Coal swamps contained a wealth of plant life now extinct. In fact, seams of coal can be identified by microscopically examining fossil spores contained in layers of rock. These plants would die, turn into peat, be compacted twenty-fold, and become coal . Thus, the Pennsylvania Period became known as the Great Coal Age . Important oil and gas deposits originate from this time period, too.
Mountains form .
At the end of the Paleozoic Era, during the Permian Period which began 275 million years ago, there was tremendous mountain-building throughout the planet including Appalachia. Their height may have been as tall as the highest Alaskan mountains are today. West Virginia has not been under a sea since then. Peneplain forms . The next era, the Mesozoic, is familiar to most people.