|
|
|
|
|
|
Introduction |
|
|
|
 |
Although
coal has been discovered in rocks as old as the Precambrian Era, most
coal dates from the Devonian Period
(some 400 million years ago (mya)). At this time, land-based plants with woody tissue became abundant
thereby making it possible for peat deposits to accumulate to a size that would eventually make mineable
coal seams. As the geologic time scale to the left shows, the two major
world-wide coal forming periods were the Pennsylvanian (320 to 286 mya) and the
Paleocene to Early Eocene (66 to 52 mya). In the United States, eastern coals are
of Pennsylvanian age
whereas western coals are Paleocene to Early Eocene in age.
On the time scale,
periods that were important coal producers highlight when moused
over. Click on one of these time periods to learn more about
North American coal generation in the geologic past. |
|
| |
|
Click 'NEXT' to continue
|
|
