View source for Coast

{{short description|Area where land meets the sea or ocean}}
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{{Other uses}}
{{Redirect-multi|3|Shore|Shoreline|Seacoast|other uses|Shore (disambiguation)|and|Shoreline (disambiguation)|the specific area|Seacoast Region (New Hampshire)}}
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[[File:Spring Lake, New Jersey Beach at Sunrise.jpg|thumb|[[Sunrise]] on the [[Jersey Shore]] coastline at [[Spring Lake, New Jersey|Spring Lake]], [[New Jersey]], U.S.]]
[[File:Knights Point - Tasmánské moře - panoramio.jpg|thumb|Rugged coastline of the [[West Coast, New Zealand|West Coast Region]] of New Zealand]]
[[File:17-08-islcanus-RalfR-DSC 3282.jpg|thumb|Southeast coast of [[Greenland]]]]
[[File:0.1. Mar Mediterrània - Serra de Tramuntana. Torrent de Pareis. (Escorca, Mallorca).jpg|thumb|[[Escorca]] coast, [[Serra de Tramuntana]] ([[Balearic Islands]])]]

A '''coast''' (also called the '''coastline''', '''shoreline''', or '''seashore''') is the [[land]] next to the [[sea]] or the line that forms the boundary between the land and the [[ocean]] or a [[lake]].<ref>{{cite American Heritage Dictionary |coast |access-date=2024-07-19}}</ref><ref>{{cite Merriam-Webster|coastline |access-date=2024-07-19}}</ref> Coasts are influenced by the [[topography]] of the surrounding landscape and by aquatic [[erosion]], such as that caused by [[wind wave|waves]]. The [[geology|geological]] composition of [[rock (geology)|rock]] and [[soil]] dictates the type of shore that is created. [[Earth]] has about {{cvt|620,000|km|mi}} of coastline.

Coasts are important zones in natural [[ecosystem]]s, often home to a wide range of [[biodiversity]]. On land, they harbor ecosystems, such as [[freshwater marsh|freshwater]] or [[estuary|estuarine]] [[wetland]]s, that are important for birds and other [[terrestrial animal]]s. In wave-protected areas, coasts harbor [[salt marsh]]es, [[mangrove]]s, and [[seagrass meadow|seagrasses]], all of which can provide [[nursery habitat]] for fin[[fish]], [[shellfish]], and other [[aquatic animal]]s.<ref name=":1">{{cite book |url=http://link.springer.com/10.1007/978-90-481-2406-0 |title=Ecological Connectivity Among Tropical Coastal Ecosystems |date=2009 |publisher=[[Springer Science+Business Media|Springer Netherlands]] |isbn=978-90-481-2405-3 |editor-last=Nagelkerken |editor-first=Ivan |location=[[Dordrecht]] |language=en |doi=10.1007/978-90-481-2406-0}}</ref><ref name=":4">{{cite journal |last1=Nagelkerken|first1=I. |last2=Blaber|first2=S.J.M. |last3=Bouillon|first3=S. |last4=Green|first4=P. |last5=Haywood|first5=M. |last6=Kirton|first6=L.G. |last7=Meynecke|first7=J.-O. |last8=Pawlik|first8=J. |last9=Penrose|first9=H.M. |last10=Sasekumar|first10=A. |last11=Somerfield|first11=P.J. |date=2008 |title=The habitat function of mangroves for terrestrial and marine fauna: A review |url=https://linkinghub.elsevier.com/retrieve/pii/S0304377007001830 |journal=[[Aquatic Botany]] |language=en |volume=89 |issue=2|pages=155–185 |doi=10.1016/j.aquabot.2007.12.007 |bibcode=2008AqBot..89..155N|url-access=subscription }}</ref> [[Rocky shore]]s are usually found along exposed coasts and provide habitat for a wide range of [[sessility (motility)|sessile animals]] (e.g. [[mussel]]s, [[starfish]], [[barnacle]]s) and various kinds of [[seaweed]]s.

In [[physical oceanography]], a shore is the wider fringe that is geologically modified by the action of the body of water past and present, and the [[beach]] is at the edge of the shore, including the [[intertidal zone]] where there is one.<ref>{{cite book |first1=George L.|last1=Pickard |first2=William J.|last2=Emery |title=Descriptive Physical Oceanography |edition=5th (illustrated) |publisher=[[Elsevier]] |year=1990 |pages=7–8 |isbn=0-7506-2759-X}}</ref> Along [[tropics|tropical]] coasts with clear, nutrient-poor water, [[coral reef]]s can often be found at depths of {{cvt|1–50|m|ft}}.

According to an atlas prepared by the [[United Nations]], about 44% of the [[world population|human population]] lives within {{cvt|150|km|mi}} of the sea {{as of|2013|lc=on}}.<ref name="UN Atlas">{{cite web |title=UN Atlas of the Oceans |url=https://coastalchallenges.com/2010/01/31/un-atlas-60-of-us-live-in-the-coastal-areas |publisher=CoastalChallenges.com |archive-url=https://web.archive.org/web/20131102170907/http://coastalchallenges.com/2010/01/31/un-atlas-60-of-us-live-in-the-coastal-areas/ |archive-date=2 November 2013 |access-date=2013-10-31}}</ref> Due to its importance in society and its high population concentrations, the coast is important for major parts of the global food and economic system, and they provide many [[ecosystem service]]s to humankind. For example, important human activities happen in [[port]] cities. Coastal [[fishery|fisheries]] (commercial, recreational, and subsistence) and [[aquaculture]] are major economic activities and create jobs, livelihoods, and [[protein]] for the majority of coastal human populations. Other coastal spaces like [[beach]]es and [[seaside resort]]s generate large revenues through [[tourism]].

[[Marine coastal ecosystem]]s can also provide protection against [[sea level rise]] and [[tsunami]]s. In many countries, [[mangrove]]s are the primary source of wood for fuel (e.g. [[charcoal]]) and building material. Coastal ecosystems like mangroves and [[seagrass]]es have a much higher capacity for [[carbon sequestration]] than many [[terrestrial ecosystem]]s, and as such can play a critical role in the near-future to help [[climate change mitigation|mitigate climate change]] effects by uptake of [[carbon dioxide in Earth's atmosphere|atmospheric anthropogenic carbon dioxide]]. 

