Meaning of Isthmus Explained with Examples

The term isthmus is derived from the Greek word isthmós, meaning 'narrow neck of land'.

The Bering Strait land bridge theory on settlement of Americas, which suggests that early humans from Asia used a land bridge to migrate to the Americas, aptly highlights the importance of these geological structures for humans. Modern-day land bridges joining two masses of land do exist. They are known as isthmuses. They are not as large as the ones that existed in the past, but still play a crucial role in shaping a region.

In geography, an isthmus is a narrow strip of land with water on either sides, which connects two large masses of land. An isthmus is primarily formed as result of tectonic movement and volcanic activity. At times, even the erosion and deposition activity of wind and water can lead to the formation of this landform.

Erosion results in the formation of an isthmus when a specific stretch of land is made of softer material, and thus, erodes faster than the adjacent landmass.

Additionally, there is a geographic feature known as tombolo, which is often considered a type of isthmus. In this case, the narrow piece of land is usually a strip or bar, connecting an island to the mainland. These islands are thus called tied islands. These deposition landforms form as a result of the action of waves and tides.

As isthmuses are narrow, it's easier to build navigable canals across them to facilitate transportation. Among the several trans-isthmian canals across the world, two in particular are very famous: the Panama Canal across the Isthmus of Panama, and the Suez Canal across the Isthmus of Suez. It's also worth noting that these landforms are of strategic importance in the field of trade and commerce, as well as from a defense perspective.

The most famous example of an isthmus in the world is the Isthmus of Panama, which connects the continent of North America to South America. This landform, dubbed as the isthmus that changed the world, separated the Pacific Ocean from the Atlantic Ocean, and led to the formation of the Gulf Stream.

It is also credited for the Great American Interchange, a paleozoogeographic event marked by the migration of North American species to South America, and vice versa, and the current climate of this region.

The 75-mile-wide Isthmus of Suez lies between the Mediterranean Sea and the Red Sea, and connects the continents of Asia and Africa. If the entire Isthmus of Panama lies in the Central American nation of Panama, the entire Isthmus of Suez lies in Egypt―a transcontinental country, lying partly in Africa and partly in Asia.

The Suez Canal on this isthmus, which opened in November 1869, forms the backbone of maritime transportation in the Middle East. It allows ships to travel between Asia and Europe without having to navigate around the continent of Africa, thus reducing the distance of the entire journey by 4,300 miles.

In Asia, there is the Kra Isthmus connecting the Malay Peninsula with the mainland of Asia, with the Andaman Sea to the west and the Gulf of Thailand to the east. In 1677, the construction of a canal, then known as the Kra Canal project, was contemplated to link the Andaman Sea with the Gulf of Thailand.

There has been no development since then, except that the site of the project has been shifted from the Kra Isthmus, and renamed the Thai Canal Project.

In Canada, there is the Isthmus of Chignecto, which connects the Nova Scotia Peninsula to North America, and separates the Bay of Fundy from the Gulf of St. Lawrence. It is mere 15 miles wide at its narrowest point. The most interesting thing about the Isthmus of Chignecto is its elevation above sea level, which is so low that a mere 12 meter rise in sea level can flood the isthmus, and turn Nova Scotia into an island.

The Eaglehawk Neck, simply called the neck at times, is an isthmus linking the Forestier Peninsula to the Tasman Peninsula in Australia. It separates the Pirates Bay from the Eaglehawk Bay. It is not just narrow―measuring mere 30 meters at its narrowest point, but also very small, with a length of just 400 meters.

If an isthmus is a narrow strip of land connecting two large masses of land, a strait is a naturally formed narrow channel of water connecting two large bodies of water. Yet another difference between the two is that, an isthmus lies between two bodies of water, while a strait lies between two masses of land.

Some of the most famous straits in the world are the Strait of Gibraltar, connecting the Mediterranean Sea
and the Atlantic Ocean; Strait of Magellan, connecting the Atlantic and Pacific Oceans; and the Strait of Hormuz, linking the Gulf of Oman and the Persian Gulf.