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Earth Geology Geologic Time Scale

Explore this time scale by clicking on a time period name for more information about the period. Click on the "What's Happening" column for a brief discussion of the local and regional geologic history of that time period. For example, start with the Hadean Eon, read about Earth's Birth, then follow the pointing hands to move through time... 
Geologic Time Scale
Time Division Name
Time Span
(mya = million years ago)
What's Happening
Hadean Eon
4,600 to 3,800 mya
Earth's Birth
Archaean Eon
3,800 to 2,500 mya
Earliest life
Proterozoic Eon
2,500 to 544 mya
St. Francis Mtns.
Paleozoic Era
Cambrian Period
544 to 505 mya
Marine deposition
Ordovician Period
505 to 440 mya
Marine deposition
Silurian Period
440 to 410 mya
Devonian Period
410 to 360 mya
Mississippian Period
360 to 325 mya
Marine deposition
Pennsylvanian Period
325 to 286 mya
Deposition & erosion
Permian Period
286 to 245 mya
Uplift and erosion
Mesozoic Era
Triassic Period
245 to 208 mya
Jurassic Period
208 to 146 mya
Cretaceous Period
146 to 65 mya
Cenozoic Era
Tertiary Period
Paleocene Epoch
65 to 57.8 mya
Eocene Epoch
.57.8 to 36.6 mya
Oligocene Epoch
36.6 to 23.7 mya
Age of Mammals
Miocene Epoch
23.7 to 5.3 mya
Ice Ages
Pliocene Epoch
 5.3 to 1.8 mya
Quaternary Period
Pleistocene Epoch
1.8 to 0.01 mya
Ice ages
Holocene Epoch
0.01 mya to Now
Age of Man

The relative time scale gives a better representation of the true scale of time. Check it out for yourself!