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[[File:17-08-islcanus-RalfR-DSC 3282.jpg|thumb|upright=1.2|Southeast coast of [[Greenland]]]] |
[[File:17-08-islcanus-RalfR-DSC 3282.jpg|thumb|upright=1.2|Southeast coast of [[Greenland]]]] |
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[[File:0.1. Mar Mediterrània - Serra de Tramuntana. Torrent de Pareis. (Escorca, Mallorca).jpg|thumb|275px|[[Escorca]] coast, [[Serra de Tramuntana]] ([[Balearic Islands]])]] |
[[File:0.1. Mar Mediterrània - Serra de Tramuntana. Torrent de Pareis. (Escorca, Mallorca).jpg|thumb|275px|[[Escorca]] coast, [[Serra de Tramuntana]] ([[Balearic Islands]])]] |
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The '''coast'''{{snd}}also called the '''coastline''', '''shoreline''', or '''seashore'''{{snd}}is defined as the area where [[land]] meets the [[ocean]], <ref>{{cite American Heritage Dictionary|coast |access-date=2024-06-12}}</ref><ref>{{cite web |title=coast |url=https://bartleby.com/61/43/C0434300.html |year=2000 |website=[[The American Heritage Dictionary of the English Language]] |edition=4th |via=[[Bartleby.com]] |archive-url=https://web.archive.org/web/20090201151523/http://www.bartleby.com/61/43/C0434300.html |archive-date=2009-02-01 |url-status=dead |access-date=2008-12-11}}</ref> or as "a line that forms the boundary between the land and the ocean or a [[lake]]".<ref>{{cite Merriam-Webster|coastline |access-date=2024-06-12}}</ref> Shores are influenced by the [[topography]] of the surrounding landscape, as well as by water induced [[erosion]], such as [[wind wave|waves]]. The [[geology|geological]] composition of [[rock (geology)|rock]] and [[soil]] dictates the type of shore that is created. [[Earth]] contains roughly {{cvt|620,000|km|mi}} of coastline. |
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According to an atlas prepared by the [[United Nations]], 44% of |
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⚫ | Coasts are important zones in natural [[ecosystem]]s, often home to a wide range of [[biodiversity]]. On land, they harbor important ecosystems such as [[freshwater marsh|freshwater]]or[[estuary|estuarine]] [[wetland]]s, which are important for bird populations and other [[terrestrial animal]]s. In wave-protected areas, they harbor [[salt marsh]]es, [[mangrove]]s or [[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}}</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. |
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In [[physical oceanography]], a shore is the wider fringe that is geologically modified by the action of the body of water past and present, while the [[beach]] is at the edge of the shore, representing 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 between depths of {{cvt|1–50|m|ft}}. |
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⚫ | 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]]. |
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[[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]]. |
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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" /> |
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⚫ | 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|page=71|doi=10.3389/fmars.2020.00071|issn=2296-7745|hdl=2440/123896|hdl-access=free|doi-access=free}}</ref> |
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⚫ | 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). |
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{{TOC level|3}} |
{{TOC level|3}} |
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==Size== |
==Size== |
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[[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''' ( |
[[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>]] |
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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> |
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> |
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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 |
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]]). |
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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]].{{citation needed|date=August 2021}}<ref>{{Cite web |title= |
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]].{{citation needed|date=August 2021}}<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. |
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===Challengesof precisely measuring the coastline=== |
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{{excerpt|Coastline paradox|paragraphs=1,2|files=0}} |
{{excerpt|Coastline paradox|paragraphs=1,2|files=0}} |
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==Formation {{anchor|Formation of Coasts}}== |
==Formation {{anchor|Formation of Coasts}}== |
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[[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:Porto Covo pano April 2009-4.jpg|thumb|upright=1.2|Atlantic rocky coastline, showing a surf area. [[Porto Covo]], west coast of Portugal]] |
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[[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. |
[[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}} |
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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= |
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> |
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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]]. |
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]]. |
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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. |
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> |
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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). |
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). |
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{{further information|Concordant coastline|Discordant coastline}} |
{{further information|Concordant coastline|Discordant coastline}} |
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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. |
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. |
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===High and low energy coasts=== |
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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" /> |
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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" /> |
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====Destructive and constructive waves==== |
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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" /> |
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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" /> |
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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" /> |
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===Rivieras=== |
===Rivieras=== |
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''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 = |
''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 [[Marseilles]].<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" /> |
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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" /> |
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" /> |
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* A [[flat coast]] is one where the land gradually descends into the sea. |
* A [[flat coast]] is one where the land gradually descends into the sea. |
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* A [[graded shoreline]] is one where wind and water action has produced a flat and straight coastline. |
* A [[graded shoreline]] is one where wind and water action has produced a flat and straight coastline. |
