May 24 2014
An outcrop is a bedrock that is exposed, or old superficial deposits on the Earth’s surface. In most places outcrops are covered by a mantle of soil and vegetation. However, the rock may crop out, or be exposed, in places where the overlying cover is removed by tectonic uplift or erosion.
This sort of exposure will occur in areas such as mountain ridges, river banks, and steep hillsides, which have rapid erosion and weathering rates.
Human excavations, such as the building of transport routes and quarrying, may also cause the exposure of bedrocks at the Earth’s surface.
Some of the typical examples of outcrops include Vasquez Rocks in California, which are composed of uplifted sandstone and several roadside outcrops of shales, and Ordovician limestones in south-eastern Indiana.
Outcrops are useful in providing direct observation and sampling of the bedrocks for geological studies, and for creating geological maps. Outcrops are critical for analyzing paleo-environment, evolution, and fossil assemblages, as they provide a record of relative changes within geological strata.
Sampling, mapping, and accurate descriptions for analysis of outcrops, made possible the development of fundamental geologic laws, such as the principle of faunal succession, the principle of lateral continuity, the principle of original horizontality, and the law of superposition.
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