BIGINNING#3 (Geological Time Scale)

                         EONS>ERAS>PERIODS>EPOCH>AGES

Now if we talk about geological time scale , it is vast consisting of Eons, Eras, Periods , Epoch & Ages.

There are four(4) Eons in which first three(3) are Pre-Cambrian (negligibly old) and the last one is Cambrian which is sub divided into three (3) Eras which are further divided into many periods then epoch then ages. 

Here the Hadean, Archean & Proterozoic eons are Pre-Cambrian (they are negligibly old)

The earliest life i.e. single celled organism appeared here (bacteria and all that).

The last one is Phanerozoic eon. we are living in this eon.

The Phanerozoic eon is further sub divided into three eras;-

1.Caenozoic
2.Mesozoic
3.Paleazoic

And the above mentioned eras are further subdivided into their respective periods .

paleaozoic:-

1. Cambrien  (approx 560 million yrs ago )

2.Ordovivian (500 mya ago known for the emergence of algae0

3.Silurian (435mya)

4.Devonian (410mya known for the arrival of amphibians)

5.Carboniferous(360mya known for the emergence of Reptiles)

6.Permian (240mya Reptiles dominated)

Mesozoic:-

1.Triasic (nearly 245mya Frogs and Turtles came)

2.Jurassic (205mya DINOSAURS ARRIVAL)

3.Cretaceous( 138mya famous for extinction of dinosaurs)

Caenozoic

1.Tertiary\

2.Quaternary

Now the Tertiary and Quaternary Periods are further subdivided into their respective Epochs:-

Tertiary

1.Paleocene

2.Eocene

3.Oligocene

4.Miocene

5.Pliocene

Quaternary

1.Plastocene

2.Holocene(we are living in this epoch)