Outcrop

Last updated
Outcrop of volcanic rock in Germany Rockeskyller Kopf 3.JPG
Outcrop of volcanic rock in Germany

An outcrop or rocky outcrop is a visible exposure of bedrock or ancient superficial deposits on the surface of the Earth and other terrestrial planets. [1]

Contents

Features

In most places, bedrock or superficial deposits are covered by soil and vegetation. Where these are removed through erosion, tectonic uplift, or excavation by humans, the underlying rock may crop out, or be exposed. Most frequently, this occurs on steep hillsides, mountain ridges and mountaintops, river banks, and areas which are tectonically active. For example, Finland has many coastal and littoral outcrops due to glacial erosion during the last glacial maximum (c. 11000 BC), followed by scouring by sea waves, then isostatic uplift.

Study

Outcrops allow direct observation and sampling of the bedrock in situ for geologic analysis and creating geological 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, and 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.

Types of outcrops

Outcrops occur in numerous forms, including, but not limited to: [2]

Examples

On Ordnance Survey maps in Great Britain, cliffs are distinguished from outcrops: cliffs have a continuous line along the top edge with lines protruding down; outcrops have a continuous line around each area of bare rock. An outcrop example in California is the Vasquez Rocks, familiar from location shooting use in many films, composed of uplifted sandstone. [3] [4] Yana is another example of outcrops, located in Uttara Kannada district in Karnataka, India.

See also

References

  1. ↑ Howell, J. V., 1960, Glossary of Geology and Related Sciences. Washington, DC: American Geological Institute, pp. 207–208
  2. ↑ Fitzsimons, James A.; Michael, Damian R. (2017-07-01). "Rocky outcrops: A hard road in the conservation of critical habitats" . Biological Conservation. Small Natural Features. 211: 36–44. doi:10.1016/j.biocon.2016.11.019. ISSN   0006-3207.
  3. ↑ "oxy.edu. Vazquez Rocks. access date:5/22/2010". Archived from the original on 2011-06-08. Retrieved 2010-05-24.
  4. ↑ "parks.lacounty.gov. Vazquez Rocks Natural Area and Nature Center. access date:5/22/2010". Archived from the original on 2012-09-20. Retrieved 2010-05-24.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.