11/23/2023 0 Comments Himalayas plate boundaryNational Park Service sites in the Appalachian Mountains have rocks and landscapes resulting from collision of North America with accreted terranes and the ancient continent of Gondwanaland. Modified from “Earth: Portrait of a Planet, by S. The line of the cross section (D-D’) is shown on the Appalachian geologic map. Tectonic Provinces of the Southern Appalachian Mountains Rocks beneath young sediments on the Coastal Plain of Florida and areas offshore from Georgia and the Carolinas are stranded pieces of Africa, left behind when the Atlantic opened. In places the Atlantic Ocean opened some distance east of the zone of “suturing” between the continents. The Piedmont Province is an array of accreted terranes, metamorphosed sedimentary layers and crust of the Iapetus Ocean that were caught up in the collision. Farther east, the rocks formed elsewhere and were attached (accreted) to the edge of North America as the ocean closed. The Valley and Ridge Province is folded and faulted sedimentary strata of the ancient continental margin, and the Blue Ridge Province is a piece of the deeper, hard crust that was uplifted and shoved westward. In the western part of the Appalachian Mountains, the rocks were originally part of North America. In the process volcanic islands, continental fragments and the supercontinent of Gondwanaland collided with the ancient continental margin of North America. Examples of these ancient passive continental margin layers are found today along the Blue Ridge Parkway and in Great Smoky Mountains National Park.įrom about 400 to 300 million years ago the Iapetus Ocean gradually closed during subduction. As the ocean widened, the edge of ancient North America subsided, and a blanket of sedimentary layers buried the rift valleys and eroded mountain ranges. Sedimentary and volcanic layers that were deposited in the rift valleys are exposed in Shenandoah National Park and along the Blue Ridge Parkway. The resulting continental rift zone was much like today’s Basin and Range Province, with long mountain ranges separated by down-dropped valleys. Norton and Company, 298 pp., 2005, About 750 million years ago a very ancient supercontinent began to rip apart. Illustrations above modified from “Parks and Plates: The Geology of our National Parks, Monuments and Seashores,” by Robert J. The Blue Ridge Province is part of North America’s ancient continental margin, while the Valley and Ridge Province contains sedimentary layers of North America that were folded and faulted during the collision. Ancient ocean rocks are left behind as the Piedmont Province, along with a sliver of Africa that now lies beneath the Coastal Plain of Florida and offshore regions of Georgia and the Carolinas (purple). Later rifting opened the Atlantic Ocean, isolating the mountains as separate ranges on different continents.Ītlantic Ocean Opens. The Appalachian Mountains, along with the Caledonide Mountains in Greenland, the British Isles and Scandinavia, as well as the Atlas Mountains in northeastern Africa, are parts of a continental collision zone that formed 500 to 300 million years ago. Norton and Company, 298 pp., 2005, Tectonic Development of the Appalachian-Ouachita-Marathon Mountain Range Modified from “Parks and Plates: The Geology of our National Parks, Monuments and Seashores,” by Robert J. D-D’ is the line of the cross section showing in the tectonic provinces of the Appalachian Mountains. Acadia National Park is in the northern Appalachians in Maine. Hot Springs National Park is in the Ouachita Mountains, while the Marathon Mountains extend into Big Bend National Park. The Blue Ridge Parkway follows the crest of the mountains in Virginia and North Carolina, connecting Shenandoah and Great Smoky Mountains national parks. Four-letter codes refer to some of the National Park Service sites listed near the top of this page. After 300 million years the mountains have eroded deeply and are covered in places by young sediments of the Atlantic and Gulf coastal plains. The Appalachian Mountains are part of a collisional mountain range that includes the Ouachita Mountains of Arkansas and Oklahoma, and the Marathon Mountains in west Texas. SHEN-Shenandoah National Park, Virginia. RUCA-Russell Cave National Monument, Alabama. OBED-Obed Wild and Scenic River, Tennessee. NERI-New River Gorge National River, West Virginia.GRSM-Great Smoky Mountains National Park, North Carolina & Tennessee.GARI-Gauley River National Recreation Area, West Virginia. DEWA-Delaware Water Gap National Recreation Area, Pennsylvania.CHAT-Chattahoochee River National Recreation Area, Georgia.BLUE-Bluestone National Scenic River, West Virginia.ACAD-Acadia National Park, Maine- īISO-Big South Fork National River and Recreation Area, North Carolina & Tennessee- īLRI-Blue Ridge Parkway, Virginia & North Carolina.
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