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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 Motagua Fault, which crosses through Guatemala, is a transform boundary between the southern edge of the North American plate and the northern edge of the Caribbean plate. New Zealand's Alpine Fault is another active transform boundary. The Dead Sea Transform (DST) fault which runs through the Jordan River Valley in the Middle East.
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]
A geological contact is a boundary which separates one rock body from another. [1] A contact can be formed during deposition, by the intrusion of magma, [2] or through faulting or other deformation of rock beds that brings distinct rock bodies into contact. [3]
Figure 1. This BLM map depicts the principal meridians and baselines used for surveying states (colored) in the PLSS. The following are the principal and guide meridians and base lines of the United States, with the year established and a brief summary of what areas' land surveys are based on each.
In structural geology, a suture is a joining along a major fault zone, of separate terranes, tectonic units that have different plate tectonic, metamorphic and paleogeographic histories. The suture is often represented on the surface by an orogen or mountain range.
Nearly the entire western boundary of Illinois is the Mississippi River, except for a few areas where the river has changed course. Illinois' southeastern and southern boundary is along the Wabash River and the Ohio River, whereas its northern boundary and much of its eastern boundary are straight survey (longitudinal and latitudinal) lines ...
Corresponding to the southeast geological region of Minnesota, the colloquial "Driftless Area" (though the whole region was glaciated) begins at about Fort Snelling. Starting as a narrow sliver against the Mississippi, it widens to the west as one goes south. The western boundary is the Bemis-Altamont moraine.