Mother Earth has experienced many changes during her four and a half billion existence. Earth has experienced many different climates and many different species. Because of these changes, geologists have divided Earth's history into different periods. One of these periods was the Pennsylvanian period. The Pennsylvanian period is a subdivision of the Carboniferous period. The Pennsylvanian period saw the introduction of many different species that are still present today, as well as a very different climate and geographic features than those present today. Before we get into some of the physical features of the Pennsylvanian period, it's important to know exactly when it occurred. . There have been differing opinions as to the exact length of this period, but most scientists agree that the Pennsylvanian period lasted about thirty million years. (Kazlev) The Pennsylvanian period is the younger of the two subdivisions of the Carboniferous period. The Pennsylvanian period occurred from approximately three hundred and twenty-three million years ago to approximately two hundred and ninety million years ago. () The entire Carboniferous period, which lasted about sixty-four million years, represents only about 1.6% of all geologic time. ()The climate of the Pennsylvanian period is very different from that of ours today. The climate can be described as being similar to that of a rainforest. "The Pennsylvanian was the time of the great 'coal swamp forests' that dominated the equatorial regions of the planet." (Kazlev) There were vast swampy areas that spanned several countries. Much of the world was underwater and this is what allowed some of the species that emerged to be so successful. Although ...... middle of paper ...... due to the coal that was produced during this period, it can be debated that the Pennsylvanian period, and indeed the entire Carboniferous period, is the most important era in Earth's history. Without the coal produced during this period, many of Earth's energy problems would still not have been solved. However, all good things must come to an end and the Pennsylvanian period did indeed come to an end. At the end of the Pennsylvanian period, there were significant climate changes and the extinction of some aquatic life. There were fewer seedless plants and more seeded plants. () Although the Pennsylvanian period ended, much was accomplished during this period for the land. Humans today can be grateful for everything that happened during this time, as it contributed greatly to Earth's success today..