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Geological Survey Professional Paper 294—K
The Rocks and Fossils of Glacier National Park: The Story of Their Origin and History |
APPENDIX B: Approximate geologic time scale
[The ± figures express probable degree of accuracy of estimates]
| Geologic age | Approximate number of million years ago1 |
Approximate length in millions of years1 |
|
| Quaternary | 0-1 | ±50,000 years | 1 |
| Tertiary: | |||
| Pliocene | 1-12 | ±1-2 million years | 11 |
| Miocene | 12-28 | 16 | |
| Oligocene | 28-40 | 12 | |
| Eocene | 40-60 | 20 | |
| Paleocene | |||
| Cretaceous | 60-130 | ±5 million years | 70 |
| Jurassic | 130-155 | 25 | |
| Triassic | 155-185 | 30 | |
| Permian | 185-210 | ±10 million years | 25 |
| Carboniferous | 2210-265 | 55 | |
| Devonian | 265-320 | 55 | |
| Silurian | 320-360 | 40 | |
| Ordovician | 360-440 | 80 | |
| Cambrian | 440-520 | 80 | |
| Precambrian | 550-2,100 | ±10-300 million years3 | 5,100+ |
1From the report of the National Research Council, Committee on the Measurement of Geologic Time, 1949-50, with minor modifications.
2Estimate of J. P. Marble, chairman, Committee on the Measurement of Geologic Time, March 17, 1954.
3The figure depends on the age of the crust of the earth. For the age of the crust of the earth, the data are at present uncertain, but the order of magnitude is about 3,250 million years.
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Last Updated: 08-Jul-2008