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Strait

geography Maturity 11-13 Next article →

A strait is a specific type of marine feature. It is a body of water that connects two seas or ocean basins.

Strait
Strait

Most straits are narrow channels located between two land masses. Unlike rivers, the surface water in a strait is usually at the same elevation on both sides. This allows the water to flow in either direction. However, the physical shape of the land often constricts this flow. This constriction can create a dominant directional current in some areas.

Brändö sund 28 april 2011
Brändö sund 28 april 2011

Geological processes often occur within these narrow passages. Straits frequently act as loci for sediment accumulation. This means particles like sand collect in these areas over time. These sand-sized deposits usually gather at the two exits of the strait. This process forms underwater features known as subaqueous fans or deltas. The specific shape of the seabed and the strength of the currents determine how these deposits grow. Some straits are not navigable for ships. This can happen if they are too narrow or too shallow. The presence of an archipelago or a reef can also block passage.

Terminology for these features can vary depending on the region. The terms channel, pass, or passage are often used as synonyms for a strait. In Scotland, people may use the words firth or Kyle to describe them. It is important to distinguish straits from other water features. For example, humans build artificial channels called canals to connect oceans. The Suez Canal is a well-known example of a man-made connection. While rivers and canals also connect large bodies of water, they are not usually called straits. Rivers typically have a one-way flow caused by changes in elevation. Straits generally remain free-flowing or can switch directions because they maintain a consistent elevation.

Straits are the geographic converse of an isthmus. An isthmus is a narrow strip of land that connects two larger land masses. A strait does the opposite by connecting two larger areas of ocean.

ISS-44 Strait of Gibraltar
ISS-44 Strait of Gibraltar

Because they connect major maritime regions, straits are often economically vital. They serve as essential shipping routes for global trade. This importance has led to historical conflicts, as wars have been fought to control them. Their strategic value makes them central to both commerce and international relations.

Modern technology allows us to harness the energy found in these waters. Some straits have the potential to generate significant tidal power. This is done using tidal stream turbines to capture the movement of the water. Tides are more predictable than other renewable sources like wind or wave power. For instance, the Pentland Firth may be capable of generating 10 GW of power. In New Zealand, the Cook Strait may be capable of generating 5.6 GW. Even though the total energy available in the flow of the Cook Strait is 15 GW, the turbine potential is a specific subset of that energy.

International law governs how ships move through these waters. There is a specific legal regime called transit passage. This applies to straits used for international navigation that connect two areas of high seas or an exclusive economic zone. Examples include the Strait of Gibraltar, the Strait of Dover, and the Strait of Hormuz. In these areas, no navigational exclusions are permitted. Another rule is called innocent passage. This applies to all territorial waters and certain internal waters. It is used in straits like the Strait of Tiran or the Strait of Juan de Fuca. It also allows ships to take shortcuts through straits formed by offshore islands, such as the Strait of Messina.

When ships use innocent passage, they must follow specific rules. They are allowed to pass through, but they cannot engage in certain activities. These disallowed activities include fishing, research, propaganda, espionage, or taking on weapons and aircraft. Passing ships must also follow the safety and environmental regulations of the sovereign state. In some cases, if a country is a legally recognized archipelagic state, ships can use archipelagic sea lanes passage. This allows for travel between the islands of that nation. These complex legal systems ensure that the world's most important water passages remain organized and safe for all users.

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File:ISS-44 Strait of Gibraltar.jpg
ISS-44 Strait of Gibraltar.jpg
File:Strait.svg
Strait.svg
File:Brändö sund 28 april 2011.jpg
Brändö sund 28 april 2011.jpg
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