Isthmus

An isthmus is a narrow strip of land that connects two larger lands and separates two bodies of water. The term comes from the Greek isthmos, meaning a neck or narrow land bridge. Isthmuses play a key role in shaping transportation routes, climate patterns, and regional ecosystems, as they can channel trade and migration while influencing marine and coastal environments on either side.

Form and classification note that an isthmus contrasts with a peninsula, which extends into water from the mainland, and with a strait, which is a waterway connecting two bodies of water. An isthmus may form through tectonic uplift, sediment deposition, and changes in sea level, or be reinforced and modified by human activity, such as canal construction or road and rail networks that link the two shores.

Notable examples include the Isthmus of Panama, which connects North and South America and separates the Caribbean Sea from the Pacific Ocean; it hosts the Panama Canal, a major global maritime route. The Isthmus of Suez links Africa and Asia and separates the Mediterranean Sea from the Red Sea, where the Suez Canal allows direct navigation between the Indian Ocean and the Mediterranean. Other historically important isthmuses include the Isthmus of Corinth in Greece, the Isthmus of Kra in Thailand, and the Isthmus of Tehuantepec in Mexico. Isthmuses can become focal points for biodiversity and climate regulation, and they remain vulnerable to sea-level rise and coastal erosion.

See also: geographical landforms, peninsulas, canals.