Cartography Word of the Day: Isthmus

A narrow area between two bigger masses-but not necessarily defined by water

The word isthmus does indeed have a certain necessary meaning. An isthmus, properly, is an area of land bounded on two sides by water that serves to connect two larger land masses.

The Peloponnese, highlighting the Isthmus of Cornith (NASA MODIS)

Even the comparatively geographically-uninformed could come up with at least a couple of examples: the isthumus of Panama, which is considered the boundary between North and South America and hosts a certain strategically important canal; the isthmus of Suez, which demarcs the Suez Peninsula from the main part of Egypt (as well as northease Africa from southwest Asia) and also hosts a strategically important canal.

There are other isthmi which are at least locally and regionally important and bear mentioning:

• Isthmus of Tehuantepec: in south-central Mexico, the shortest distance between the Gulf of Mexico and the Pacific Ocean, considered the natural boundary between Central America and the main part of North America.
• Isthmus of Chignecto: Connects the Nova Scotian mainland to North America.
• Isthmus of Perekop: Connects the Crimean Peninsula to mainland Ukraine.
• Madison Isthmus: between Lakes Mendota and Monona in Wisconsin, contains the central business district and governmental quarter of the Wisconsin state capital of Madison.
• Auckland Isthmus: defines the city of Auckland, New Zealand, on the north and south, connects the northern peninsula of NZ’s North Island to its main section

The precise meaning of the word is unclear, but the source is not: the word comes from a feature called the Isthmus of Corinth. a neck of land 6.3 km (3.91 mi) through at its narrowest point. This eponymous example forms the union between the contintenal peninsular of Greece and the Peloponnese Peninsula (refer to the illustration above), though some would argue that the Peloponnese is properly now as island since the construction across that isthmus of the Corinth Canal in 1891.

Political Isthmi

To this definition we would add isthmi created by political necessity. Areas such as the “Chicken’s Neck” in northeastern India (more properly known as the Siliguri Corridor, after the region’s most prominent city) are notable because of their smallness when compared to the great size of the rest of the country which it is part of.

India, highlighting the “Chicken’s Neck” or Siliguri Corridor (CIA Factbook

The Chicken’s Neck forms the bridge between the main part of India and its landlocked northeastern states. It is remarkable indeed that India, a country that measures 2,933 km (1,822 miles) from east to west and 3,214 km (1,997 miles) from north to south is united to its northeastern extremity by a strip of territory merely 21 km (approx 13 mi) wide. All land transportation between central India and its northeastern states must use this corridor, as open trade with Bangladesh does not yet exist.

Reference: Wikipedia entries on Isthmus, Chicken’s Neck