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Jai Ganesh

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Inland Sea

Inland Sea

Gist

Inland seas are landlocked seas that are only connected to the ocean through narrow channels. They usually contain many islands, channels, sounds, and straits. Inland sea was first defined for the Seto Inland Sea, separating the three main islands of Japan and connected to the Pacific Ocean through narrow channels.

Summary

Inland Sea is the body of water lying between the Japanese islands of Honshu, Shikoku, and Kyushu. It is composed of five distinct basins linked together by channels. Its east-west length is about 270 miles (440 km), and its waters are easily navigable. The sea has an irregular coastline and is dotted with hundreds of small islands, the largest of which is Awaji Island in the east. Entrance to the Inland Sea from the Philippine Sea and the Pacific Ocean is afforded by the Bungo Strait and the Kii Strait. The narrow Shimonoseki Strait at the western end leads to the East China Sea. The Inland Sea is a major transportation route between the Asian continent and Kyushu’s Kansai area. Industries along the sea flourish together with trading and fishing ports and the commercial centre of Ōsaka-Kōbe. The shores of the Inland Sea were Japan’s leading salt-producing region until industrialization was given priority after World War II. The salt fields are no longer used, but a petrochemical industry is flourishing. Popular among vacationers for its scenery, the entire Inland Sea region is included in the Inland Sea National Park.

Details

Inland seas, also called epeiric or epicontinental seas, are shallow seas over part of a continent.

They usually happen with marine transgressions, when the sea overtops the land. They are caused by either global high ('eustatic') sea level or the formation of large geologic basins which eventually connect to the ocean.

There have been, at some periods, shallow seas inside continents. Much of present-day North America was covered by an epicontinental sea called the Sundance Sea during the Jurassic period. In the Cretaceous an even larger area was covered by the Western Interior Seaway. A modern example is the Baltic Sea. The North Sea is not an inland sea, but it does sit on continental shelf, and so is epeiric (that is what the word means). The Hudson Bay is often considered an epeiric sea because its depth averages 100ft (30 m) whereas, for example, the Bay of Bengal is 2,600 metres (8000 ft) deep. So epeiric seas are on the continental plate, as are inland seas. The inland seas, however, are more enclosed.

Examples:

Amazon basin

The Amazon basin originally emptied into the Pacific Ocean when South America and Africa were part of Gondwana.

After the breakup of Gondwana, the Amazon found its exit blocked by the rise of the Andes about 15 million years ago (mya). A great inland sea developed, at times draining north through what is now Venezuela before finding its present eastward outlet into the South Atlantic. Gradually this inland sea became a vast freshwater lake and wetlands where sediment flattened its profiles and the marine inhabitants adapted to life in freshwater. Over 20 species of stingray, most closely related to those found in the Pacific Ocean, live today in the freshwaters of the Amazon, which is also home to a freshwater dolphin.

Mediterranean

The Mediterranean Sea looks like a clear-cut example of an inland sea, but its deepest point is 5,267 m (17,280 ft) in the Calypso Deep of the Ionian Sea. The Mediterranean is a genuine sea which has been squashed almost out of existence by the movement of Africa against the European tectonic plate. It was formerly part of the ancient Tethys Ocean, which surrounded the old global supercontinent of Pangaea. So the Mediterranean is different from those inland seas which sit on top of continental plates.

Black Sea

The Black Sea, on the other hand, is a genuine inland sea because it sits on continental plates which have subsided.

Western Interior Seaway

A vast inland sea extended from the Gulf of Mexico deep into present-day Canada during the Cretaceous. It split the continent of North America into two halves, Laramidia and Appalachia, for most of the mid- and late-Cretaceous period. It was 2,500 feet (760 m) deep, 600 miles (970 km) wide and over 2,000 miles (3,200 km) long.

At the same time, much of the low plains of modern-day northern France and northern Germany were covered by an inland sea, where the chalk was deposited that gave the Cretaceous Period its name.

Sundance Sea

The Sundance Sea existed in North America during the mid to late Jurassic period of the Mesozoic Era. It was an arm of what is now the Arctic Ocean, and extended through what is now western Canada into the central western United States. The sea receded when highlands to the west began to rise. The sedimentary rocks which formed in and around the Sundance Sea are often rich in fossils.

Additional Information

An inland sea (also known as an epeiric sea or an epicontinental sea) is a continental body of water which is very large in area and is either completely surrounded by dry land or connected to an ocean by a river, strait or "arm of the sea". An inland sea will generally be brackish, with higher salinity than a freshwater lake but usually lower salinity than seawater. As with other seas, inland seas experience tides governed by the orbits of the Moon and Sun.