However, the economic importance of coasts makes many of these communities [[effects of climate change|vulnerable to climate change]], which causes increases in [[extreme weather]] and sea level rise, as well as related issues like [[coastal erosion]], [[saltwater intrusion]], and [[coastal flooding]].<ref name=":0">{{cite web |title=Climate change and the coasts |website=[[World Ocean Review]] |url=https://worldoceanreview.com/en/wor-5/climate-change-threats-and-natural-hazards/climate-change-and-the-coasts |access-date=2020-12-19 |language=en-US}}</ref> Other coastal issues, such as [[marine pollution]], [[marine debris]], coastal development, and [[marine ecosystem]] destruction, further complicate the human uses of the coast and threaten coastal ecosystems.<ref name=":0" />

The interactive effects of climate change, [[habitat destruction]], [[overfishing]], and [[water pollution]] (especially [[eutrophication]]) have led to the demise of coastal ecosystem around the globe. This has resulted in population collapse of fisheries stocks, [[biodiversity loss|loss of biodiversity]], increased [[invasive species|invasion of alien species]], and loss of healthy habitats. International attention to these issues has been captured in [[Sustainable Development Goal 14]] "Life Below Water", which sets goals for international policy focused on preserving marine coastal ecosystems and supporting more [[sustainable development|sustainable economic practices]] for coastal communities.<ref name=":17">United Nations (2017) Resolution adopted by the General Assembly on 6 July 2017, [[:File:A RES 71 313 E.pdf|Work of the Statistical Commission pertaining to the 2030 Agenda for Sustainable Development]] ([https://undocs.org/A/RES/71/313 A/RES/71/313])</ref> Likewise, the United Nations has declared 2021–2030 the [[UN Decade on Ecosystem Restoration]], but restoration of coastal ecosystems has received insufficient attention.<ref name=":3">{{Cite journal|last1=Waltham|first1=Nathan J.|last2=Elliott|first2=Michael|last3=Lee|first3=Shing Yip|last4=Lovelock|first4=Catherine|last5=Duarte|first5=Carlos M.|last6=Buelow|first6=Christina|last7=Simenstad|first7=Charles|last8=Nagelkerken|first8=Ivan|last9=Claassens|first9=Louw|last10=Wen|first10=Colin K-C|last11=Barletta|first11=Mario|date=2020|title=UN Decade on Ecosystem Restoration 2021–2030—What Chance for Success in Restoring Coastal Ecosystems?|journal=Frontiers in Marine Science|volume=7|article-number=71|doi=10.3389/fmars.2020.00071|issn=2296-7745|hdl=2440/123896|hdl-access=free|doi-access=free|bibcode=2020FrMaS...7...71W }}</ref>

Since coasts are constantly changing, a coastline's exact [[perimeter]] cannot be determined; this measurement challenge is called the [[coastline paradox]]. The term ''coastal zone'' is used to refer to a region where interactions of sea and land processes occur.<ref>{{Cite web|last=Nelson|first=Stephen A.|year=2007|title=Coastal Zones|url=http://www.tulane.edu/~sanelson/geol204/coastalzones.htm|archive-url=https://web.archive.org/web/20130316085932/http://www.tulane.edu/~sanelson/geol204/coastalzones.htm|archive-date=2013-03-16|access-date=2008-12-11}}</ref> Both the terms ''coast'' and ''coastal'' are often used to describe a geographic location or region located on a coastline (e.g., New Zealand's [[West Coast Region|West Coast]], or the [[East Coast of the United States|East]], [[West Coast of the United States|West]], and [[Gulf Coast of the United States|Gulf Coast]] of the [[United States]].) Coasts with a narrow continental shelf that are close to the open ocean are called ''[[pelagic]]'' ''coast'', while other coasts are more sheltered coast in a [[gulf]] or [[bay]]. A [[shore]], on the other hand, may refer to parts of land adjoining any large body of water, including oceans (sea shore) and lakes (lake shore). 

{{TOC level|3}}

==Size==
[[File:Somalia 16.08.2009 08-30-13.jpg|thumb|right|[[Somalia]] has the longest coastline in Africa.<ref>[https://www.researchgate.net/publication/222296321_The_Indian_Ocean_Coast_of_Somalia "The Indian Ocean Coast of Somalia"]. ''Marine Pollution Bulletin''. '''41''' (1–6): 141–159. December 2000. doi: 10.1016/S0025-326X(00)00107-7</ref>]]
The [[Earth]] has approximately {{convert|620000|km|mi}} of coastline. Coastal habitats, which extend to the margins of the [[continental shelves]], make up about 7 percent of the Earth's oceans,<ref>{{cite web |title=Ocean Habitats |url=https://www.nps.gov/subjects/oceans/ocean-habitats.htm |website=Oceans, Coasts & Seashores |publisher=National Park Service |access-date=25 September 2021 |date=1 December 2016}}</ref> but at least 85% of commercially harvested fish depend on coastal environments during at least part of their life cycle.<ref>{{cite journal |last1=Lellis-Dibble |first1=K.A. |last2=McGlynn |first2=K.E. |last3=Bigford |first3=T.E. |year=2008 |title=Estuarine fish and shellfish species in US commercial and recreational fisheries: economic value as an incentive to protect and restore estuarine habitat |journal=NOAA Technical Memo |volume=NMFS-F/SPO |url=https://repository.library.noaa.gov/view/noaa/3612 |access-date=24 September 2021}}</ref> {{asof|October 2010|post=,}} about 2.86% of [[exclusive economic zones]] were part of [[marine protected areas]].<ref name="iucn.org">{{cite web |url=http://www.iucn.org/knowledge/publications_doc/publications/?6500/Global-ocean-protection--present-status-and-future-possibilities/ |title=Global Ocean Protection: Present Status and Future Possibilities |publisher=Iucn.org |date=2010-11-23 |access-date=2012-06-07 |archive-date=2012-03-19 |archive-url=https://web.archive.org/web/20120319150750/http://www.iucn.org/knowledge/publications_doc/publications/?6500/Global-ocean-protection--present-status-and-future-possibilities/ }}</ref>

The definition of coasts varies. Marine scientists think of the "wet" (aquatic or [[Intertidal zone|intertidal]]) vegetated habitats as being [[Coastal ecosystem|coastal ecosystems]] (including seagrass, salt marsh etc.) whilst some terrestrial scientists might only think of coastal ecosystems as purely terrestrial plants that live close to the seashore (see also [[Ecosystem service#Estuarine and coastal ecosystem services|estuaries and coastal ecosystems]]).

