bedrock#Weathering of bedrock

File:Rockhead at Sandside Bay, Caithness, Scotland.jpg, Caithness, Scotland]]

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.{{cite book |editor1-last=Jackson |editor1-first=Julia A. |title=Glossary of geology |date=1997 |publisher=American Geological Institute |location=Alexandria, Virginia |isbn=0922152349 |edition=4th |chapter=Bedrock}} An exposed portion of bedrock is often called an outcrop.{{sfn|Jackson|1997|loc="Outcrop"}} The various kinds of broken and weathered rock material, such as soil and subsoil, that may overlie the bedrock are known as regolith.{{sfn|Jackson|1997|loc="Regolith"}}{{cite book |last1=Allaby |first1=Michael |title=A dictionary of geology and earth sciences |date=2013 |publisher=Oxford University Press |location=Oxford |isbn=9780199653065 |edition=4th |chapter=Regolith}}

Engineering geology

The surface of the bedrock beneath the soil cover (regolith) is also known as rockhead in engineering geology,{{Cite book|chapter-url=https://books.google.com/books?id=SXHyRIEryEcC&pg=PA16|title=Engineering Geology: Principles and Practice|last=Price|first=David George|publisher=Springer|year=2009|isbn=978-3540292494|editor-last=de Freitas|editor-first=Michael H.|pages=16|chapter=The Basis of Engineering Geology}}{{cite book|url=https://books.google.com/books?id=ayPapNgD1hMC&q=bedrock+contour+map+rockhead&pg=PA113|title=Geology for Civil Engineers|author=McLean|first1=A.C.|last2=Gribble|first2=C.D.|publisher=CRC Press|isbn=978-0419160007|edition=Second|date=9 September 1985|page=113}} 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.{{cite magazine|last=Swinford|first=E. Mac|date=2004|title=What the glaciers left behind {{snd}}the drift-thickness map of Ohio|url=https://geosurvey.ohiodnr.gov/portals/geosurvey/PDFs/Newsletter/2004No.1.pdf|magazine=Ohio Geology|publisher=Ohio Department of Natural Resources, Division of Geological Survey|issue=1|pages=1, 3–5|archive-url=https://web.archive.org/web/20121002225931/http://www.dnr.state.oh.us/Portals/10/pdf/newsletter/2004No.1.pdf|archive-date=2 October 2012|access-date=12 September 2012|url-status=live}}

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.{{cite journal|last1=Lidmar-Bergström|first1=Karna|last2=Olsson|first2=Siv|last3=Olvmo|first3=Mats|date=January 1997|title=Palaeosurfaces and associated saprolites in southern Sweden|url=http://sp.lyellcollection.org/cgi/content/abstract/120/1/95|journal=Geological Society, London, Special Publications|volume=120|issue=1|pages=95–124|bibcode=1997GSLSP.120...95L|doi=10.1144/GSL.SP.1997.120.01.07|s2cid=129229906|access-date=April 21, 2010|author-link1=Karna Lidmar-Bergström|url-access=subscription}} Rock fragments can disconnect from the underlying bedrock, where they are found within a weathering or soil profile as floaters.{{cite web|title=Floaters|url=https://geography.as.uky.edu/node/474132|publisher= University of Kentucky, College of Arts & Sciences |date= 17 February 2021|access-date= June 1, 2025}}

Geological map

A geological 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).{{cite web|url=https://www.bgs.ac.uk/products/digitalmaps/digmapgb_solid.html|title=Digital Geology – Bedrock geology theme|publisher=British Geological Survey|archive-url=https://web.archive.org/web/20091213185511/http://www.bgs.ac.uk/products/digitalmaps/digmapgb_solid.html|archive-date=13 December 2009|access-date=12 November 2009|url-status=live}}

References

External links

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Category:Petrology

Category:Rocks

Category:Earth's crust