Definition

What constitutes an "inland sea" is complex and somewhat necessarily vague. The United States Hydrographic Office defined it as "a body of water nearly or completely surrounded by land, especially if very large or composed of salt water".

Geologic engineers Heinrich Ries and Thomas L. Watson say an inland sea is merely a very large lake. Rydén, Migula, and Andersson and Deborah Sandler of the Environmental Law Institute add that an inland sea is "more or less" cut off from the ocean. It may be semi-enclosed,[4] or connected to the ocean by a strait or "arm of the sea". An inland sea is distinguishable from a bay in that a bay is directly connected to the ocean.

The term "epeiric sea" was coined by Joseph Barrell in 1917. He defined an epeiric sea as a shallow body of water whose bottom is within the wave base (e.g., where bottom sediments are no longer stirred by the wave above). An epeiric sea as one with limited connection to an ocean, and shallow. An inland sea is only an epeiric sea when a continental interior is flooded by marine transgression due to sea level rise or epeirogenic movement.

An epicontinental sea is synonymous with an epeiric sea. The term "epicontinental sea" may also refer to the waters above a continental shelf. This is a legal, not geological, term. Epeiric, epicontinental, and inland seas occur on a continent, not adjacent to it.

The law of the sea does not apply to inland seas.

Modern inland seas

In modern times, continents stand high, eustatic sea levels are low, and there are few inland seas.

* The Marmara Sea located in modern-day Turkey is surrounded by land all around, except where it connects the two Turkish Straits, the Bosphorus and the Dardanelles.
* The Baltic Sea is a brackish inland sea, arguably the largest body of brackish water in the world. Other possibilities include the White Sea and the northern half of the Black Sea (its deep southern basin is a closed-off relic of the now-vanished Tethys Sea). The origin of the Baltic Sea basin is not clear as there are differing views on the role of erosion and tectonics.
* Hudson Bay, including James Bay at its southern end, reaches within the North American continent from Baffin Island, Nunavut in the north to Quebec, Ontario and Manitoba in the south. The bay shares some similarities with the Gulf of Bothnia in Fennoscandia; it lies in the middle of a shield and it was the centre of an ice sheet during the Quaternary glaciations. However, the origin of both depressions is unrelated to glacier erosion.
* The Seto Inland Sea in Japan is not a true inland sea but rather a body of water separating Honshū, Shikoku, and Kyūshū, three of the four main islands of Japan.
* The Caspian Sea is a very large, inland body of water at least hundreds of miles from the nearest part of the World Ocean (such as the Persian Gulf) and has some characteristics of the sea, like being composed of at least a good portion of saltwater. However, it is also considered the largest lake in the world.

The Great Lakes, despite being completely fresh water, have been referred to as resembling or having characteristics like inland seas from a USGS management perspective. Lake Ontario is the only Great Lake connected to the Atlantic Ocean after Niagara Falls.

Modern examples might also include the recently (less than 10,000 years ago) reflooded Persian Gulf, and the South China Sea that presently covers the Sunda Shelf.

Former epicontinental seas in Earth's history

At various times in the geologic past, inland seas covered central areas of continents during periods of high sea level that result in marine transgressions. Inland seas have been greater in extent and more common than at present.

* During the Oligocene and Early Miocene large swaths of Patagonia were subject to a marine transgression. The transgression might have temporarily linked the Pacific and Atlantic oceans, as inferred from the findings of marine invertebrate fossils of both Atlantic and Pacific affinity in La Cascada Formation. Connection would have occurred through narrow epicontinental seaways that formed channels in a dissected topography.
* A vast inland sea, the Western Interior Seaway, extended from the Gulf of Mexico deep into present-day Canada during the Cretaceous.
* At the same time, much of the low plains of modern-day northern France and northern Germany were inundated by an inland sea, where the chalk was deposited that gave the Cretaceous Period its name.
* The Amazon, originally emptying into the Pacific, as South America rifted from Africa, found its exit blocked by the rise of the Andes about 15 million years ago. A great inland sea developed, at times draining north through what is now Venezuela before finding its present eastward outlet into the South Atlantic. Gradually this inland sea became a vast freshwater lake and wetlands where sediment flattened its profiles and the marine inhabitants adapted to life in freshwater. Over 20 species of stingray, most closely related to those found in the Pacific Ocean, can be found today in the freshwaters of the Amazon, which is also home to a freshwater dolphin. In 2005, fossilized remains of a giant crocodilian, estimated to have been 46 ft (14 m) in length, were discovered in the northern rainforest of Amazonian Peru.
* In Australia, the Eromanga Sea existed during the Cretaceous Period. It covered large swaths of the eastern half of the continent.

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