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* 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" /> |
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* An [[erosional coast]] is on average undergoing erosion, while a [[depositional coast]] is accumulating material.<ref name="Vaia" /> |
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*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" /> |
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== Landforms == |
== Landforms == |
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* A [[natural arch]] is formed when a headland is eroded through by waves. |
* A [[natural arch]] is formed when a headland is eroded through by waves. |
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* [[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. |
* [[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. |
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* A [[stack (geology)|stack]] is formed when a headland is eroded away by wave and wind action. |
* 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. |
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* A [[Stack (geology)|stump]] is a shortened sea stack that has been eroded away or fallen because of instability. |
* A [[Stack (geology)|stump]] is a shortened sea stack that has been eroded away or fallen because of instability. |
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* 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. |
* 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. |
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* 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" /> |
* 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}} |
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===Coastal features formed by sediment=== |
===Coastal features formed by sediment=== |
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==Coastal waters== |
==Coastal waters== |
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{{See also|Eutrophication#Coastal waters}} |
{{See also|Eutrophication#Coastal waters}} |
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[[File: |
[[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]].]] |
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"Coastal waters" (or "coastal seas") is a rather general term used differently in different contexts, ranging geographically from the waters within a few kilometers of the coast, through to the entire [[continental shelf]] which may stretch for more than a hundred kilometers from land.<ref>{{Cite book |
"Coastal waters" (or "coastal seas") is a rather general term used differently in different contexts, ranging geographically from the waters within a few kilometers of the coast, through to the entire [[continental shelf]] which 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> Thus the term coastal waters is used in a slightly different way in discussions of legal and economic boundaries<ref>{{Cite web |title=Coastal waters Definition: 255 Samples |url=https://www.lawinsider.com/dictionary/coastal-waters |access-date=2022-06-22 |website=Law Insider |language=en}}</ref> (see [[territorial waters]] and [[international waters]]) or when considering the geography of coastal landforms or the ecological systems operating through the continental shelf ([[marine coastal ecosystem]]s). The research on coastal waters often divides into these separate areas too. |
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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= |
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> |
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"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. |
"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. |
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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 |pages=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]]. |
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 |pages=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]]. |
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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 | |
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}}</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 |hdl=10072/377577 |hdl-access=free }}</ref> |
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== In geology == |
== In geology == |
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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 |
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> |
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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/> |
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/> |
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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}} |
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}} |
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== Global goals == |
== Global goals == |
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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 |
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" /> |
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==See also== |
==See also== |
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== References == |
== References == |
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{{reflist| |
{{reflist|refs= |
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<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> |
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<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> |
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<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> |
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<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 |doi=10.3389/feart.2019.00190 |doi-access=free |bibcode=2019FrEaS...7..190G }}</ref> |
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<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 |accessdate=13 April 2024 }}</ref> |
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}} |
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==Further reading== |
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*{{cite book |
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|last1=Scheffers|first1=Anja M. |
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|last2=Scheffers|first2=Sander R. |
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|last3=Kelletat|first3=Dieter H. |
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|title=The Coastlines of the World with Google Earth: Understanding our Environment |
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|date=2012 |
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|publisher=Springer |
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|location=New York |
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|isbn=978-94-007-0737-5}} |
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==External links== |
==External links== |
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{{Wikiversity}} |
{{Wikiversity}} |
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{{Coastal geography}} |
{{Coastal geography}}{{Vegetation}}{{Authority control}} |
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{{Authority control}} |
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[[Category:Coasts| ]] |
[[Category:Coasts| ]] |
The coast – also called the coastline, shoreline, or seashore – is defined as the area where land meets the ocean, [1][2] or as "a line that forms the boundary between the land and the ocean or a lake".[3] Shores are influenced by the topography of the surrounding landscape, as well as by water induced erosion, such as waves. The geological composition of rock and soil dictates the type of shore that is created. Earth contains roughly 620,000 km (390,000 mi) of coastline.
