Mountains. Physiographic regions A physiographic region is a large portion of land that is grouped by several factors. Each region has similar geology, topography, and groups of plants and animals. There are eight physiographic regions in the United States. Each region is divided into provinces, there are 25 provinces in the United States. Each region is then divided into sections, creating 85 different physio-graphic sections in the United States. The Appalachian Plateau is a province of the physiographic region of the Appalachian Highlands. The Appalachian Plateau province is divided into seven physiographic sections: Mohawk, Catskill, Southern New York, Allegheny Mountains, Kanawha, Cumberland Plateau, and the Cumberland Mountains. Each section is classified under the Appalachian Plateau province because of its similarities in geologic makeup, topography, and wildlife. Likewise, the Appalachian Plateau falls under the classification of Appalachian Highlands because of those similar characteristics. Geology The rock underlying the Appalachian Plateau consists of a base of Precambrian rock, overlain by sedimentary rock from the Paleozoic Era. On top of the basement is a thick layer, approximately 20,000 feet, of a mixture of Cambrian, Ordovician, and Middle Silurian rock. This rock consists of shale, siltstone, and sandstone. Above this layer is the Upper Silurian evaporate basin, or basin of chemically formed sedimentary rocks. The Plateau fold belt consists of structurally complex Paleozoic strata which were thrust faulted over the younger evaporates. When the Appalachian mountains were formed, the plateau was lifted. Ridges and valleys all die down underneath the plateau. There are multiple valleys throughout the region which consist of exposed areas of limestone and shale. History Native Americans Archaeologists have evidence that Native Americans lived in the Appalachian region more than twelve thousand years ago; however, it is hard to say exactly when the occupants first inhabited the land. Human artifacts were collected near the Meadowcroft Rockshelter in southern Pennsylvania that were at least sixteen thousand years old. Because the early Native Americans were hunter-gatherers living off the land, they left little material traces of their lives behind them. This is why it is so hard for researchers to determine when they settled in this area. Much like many historic Native American tribes, the early Appalachian inhabitants survived as nomads, following their food on a seasonal basis. Around this period, North America was still recuperating from its last glacial period, and the climate was very different from the present. The climate and