Geologic time in general means a LOT of time. This is because geologic processes take very long periods of time to complete.

An example of such a process is the creation of the long sandy beaches on the east side of South America by the slow erosion of the Andes Mountains on the west side of South America by rivers that carry the sand to the beaches.

This is the breakdown of the geological time scale. Each section is seperated based on different types of rock and fossils found in the rock.

Listings of animals show where they are found in the geological time scale.
Era, Period and Epoch headings end where there is insufficent data to make such distinctions.

Time is noted on the right, in millions of years ago.

________________________________________________________________________
|     EON       |       ERA        |       PERIOD      |     EPOCH      |
|---------------|------------------|-------------------|----------------| 0
| Phanerozoic   |     Cenozoic     |   Quarternary     |    Holocene    |
|               |                  |                   |  Pleistocene   |
|               |                  |-------------------|----------------| 2
|               |                  |     Neogene       |    Pliocene    |
|               |                  |                   |----------------| 5
|               |                  |                   |    Miocene     |
|               |                  |-------------------|----------------| 24
|               |                  |     Paleogene     |   Oligocene    |
|               |                  |                   |----------------| 37
|               |                  |                   |     Eocene     |
|               |                  |                   |----------------| 58
|               |                  |                   |   Paleocene    |
|               |------------------|-------------------|----------------| 65
|               |     Mezozoic     |    Cretaceous     |
|               |                  |-------------------| 144
|               |                  |     Jurassic      |     * birds
|               |                  |-------------------| 208
|               |                  |     Triassic      |     * mammals
|               |------------------|-------------------| 245
|               |     Paleozoic    |     Permaian      |
|               |                  |-------------------| 286
|               |                  |   Carboniferous   |     * reptiles
|               |                  |-------------------| 360
|               |                  |     Devonian      |     * amphibians 
|               |                  |-------------------| 408
|               |                  |     Silurian      |     * land plants
|               |                  |-------------------| 438
|               |                  |     Ordovician    |
|               |                  |-------------------| 505
|               |                  |      Cambrian     |     * fishes
|---------------|------------------|-------------------| 570
|  Proterozoic  |  Neoproterozoic  |
|               |------------------| 1000
|               | Mesoproterozoic  |      * invertebrates
|               |------------------| 1600
|               | Paleoproterozoic |
|---------------|------------------| 2500
|   Archean     |       Late       |
|               |------------------| 3000
|               |      Middle      |       * first prokaryotes
|               |------------------| 3400
|               |      Early       |
|---------------|------------------| 3800
|   Hadean      |
|---------------| 4600

Notes:
  • The most recent records are the most extensive and take up most of the space on the scale, although Proterozoic, Archean and Hadean Eons account for 90% of the time scale.
  • The Neogene and Paleogene periods are often combined and called the Tertiary peroid.

  • Reference: http://www.ucmp.berkeley.edu/exhibit/geology.html

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