Geologic Time
and The Geologic Time Scale:

jump to: 3 main subdivisions of table | Geologic Table | Life Characteristics used

The division of Earth's history is divided into smaller units based on geologic changes that have occurred through time.

Examples include

• Plate techtonics
• Volcanism
• Ice Ages

it is also Based on the type of life forms living during certain periods of time.

Examples include

• Speciation
• Natural Selection

Subdivisions of Geologic Time:

Three main types of subdivisions of geologic time

Eras:
Are major subdivisions of the geologic time scale and are based on differences of life forms.

Periods:
Based on the type of life existing at the time and on major geologic events like mountain building and plate tectonic movement.

Epochs:
Based on more specific and shorter time periods of life and geologic events.

Above Scale Created by Andrew Macrae. The graphics original source is http://www.geo.ucalgary.ca/~macrae/timescale/timescale.html. (Will open in new browser window)

Detailed Geologic Time Line Table 70K in Size. (Will open in new browser window)

More Detailed Geologic Time Line Table 205K in Size.(Will open in new browser window)

Lifes characteristics that have been used
to classify the Geologic Time Table:

Species
A group of individuals that breed among themselves to make offspring.

Natural Selection
The process by which living organisms with traits best suited to an environment survive, while others die out because they lack those desirable traits.

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