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GEOLOGIC TIME SCALE.

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Presentation on theme: "GEOLOGIC TIME SCALE."— Presentation transcript:

1 GEOLOGIC TIME SCALE

2 Because the time span of Earth’s past is so great, geologists use the geologic time scale to show Earth’s history. Geologic Time Scale: A record of the life forms and geologic events in Earth’s history.

3 Precambrian Time The beginning of geologic time.
Covers about 88% of Earth’s history. Ended 544 million years ago.

4 After Precambrian time, the basic units of the geologic time scale are eras and periods.
Eras: One of the three long units of geological time between the Precambrian and the present. The three eras are the Paleozoic Era, the Mesozoic Era, and the Cenozoic Era.

5 Paleozoic Era Paleozoic Era: Began about 544 million years ago and lasted for 300 million years. The word “paleo” means “ancient or early.”

6

7 Mesozoic Era Mesozoic Era: The “Age of Reptiles.” Began about 245 million years ago and lasted about 180 million years. The word “meso” means “middle.”

8 Cenozoic Era Cenozoic Era: Began about 66 million years ago and continues to the present. The word “ceno” means “recent” and “zoic” means “ “life.” Mammals became common during this time.

9 Eras are subdivided into units of geological time called periods.
Periods: One of the units of geological time into which geologists divide eras.


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