Strait

Lore & Background

Straits are the converse of isthmuses: a strait lies between two land masses and connects two large areas of ocean, while an isthmus lies between two areas of ocean and connects two large land masses. Some straits have the potential to generate significant tidal power using tidal stream turbines, as tides are more predictable than wave or wind power. The Pentland Firth may be capable of generating 10 GW, and Cook Strait in New Zealand may be capable of generating 5.6 GW, though the total energy available in the flow is 15 GW. Numerous artificial channels called canals have been constructed to connect two oceans or seas over land, such as the Suez Canal. Although rivers and canals often provide passage between two large lakes and seem to suit the formal definition of strait, they are not usually referred to as such. Rivers and canals generally have a directional flow tied to changes in elevation, whereas straits often are free flowing in either direction or switch direction, maintaining the same elevation. The term strait is typically reserved for much larger, wider features of the marine environment, though there are exceptions with straits being called canals, such as Pearse Canal.

Reader's Guide

Straits hold significance as both natural and geopolitical features. They are narrow channels connecting two seas or water basins, often lying between land masses, and serve as critical shipping routes. Their economic importance is underscored by wars fought for control of them. Legally, straits used for international navigation are subject to regimes of transit passage, innocent passage, or archipelagic sea lanes passage, depending on their location and the sovereign waters involved. Transit passage applies in territorial waters for straits connecting two areas of high seas or exclusive economic zones, such as the Strait of Gibraltar, Strait of Dover, and Strait of Hormuz. Innocent passage applies to territorial waters and certain internal waters, with restrictions on activities like fishing, research, and espionage. Examples include the Straits of Tiran, Strait of Juan de Fuca, and Strait of Baltiysk. Innocent passage can also be used for shortcuts through straits formed by offshore islands, as with the Strait of Messina and Pentland Firth. Archipelagic sea lanes passage applies when passing between islands of a recognized archipelagic state. Additionally, straits are sites of sediment accumulation and have potential for tidal power generation, with the Pentland Firth and Cook Strait cited as examples.

Did You Know?

• Straits are the converse of isthmuses: a strait lies between two land masses and connects two large areas of ocean.
• The Pentland Firth may be capable of generating 10 GW of tidal power.
• The regime of transit passage applies in territorial waters for straits used for international navigation, such as the Strait of Gibraltar.
• Some straits are not navigable due to being too narrow, too shallow, or due to a reef or archipelago.