachian Mountain were formed The Paleozoic Era in the Paleozoic era. • Large shallow seas covered much of the connents. • Many of the fossils found have been marine (ocean) creatures and plants.

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The Devonian Period Carboniferous Period 419-359 million years ago 359 – 299 million years ago (age of the fishes)

Saw the emergence of early Saw the development of early sharks. amphibians and reples

At the end of the Paleozoic Era more than Possibly due to a asteroid 90 percent of all marine species and or meteor Impact. 70 percent of all land species died off.

The Mesozoic Era • The era of middle life. • 248 – 65 million years ago.

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The Mesozoic Era Mesozoic Era

Early mammals evolved in the middle of the Early birds evolved in the middle of the Triassic Period. Jurassic Period.

Again possibly due to a asteroid or meteor Impact.

Dinosaurs became exnct at the end of the Mesozoic Era.

The Cenozoic Era Cenozoic Mammals • Era of recent life. The Cenozoic Era is divided into two • 65 million years ago periods. to the present. • Quarternary • Terary

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The Cenozoic Era is divided into two period. Earliest humans appeared about Quaternary Period 1.5 – 2 million years ago. • 1.8 million year ago

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Today… • Today we are in the Holocene Epoch of the Quaternary Period of the Cenozoic Era.

Which unit is the largest? Which unit is the smallest?

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