While there is general agreement in the scientific community regarding the definition of coast, in the political sphere, the delineation of the extents of a coast differ according to [[jurisdiction]].<ref>{{cite treaty |title=United Nations Convention on the Law of the Sea of 10 December 1982 |url=https://www.un.org/depts/los/convention_agreements/convention_overview_convention.htm |article=5, 7 |publisher=United Nations |access-date=13 October 2023 |quote=Article 5: "The normal baseline for measuring the breadth of the territorial sea is the low-water line along the coast as marked on large-scale charts officially recognized by the coastal State." Article 7.1: "In localities where the coastline is deeply indented and cut into, or if there is a fringe of islands along the coast in its immediate vicinity, the method of straight baselines joining appropriate points may be employed in drawing the baseline from which the breadth of the territorial sea is measured."}}</ref><ref>{{Cite web |title="The Coast" is Complicated: A Model to Consistently Describe the Nation's Coastal Population |url=https://coast.noaa.gov/htdata/SocioEconomic/the_coast_is_complicated_april_2013.pdf |url-status=live |archive-url=https://web.archive.org/web/20230614012437/https://coast.noaa.gov/htdata/SocioEconomic/the_coast_is_complicated_april_2013.pdf |archive-date=June 14, 2023 |access-date=June 13, 2023 |website=NOAA}}</ref> Government authorities in various countries may define coast differently for economic and social policy reasons. 

===Challenges of precisely measuring the coastline===
{{excerpt|Coastline paradox|paragraphs=1,2|files=0}}

==Formation {{anchor|Formation of Coasts}}==
[[File:Porto Covo pano April 2009-4.jpg|thumb|upright=1.2|Atlantic rocky coastline, showing a surf area. [[Porto Covo]], west coast of Portugal]]
[[File:Spiaggia rosa, isola di budelli, sardegna.jpg|thumb|upright=1.2|Seaside in [[Budelli]], Italy. Budelli beach is famous for the color of its sand, which is pink due to the presence of fragments of a microorganism called ''Miniacina miniacea''.<ref>{{cite web|url=https://www.sardegnaturismo.it/it/esplora/spiaggia-rosa|title=Spiaggia Rosa|date=20 November 2015 |access-date=27 December 2024|language=it}}</ref>]]

[[Tide]]s often determine the range over which [[sediment]] is deposited or eroded. Areas with high tidal ranges allow waves to reach farther up the shore, and areas with lower tidal ranges produce deposition at a smaller elevation interval. The tidal range is influenced by the size and shape of the coastline. Tides do not typically cause erosion by themselves; however, [[tidal bore]]s can erode as the waves surge up the river [[Estuary|estuaries]] from the ocean.<ref>{{Cite book|last=Davidson|first=Jon P.|title=Exploring earth: an introduction to physical geology|date=2002|publisher=Prentice Hall|others=Walter E. Reed, Paul M. Davis|isbn=0-13-018372-5|edition=2nd|location=Upper Saddle River, NJ|oclc=45917172}}</ref>{{rp|421}}

Geologists classify coasts on the basis of [[tidal range]] into ''macrotidal coasts'' with a tidal range greater than {{Convert|4|m|ft|abbr=on}}; ''mesotidal coasts'' with a tidal range of {{Convert|2 to 4|m|ft|abbr=on|sigfig=2}}; and ''microtidal coasts'' with a tidal range of less than {{Convert|2|m|ft|abbr=on|sigfig=1}}. The distinction between macrotidal and mesotidal coasts is more important. Macrotidal coasts lack [[barrier islands]] and [[lagoons]], and are characterized by funnel-shaped estuaries containing sand ridges aligned with tidal currents. Wave action is much more important for determining [[bedforms]] of sediments deposited along mesotidal and microtidal coasts than in macrotidal coasts.<ref>{{cite book |last1=Blatt |first1=Harvey |last2=Middleton |first2=Gerard |last3=Murray |first3=Raymond |title=Origin of sedimentary rocks |date=1980 |publisher=Prentice-Hall |location=Englewood Cliffs, N.J. |isbn=0-13-642710-3 |edition=2d |pages=656–659}}</ref>

Waves erode coastline as they break on shore releasing their energy; the larger the wave the more energy it releases and the more sediment it moves. Coastlines with longer shores have more room for the waves to disperse their energy, while coasts with cliffs and short shore faces give little room for the wave energy to be dispersed. In these areas, the wave energy breaking against the cliffs is higher, and air and water are compressed into cracks in the rock, forcing the rock apart, breaking it down. Sediment deposited by waves comes from eroded cliff faces and is moved along the coastline by the waves. This forms an [[abrasion coast|abrasion]] or [[cliffed coast]].

Sediment deposited by rivers is the dominant influence on the amount of sediment located in the case of coastlines that have estuaries.<ref name=":2">{{Cite book|last=Easterbrook|first=Don J.|title=Surface processes and landforms|date=1999|publisher=Prentice Hall|isbn=0-13-860958-6|edition=2nd|location=Upper Saddle River, N.J.|oclc=39890526}}</ref> Today, riverine deposition at the coast is often blocked by dams and other human regulatory devices, which remove the sediment from the stream by causing it to be deposited inland. Coral reefs are a provider of sediment for coastlines of tropical islands.<ref>{{Cite web|title=How is beach sand created? - Woods Hole Oceanographic Institution|url=https://www.whoi.edu/how-is-beach-sand-created/|url-status=live|access-date=2021-08-10|website=Woods Hole Oceanographic Institution|language=|archive-url=https://web.archive.org/web/20210628213754/https://www.whoi.edu/how-is-beach-sand-created/ |archive-date=2021-06-28 }}</ref>

Like the ocean which shapes them, coasts are a dynamic environment with constant change. The [[Earth]]'s natural processes, particularly [[sea level rise]]s, waves and various [[weather]] phenomena, have resulted in the [[erosion]], [[Accretion (geology)|accretion]] and reshaping of coasts as well as flooding and creation of [[continental shelf|continental shelves]] and drowned river valleys ([[ria]]s).

