Era
Quaternary
56
Cretaceous
33
Tertiary
17
Holocene
12
Jurassic
10
Cenozoic
9
Pliocene
9
Paleozoic
8
Precambrian
8
Eocene
7
Proterozoic
7
Permian
6
Pleistocene
5
Cambrian
4
Mesozoic
4
Miocene
4
Ordovician
4
20th century
3
Carboniferous
3
Devonian
3
Paleocene
3
1878-1974
2
1881-1971
2
1882-1966
2
Mississippian
2
Paleogene
2
Silurian
2
1770-1838
1
1774-1809
1
1823-1959
1
1874-1988
1
18th century
1
19th century
1
2001
1
21st century
1
Neogene
1
Oligocene
1
Triassic
1