Coasts are important zones in natural ecosystems, often home to a wide range of biodiversity. On land, they harbor important ecosystems such as freshwaterorestuarine wetlands, which are important for bird populations and other terrestrial animals. In wave-protected areas, they harbor salt marshes, mangrovesorseagrasses, all of which can provide nursery habitat for finfish, shellfish, and other aquatic animals.[4][5] Rocky shores are usually found along exposed coasts and provide habitat for a wide range of sessile animals (e.g. mussels, starfish, barnacles) and various kinds of seaweeds.
Inphysical oceanography, a shore is the wider fringe that is geologically modified by the action of the body of water past and present, while the beach is at the edge of the shore, representing the intertidal zone where there is one.[6] Along tropical coasts with clear, nutrient-poor water, coral reefs can often be found between depths of 1–50 m (3.3–164.0 ft).
According to an atlas prepared by the United Nations, about 44% of the human population lives within 150 km (93 mi) of the sea as of 2013[update].[7] 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 services to humankind. For example, important human activities happen in port cities. Coastal 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 beaches and seaside resorts generate large revenues through tourism.
Marine coastal ecosystems can also provide protection against sea level rise and tsunamis. In many countries, mangroves are the primary source of wood for fuel (e.g. charcoal) and building material. Coastal ecosystems like mangroves and seagrasses have a much higher capacity for carbon sequestration than many terrestrial ecosystems, and as such can play a critical role in the near-future to help mitigate climate change effects by uptake of atmospheric anthropogenic carbon dioxide.
However, the economic importance of coasts makes many of these communities 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.[8] 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.[8]
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, loss of biodiversity, increased 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 economic practices for coastal communities.[9] Likewise, the United Nations has declared 2021-2030 the UN Decade on Ecosystem Restoration, but restoration of coastal ecosystems has received insufficient attention.[10]
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.[11] 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, or the East, West, and 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 gulforbay. 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).
The Earth has approximately 620,000 kilometres (390,000 mi) of coastline. Coastal habitats, which extend to the margins of the continental shelves, make up about 7 percent of the Earth's oceans,[13] but at least 85% of commercially harvested fish depend on coastal environments during at least part of their life cycle.[14] As of October 2010,[update] about 2.86% of exclusive economic zones were part of marine protected areas.[15]
The definition of coasts varies. Marine scientists think of the "wet" (aquatic or intertidal) vegetated habitats as being 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 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.[citation needed][16] Government authorities in various countries may define coast differently for economic and social policy reasons.
The coastline paradox is the counterintuitive observation that the coastline of a landmass does not have a well-defined length. This results from the fractal curve–like properties of coastlines; i.e., the fact that a coastline typically has a fractal dimension. Although the "paradox of length" was previously noted by Hugo Steinhaus,[17] the first systematic study of this phenomenon was by Lewis Fry Richardson,[18][19] and it was expanded upon by Benoit Mandelbrot.[20][21]
Tides 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 bores can erode as the waves surge up the river estuaries from the ocean.[22]: 421
Geologists classify coasts on the basis of tidal range into macrotidal coasts with a tidal range greater than 4 m (13 ft); mesotidal coasts with a tidal range of 2 to 4 m (6.6 to 13 ft); and microtidal coasts with a tidal range of less than 2 m (7 ft). 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.[23]
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 abrasionorcliffed coast.
Sediment deposited by rivers is the dominant influence on the amount of sediment located in the case of coastlines that have estuaries.[24] 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.[25]
Like the ocean which shapes them, coasts are a dynamic environment with constant change. The Earth's natural processes, particularly sea level rises, waves and various weather phenomena, have resulted in the erosion, accretion and reshaping of coasts as well as flooding and creation of continental shelves and drowned river valleys (rias).
More and more of the world's people live in coastal regions.[26] According to a United Nations atlas, 44% of all people live within 150 km (93 mi) of the sea.[7] Many major cities are on or near good harbors and have port facilities. Some landlocked places have achieved port status by building canals.
Nations defend their coasts against military invaders, smugglers and illegal migrants. Fixed coastal defenses have long been erected in many nations, and coastal countries typically have a navy and some form of coast guard.
