Outcrop

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 ( 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:

• Cliffs
• Tors
• Escarpments
• Inselbergs

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. Yana is another example of outcrops, located in Uttara Kannada district in Karnataka, India. File:Serrotebranco.JPG|Serrote Branco outcrop in Caicó, Brazil File:Granodiorite of the Fennoscandian Shield.jpg|Precambrian outcrop in Finland File:Śląskie Kamienie - Dívči Kameny.JPG|Granite outcrops at Silesian Stones Mountain in southwestern Poland File:Yana Rock no border.jpg|Outcrop near Yana, India File:Roubidoux sandstone bluff.JPG|Outcrop of the Roubidoux Formation in the Ozarks of southern Missouri File:Vasquez Rocks County Park.jpg|Outcrop in the Vasquez Rocks Natural Area Park of southern California File:12 1072m - Valley of Desolation.jpg|Valley of Desolation in the Camdeboo National Park

References

References

1. Howell, J. V., 1960, ''Glossary of Geology and Related Sciences''. Washington, DC: American Geological Institute, pp. 207–208
2. Fitzsimons, James A.. (2017-07-01). "Rocky outcrops: A hard road in the conservation of critical habitats". Biological Conservation.
3. "oxy.edu. Vazquez Rocks. access date:5/22/2010".
4. "parks.lacounty.gov. Vazquez Rocks Natural Area and Nature Center. access date:5/22/2010".