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A ria (; gl, ría) is a coastal
inlet An inlet is a (usually long and narrow) indentation of a shoreline, such as a small arm, bay, sound, fjord, lagoon or marsh, that leads to an enclosed larger body of water such as a lake, estuary, gulf or marginal sea. Overview In marine geogra ...
formed by the partial submergence of an unglaciated river valley. It is a drowned river valley that remains open to the sea.


Definitions

Typically rias have a dendritic, treelike outline although they can be straight and without significant branches. This pattern is inherited from the dendritic drainage pattern of the flooded river valley. The drowning of river valleys along a stretch of coast and formation of rias results in an extremely irregular and indented coastline. Often, there are naturally occurring islands, which are summits of partly submerged, pre-existing hill peaks. (Islands may also be artificial, such as those constructed for the Chesapeake Bay Bridge-Tunnel.) A ria coast is a coastline having several parallel rias separated by prominent ridges, extending a distance inland.Goudie, A. (2004) ''Encyclopedia of Geomorphology.'' Routledge. London, England.Bird, E.C.F. (2008) ''Coastal Geomorphology: An Introduction'', 2nd ed. John Wiley and Sons Ltd. West Sussex, England. The sea level change that caused the submergence of a river valley may be either eustatic (where global sea levels rise), or isostatic (where the local land sinks). The result is often a very large estuary at the mouth of a relatively insignificant river (or else sediments would quickly fill the ria). The Kingsbridge Estuary in Devon, England, is an extreme example of a ria forming an estuary disproportionate to the size of its river; no significant river flows into it at all, only a number of small streams. The word '' ria'' comes from Galician '' ría'', which is related to Spanish and Galician ''
río Rio or Río is the Portuguese, Spanish, Italian, and Maltese word for "river". When spoken on its own, the word often means Rio de Janeiro, a major city in Brazil. Rio or Río may also refer to: Geography Brazil * Rio de Janeiro * Rio do Sul, a ...
'' and Portuguese '' rio'' (river). Rias are present all along the
Galicia Galicia may refer to: Geographic regions * Galicia (Spain), a region and autonomous community of northwestern Spain ** Gallaecia, a Roman province ** The post-Roman Kingdom of the Suebi, also called the Kingdom of Gallaecia ** The medieval King ...
n coast in Spain. As originally defined, the term was restricted to drowned river valleys cut parallel to the structure of the
country rock Country rock is a genre of music which fuses rock and country. It was developed by rock musicians who began to record country-flavored records in the late 1960s and early 1970s. These musicians recorded rock records using country themes, vocal s ...
that was at right angles to the coastline. However the definition of ria was later expanded to other flooded river valleys regardless of the structure of the country rock. For a time European geomorphologists considered rias to include any broad estuarine river mouth, including fjords. These are long narrow
inlet An inlet is a (usually long and narrow) indentation of a shoreline, such as a small arm, bay, sound, fjord, lagoon or marsh, that leads to an enclosed larger body of water such as a lake, estuary, gulf or marginal sea. Overview In marine geogra ...
s with steep sides or cliffs, created in a valley carved by glacial activity. In the 21st century, however, the preferred usage of ''ria'' by geologists and geomorphologists is to refer solely to drowned unglaciated river valleys. It therefore excludes fjords by definition, since fjords are products of glaciation.


