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Paleogeographic reconstruction showing the Illinois Basin area during the Middle Devonian period. [9] Almost all Silurian rocks in Illinois are deep-water limestone and dolomite deposits; reef habitats were common, and fossils of reef organisms are locally highly abundant, including corals, brachiopods, crinoids, stromatoporoids, and bryozoans. [6]
Thornton Quarry, just south of Chicago, Illinois. One of the largest aggregate quarries in the world, 1.5 miles (2.4 km) long, 0.5 miles wide, and up to 450 feet deep, site of a Silurian reef. Quarried since 1836. The quarry also acts as an emergency flood control reservoir as part of Chicago Deep Tunnel project.
The Illinois Basin is a Paleozoic depositional and structural basin in the United States, centered in and underlying most of the state of Illinois, and extending into southwestern Indiana and western Kentucky. The basin is elongate, extending approximately 400 miles (640 km) northwest-southeast, and 200 miles (320 km) southwest-northeast.
The stable platform is an area in which the North American Craton forms a basement and is covered by sediment. This area now forms much of the Interior Plains and the slope of the Appalachians below the mountains proper. [7] This area has been covered by a shallow inland sea, which became the site of deposition for most of the overlying ...
The Garden of the Gods Wilderness is a 3,318-acre (13.43 km 2) parcel of land listed as a Wilderness Area of the United States. It is located within the Shawnee National Forest in Hardin, Pope, Saline, and Gallatin counties in the U.S. state of Illinois. The nearest town of any size is Equality. [1]
Locations of quakes magnitude 2.5 or greater in the Wabash Valley (upper right) and New Madrid (lower left) Seismic Zones. The Wabash Valley seismic zone (also known as the Wabash Valley fault system or fault zone) is a tectonic region located in the Midwestern United States, centered on the valley of the lower Wabash River, along the state line between southeastern Illinois and southwestern ...
Natural Landmarks in Illinois range from 53 to 6,500 acres (21.4 to 2,630.5 ha; 0.1 to 10.2 sq mi) in size. Owners include private individuals or organizations, and several county, state and federal agencies. [2] The National Natural Landmarks Program is administered by the National Park Service, a branch of the Department of the Interior. The ...
Watersheds of Illinois is a list of basins or catchment areas into which the State of Illinois can be divided based on the place to which water flows.. At the simplest level, in pre-settlement times, Illinois had two watersheds: the Mississippi River and Lake Michigan, with almost the entire State draining to the Mississippi, except for a small area within a few miles of the Lake.