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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.
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]
The deep sea is broadly defined as the ocean depth where light begins to fade, at an approximate depth of 200 m (660 ft) or the point of transition from continental shelves to continental slopes. [ 1 ] [ 2 ] Conditions within the deep sea are a combination of low temperatures, darkness, and high pressure . [ 3 ]
Oceanic trenches typically extend 3 to 4 km (1.9 to 2.5 mi) below the level of the surrounding oceanic floor. The greatest ocean depth to be sounded is in the Challenger Deep of the Mariana Trench, at a depth of 10,911 m (35,798 ft) below sea level.
A seafloor map captured by NASA. Bathymetry (/ b ə ˈ θ ɪ m ə t r i /; from Ancient Greek βαθύς (bathús) 'deep' and μέτρον (métron) 'measure') [1] [2] is the study of underwater depth of ocean floors (seabed topography), lake floors, or river floors.
The Illinois side includes Henry County, Mercer County, and Rock Island County. [4] In extreme northwestern Illinois the Driftless Zone, a region of unglaciated and therefore higher and more rugged topography, occupies a small part of the state. Charles Mound, located in this region, is the state's highest elevation above sea level.
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The two major resources mined at sea include oil and minerals. Over the last 30 years, deep-sea mining has generated between $9 -$11 billion USD in the United States of America. [43] [44] Although this sector seems profitable, it is a high risk, high reward industry with many harmful environmental impacts. [45]