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Geologic Time Scale Definition

The geologic time scale is an arrangement of events used as a measure of the relative or absolute age of any part of geological time. Earth's 4.6 billion year history is organized this way.

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Rock Layers (Geologic Time)

Fun Facts

  • The geologic time scale subdivides time into duration, eons, eras, periods, epochs, and ages.
  • By examining where fossils are found in rock layers, scientists have been able to put together the geologic time scale.
  • Rock layers tell us when different organisms went extinct and when new organisms showed up on Earth.

Why Do We Need To Know About Geologic Time Scale

Learning about the geologic time scale helps us understand Earth’s history. Paleontologists look at fossils and geologists study rocks to learn about Earth’s past and how life evolved over billions of years.

These studies are useful for finding natural resources and learning about changes in the environment. For example, finding the KT boundary helps us learn about big extinctions and why they happened. This information is useful for guessing what might happen in the future and for studying rocks on Mars and the Moon.

Frequently Asked Questions

How old is Earth and what do we use to keep track of major Earth events?
Earth is 4.6 billion years old and the geologic time scale is used to keep track of the events that have happened since Earth was formed.
What caused most of the dinosaurs to go extinct and how do scientists know?
A big meteor hit Earth, and scientists know this because they have found a rock layer they named the K-T boundary that show dinosaurs living before that layer but none after.
Explain how weathering and erosion can lead to creating some of the landforms we see?
Weathering and erosion made things like the Grand Canyon because the river weathered the rocks and erosion moved it down the river.
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