Duration of earth’s history:

It is divided into five geological life spans called eras:

(1) Archeozoic (Era of down of earth)

(2) Proterozoic (early life)

(3) Paleozoic (Ancient life)

(4) Mesozoic (Medival life)

(5) Cenozoic (Modern life)

Eras are further divided into periods & periods further divided into epochs.

*Paleozoic is further divided into 4 periods namely, Permian, carboniferous, devonion, and Silurian.

*Mesozoic is further divided into 3 periods namely, Triassic, Jurassic and cretaceous.

*Cenozoic is further divided into 2 periods namely, tertiary and quaternary.