Locations


Europe

* Portugal: has no ''rias'' as such: the Ria de Aveiro in Aveiro, and Ria Formosa in Eastern Algarve are actually lagoons. * Atlantic coast of Spain **
Galicia Galicia may refer to: Geographic regions * Galicia (Spain), a region and autonomous community of northwestern Spain ** Gallaecia, a Roman province ** The post-Roman Kingdom of the Suebi, also called the Kingdom of Gallaecia ** The medieval King ...
: *** The Rías Baixas, including the Ria of Vigo, Ria of Pontevedra,
Ría de Arousa The ''Ría de Arousa'' is a ria, a saline estuary, that forms a firth situated on Galicia, Spain. It is one of the five ''Rías Baixas''. The Ría de Arousa estuary is the largest of the estuaries of Galicia. It is part of the Rias Baixas and is ...
, Ria of
Muros Muros may refer to: *Muros, A Coruña, a municipality in the province of A Coruña in the autonomous community of Galicia, Spain *Muros, Sardinia, a comune in the province of Sassari in the region Sardini, Italy *Muros (comarca), a comarca in the P ...
and Noia, Ria of Corcubion, Cee and Ría de Aldán. *** The Rías Altas, including the Ria of Corunna, Ria of
Ares Ares (; grc, Ἄρης, ''Árēs'' ) is the Greek god of war and courage. He is one of the Twelve Olympians, and the son of Zeus and Hera. The Greeks were ambivalent towards him. He embodies the physical valor necessary for success in war b ...
and Betanzos, Ria of Cedeira, Ria of O Barqueiro, Ria of Ferrol, Ria of Ortigueira, Ria of Viveiro, Ria of Foz and Ria of Ribadeo. ** Asturias: Ria of
Avilés Avilés (; ) is a town in Asturias, Spain. Avilés is, along with Oviedo and Gijón, one of the main cities in the Principality of Asturias. The town occupies the flattest land in the municipality, partially in a land that belonged to the sea, ...
, Ria of Ribadeo, Ria of Navia, Ria of Villaviciosa, Ria of Ribadesella, Ria of Llanes, Ria of Tina Mayor. ** Cantabria: Ria of Tina Mayor, Ria of Tina Menor, Ría de
San Vicente de la Barquera San Vicente de la Barquera is a municipality of Cantabria in northern Spain. It had a population of 4,412 in 2002. Tourism is its main activity due to the area's natural environment and heritage. Approximately 80% of the municipal area belongs ...
, Ría of la Rabia, Ría of San Martín de la Arena, Ría of Mogro, Ría of Solía, Ría of Carmen, Ría of Boo, Ría of Tijero, Ría of Cubas, Ría de Ajo, Ría of Cabo Quejo, Ría of Treto, Ría of Oriñón. **
Basque Country Basque Country may refer to: * Basque Country (autonomous community), as used in Spain ( es, País Vasco, link=no), also called , an Autonomous communities of Spain, autonomous community of Spain (shown in pink on the map) * French Basque Country o ...
: Ria of Bilbao, mouth of the rivers Nervión, Ibaizabal, and Cadagua. ** Andalusia: Ria of Carreras, Ria of Huelva at the mouth of the rivers Odiel and Tinto. * Brittany: The rias in northern Brittany are called ''Abers'': '' Aber Wrac'h'' (), ''Aber Benoît'' (), ''Aber Ildut'' () etc. The Roadstead of Brest also includes several rias. * Ireland: Bantry Bay, on the southwest coast of Ireland, is an example of an Irish ria. * Wales: Milford Haven Waterway in
Pembrokeshire Pembrokeshire ( ; cy, Sir Benfro ) is a Local government in Wales#Principal areas, county in the South West Wales, south-west of Wales. It is bordered by Carmarthenshire to the east, Ceredigion to the northeast, and the rest by sea. The count ...
is a ria. * England: The south coast of England is a submergent coastline which contains many rias, including Southampton Water, Poole Harbour, the estuary of the River Medina on the Isle of Wight, the estuaries of the Exe, Teign and Dart, then Kingsbridge Estuary, Plymouth Sound in Devon, and the estuaries of the
River Fowey The River Fowey ( ; kw, Fowi) is a river in Cornwall, England, United Kingdom. It rises at Fowey Well (originally kw, Fenten Fowi, meaning ''spring of the river Fowey'') about north-west of Brown Willy on Bodmin Moor, not far from one of i ...
, River Fal and Helford River in Cornwall. On the north coast is the River Camel and the River Taw. In Essex are the River Blackwater and River Crouch. * Croatia: Lim, Rijeka Dubrovačka * Montenegro: The Bay of Kotor * Italy: The Fiordo di Furore on the Amalfi Coast in Campania is a ria, despite its name. * Malta: Grand Harbour and Marsamxett Harbour


Africa

* Kenya: Kilindini Harbour, which is a deep channel between Mombasa island and South Coast mainland, is a ria.


Asia

* Sanriku Coast: North Japan, east coast of Honshū Island (main island). Sendai city, Miyagi Prefecture and Iwate Prefecture are included. * Ago Coast in Shima (Mie Prefecture) is a Ria coast, well known for its pearls. * Coasts on western, southern sides of the Korean Peninsula: Rias formed by sea level rising after Ice Age. * The Chinese east coast, from the
Guangdong province Guangdong (, ), alternatively romanized as Canton or Kwangtung, is a coastal province in South China on the north shore of the South China Sea. The capital of the province is Guangzhou. With a population of 126.01 million (as of 2020) ...
( Hong Kong coastlines included) to Shanghai. * The Musandam Peninsula in Oman, comprising the southern shore of the
Strait of Hormuz The Strait of Hormuz ( fa, تنگه هرمز ''Tangeh-ye Hormoz'' ar, مَضيق هُرمُز ''Maḍīq Hurmuz'') is a strait between the Persian Gulf and the Gulf of Oman. It provides the only sea passage from the Persian Gulf to the ...
.


