Encyclopedic Entry

Storms may make isthmuses like this one dangerous places to live.

Photograph by Ajay Ravi, My Shot

Biological Isthmus
You have a dozen isthmuses inside you right now! In anatomy, an isthmus is the narrow connection between organs. The isthmus of the fauces, for instance, is where the back of your mouth meets your throat.

Passing Through
It takes ships about 8-10 hours to cross the Isthmus of Panama through the Panama Canal. About 14,000 ships make the crossing between the Atlantic and Pacific Oceans every year.

An isthmus is a narrow strip of land that connects two larger landmasses and separates two bodies of water. 
 
Isthmuses have been strategic locations for centuries. They are natural sites for ports and canals linking terrestrial and aquatic trade routes. Isthmuses are also key sites for communications and cultural exchange, as well as military outposts.
 
Isthmuses
 
The Isthmus of Panama in Panama links the continents of North and South America, and separates the Pacific and Atlantic Oceans. The Panama Canal stretches 77 kilometers (48 miles) across the isthmus, and allows cargo ships to travel from eastern North America to western North America without having to go around South America. The Panama Canal revolutionized shipping and travel in the 20th century, allowing for faster and more efficient transportation of goods and people.
 
The Isthmus of Suez in eastern Egypt connects the continents of Africa and Asia, and separates the Mediterranean and Red Seas. The Suez Canal is 192 kilometers (119 miles) long and allows cargo ships to travel between Europe, North Africa, western Asia (via the Mediterranean Sea in the north) and eastern and southern Asia without having to go around Africa. The Suez Canal facilitated trade and travel in the 19th century, and continues to define the oil trade today.
 
The city of Seattle, Washington, is located on an isthmus between the Puget Sound (part of the Pacific Ocean) and Lake Washington. The region has been continuously inhabited for more than 4,000 years. The earliest settlers of the area were the Duabish, who settled near the ocean, and the Hachuabish, who settled near the freshwater lake. European settlers, who quickly saw the isthmus' potential for trade along the west coast of North America as well as across the Pacific, collectively referred to these Native Americans as the Duwamish.
 
Tombolos
 
Tombolos are a type of isthmus. A tombolo forms as tides and waves create a thin strip of land between a coastal island and the mainland. The island connected to the mainland in a tombolo is called a tied island. (The built-up sandbar "ties" the island to the mainland.)
 
Mount Maunganui, New Zealand, is a tombolo town located on a sandbar connecting the volcanic island of Mauao to the mainland. Mauao is an extinct volcano, and is a popular spot for hiking and sightseeing the local beaches. Those beaches offer diverse opportunities due to the tombolo formation. Beaches on the side of Mount Maunganui's isthmus facing Tauranga Harbor are calm and protected. Beaches on the other side of Mount Maunganui face the open ocean (the Pacific), with dramatic waves that are popular with surfers.
 
Perhaps the most famous tombolo is the Rock of Gibraltar, a tied island narrowly connected to the southwestern tip of Europe's Iberian Peninsula. The Rock of Gibraltar is the northern part of the "Pillars of Hercules," which form the narrow western entrance to the Mediterranean Sea. This strategic location has made the Rock of Gibraltar a key site for traders and explorers since the Phoenicians. Today, the Rock of Gibraltar borders Spain, but is part of the British territory of Gibraltar.

Vocabulary

Term Part of Speech Definition Encyclopedic Entry

aquatic

Adjective

having to do with water.

beach

Noun

narrow strip of land that lies along a body of water.

Encyclopedic Entry: beach

border

Verb

to exist on the edge of a boundary.

canal

Noun

artificial waterway.

cargo

Noun

goods carried by a ship, plane, or other vehicle.

city

Noun

large settlement with a high population density.

coast

Noun

edge of land along the sea or other large body of water.

Encyclopedic Entry: coast

collective

Adjective

combined or unified.

communication

Noun

sharing of information and ideas.

continent

Noun

one of the seven main land masses on Earth.

Encyclopedic Entry: continent

define

Verb

to identify or associate with.

diverse

Adjective

varied or having many different types.

efficient

Adjective

performing a task with skill and minimal waste.

extinct volcano

Noun

volcano that will no longer erupt.

facilitate

Verb

to help or make easier.

harbor

Noun

part of a body of water deep enough for ships to dock.

Encyclopedic Entry: harbor

inhabit

Verb

to live in a specific place.

isthmus

Noun

narrow strip of land connecting two larger land masses.

Encyclopedic Entry: isthmus

landmass

Noun

large area of land.

military

Noun

armed forces.

ocean

Noun

large body of salt water that covers most of the Earth.

Encyclopedic Entry: ocean

oil

Noun

fossil fuel formed from the remains of marine plants and animals. Also known as petroleum or crude oil.

open ocean

Noun

area of the ocean that does not border land.

outpost

Noun

settlement or station located in a remote area.

peninsula

Noun

piece of land jutting into a body of water.

Encyclopedic Entry: peninsula

port

Noun

place on a body of water where ships can tie up or dock and load and unload cargo.

Encyclopedic Entry: port

potential

Noun

possibility.

region

Noun

any area on the Earth with one or more common characteristics. Regions are the basic units of geography.

Encyclopedic Entry: region

revolutionize

Verb

to completely change a process or way of doing something.

sandbar

Noun

underwater or low-lying mound of sand formed by tides, waves, or currents.

sea

Noun

large part of the ocean enclosed or partly enclosed by land.

Encyclopedic Entry: sea

settler

Noun

person who migrates and establishes a residence in a largely unpopulated area.

shipping

Noun

transportation of goods, usually by large boat.

site

Noun

specific place where something is located.

sound

Noun

body of water, larger than a bay, partially surrounded by land.

strategic

Adjective

important part of a place or plan.

terrestrial

Adjective

having to do with the Earth or dry land.

territory

Noun

land an animal, human, or government protects from intruders.

tide

Noun

rise and fall of the ocean's waters, caused by the gravitational pull of the moon and sun.

Encyclopedic Entry: tide

tied island

Noun

island permanently linked to the mainland through a narrow strip of sand built up through the action of waves and tides.

tombolo

Noun

coastal landform created as waves and tides create a narrow, permanent isthmus between a coastal island and the mainland.

trade route

Noun

path followed by merchants or explorers to exchange goods and services.

transportation

Noun

movement of people or goods from one place to another.

volcanic island

Noun

land formed by a volcano rising from the ocean floor.

wave

Noun

moving swell on the surface of water.

Credits

Media Credits

The audio, illustrations, photos, and videos are credited beneath the media asset, except for promotional images, which generally link to another page that contains the media credit. The Rights Holder for media is the person or group credited.

Editor

Jeannie Evers

Producer

Caryl-Sue, National Geographic Society

Sources

Dunn, Margery G. (Editor). (1989, 1993). "Exploring Your World: The Adventure of Geography." Washington, D.C.: National Geographic Society.

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