What Does Isthmus Mean in Geography?

The word Isthmus is a geographic term given to a narrow strip of land that connects the two large bodies of land and separates two large bodies of water. The word Isthmus came from an ancient Greek word “isthmus” which means “neck”.

To get a clear sense, visualize the location of Panama. It is situated in the narrow strip of land and connects the two large landmasses North and South Americas. Also, it separates two large bodies of water the Pacific and Atlantic Oceans. Therefore, that geographic location is known as Isthmus of Panama.

It will be much effective to define isthmus using an illustration as provided below:

The image of the Panama Isthmus
The Isthmus of Panama/ credit: Wikimedia

What is the importance of Isthmus?

Isthmuses are important for two primary reasons. Firstly, they enable land-based transportation to pass from one landmass to the other. For example, Isthmus of Panama allows business and civilian transportations to go from North America to South America, or another way around without using ships. In a way, isthmuses serve as natural bridges that connect landmasses so people and transportations can go back and forth between two landmasses.

The second importance is that isthmus is narrow enough to build a water passage across it. You may have already heard about the Panama Canal. It is a man-made canal. The U.S government built to connect the Atlantic with Pacific Oceans with the intention of shortening the maritime routes. If there wasn’t an isthmus between two Americas, it would have been too labor-intensive or even impossible to build a canal to connect two oceans.

Can you realize how much digging would be required to run a canal all the way across either North or South America? The answer is, of course, too much. For instance, the United States spent 10 years as well as a huge amount of resources to build the Panama Canal in the Panama Isthmus. As a result, the water passage shortened the maritime routes. Previously, ships traveled around South America to get to the Pacific Ocean or vise-Versa.


Formation of Isthmus

Isthmuses are formed as results of tectonic activities. More specifically, tectonic movements causes volcanic and mountain-building activities. In a simpler language, two tectonic plates collide with each other and the force of collision leads to the formation of underwater volcanoes. Some of those underwater volcanoes create volcanic islands during the extended time. Meanwhile, a collision of the tectonic plates pushes the seafloor upward making some sections of it come out of water. Over the extent of millions of years, strong ocean currents fills up the gaps between those islands by depositing seafloor sediments. Through this process, small volcanic islands join together and attach to the bigger landmasses creating an isthmus.

For example, twenty million years ago, the Panama Isthmus did not exist. The waters of the Pacific and Atlantic Oceans covered the area of current-day Panama. This means North and South Americas weren’t attached together during that time. However, 15 million years ago, the Pacific plate collided with the Caribbean and South American plates leading to the appearance of several volcanic islands in that area. Eventually, 3 million years ago, those small islands converged creating the present-day Panama Isthmus.


Isthmus Examples

We already discussed the Isthmus of Panama, but it is not the only Isthmus in the world. I provided several other isthmuses as an example.

  1. The Isthmus of Suez.

I pretty sure when you heard the word Suez, you thought of a Suez Canal. Because similar to the Panama Canal, the Suez Canal was also constructed across Isthmus; however, we have to travel to a different continent to observe it.

The Isthmus of Suez locates between Egypt and Africa. More specifically, it connects the African and Asian continents and separates the Red and Mediterranean seas. Thanks to the construction of the Suez Canal, cargo ships from Europe, Northern Africa, and Asia can travel between the Asian and African continents without having to go around the African continent.

  1. The Isthmus of Tehuantepec

To be categorized as an isthmus, a strip of land does not have to connect huge landmasses such as continents. Isthmuses can exist within a single country. The Isthmus of Tehuantepec is a good example of this. It locates within the Mexican territory and separates the Gulf of Mexico from the Pacific Ocean. And it joins the two parts of Mexico. For the sake of clarity, you may refer to a map provided below.

Illustration of Tehuantepec Isthmus
An illustration of Tehuantepec Isthmus
  1. The Isthmus of Corinth

The Isthmus of Corinth is one of the major Isthmuses. It connects the Peloponnese peninsula with the Greece mainland. the isthmus separates the Saronic Gulf from the Gulf of Corinth. Similar to Panama and Suez Isthmuses, the Isthmus of Corinth also has a canal. It is called the Corinth Canal.

The history of the Corinth Canal is pretty interesting. Because most of the ancient leaders who ruled the area attempted to build a canal across the Isthmus of Corinth. For example, Roman Emperor Nero brought 6000 slaves to dig up a canal in this Isthmus. But all of that effort was vain. He died, and his successor Galba abandoned the project considering it to be too costly. The construction of the Corinth Canal was completed only When Greece took Independence from Ottoman Empire.

A picture of the Corinth Canal that crosses the Corinth Isthmus
A picture of the Corinth Canal
  1. The Karelian Isthmus.

The Karelian Isthmus is the 30-70 miles (45-110 km) wide strip of land that locates in the Finnish and Russian border. It connects Russia with Finland. And it separates the Gulf of Finland and Lake Ladoga.

  1. The Kra Isthmus

The Kra Isthmus is one of the notable Isthmuses in Asia. It locates between the Gulf of Thailand and the Andaman Sea. The isthmus connects the Malay Peninsula with Thailand.

We mentioned that governments built a canal across most of isthmuses. However, Kra Isthmus does not have a canal yet but there is a proposal to build one. However, the project hasn’t started yet. If they build a canal across the Kra Isthmus, it will connect the Andaman Sea to the Gulf of Thailand or another way around.


Do not confuse Strait with Isthmus

Strait is another geographic term. Some people think that strait and isthmus are the same things. In fact, they are different. As we defined above, an isthmus connects two landmasses and separates two bodies of water. Contrary to an isthmus, strait separates two landmasses and joins two bodies of water.


Is Florida Isthmus?

The correct answer is No. Florida is not an isthmus. It is a peninsula.  According to the geographic definition, isthmus should connect two landmasses as a land bridge. Florida is a single landmass surrounded by water in three fronts.



American Association for the Advancement of Science


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By Arslan Batyrovich

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