Oceania

* Papua New Guinea: Rias formed by eroded volcanic lava flow are found all around the town of Tufi at Cape Nelson, in Papua New Guinea's Oro Province. * Australia: The east coast of Australia features several rias around
Sydney Sydney ( ) is the capital city of the state of New South Wales, and the most populous city in both Australia and Oceania. Located on Australia's east coast, the metropolis surrounds Sydney Harbour and extends about towards the Blue Mountain ...
, including
Georges River The Georges River, also known as Tucoerah River, is an intermediate tide-dominated drowned valley estuary, located to the south and west of Sydney, New South Wales, Australia. The river travels for approximately in a north and then easterly ...
, Port Hacking, and Port Jackson, which includes Sydney Harbour. There are many examples in Western Australia, including the Swan River around Perth and several rivers in the west
Kimberley Kimberly or Kimberley may refer to: Places and historical events Australia * Kimberley (Western Australia) ** Roman Catholic Diocese of Kimberley * Kimberley Warm Springs, Tasmania * Kimberley, Tasmania a small town * County of Kimberley, a ...
region. * New Zealand: Rias of various scales abound on the eastern shores of the upper
North Island The North Island, also officially named Te Ika-a-Māui, is one of the two main islands of New Zealand, separated from the larger but much less populous South Island by the Cook Strait. The island's area is , making it the world's 14th-largest ...
. On the west coast, in contrast, they are fewer but larger. Kaipara Harbour is the country's largest, and the Hokianga Harbour, further north, is of historical significance to the native Māori people. The Marlborough Sounds at the northern tip of the
South Island The South Island, also officially named , is the larger of the two major islands of New Zealand in surface area, the other being the smaller but more populous North Island. It is bordered to the north by Cook Strait, to the west by the Tasman ...
form a large network of rias. * Hawaii: Pearl Harbor on Oahu is a ria, with the branches of West Loch, Middle Loch, East Loch, and Southeast Loch formed by the submerged drainages of Waikele, Waiau, Waimalu, and Hālawa streams respectively.


North America

* United States: Narragansett Bay,
New York Harbor New York Harbor is at the mouth of the Hudson River where it empties into New York Bay near the East River tidal estuary, and then into the Atlantic Ocean on the east coast of the United States. It is one of the largest natural harbors in t ...
, Delaware Bay, Indian River Bay, the Chesapeake Bay, and Charleston Harbor are rias on the
East Coast East Coast may refer to: Entertainment * East Coast hip hop, a subgenre of hip hop * East Coast (ASAP Ferg song), "East Coast" (ASAP Ferg song), 2017 * East Coast (Saves the Day song), "East Coast" (Saves the Day song), 2004 * East Coast FM, a ra ...
.
Willapa Bay Willapa Bay () is a bay located on the southwest Pacific coast of Washington state in the United States. The Long Beach Peninsula separates Willapa Bay from the greater expanse of the Pacific Ocean. With over of surface area Willapa Bay is th ...
and Grays Harbor in Washington and
San Francisco Bay San Francisco Bay is a large tidal estuary in the U.S. state of California, and gives its name to the San Francisco Bay Area. It is dominated by the big cities of San Francisco, San Jose, and Oakland. San Francisco Bay drains water from a ...
in California on the
West Coast West Coast or west coast may refer to: Geography Australia * Western Australia *Regions of South Australia#Weather forecasting, West Coast of South Australia * West Coast, Tasmania **West Coast Range, mountain range in the region Canada * Britis ...
are also rias. * Canada:
Charlottetown Charlottetown is the capital and largest city of the Canadian province of Prince Edward Island, and the county seat of Queens County. Named after Queen Charlotte, Charlottetown was an unincorporated town until it was incorporated as a city in ...
Harbour, Prince Edward Island


South America

* Argentina: Patagonia has the Deseado ria, on the coast of
Santa Cruz Province Santa Claus, also known as Father Christmas, Saint Nicholas, Saint Nick, Kris Kringle, or simply Santa, is a legendary figure originating in Western Christian culture who is said to bring children gifts during the late evening and overnigh ...
, on the Atlantic Ocean. Also, the "bay" that is
Bahía Blanca Bahía Blanca (; English: White Bay) is a city in the southwest of the provinces of Argentina, province of Buenos Aires Province, Buenos Aires, Argentina, by the Atlantic Ocean, and is the seat of government of the Bahía Blanca Partido. It had 3 ...
is a ría.


Consequences

The funnel-like shape of rias can amplify the effects of tsunamis, as demonstrated in the
seismicity of the Sanriku coast The seismicity of the Sanriku coast identifies and describes the seismic activity of an area of Japan. Seismicity refers to the frequency, type and size of earthquakes experienced over a period of time. The is a descriptive term referring to th ...
, most recently in the
2011 Tōhoku earthquake and tsunami The occurred at 14:46 JST (05:46 UTC) on 11 March. The magnitude 9.0–9.1 (M) undersea megathrust earthquake had an epicenter in the Pacific Ocean, east of the Oshika Peninsula of the Tōhoku region, and lasted approximately six minutes ...
.


See also

* Estuary * Firth *
Loch ''Loch'' () is the Scottish Gaelic, Scots language, Scots and Irish language, Irish word for a lake or sea inlet. It is Cognate, cognate with the Manx language, Manx lough, Cornish language, Cornish logh, and one of the Welsh language, Welsh w ...
* Fjord * List of waterways


References


Further reading

*Perillo, Gerardo, ''Geomorphology and Sedimentology of Estuaries'', Volume 53. pp. 17–47. Elsevier Science (1995) *von Richthofen, F. ''Fuhrer fur Forschungsreisende ("Guide for Explorers")'', pp. 308–310. Berlin, Oppenheim (1886) {{Authority control Coastal and oceanic landforms Galician words and phrases Portuguese words and phrases