==Importance for humans and ecosystems==

=== Human settlements ===
{{Further|Port|island nation|Coastal management|Coastal development hazards}}
[[File:The CHW system.png|thumb|upright=1.4|The Coastal Hazard Wheel system published by UNEP for global coastal management]]
More and more of the world's people live in coastal regions.<ref>{{Cite journal |last=Goudarzi |first=Sara |date=July 18, 2006 |title=Flocking to the Coast: World's Population Migrating into Danger |url=http://www.livescience.com/environment/060718_map_settle.html |journal=Live Science |access-date=2008-12-14}}</ref> According to a [[United Nations]] atlas, 44% of all people live within 150 km (93 mi) of the sea.<ref name="UN Atlas" /> Many major cities are on or near good [[harbor]]s and have [[port]] facilities. Some [[landlocked]] places have achieved port status by building [[canal]]s.

Nations defend their coasts against military invaders, smugglers and illegal migrants. Fixed [[Coastal defence and fortification|coastal defenses]] have long been erected in many nations, and coastal countries typically have a [[navy]] and some form of [[coast guard]].<gallery widths="220px" heights="160px" class="center" perrow="2" caption="">
File:花蓮新社梯田.jpg|[[Paddy field]]s by the coast of [[Fengbin, Hualien]]
File:170209 219 R.jpg|Coastline of [[Barcelona]] as viewed from Port Fòrum, with [[Montjuïc]] and [[Port Vell]] can also be seen.
</gallery>

==== Tourism ====
Coasts, especially those with beaches and warm water, attract tourists often leading to the development of [[seaside resort]] communities. In many [[island nation]]s such as those of the [[Mediterranean]], [[South Pacific Ocean]] and [[Caribbean]], [[Tourism|tourism is central to the economy]]. Coasts offer recreational activities such as swimming, fishing, surfing, boating, and [[Sun tanning|sunbathing]]. 

[[Growth management]] and [[coastal management]] can be a challenge for coastal local authorities who often struggle to provide the infrastructure required by new residents, and poor management practices of construction often leave these communities and infrastructure vulnerable to processes like [[coastal erosion]] and [[sea level rise]]. In many of these communities, management practices such as [[beach nourishment]] or when the coastal infrastructure is no longer financially sustainable, [[managed retreat]] to remove communities from the coast.<gallery widths="220px" heights="160px" class="center" perrow="3" caption="">
File:Maarianhamina SNV10312 -2B.jpg| A passenger car ferry arrives at the coast of [[Mariehamn]], [[Åland]].
File:Amalfi Coast (Italy, October 2020) - 75 (50558355441).jpg|[[Amalfi Coast]], Italy, attracts international tourists of all classes annually<ref name="uniq">{{cite web |title = Bay of Naples & Amalfi Coast History |url = http://www.uniquecostiera.com/naplesAmalfiCoastHistory.html |work = Unique Costiera |access-date = 28 June 2011 |archive-url = https://web.archive.org/web/20111031120459/http://www.uniquecostiera.com/naplesAmalfiCoastHistory.html |archive-date = 31 October 2011 }}</ref> and is listed as a [[UNESCO]] [[World Heritage Site]].<ref name="unesco">{{cite web |title = Costiera Amalfitana |url = https://whc.unesco.org/en/list/830 |publisher = [[UNESCO World Heritage Centre]] |access-date = 14 September 2015}}</ref>
</gallery>

=== Ecosystem services ===
{{see also|Marine coastal ecosystem}}
{{Excerpt|Ecosystem service#Estuarine and coastal ecosystem services|paragraphs=1,2}}

== Types ==
===Emergent coastline===
{{further information|Emergent coastline|Submergent coastline}}
According to one principle of classification, an emergent coastline is a coastline that has experienced a fall in sea level, because of either a global sea-level change, or local uplift. Emergent coastlines are identifiable by the coastal [[landform]]s, which are above the high tide mark, such as [[raised beach]]es. In contrast, a submergent coastline is one where the sea level has risen, due to a global sea-level change, local [[subsidence]], or [[isostatic rebound]]. Submergent coastlines are identifiable by their submerged, or "drowned" landforms, such as [[ria]]s (drowned valleys) and [[fjord]]s

===Concordant coastline===
{{further information|Concordant coastline|Discordant coastline}}
According to the second principle of classification, a concordant coastline is a coastline where bands of different rock types run parallel to the shore. These rock types are usually of varying [[Geological resistance|resistance]], so the coastline forms distinctive landforms, such as coves. Discordant coastlines feature distinctive landforms because the rocks are [[erosion|eroded]] by the ocean [[wave]]s. The less resistant rocks erode faster, creating [[inlet]]s or [[bay]]; the more resistant rocks erode more slowly, remaining as [[headland]]s or [[outcrop]]pings.

