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STRATIGRAPHY
Lesson 3 - Page 1

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GEOLOGIC TIME

The Earth is more than 4.5 billion years old. This is a very large number. One way to understand this amount of time, is to use seconds instead of years. If you looked at a watch, it would take a little more than 11.5 days for a million seconds to go by. Now remember that a billion is one thousand times one million. This means that it takes almost 32 years for a billion seconds to go by! Even if you canít visualize the time, just remember the Earth has existed for a long time.

This picture shows the history of the Earth as if it took place in 24 hours. The creation of the major types of animals was not until 20:00. Humans have only been on the Earth for a very short period, only 30 seconds before 24:00!


24 hour clock

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