Coasts, especially those with beaches and warm water, attract tourists often leading to the development of seaside resort communities. In many island nations such as those of the Mediterranean, South Pacific Ocean and Caribbean, tourism is central to the economy. Coasts offer recreational activities such as swimming, fishing, surfing, boating, and 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.
Estuarine and marine coastal ecosystems are both marine ecosystems. Together, these ecosystems perform the four categories of ecosystem services in a variety of ways: The provisioning services include forest products, marine products, fresh water, raw materials, biochemical and genetic resources. Regulating services include carbon sequestration (contributing to climate change mitigation) as well as waste treatment and disease regulation and buffer zones. Supporting services of coastal ecosystems include nutrient cycling, biologically mediated habitats and primary production. Cultural services of coastal ecosystems include inspirational aspects, recreation and tourism, science and education.
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 landforms, which are above the high tide mark, such as raised beaches. 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 rias (drowned valleys) and fjords
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 resistance, so the coastline forms distinctive landforms, such as coves. Discordant coastlines feature distinctive landforms because the rocks are eroded by the ocean waves. The less resistant rocks erode faster, creating inletsorbay; the more resistant rocks erode more slowly, remaining as headlandsoroutcroppings.
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.[28] 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.[29]
High energy coasts are exposed to the direct impact of waves and storms, and are generally erosional environments.[29] 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.[30]
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.[31] 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 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.[32] Low waves that are further apart and break by 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.[32]
Riviera is an Italian word for "shoreline",[33][34][35] ultimately derived from Latin 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 French territory past Monaco and sometimes as far as Marseilles.[33][36][37] 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".[34]
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.[33] Such places using the term include the Australian RivierainQueensland and the Turkish Riviera along the Aegean Sea.[34]
The following articles describe some coastal landforms:
"Coastal waters" (or "coastal seas") is a rather general term used differently in different contexts, ranging geographically from the waters within a few kilometers of the coast, through to the entire continental shelf which may stretch for more than a hundred kilometers from land.[38] Thus the term coastal waters is used in a slightly different way in discussions of legal and economic boundaries[39] (see territorial waters and international waters) or when considering the geography of coastal landforms or the ecological systems operating through the continental shelf (marine coastal ecosystems). The research on coastal waters often divides into these separate areas too.
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.[40] 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[41] while in the United States the US EPA considers this region to extend much further offshore.[42][43]
"Coastal waters" has specific meanings in the context of commercial coastal shipping, and somewhat different meanings in the context of naval littoral warfare.[citation needed] Oceanographers and marine biologists have yet other takes. Coastal waters have a wide range of marine habitats from enclosed estuaries to the 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.[44] In coastal environments, the littoral zone extends from the high water mark, which is rarely inundated, to shoreline areas that are permanently submerged.
Coastal waters can be threatened by coastal eutrophication and harmful algal blooms.[45][46][47]
The identification of bodies of rock formed from sediments deposited in shoreline and nearshore environments (shoreline and nearshore 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.[48]
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 (acoarsening upwards sequence). Geologists refer to these are parasequences. 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 laminations reflecting various kinds of tidal cycles.[48]
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 (about 100 to 66 million years ago). These are beautifully exposed along the Book CliffsofUtah and Colorado.[49]
The following articles describe the various geologic processes that affect a coastal zone:
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Larger animals that live in coastal areas include puffins, sea turtles and rockhopper penguins, among many others. Sea snails and various kinds of 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 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 sessile animals such as corals, sponges, starfish, mussels, seaweeds, fishes, and sea anemones.
There are many kinds of seabirds on various coasts. These include pelicans and cormorants, who join up with terns and oystercatchers to forage for fish and shellfish. There are sea lions on the coast of Wales and other countries.
Coastal fish, also called inshore fish or neritic fish, inhabit the sea between the shoreline and the edge of the continental shelf. Since the continental shelf is usually less than 200 metres (660 ft) deep, it follows that pelagic coastal fish are generally epipelagic fish, inhabiting the sunlit epipelagic zone.[50] Coastal fish can be contrasted with oceanic fishoroffshore fish, which inhabit the deep seas beyond the continental shelves.
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, seagrasses, macroalgal beds, and salt marsh are important coastal vegetation types in tropical and temperate environments respectively.[4][5] Restinga is another type of coastal vegetation.
