Geology of West Virginia

Geology Of West Virginia

Prior to one billion years ago, the geologic history of West Virginia is obscure. The oldest evidences of life found in West Virginia occur in rocks about 600 million years old, in the Antietam Formation of Lower Cambrian age. The oldest exposed rock, the Catoctin greenstone, began to form between about 1,100 and 800 million years ago. Lava was deposited in the extreme eastern part of the State. About 300 million years later, by the end of Cambrian time, a shallow sea covered essentially all of West Virginia. Marine deposition took place throughout most of this and the succeeding Ordovician Period. The Taconic orogeny near the end of Ordovician time formed a high mountainous area east of West Virginia. Near the end of Devonian time, the sea was rapidly retreating westward and the continental red beds of the Hampshire Formation were being deposited over most of the State. Approximately 330 million years ago, resulting in the deposition of the Greenbrier Formation, predominantly limestone, the last marine deposit of significance in the State. Roughly 270 to 225 million years ago, the Appalachian Orogeny began. This orogeny played a major part in the formation of the Appalachian Mountains as we know them today. West Virginia was uplifted, important deposition of sediments ceased, and erosion began taking place. About 310 million years ago, West Virginia was essentially a land area, subject to erosion. Swamp conditions prevailed more than 50 million years, resulting in the deposition of thousands of feet of nonmarine sandstone and shale and the many important coal seams that we know today.