A strait is a narrow body of water that connects two larger bodies of water.

It may be formed by a fracture in an isthmus, a narrow body of land that connects two bodies of water. Tectonic shifts can lead to straits like this. One strait that was formed by tectonic activity is the Strait of Gibraltar, the only link between the Mediterranean Sea and the Atlantic Ocean. The Strait of Gibraltar is actually closing, as the African tectonic plate slides north. In a few thousand years, the Strait of Gibraltar will be the Isthmus of Gibraltar, and the Mediterranean will be a large, salty, inland sea.

If fractures in an isthmus are created by human activity, the straits are usually called canals. The Suez Canal was constructed in 1869 as a waterway between the Mediterranean Sea and the Red Sea. The Suez Canal allows transportation between Europe and Asia without having to go around the entire continent of Africa. It is an important economic strait.

A strait can also be formed by a body of water overflowing land that has subsided or has been eroded. The Bosporus, which links the Black Sea and the Aegean Sea, was formed this way. Land at the southwestern edge of the Black Sea eroded and crumbled, creating a strait. Although scientists know that the Black Sea was once an enclosed lake, they do not know for sure whether the Black Sea flooded into the Aegean, or the Aegean flooded into the Black Sea. The Bosporus is an extremely important strait, separating the continents of Europe and Asia. Besides two entire continents, the Bosporus also separates a single country. It splits the European part of Turkey, called Thrace, and the Asian part, called Anatolia.

Strategic Straits

Historically, straits have had great strategic importance. Whoever controls a strait is likely to control the sea and shipping routes of the entire region.

The Strait of Hormuz connects the Persian Gulf and a part of the Arabian Sea called the Gulf of Oman. Great quantities of petroleum from Middle Eastern states are shipped through the Strait of Hormuz.

The strait is jointly controlled by Oman, the United Arab Emirates, and Iran. These countries, which all export oil, are rarely in dispute with each other. They all have military centers in the region. Countries that import oil from the region also patrol the Strait of Hormuz. Sometimes, these military patrols can lead to conflict. In 2008, the United States accused Iran of harassing U.S. warships with small speedboats. Iran denied the allegations. The two countries were close to conflict for months before the dispute was settled without violence.

Their narrow passages can make some straits difficult to navigate. The Strait of Magellan is a very thin waterway between the southern tip of South America and the group of islands known as Tierra del Fuego. The strait links the Pacific and Atlantic Oceans. The stormy waters south of Tierra del Fuego (close to Antarctica) made the Strait of Magellan, to the north, more attractive to mariners. Although the landmasses protect the strait from harsh Antarctic weather, the Strait of Magellan is still difficult to navigate. It is narrow and the islands of Tierra del Fuego can lead to confusion in stormy weather. The temperatures can reach freezing. Strong wind and waves make visibility and steering complex.

Whaling ships of the 19th century, sailing from the East Coast of the United States to the whaling grounds of the South Pacific, would sometimes stay for weeks around the Strait of Magellan, waiting for calm, clear days for passage.