An isthmus (/ˈɪsməs, ˈɪsθməs/;[1] pl. isthmuses or isthmi; from Ancient Greek ἰσθμός (isthmós) 'neck')[2] is a narrow piece of land connecting two larger areas across an expanse of water by which they are otherwise separated.[3] A tombolo is an isthmus that consists of a spit or bar, and a strait is the sea counterpart of an isthmus, a narrow stretch of sea between two landmasses that connects two larger bodies of water.
Isthmus and land bridge are related terms, with isthmus having a broader meaning. A land bridge is an isthmus connecting Earth's major land masses. The term land bridge is usually used in biogeology to describe land connections that used to exist between continents at various times and were important for the migration of people and various species of animals and plants, e.g. Beringia and Doggerland.[4]
An isthmus is a land connection between two bigger landmasses, while a peninsula is rather a land protrusion that is connected to a bigger landmass on one side only and surrounded by water on all other sides. Technically, an isthmus can have canals running from coast to coast (e.g. the Panama Canal), and thus resemble two peninsulas; however, canals are artificial features distinguished from straits.
The world's major isthmuses include:
Of historic importance were:
The cities of Auckland, Manila, Seattle, and Madison, Wisconsin are located on isthmuses.
Canals are often built across isthmuses, where they may be a particularly advantageous shortcut for marine transport. For example:
