Geological History of Earth

The earth is believed to have originated about 4600 million years ago.The main geological events in the history of earth can be categorized into the following eras.

1. Pre-Cambrian Era : This is the longest era of the classification of the history of earth. It marks the origin of earth. This era ended 570 million years ago. The chief events that took place in this era include formation of crust, continents and oceans, origin of life, formation of present day atmosphere, etc.

2. Paleozoic Era : Pre- Cambrian Era was followed by Paleozoic Era. This era contains six time-periods :

(i) Cambrian period
(ii) Ordovician period
(iii) Silurian period
(iv) Divonian period
(v) Carboniferous period
(iv) Permian period

This era ended 225 million years ago; the geological events of importance include Caledonian mountains rise, Appalachians and Central European mountains come up, life comes ashore, etc.

3. Mesozoic Era : This era started about 225 million years ago and ended about 65 million years ago. This era includes three main periods :
(i) Triassic period
(ii) Jurassic period
(iii) Cretaceous period

Important events of this era were: Urals rise up, India splits from Antarctica, Pangaea starts to break up, etc.

4. Cenozoic Era : This era is the last in the classification. It started about 65 million years ago. Cenozoic era is made up of two periods : Tertiary period and Quaternary period. The Tertiary period contains the following five epochs : (i) Paleocene, (ii) Eocene, (iii) Oligocene, (iv) Miocene, and (v) Pliocene.

The Quaternary period can be divided into two epochs : Pleistocene and Holocene. The main developments of this era include formation of the Rockies, Himalayas and Alps, Australia splits away from
Antarctica, India collides with Asia. The current time can be put into the Cenozoic Era, Quaternary period and Holocene Epoch.