What Is an Isthmus?

Isthmus connecting North and South Bruny Island in Tasmania.
Isthmus connecting North and South Bruny Island in Tasmania.

An isthmus is a thin piece of land that links two larger land areas that are otherwise separated by large bodies of water. The size of an isthmus can range from small to wide and long, connecting two continents. An isthmus can be contrasted with a strait, which is a narrow body of water or channel connecting two separate larger water bodies. To ease marine transport, a canal can be built across an isthmus. For instance, the Panama Canal has been built across the Isthmus of Panama in order to connect the Atlantic and Pacific Oceans. The Suez Canal is also significant, which connects the Red Sea to the Mediterranean Sea.


An isthmus can be formed in several ways depending on the geography of the area. Some isthmuses, like the Isthmus of Panama, are believed to have resulted from volcanic activities which created chains of islands. Over time, the islands blocked a channel and collected sediment, leading to the formation of the isthmus.

Other isthmuses may have resulted from the dislocation of tectonic plates, increasing water level along the fault line, and the action of waves and tides. The movement of tides and waves create a sandbar between the coastal island and the mainland. The sandbar is a unique isthmus known as a tombolo. An example of a tombolo is the Rock of Gibraltar, which is located at one of the entrances to the Mediterranean Sea.


Isthmuses have been of great importance, both and past. They have served as strategic locations for military and trade purposes, and have also become key locations for sports and the creation of canals to facilitate trade and movements across continents.

Noteable Examples

Some of the major isthmuses include the Isthmus of Panama, which is 30 miles wide at the narrowest point and joins the Americas. It was formed approximately 3 million years ago and separates the North Atlantic from the Pacific Ocean. The Isthmus of Suez is located in Egypt and connects Africa to Asia. It is 75 miles wide and separates the Mediterranean Sea and the Red Sea. Other major isthmuses include the Isthmus of Cape Cod, the Isthmus of Perekop, the Isthmus of Tehuantepec, and the Isthmus of Kra.


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