===High and low energy coasts===
<!--target for redirect [[High energy coast]], [[High energy underwater environment]], [[Low energy coast]] -->
Parts of a coastline can be categorised as high energy coast or low energy coast. The distinguishing characteristics of a high energy coast are that the average wave energy is relatively high so that erosion of small grained material tends to exceed deposition, and consequently landforms like cliffs, headlands and wave-cut terraces develop.<ref name="field studies" /> Low energy coasts are generally sheltered from waves, or in regions where the average wind wave and swell conditions are relatively mild. Low energy coasts typically change slowly, and tend to be depositional environments.<ref name="Vaia" /> 

High energy coasts are exposed to the direct impact of waves and storms, and are generally erosional environments.<ref name="Vaia" /> High energy storm events can make large changes to a coastline, and can move significant amounts of sediment over a short period, sometimes changing a shoreline configuration.<ref name="Guisado-Pintado and Jackson 2019" />

====Destructive and constructive waves====

Swash is the shoreward flow after the break, backwash is the water flow back down the beach. The relative strength of flow in the swash and backwash determines what size grains are deposited or eroded. This is dependent on how the wave breaks and the slope of the shore.<ref name="field studies method" />
Depending on the form of the breaking wave, its energy can carry granular material up the beach and deposit it, or erode it by carrying more material down the slope than up it. Steep waves that are close together and break with the surf [[plunging breaker|plunging]] down onto the shore slope expend much of their energy lifting the sediment. The weak swash does not carry it far up the slope, and the strong backwash carries it further down the slope, where it either settles in deeper water or is carried along the shore by a longshore current induced by an angled approach of the wave-front to the shore. These waves which erode the beach are called destructive waves.<ref name="BBC" />
Low waves that are further apart and break by [[Spilling breaker|spilling]], expend more of their energy in the swash which carries particles up the beach, leaving less energy for the backwash to transport them downslope, with a net constrictive influence on the beach.<ref name="BBC" />

===Rivieras===
[[File:Cinque Terre (Italy, October 2020) - 11 (50543748322).jpg|thumb|The [[Cinque Terre]], along the [[Italian Riviera]]]]

''Riviera'' is an Italian word for "shoreline",<ref name="Chambers">{{Cite encyclopedia|title=riviera |encyclopedia=Chambers Concise Dictionary |year=2004 |publisher=Allied Chambers |location=New Delhi |page=[https://books.google.com/books?id=iwWuY9tAVq8C&pg=PA1045 1045] |isbn = 978-81-86062-36-4}}</ref><ref name="Kolb">{{Cite book|first=Martina |last=Kolb |year=2013 |title=Nietzsche, Freud, Benn, and the Azure Spell of Liguria |location=Toronto, Ontario |publisher=University of Toronto Press |page=[https://books.google.com/books?id=I03va9L2GuoC&pg=PA30 30] |isbn=978-1-4426-4329-1 }}</ref><ref>The more common ones are ''puntellare'' and ''litorale''.</ref> ultimately derived from Latin {{Lang|la|ripa}} ("riverbank"). It came to be applied as a proper name to the coast of the [[Ligurian Sea]], in the form ''riviera ligure'', then shortened to ''riviera''.  Historically, the Ligurian Riviera extended from Capo Corvo (Punta Bianca) south of [[Genoa]], north and west into what is now [[France|French]] territory past [[Monaco]] and sometimes as far as [[Marseille]].<ref name="Chambers" /><ref>{{Cite book |first=Rosa |last=Baughan |year=1880 |title=Winter havens in the sunny South, a complete handbook to the Riviera |location=London |publisher=The Bazaar |url=https://books.google.com/books?id=zg8IAAAAQAAJ |url-status=live |archive-url=https://web.archive.org/web/20170202104650/https://books.google.com/books?id=zg8IAAAAQAAJ |archive-date=2017-02-02 }}</ref><ref>{{Cite book |first=Charles B. |last=Black |year=1887 |title=The Riviera, Or The Coast from Marseilles to Leghorn, Including Carrara, Lucca, Pisa, Pistoja and Florence |edition=Third |location=Edinburgh |publisher=Adam and Charles Black |url=https://books.google.com/books?id=KKsaAAAAYAAJ |url-status=live |archive-url=https://web.archive.org/web/20170202213756/https://books.google.com/books?id=KKsaAAAAYAAJ |archive-date=2017-02-02 }}</ref> Today, this coast is divided into the [[Italian Riviera]] and the [[French Riviera]], although the French use the term "Riviera" to refer to the Italian Riviera and call the French portion the "Côte d'Azur".<ref name="Kolb" />

As a result of the fame of the Ligurian rivieras, the term came into English to refer to any shoreline, especially one that is sunny, topographically diverse and popular with tourists.<ref name="Chambers" /> Such places using the term include the [[Australian Riviera]] in [[Queensland]] and the [[Turkish Riviera]] along the [[Aegean Sea]].<ref name="Kolb" />

===Other coastal categories===
* A [[cliffed coast]] or abrasion coast is one where marine action has produced steep declivities known as [[cliff]]s.
* A [[flat coast]] is one where the land gradually descends into the sea.
* A [[graded shoreline]] is one where wind and water action has produced a flat and straight coastline.
* A [[primary coast]] isone which is mainly undergoing early stage development by major long-term processes such as tectonism and climate change A [[secondary coast]] is one where the primary processes have mostly stabilised, and more localised processes have become prominent.<ref name="Vaia" />
* An [[erosional coast]] is on average undergoing erosion, while a [[depositional coast]] is accumulating material.<ref name="Vaia" />
*An [[active coast]] is on the edge of a tectonic plate, while a [[passive coast]] is usually on a substantial continental shelf or away from a plate edge.<ref name="Vaia" />

== Landforms ==
The following articles describe some coastal landforms:

[[File:Accreting coast Image6.svg|thumb|Coastal landforms. The feature shown here as a [[bay]] would, in certain (mainly southern) parts of [[Great Britain|Britain]], be called a [[cove]]. That between the cuspate foreland and the tombolo is a British bay.]]

{{div col|colwidth=24em}}
* [[Barrier island]]
* [[Bay]]
* [[Cove]]
* [[Headland]]
* [[Peninsula]]
{{div col end}}

===Cliff erosion===
* Much of the sediment deposited along a coast is the result of erosion of a surrounding [[cliff]], or bluff. [[Cliffed coast|Sea cliffs]] retreat landward because of the constant undercutting of slopes by waves. If the slope/cliff being undercut is made of unconsolidated sediment it will erode at a much faster rate than a cliff made of bedrock.<ref name=":2" />
* A [[natural arch]] is formed when a headland is eroded through by waves.
* [[Sea cave]]s are made when certain rock beds are more susceptible to erosion than the surrounding rock beds because of different areas of weakness. These areas are eroded at a faster pace creating a hole or crevice that, through time, by means of wave action and erosion, becomes a cave.
* A [[stack (geology)|stack]] is formed when a headland is eroded away by wave and wind action or an arch collapses leaving an offshore remnant.
* A [[Stack (geology)|stump]] is a shortened sea stack that has been eroded away or fallen because of instability.
* Wave-cut notches are caused by the undercutting of overhanging slopes which leads to increased stress on cliff material and a greater probability that the slope material will fall. The fallen debris accumulates at the bottom of the cliff and is eventually removed by waves.
* A [[wave-cut platform]] forms after erosion and retreat of a sea cliff has been occurring for a long time. Gently sloping wave-cut platforms develop early on in the first stages of cliff retreat. Later, the length of the platform decreases because the waves lose their energy as they break further offshore.<ref name=":2" />{{clarify|what makes the platform get shorter?|date=April 2024}}

