Outcrop (geology)

Exposure of clay and sandstones from the Keuper on the Schwanberg near Iphofen

Exposure of limestones from the Upper Jurassic on the Trinity Mountain in the Swabian Alb

Payson outcrop with gypsum sandstones on the western edge of the Erebus crater on Mars (photo of the Opportunity Rover)

An outcrop (sometimes also called a crack or outcrop , but see →  Outcrop ) is a point on the earth's surface where rock that is connected to the regional rock bedrock (so-called adjacent rock ) emerges uncovered. Under humid (humid) climatic conditions, especially in the plains, this is often largely covered by soil and vegetation and therefore not exposed. If, in addition to the type of rock, coarse structures such as fissures , stratification or foliation can also be identified and measured in an outcrop , it is referred to as relatively good, and if details such as sediment structures are also recognizable, ideal outcrop conditions. Outcrops are also places for taking rock samples for scientific or technical purposes.

One differentiates:

• natural outcrops:
  • free-standing rocks , individual rock walls (e.g. stratified steps ), or, particularly large areas, high mountain massifs
  • Steep banks of rivers, gorges , canyons and cliffs
  • Wrecking edges of landslides
• artificial (anthropogenic) outcrops:
  • Mining fronts of opencast mines and quarries , gravel pits , construction pits
  • Tunnel in underground mining
  • Road or rail cuts
  • Trenches etc.

In the broadest sense, the rock samples obtained through geological drilling (→  drill core ) can also be described as artificial outcrops.

In humid climates, a soil profile can often be observed above the adjacent rock on both artificial and natural, relatively “fresh” steep sections of the terrain (e.g. on cliffs or in active quarries) .

All types of information are the most important sources of data for geology in general (see →  Geo-archive ) and for geological mapping in particular, as they can be used to read off the geological conditions to be found at exactly this point. If there is a lack of information in a certain area, reading stones - loose rock fragments heaped in the ground - can be used to infer what is possibly deeper. With the smartphone application OutcropWizard outcrops can be found and explored.

See also

• Outcrop (mining)

Individual evidence

1. ↑ Christiane Martin, Manfred Eiblmaier (ed.): Dictionary of earth sciences. Vol. 1: A – Edi, Spektrum Akademischer Verlag, Heidelberg [ua] 2000, p. 158.
2. ↑ Geology as a place of learning. Module H: Geological working methods. Bavarian State Ministry for Environment and Health, State Institute for School Quality and Educational Research, Munich 2010 ( PDF ( Memento from September 29, 2015 in the Internet Archive )), p. 299 ff.
3. ↑ see e.g. B. Karl Jüttner: Outcrops as geological documents in the lower Thayalande. Yearbook of the Vienna branch of the Reich Office for Soil Research (Jb. Geol. Bundesanst.). Vol. 89, 1939, pp. 377-411 ( PDF 2.2 MB).

Web links

Commons : Outcrops  - collection of images, videos, and audio files

• Many examples of natural and artificial outcrops based on various protected geotopes in Lower Saxony.