Coasts also face many human-induced environmental impacts and coastal development hazards. The most important ones are:
The pollution of coastlines is connected to marine pollution which can occur from a number of sources: Marine debris (garbage and industrial debris); the transportation of petroleumintankers, increasing the probability of large oil spills; small oil spills created by large and small vessels, which flush bilge water into the ocean.
Marine pollution occurs when substances used or spread by humans, such as industrial, agricultural and residential waste, particles, noise, excess carbon dioxideorinvasive organisms enter the ocean and cause harmful effects there. The majority of this waste (80%) comes from land-based activity, although marine transportation significantly contributes as well.[52] It is a combination of chemicals and trash, most of which comes from land sources and is washed or blown into the ocean. This pollution results in damage to the environment, to the health of all organisms, and to economic structures worldwide.[53] Since most inputs come from land, either via the rivers, sewage or the atmosphere, it means that continental shelves are more vulnerable to pollution. Air pollution is also a contributing factor by carrying off iron, carbonic acid, nitrogen, silicon, sulfur, pesticides or dust particles into the ocean.[54] The pollution often comes from nonpoint sources such as agricultural runoff, wind-blown debris, and dust. These nonpoint sources are largely due to runoff that enters the ocean through rivers, but wind-blown debris and dust can also play a role, as these pollutants can settle into waterways and oceans.[55] Pathways of pollution include direct discharge, land runoff, ship pollution, bilge pollution, atmospheric pollution and, potentially, deep sea mining.
Marine debris, also known as marine litter, is human-created solid material that has deliberately or accidentally been released in seas or the ocean. Floating oceanic debris tends to accumulate at the center of gyres and on coastlines, frequently washing aground, when it is known as beach litter or tidewrack. Deliberate disposal of wastes at sea is called ocean dumping. Naturally occurring debris, such as driftwood and drift seeds, are also present. With the increasing use of plastic, human influence has become an issue as many types of (petrochemical) plastics do not biodegrade quickly, as would natural or organic materials.[56] The largest single type of plastic pollution (~10%) and majority of large plastic in the oceans is discarded and lost nets from the fishing industry.[57] Waterborne plastic poses a serious threat to fish, seabirds, marine reptiles, and marine mammals, as well as to boats and coasts.[58]
A growing concern regarding plastic pollution in the marine ecosystem is the use of microplastics. Microplastics are beads of plastic less than 5 millimeters wide,[59] and they are commonly found in hand soaps, face cleansers, and other exfoliators. When these products are used, the microplastics go through the water filtration system and into the ocean, but because of their small size they are likely to escape capture by the preliminary treatment screens on wastewater plants.[60] These beads are harmful to the organisms in the ocean, especially filter feeders, because they can easily ingest the plastic and become sick. The microplastics are such a concern because it is difficult to clean them up due to their size, so humans can try to avoid using these harmful plastics by purchasing products that use environmentally safe exfoliates.
Between 1901 and 2018, the average global sea level rise was 15–25 cm (6–10 in), with an increase of 2.3 mm (0.091 in) per year since the 1970s.[63]: 1216 This is faster than the sea level has risen over the past 3,000 years, if not longer.[63]: 1216 The rate accelerated to 4.62 mm (0.182 in)/yr for the decade 2013–2022.[64] Climate change due to human activities is the main cause.[65]: 5, 8 Between 1993 and 2018, melting ice sheets and glaciers accounted for 44% of sea level rise, with another 42% resulting from thermal expansionofwater.[66]: 1576
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 ecosystems and supporting more sustainable economic practices for coastal communities.[9] Likewise, the United Nations has declared 2021–2030 the UN Decade on Ecosystem Restoration, but restoration of coastal ecosystems has received insufficient attention.[10]
The left bank of the Vistula, when measured with increased precision would furnish lengths ten, hundred and even thousand times as great as the length read off the school map. A statement nearly adequate to reality would be to call most arcs encountered in nature not rectifiable.
Press Release Number: 21042023.
This corresponds to a mean sea-level rise of about 7.5 cm over the whole altimetry period. More importantly, the GMSL curve shows a net acceleration, estimated to be at 0.08mm/yr2.
Box SYN-1: Sustained warming could lead to severe impacts
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