The geology of Alabama is marked by abundant geologic resources and a variety of geologic structures from folded mountains in the north to sandy beaches along the Gulf of Mexico coast. Alabama spans three continental geologic provinces as defined by the United States Geological Survey, the Atlantic Plain, Appalachian Highlands, and Interior Plains. The Geological Survey of Alabama breaks these provinces down into more specific physiographic provinces.
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East Gulf Coastal Plain
The broad, flat coastal plain stretches across the southern portion of the state, extending north from the Gulf coast to the fall line near Montgomery, Alabama.
Appalachian Highlands
Extending north from the fall line to far northern Alabama, the Appalachian Highlands encompass the hills, valleys, mountains, and plateaus that make up the southern extent of the Appalachian Mountains. This province is further subdivided into the Piedmont, Valley and Ridge, and Appalachian Plateaus provinces.
Interior Plains
Extreme north Alabama marks the southeast border of the Interior Plains province, characterized by flat or gently rolling terrain. In Alabama, this province generally lies north of the Tennessee River. This province is further divided into the Interior Low Plateaus province.
Seismology
Alabama experiences frequent small earthquakes detectable only by instruments, and occasional moderate earthquakes large enough to be felt over a wide area and resulting in minor damage. The largest earthquake in recorded Alabama history measured an estimated magnitude of 5.1 and occurred October 18, 1916 near Irondale, and resulted in widespread panic, damage to structures, and dramatic changes in water well levels. Since 1886, slightly more than 10 percent of earthquakes with an epicenter in Alabama have been an estimated magnitude 3 or greater. The April 29, 2003 earthquake centered near Fort Payne, Alabama was felt over a wide area and received extensive media coverage.
Two fault zones are found in Alabama, the Southern Appalachian Seismic Zone (also known as the Eastern Tennessee Seismic Zone) in northeast and central Alabama, and the Bahamas Fracture Seismic Zone in southwest Alabama. Alabama also lies within the influence of the New Madrid Seismic Zone and the South Carolina Seismic Zone, earthquakes in those zones have resulted in damage in Alabama. The northeast corner of the state is subject to the greatest peak accelerations due to the presence of the East Tennessee Seismic Zone.
Meteor crater
A meteor crater over five miles in diameter was identified near Wetumpka, Alabama in 1969-1970. Conclusive evidence of the origin of the Wetumpka Impact Crater was found by Auburn University geology professor David T. King in 1998.