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Soil with broken rock fragments overlying bedrock, Sandside Bay, Caithness
Soil profile with bedrock labeled R

Bedrock in geology is the lithified rock that lies under loose softer material called regolith within the surface of the Earth's crust or other terrestrial planets.


Components of bedrockEdit

Bedrock essentially refers to the substructure composed of hard rock exposed or buried at the earth's surface; an exposed portion of bedrock is often called an outcrop. Bedrock may have various chemical and mineralogical compositions and can be igneous, metamorphic or sedimentary in origin. The bedrock may be overlain by broken and weathered regolith which includes soil and the subsoil.[citation needed]

Engineering geologyEdit

The surface of the bedrock beneath the soil cover (regolith) is also known as rockhead in engineering geology,[1][2] and its identification by digging, drilling or geophysical methods is an important task in most civil engineering projects. Superficial deposits (also known as drift) can be extremely thick, such that the bedrock lies hundreds of meters below the surface.[3]

Weathering of bedrockEdit

Bedrock when exposed or within the subsurface may experience weathering and erosion by external factors. Weathering may be physical or chemical and alters the structure of the rock and may cause it to erode and or alter over time based on the interactions between the mineralogy and its interactions. Bedrock may also experience subsurface weathering at its upper boundary, forming saprolite.[4]

Geologic mapEdit

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.[5]


  1. ^ Price, David George, Engineering Geology: Principles and Practice, Springer, 2009, p. 16 ISBN 978-3540292494
  2. ^ Gribble C. & McLean A. (2003). Geology for Civil Engineers. CRC Press. p. 113. ISBN 978-0-203-36215-0.
  3. ^ "Swinford, E. Mac What the glaciers left behind – drift thickness map of Ohio, Ohio Department of Natural Resources, Division of Geological Survey, newsletter 2004, No.1" (PDF). Archived from the original (PDF) on 2 October 2012. Retrieved 12 September 2012.
  4. ^ Lidmar-Bergström, Karna; Olsson, Siv; Olvmo, Mats (1997). "Palaeosurfaces and associated saprolites in southern Sweden". Geological Society, London, Special Publications. 120 (1): 95. Bibcode:1997GSLSP.120...95L. doi:10.1144/GSL.SP.1997.120.01.07. Retrieved 21 April 2010.
  5. ^ BGS. "Digital Geology – Bedrock geology theme". Archived from the original on 13 December 2009. Retrieved 12 November 2009.

Further readingEdit

  • Rafferty, John P. "Bedrock GEOLOGY". Encyclopedia Britannica. Encyclopedia Britannica. Retrieved 1 April 2019.
  • Harris, Clay, The Gale Encyclopedia of Science. Ed. K. Lee Lerner and Brenda Wilmoth Lerner. Vol. 1. 5th ed. Farmington Hills, MI: Gale, 2014. p515-516.