Geological time

Geological time is the time scale used in geology to study the history of the Earth from its formation to the present.

It describes processes that occur over millions or billions of years, such as:

• Mountain formation
• The opening and closing of oceans
• The evolution of life
• Mass extinctions
• Volcanic activity
• Erosion and sedimentation

Division of geological time

The Earth is approximately 4,540 million years old, and to organize this enormous period, geologists have divided geological time into hierarchical units.

From largest to smallest:

• Eon
• Era
• Period
• Epoch
• Age