===Coastal features formed by sediment===
{{Div col|colwidth=24em}}
* [[Beach]]
* [[Beach cusps]]
* [[Cuspate foreland]]
* [[Dune|Dune system]]
* [[Mudflat]]
* [[Raised beach]]
* [[Ria]]
* [[Shoal]]
* [[Spit (landform)|Spit]]
* [[Strand plain]]
* [[Surge channel]]
* [[Tombolo]]
{{div col end}}

===Coastal features formed by another feature===
* [[Estuary]]
*  [[Lagoon]]
* [[Salt marsh]]
*[[Mangrove|Mangrove forests]]
*[[Kelp forest|Kelp forests]]
*[[Coral reef|Coral reefs]]
*[[Oyster reef|Oyster reefs]]

===Other features on the coast===
{{Div col|colwidth=24em}}
* [[Concordant coastline]]
* [[Discordant coastline]]
* [[Fjord]]
* [[Island]]
* [[Island arc]]
* [[Machair]]
{{div col end}}

==Coastal waters==
{{See also|Eutrophication#Coastal waters}}
[[File:Transport of carbon across territorial boundaries in territorial sea, Exclusive Economic Zone, continental shelf, high seas, and deep seabed.webp|thumb|upright=1.5|Overview of different zones of coastal waters: Input, production, transport and storage pathway of carbon in marine waters, including movement across maritime zones of national jurisdiction: [[Territorial waters|territorial sea]], [[Exclusive economic zone|Exclusive Economic Zone]] (EEZ), [[continental shelf]], [[high seas]] (international waters), and [[Marine sediment|deep seabed]].]]
"Coastal waters" (or "coastal seas") is a term that carries different meanings depending upon the context, ranging from a geographic reference to the waters within a few kilometers of the coast, to describing the entire [[continental shelf]] that may stretch for more than a hundred kilometers from land.<ref>{{Cite book |title=Ocean margin processes in global change: report of the Dahlem Workshop on Ocean Margin Processes in Global Change, Berlin, 1990, March 18–23 |date=1991 |publisher=Wiley |isbn=978-0-471-92673-3 |editor-last=Mantoura |editor-first=R. F. C |location=Chichester, New York |language=en |oclc=22765791 |editor-last2=Martin |editor-first2=Jean-Marie |editor-last3=Wollast |editor-first3=R }}</ref> The term is used in a different manner when describing legal and economic boundaries, such as [[territorial waters]]<ref>{{cite book |last1=Black |first1=Henry Campbell |last2=Garner |first2=Bryan Andrew |title=Black's law dictionary |date=2009 |publisher=West |location=St. Paul, Minn |isbn=978-0-314-19949-2 |page=729 |edition=9th}}</ref> and [[international waters]],<ref>{{cite book |last1=Black |first1=Henry Campbell |last2=Garner |first2=Bryan Andrew |title=Black's law dictionary |date=2009 |publisher=West |location=St. Paul, Minn |isbn=978-0-314-19949-2 |page=1128 |edition=9th}} (defining "navigable sea")</ref> or when describing the geography of coastal landforms or the ecological systems operating through the continental shelf ([[marine coastal ecosystem]]s).

The dynamic fluid nature of the ocean means that all components of the whole ocean system are ultimately connected, although certain regional classifications are useful and relevant. The waters of the continental shelves represent such a region.<ref>{{Cite book |last1=Simpson |first1=John H. |url=https://www.cambridge.org/core/books/introduction-to-the-physical-and-biological-oceanography-of-shelf-seas/D28A42640D9F3D5BADB6D9533D663ECD |title=Introduction to the Physical and Biological Oceanography of Shelf Seas |last2=Sharples |first2=Jonathan |publisher=Cambridge University Press |year=2012 |doi=10.1017/CBO9781139034098 |isbn=978-0-521-87762-6 |edition=1}}</ref> The term "coastal waters" has been used in a wide variety of different ways in different contexts. In [[European Union]] environmental management it extends from the coast to just a few nautical miles<ref>{{Cite web |title=coastal waters — European Environment Agency |url=https://www.eea.europa.eu/help/glossary/eea-glossary/coastal-waters |access-date=2022-06-29 |website=www.eea.europa.eu |language=en}}</ref> while in the United States the [[United States Environmental Protection Agency|US EPA]] considers this region to extend much further offshore.<ref>{{Cite web |last=US EPA |first=ORD |date=2017-11-02 |title=Coastal Waters |url=https://www.epa.gov/report-environment/coastal-waters |access-date=2022-06-29 |website=www.epa.gov |language=en}}</ref><ref>USEPA (2001) [https://www.epa.gov/sites/default/files/2018-10/documents/nutrient-criteria-manual-estuarine-coastal.pdf Nutrient Criteria Technical Guidance Manual, Estuarine and Coastal Marine Waters], U.S. Environmental Protection Agency</ref> 

"Coastal waters" has specific meanings in the context of commercial [[Maritime transport|coastal shipping]], and somewhat different meanings in the context of naval [[littoral warfare]].{{citation needed|date=June 2022}} [[Oceanography|Oceanographers]] and [[Marine biology|marine biologists]] have yet other takes. Coastal waters have a wide range of [[marine habitats]] from enclosed [[Estuary|estuaries]] to the [[Pelagic zone|open waters]] of the continental shelf.   

