Bedrock

In geology, bedrock is solid rock that lies under loose material (regolith) within the crust of Earth or another terrestrial planet.

Definition

Bedrock is the solid rock that underlies looser surface material.^[1] An exposed portion of bedrock is often called an outcrop.^[2] The various kinds of broken and weathered rock material, such as soil and subsoil, that may overlie the bedrock are known as regolith.^[3]^[4]

Engineering geology

The surface of the bedrock beneath the soil cover (regolith) is also known as rockhead in engineering geology,^[5]^[6] and its identification by digging, drilling or geophysical methods is an important task in most civil engineering projects. Superficial deposits can be very thick, such that the bedrock lies hundreds of meters below the surface.^[7]

Weathering of bedrock

Exposed bedrock experiences weathering, which may be physical or chemical, and which alters the structure of the rock to leave it susceptible to erosion. Bedrock may also experience subsurface weathering at its upper boundary, forming saprolite.^[8]

Geologic map

A geologic map of an area will usually show the distribution of differing bedrock types, rock that would be exposed at the surface if all soil or other superficial deposits were removed. Where superficial deposits are so thick that the underlying bedrock cannot be reliably mapped, the superficial deposits will be mapped instead (for example, as alluvium).^[9]

References

^ Jackson, Julia A., ed. (1997). "Bedrock". Glossary of geology (Fourth ed.). Alexandria, Virginia: American Geological Institute. ISBN 0922152349.
^ Jackson 1997, "Outcrop".
^ Jackson 1997, "Regolith".
^ Allaby, Michael (2013). "Regolith". A dictionary of geology and earth sciences (Fourth ed.). Oxford: Oxford University Press. ISBN 9780199653065.
^ Price, David George (2009). "The Basis of Engineering Geology". In de Freitas, Michael H. (ed.). Engineering Geology: Principles and Practice. Springer. p. 16. ISBN 978-3540292494.
^ McLean, A.C.; Gribble, C.D. (9 September 1985). Geology for Civil Engineers (Second ed.). CRC Press. p. 113. ISBN 978-0419160007.
^ Swinford, E. Mac (2004). "What the glaciers left behind—the drift-thickness map of Ohio" (PDF). Ohio Geology. No. 1. Ohio Department of Natural Resources, Division of Geological Survey. pp. 1, 3–5. Archived (PDF) from the original on 2 October 2012. Retrieved 12 September 2012.
^ Lidmar-Bergström, Karna; Olsson, Siv; Olvmo, Mats (January 1997). "Palaeosurfaces and associated saprolites in southern Sweden". Geological Society, London, Special Publications. 120 (1): 95–124. Bibcode:1997GSLSP.120...95L. doi:10.1144/GSL.SP.1997.120.01.07. S2CID 129229906. Retrieved 21 April 2010.
^ "Digital Geology – Bedrock geology theme". British Geological Survey. Archived from the original on 13 December 2009. Retrieved 12 November 2009.