Editing Erosion (section)

===Coastal erosion===
{{main|Coastal erosion}}
{{See also|Beach evolution}}
[[File:Wavecut platform southerndown pano.jpg|thumb|[[Wave cut platform]] caused by erosion of cliffs by the sea, at [[Southerndown]] in South Wales]]
[[File:Erosion of Boulder Clay in Filey Bay.JPG|thumb|Erosion of the [[boulder clay]] (of [[Pleistocene]] age) along cliffs of [[Filey]] Bay, Yorkshire, England]]
Shoreline erosion, which occurs on both exposed and sheltered coasts, primarily occurs through the action of currents and [[ocean surface wave|waves]] but sea level (tidal) change can also play a role.
[[File:Sea dune Erosion at Talace, Wales.webm|thumb|Sea-dune erosion at [[Talacre]] beach, [[Wales]]]]

''[[Hydraulic action]]'' takes place when the air in a joint is suddenly compressed by a wave closing the entrance of the joint. This then cracks it. ''[[Wave pounding]]'' is when the sheer energy of the wave hitting the cliff or rock breaks pieces off. ''[[abrasion (geology)|Abrasion]]'' or ''[[corrasion]]'' is caused by waves launching sea load at the cliff. It is the most effective and rapid form of shoreline erosion (not to be confused with ''corrosion''). ''[[Corrosion]]'' is the dissolving of rock by [[carbonic acid]] in sea water.<ref>Geddes, Ian. "Lithosphere". Higher geography for cfe: physical and human environments, Hodder Education, 2015.</ref> [[Limestone]] cliffs are particularly vulnerable to this kind of erosion. ''Attrition'' is where particles/sea load carried by the waves are worn down as they hit each other and the cliffs. This then makes the material easier to wash away. The material ends up as [[shingle beach|shingle]] and sand. Another significant source of erosion, particularly on carbonate coastlines, is boring, scraping and grinding of organisms, a process termed ''[[bioerosion]]''.<ref>Glynn, Peter W. "Bioerosion and coral-reef growth: a dynamic balance". Life and death of coral reefs (1997): 68–95.</ref>

[[Sediment]] is transported along the coast in the direction of the prevailing current ([[longshore drift]]). When the upcurrent [[Coastal sediment supply|supply of sediment]] is less than the amount being carried away, erosion occurs. When the upcurrent amount of sediment is greater, sand or gravel banks will tend to form as a result of [[deposition (geology)|deposition]]. These banks may slowly migrate along the coast in the direction of the longshore drift, alternately protecting and exposing parts of the coastline. Where there is a bend in the coastline, quite often a buildup of eroded material occurs forming a long narrow bank (a [[spit (landform)|spit]]). [[Armor (hydrology)|Armoured]] beaches and submerged offshore [[shoal|sandbanks]] may also protect parts of a coastline from erosion. Over the years, as the shoals gradually shift, the erosion may be redirected to attack different parts of the shore.<ref>Bell, Frederic Gladstone. "Marine action and control". Geological hazards: their assessment, avoidance, and mitigation, Taylor & Francis, 1999, pp. 302–306.</ref>

Erosion of a coastal surface, followed by a fall in sea level, can produce a distinctive landform called a [[raised beach]].<ref name="Pinter2010">{{cite web| last1=Pinter |first1=N |date=2010 |title=Exercise 6 - Coastal Terraces, Sealevel, and Active Tectonics |url=http://www.geology.siu.edu/people/pinter/pdf/CoastalExercise.pdf |access-date=2011-04-21 |url-status=dead |archive-url=https://web.archive.org/web/20101010230028/http://www.geology.siu.edu/people/pinter/pdf/CoastalExercise.pdf |archive-date=2010-10-10 }}</ref>