Isthmus

An isthmus is a narrow strip of land connecting two larger land masses which is bounded by water on two sides.  The word has its origins from the Greek word isthmós which means “neck.”

Two notable isthmuses are the Isthmus of Panama which separates the continents of North America and South America and the Isthmus of Suez which divides Africa from Asia.


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Building canals to cross isthmuses is fairly common.  The Panama canal cuts a 77-kilometer (48 miles) long swath through that isthmus, connecting sea travel between the Pacific and Atlantic Oceans.   The Suez Canal, which is 192 kilometers (119 miles) long, allows ship traffic between the Red and Mediterranean Seas.

Shaded-relief map showing the Panama Canal with the Pacific Ocean in the foreground and the Caribbean Sea in the distance. Source: NASA.

Shaded-relief map showing the Panama Canal with the Pacific Ocean in the foreground and the Caribbean Sea in the distance. Source: NASA.

A tombolo is an isthmus formed when tides and waves connect a coastal island (known as a tied-island) to a mainland.   The word originates from the Latin word tumulus, meaning ‘mound’.

The Angel Road of Shōdo Island visible at low tide connects this island to the mainland of Japan. Photo: 663highland, Wikimedia.

The Angel Road of Shōdo Island visible at low tide connects this island to the mainland of Japan. Photo: 663highland, Wikimedia.

The most famous tombolo is the Rock of Gibraltar which is connected to the Iberian Peninsula.

Map showing the Rock of Gibraltar. Source: CIA World Factbook

Map showing the Rock of Gibraltar. Source: CIA World Factbook