Similarly, the term [[littoral zone]] has no single definition. It is the part of a [[sea]], [[lake]], or [[river]] that is close to the [[shore]].<ref name="Seekell2021">{{Cite journal |last1=Seekell |first1=D. |last2=Cael |first2=B. |last3=Norman |first3=S. |last4=Byström |first4=P. |year=2021 |title=Patterns and variation of littoral habitat size among lakes |journal=Geophysical Research Letters |language=en |volume=48 |issue=20 |article-number=e2021GL095046 |bibcode=2021GeoRL..4895046S |doi=10.1029/2021GL095046 |issn=1944-8007 |s2cid=244253181|doi-access=free }}</ref> In coastal environments, the littoral zone extends from the [[high water mark]], which is rarely inundated, to shoreline areas that are permanently [[Underwater|submerged]].

Coastal waters can be threatened by [[coastal eutrophication]] and [[harmful algal blooms]].<ref>{{Cite journal |last1=Maúre |first1=Elígio de Raús |last2=Terauchi |first2=Genki |last3=Ishizaka |first3=Joji |last4=Clinton |first4=Nicholas |last5=DeWitt |first5=Michael |date=2021 |title=Globally consistent assessment of coastal eutrophication |journal=Nature Communications |language=en |volume=12 |issue=1 |page=6142 |doi=10.1038/s41467-021-26391-9 |issn=2041-1723 |pmc=8536747 |pmid=34686688}}</ref><ref name=":32">{{Cite journal |last=Jickells |first=T. D. |date=1998 |title=Nutrient Biogeochemistry of the Coastal Zone |url=https://www.science.org/doi/10.1126/science.281.5374.217 |journal=Science |language=en |volume=281 |issue=5374 |pages=217–222 |doi=10.1126/science.281.5374.217 |issn=0036-8075 |pmid=9660744|url-access=subscription }}</ref><ref name=":16">{{Cite journal |last1=Glibert |first1=Patricia |last2=Burford |first2=Michele |date=2017 |title=Globally Changing Nutrient Loads and Harmful Algal Blooms: Recent Advances, New Paradigms, and Continuing Challenges |url=https://tos.org/oceanography/article/globally-changing-nutrient-loads-and-harmful-algal-blooms-recent-advances-n |journal=Oceanography |volume=30 |issue=1 |pages=58–69 |doi=10.5670/oceanog.2017.110|doi-access=free |bibcode=2017Ocgpy..30a..58G |hdl=10072/377577 |hdl-access=free }}</ref>

== In geology ==
The identification of bodies of rock formed from sediments deposited in shoreline and nearshore environments (shoreline and nearshore ''[[Facies (geology)|facies]]'') is extremely important to geologists. These provide vital clues for reconstructing the geography of ancient continents (''[[paleogeography]]''). The locations of these beds show the extent of ancient seas at particular points in geological time, and provide clues to the magnitudes of tides in the distant past.<ref name=Leeder2011>{{cite book |last1=Leeder |first1=M. R. |title=Sedimentology and sedimentary basins: from turbulence to tectonics |date=2011 |publisher=Wiley-Blackwell |location=Chichester, West Sussex, UK |isbn=978-1-4051-7783-2 |edition=2nd |pages=436–437}}</ref>

Sediments deposited in the [[shoreface]] are preserved as lenses of [[sandstone]] in which the upper part of the sandstone is coarser than the lower part (a ''coarsening upwards sequence''). Geologists refer to these are ''[[parasequence]]s''. Each records an episode of retreat of the ocean from the shoreline over a period of 10,000 to 1,000,000 years. These often show [[Lamination (geology)|laminations]] reflecting various kinds of tidal cycles.<ref name=Leeder2011/>

Some of the best-studied shoreline deposits in the world are found along the former western shore of the [[Western Interior Seaway]], a shallow sea that flooded central North America during the [[late Cretaceous]] [[Period (geology)|Period]] (about 100 to 66 million years ago). These are beautifully exposed along the [[Book Cliffs]] of [[Utah]] and [[Colorado]].{{sfn|Blatt|Middleton|Murray|1980|pp=673-674}}

===Geologic processes===
The following articles describe the various geologic processes that affect a coastal zone:
{{Div col|colwidth=24em}}
* [[Attrition (weathering)|Attrition]]
* [[Ocean current|Currents]]
* [[Denudation]]
* [[Deposition (geology)|Deposition]]
* [[Erosion]]
* [[Flood]]ing
* [[Longshore drift]]
* [[Marine sediments]]
* [[Saltation (geology)|Saltation]]
* [[Sea level change]]
** [[eustatic]]
** [[isostasy|isostatic]]
* [[Sedimentation]]
* [[Coastal sediment supply]]
** [[sediment transport]]
** [[Solution (chemistry)|solution]]
** [[subaerial]] processes
** [[Suspension (chemistry)|suspension]]
* [[Tide]]s
* [[Wind wave|Water waves]]
** [[diffraction]]
** [[refraction]]
** [[wave breaking]]
** [[wave shoaling]]
* [[Weathering]]
{{div col end}}

==Wildlife==
{{see also|Coastal ecology|Marine coastal ecosystem}}

===Animals===
{{See also|Seashore wildlife}}
{{Unsourced section|date=April 2018}}
Larger animals that live in coastal areas include [[Puffin|puffins]], [[Sea turtle|sea turtles]] and [[Rockhopper penguin|rockhopper penguins]], among many others. [[Gastropoda|Sea snails]] and various kinds of [[Barnacle|barnacles]] live on rocky coasts and scavenge on food deposited by the sea. Some coastal animals are used to humans in developed areas, such as [[Dolphin|dolphins]] and [[seagulls]] who eat food thrown for them by tourists. Since the coastal areas are all part of the [[littoral zone]], there is a profusion of marine life found just off-coast, including [[Sessility (motility)|sessile]] animals such as [[Coral|corals]], sponges, starfish, mussels, seaweeds, fishes, and [[Sea anemone|sea anemones]].

There are many kinds of [[seabird]]s on various coasts. These include [[pelican]]s and [[cormorant]]s, who join up with [[tern]]s and [[oystercatcher]]s to forage for fish and shellfish. There are [[sea lion]]s on the coast of [[Wales]] and other countries.

