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  • Produced by or belonging to a lake.
  • A protocontinent of the Northern Hemisphere, corresponding to Gondwana in the Southern Hemisphere, from which the present continents of the Northern Hemisphere have been derived by separation and continental displacement. The supercontinent from which both were derived is Pangea. Laurasia included most of North America, Greenland, and most of Eurasia, excluding India. The main zone of separation was in the North Atlantic, with a branch in Hudson Bay; geologic features on opposite sides of these zones are very similar.
  • The LaSalle Anticlinal Belt is the most prominent anticlinal feature in the Illinois Basin. It is actually a complex structure of en echelon folds, asymmetrical anticlines, and monoclines stretching from Stephenson County in northern Illinois through Lawrence County in southeastern Illinois.
  • Molten, fluid rock that is extruded onto the surface of the Earth through a volcano or fissure. Also the solid rock formed when the lava has cooled.
  • A sedimentary rock consisting primarily of calcium carbonate (the mineral, calcite). Limestone is generally formed by accumulation, mostly in place or with only short transport, of the shells of marine animals, but it may also form by direct chemical precipitation from solution in hot springs or caves and, in some instances, in the ocean.
  • To change to stone, or to petrify; especially to consolidate from a loose sediment to a solid rock.
  • The description of rocks on the basis of color, structure, mineral composition, and grain size; the physical character of a rock.
  • The vertical difference in elevation between the highest and lowest points of a land surface within a specified horizontal distance or in a limited area.
  • A homogeneous, unstratified accumulation of silt-sized material deposited by the wind.