READ: Histroy of Life on Earth
7. Geologic Time Scale
Geologic Time Scale
Geologists and other earth scientists use geologic time scales to describe when events occurred throughout the history of Earth. The time scales can be used to illustrate when both geologic events and events affecting plant and animal life occurred. All of the earth events we see happening today, such as earthquakes, volcanic eruptions, and erosion, have happened throughout history. Past catastrophic events, such as asteroids and comets also hit the earth long before humans evolved.
The geologic time scale in Figure below illustrates the timing of events such as:
- earthquakes
- volcanic eruptions
- major erosion
- meteorites hitting Earth
- the first signs of life forms
- mass exterminations
The geological time scale of Earth's past is organized according to events which took place during different periods on the time scale. Geologic time is the same as the age of the earth: between 4.04 and 4.57 billion years. Look closely for such events as the extinction of dinosaurs and many marine animals.
CK-12 Foundation, Biology. http://creativecommons.org/licenses/by-nc-sa/3.0/