====Coastal fish====
{{excerpt|Coastal fish}}

===Plants===
Many coastal areas are famous for their [[kelp]] beds. Kelp is a fast-growing [[seaweed]] that can grow up to half a meter a day in ideal conditions. [[Mangroves]], [[Seagrass|seagrasses]], macroalgal beds, and [[salt marsh]] are important coastal vegetation types in tropical and temperate environments respectively.<ref name=":1" /><ref name=":4" /> [[Restinga]] is another type of coastal vegetation.

== Threats ==
{{see also|Coastal development hazards|marine coastal ecosystem}}

Coasts also face many [[Human impact on the environment|human-induced environmental impacts]] and [[coastal development hazards]]. The most important ones are: 
* Pollution which can be in the form of [[water pollution]], [[nutrient pollution]] (leading to [[coastal eutrophication]] and [[Harmful algal bloom|harmful algal blooms]]), [[Oil spill|oil spills]] or [[marine debris]] that is contaminating coasts with plastic and other trash.
* [[Sea level rise]], and associated issues like [[coastal erosion]] and [[saltwater intrusion]].

=== Pollution ===
{{See also|Human impact on marine life}}
[[File:Marbleheadcoastline.jpg|thumb|A settled coastline in [[Marblehead, Massachusetts]]. Once a fishing port, the harbor is now dedicated to tourism and pleasure boating. Observe that the sand and rocks have been darkened by oil slick up to the high-water line.]]
[[File:Beach at Msasani Bay, Dar es Salaam, Tanzania.JPG|thumb|This stretch of coast in Tanzania's capital Dar es Salaam serves as a public waste dump.]]
[[File:Aquatic Dead Zones.jpg|thumb|[[Dead zone (ecology)|Dead zones]] occur when phosphorus and nitrogen from fertilizers cause excessive growth of microorganisms, which depletes oxygen and kills fauna.]]
The pollution of coastlines is connected to [[marine pollution]] which can occur from a number of sources: [[Marine debris]] (garbage and industrial debris); the [[Petroleum transport|transportation of petroleum]] in [[tanker (ship)|tankers]], increasing the probability of large [[oil spill]]s; small oil spills created by large and small vessels, which flush [[bilge]] water into the ocean.

==== Marine pollution ====
{{excerpt|Marine pollution|paragraphs=1-2|file=no}}

==== Marine debris ====
{{excerpt|Marine debris|paragraphs=1-2|file=no}}

==== Microplastics ====
{{excerpt|Plastic soup#Microplastics|paragraphs=1-2|file=no}}

=== Sea level rise due to climate change ===
{{Excerpt|Sea level rise|paragraphs=1-2|file=no}}

== Global goals ==
International attention to address the threats of coasts has been captured in [[Sustainable Development Goal 14]] "Life Below Water" which sets goals for international policy focused on preserving [[Marine coastal ecosystem|marine coastal ecosystems]] and supporting more [[Sustainable development|sustainable economic practices]] for coastal communities.<ref name=":17" /> Likewise, the United Nations has declared 2021–2030 the [[UN Decade on Ecosystem Restoration]], but restoration of coastal ecosystems has received insufficient attention.<ref name=":3" />

==See also==
{{portal|Geography|Oceans}}
* [[Bank (geography)]]
* [[Beach cleaning]]
* [[Coastal and Estuarine Research Federation]]
* [[European Atlas of the Seas]]
* [[Intertidal zone]]
* [[Land reclamation]]
* [[List of countries by length of coastline]]
* [[List of U.S. states by coastline]]
* Offshore or [[Intertidal zone]]
* [[Ballantine Scale]]
* [[Coastal path]]
* [[ShoreZone|Shorezone]]

== References ==
<references>
<ref name="BBC" >{{cite web |url=https://www.bbc.co.uk/bitesize/guides/zt6r82p/revision/1 |title=Coastal processes - AQA, Wave types - constructive and destructive |website=www.bbc.co.uk |access-date=13 April 2024 }}</ref>

<ref name="field studies" >{{cite web |url=https://www.field-studies-council.org/resources/16-18-geography/coasts/high-energy-coasts/ |title=High energy coasts |website=www.field-studies-council.org |access-date=13 April 2024 }}</ref>

<ref name="field studies method" >{{cite web |url=https://www.field-studies-council.org/resources/16-18-geography/coasts/high-energy-coasts/method/ |title=Method for high energy coasts |website=www.field-studies-council.org |access-date=13 April 2024 }}</ref>

<ref name="Guisado-Pintado and Jackson 2019" >{{cite journal|last1=Guisado-Pintado |first1=E |last2=Jackson |first2=D.W.T. |date=2019|title=Coastal Impact From High-Energy Events and the Importance of Concurrent Forcing Parameters: The Cases of Storm Ophelia (2017) and Storm Hector (2018) in NW Ireland. |journal=Front. Earth Sci. |volume=7 |issue=190  |article-number=190 |doi=10.3389/feart.2019.00190 |doi-access=free |bibcode=2019FrEaS...7..190G }}</ref>

<ref name="Vaia" >{{cite web |url=https://www.vaia.com/en-us/explanations/geography/coasts-geography/classification-of-coasts/ |title=Classification of Coasts |website=www.vaia.com |access-date=13 April 2024 }}</ref>
</references>

==Further reading==
*{{cite book 
|last1=Scheffers|first1=Anja M.
|last2=Scheffers|first2=Sander R.
|last3=Kelletat|first3=Dieter H.
|title=The Coastlines of the World with Google Earth: Understanding our Environment
|date=2012 
|publisher=Springer
|location=New York
|isbn=978-94-007-0737-5}}

==External links==
* [https://www.whoi.edu/ Woods Hole Oceanographic Institution] - organization dedicated to ocean research, exploration, and education

{{Commons category|Coasts}}
{{Wikiquote}}
{{Wiktionary|coast}}
{{Wikiversity}}

{{Coastal geography}}{{Vegetation}}{{Authority control}}

[[Category:Coasts| ]]
[[Category:Coastal and oceanic landforms]]
[[Category:Coastal geography]]
[[Category:Oceanographical terminology]]
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