Geologic Time Scale

Front

What is the geologic time scale?

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A system of chronological dating that relates geological strata to time, used to describe the timing and relationships of events in Earth's history.

Tags

NGSS.MS-ESS1-4

Front

What are the main divisions of the geologic time scale?

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Eons, Eras, Periods, and Epochs.

Tags

NGSS.MS-ESS1-4

Front

What is an Eon?

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The largest division of geological time, lasting hundreds of millions to billions of years.

Tags

NGSS.MS-ESS1-4

Front

What is an Era?

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A subdivision of an Eon, lasting tens to hundreds of millions of years.

Tags

NGSS.MS-ESS1-4

Front

What is a Period?

Back

A subdivision of an Era, lasting tens of millions of years.

Tags

NGSS.MS-ESS1-4

Front

What is an Epoch?

Back

The smallest division of geological time, lasting millions of years.

Tags

NGSS.MS-ESS1-4

Front

What is the Law of Superposition?

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In undisturbed sedimentary rock layers, the oldest layers are at the bottom and the youngest layers are at the top.

Tags

NGSS.MS-ESS1-4

Front

What is the significance of the Early Archean Era?

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It is the oldest known era in Earth's history, beginning around 4 billion years ago.

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NGSS.HS-ESS1-6

Front

What major events occurred during the Paleozoic Era?

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The emergence of fish, amphibians, and the first land plants.

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NGSS.MS-LS4-1

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What is the duration of the Cenozoic Era?

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It has lasted approximately 65 million years and continues to the present.