what is an outcrop

what is an outcrop

1 year ago 92
Nature

An outcrop, also known as a rocky outcrop, is a visible exposure of bedrock or ancient superficial deposits on the surface of the Earth. Outcrops allow direct observation and sampling of the bedrock in situ for geologic analysis and creating geologic maps. In situ measurements are critical for proper analysis of geological history and outcrops are therefore extremely important for understanding the geologic time scale of earth history. Some of the types of information that cannot be obtained except from bedrock outcrops or by precise drilling and coring operations, are structural geology features orientations (e.g. bedding planes, fold axes, foliation), depositional features orientations (e.g. paleo-current directions, grading, facies changes), paleomagnetic orientations. Outcrops are also very important for understanding fossil assemblages, paleo-environment, and evolution as they provide a record of relative changes within geologic strata. Accurate description, mapping, and sampling for laboratory analysis of outcrops made possible all of the geologic sciences and the development of fundamental geologic laws such as the law of superposition, the principle of original horizontality, principle of lateral continuity, and the principle of faunal succession.

Examples of outcrops include cliffs, massive granite boulders, sheer cliffs, and jumbled boulder fields. Outcrops represent a mere 2% of the total area of Shenandoah National Park, but they are home to numerous rare plants and animals, many of which are found only in rock outcrop environments. Twenty-one state rare plant species are known to exist on Park outcrops, including plants such as mountain sandwort, Appalachian fir clubmoss, and three-toothed cinquefoil. However, human impacts in the form of social trails, campsites, rock graffiti, and trash have led to severe degradation of vegetation and soils at some cliff sites as well as impacts to rare plant and animal species and communities.

Read Entire Article