The diagram below shows the major divisions of geological time;
 
Million years
Eon
Era
Period
1.8
     Phanerozoic       Cenozoic  
Quaternary
5.2
  Tertiary
Pliocene

23.5
Miocene

35.5
Oligocene

56.5
Eocene

65
  Paleocene




145
Mesozoic
Cretaceous



199
Jurassic


251
Triassic


299
Paleozoic
Permian



359
Carboniferous


416
Devonian


444
Silurian



488
Ordovician



542
Cambrian
2500
Proterozoic
  
Precambrian
4600
Archean

 
From 'Geology Today', copyright Blackwell Science Ltd.