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Strait of Gibraltar

geography Maturity 7-9 Next article →

The Strait of Gibraltar is a vital narrow waterway. It connects the Atlantic Ocean to the Mediterranean Sea. This strait also serves as a physical boundary between Europe and Africa.

The Strait of Gibraltar, April 2023
The Strait of Gibraltar, April 2023

On the northern side, you will find Spain and the British overseas territory of Gibraltar. To the south lie Morocco and the Spanish city of Ceuta. At its narrowest point, the distance between the continents is only 7.7 nautical miles. This is equal to 14.2 kilometers or 8.9 statute miles. Because the distance is so short, ferries cross the water daily. Some trips take as little as 35 minutes.

The water movements within the strait are quite complex. This movement is caused by evaporation, water temperatures, tides, and wind. The flow occurs in two different directions at once. Surface waters with lower salinity and density flow east into the Mediterranean. This is known as the Mediterranean inflow. This happens because evaporation in the Mediterranean is higher than the water added by rivers and rain.

InternalWaves Gibraltar ISS009-E-09952 54
InternalWaves Gibraltar ISS009-E-09952 54

Meanwhile, a smaller amount of deeper water flows west into the Atlantic. This is the Mediterranean outflow. This water is much saltier and denser than the Atlantic water. It sinks below the incoming surface water and forms a thermohaline layer. This layer can be traced for thousands of kilometers west of the strait.

A specific geological feature controls these currents. It is called the Camarinal Sill. This is the shallowest part of the strait at its western end. The sill limits how the cold Atlantic water mixes with the warm Mediterranean water.

Camarinal Still Water Mixing (Simplified)
Camarinal Still Water Mixing (Simplified)

The erosion caused by these incoming waters helped create the current depth of the strait. The seabed is made of Betic-Rif clayey flysch. This is covered by calcareous sediments from cold water coral communities. Strong bottom currents are also visible through exposed bedrock and sand dunes.

The history of the strait is very long. Neanderthals inhabited the area 125,000 years ago. The Rock of Gibraltar may have been one of their last outposts. Evidence shows they lived there as recently as 24,000 years ago. Throughout history, many groups have used the short crossing. These include the Carthaginians, Romans, Vandals, and Moors.

Strait of Gibraltar by Piri Reis
Strait of Gibraltar by Piri Reis

In 1492, a Spanish force overthrew the last Muslim government north of the strait. This event helped create distinct cultures on either side. The north became primarily Christian-European. The south remained primarily Muslim-Arabic. The British enclave of Gibraltar adds a third cultural group to the region.

Geologically, the strait has changed many times. About 5.97 million years ago, the connection to the Atlantic was restricted. This led to the Messinian salinity crisis. During this time, the Mediterranean became almost completely closed. This caused the salinity to rise as minerals precipitated in layers on the seabed. This process lasted about 640,000 years. Eventually, the connection was reestablished about 5.33 million years ago. This event is known as the Zanclean flood.

Strait of Gibraltar perspective multilang
Strait of Gibraltar perspective multilang

Scientists believe the African Plate moving north could close the strait again in the future.

The strait is also a very important area for biodiversity. It is an Important Bird Area for BirdLife International. Hundreds of thousands of seabirds migrate through the water every year. These include Atlantic puffins, razorbills, and several types of gulls.

StraitOfGibraltar
StraitOfGibraltar

There is also a resident pod of about 36 orcas. This is one of the few such pods left in Western European waters. However, the pod may face extinction due to long-term PCB pollution.

Today, the strait remains a major shipping route. It is a busy corridor for international trade. There have been many discussions about connecting the continents with a tunnel. In the 1980s, Spain and Morocco began discussing a tunnel. In 2003, they agreed to explore an undersea rail tunnel. This would connect their existing rail systems. While the project has faced many delays, leaders met again in 2021 to resume discussions. The United Nations Convention on the Law of the Sea also protects the area. It ensures foreign vessels and aircraft have freedom of navigation through the strait.

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🖼️ Images & Media (6)
File:The Strait of Gibraltar, April 2023.jpg
The Strait of Gibraltar, April 2023.jpg
File:StraitOfGibraltar.JPG
StraitOfGibraltar.JPG
File:Strait of Gibraltar by Piri Reis.jpg
Strait of Gibraltar by Piri Reis.jpg
File:Strait of Gibraltar perspective multilang.svg
Strait of Gibraltar perspective multilang.svg
File:InternalWaves Gibraltar ISS009-E-09952 54.jpg
InternalWaves Gibraltar ISS009-E-09952 54.jpg
File:Camarinal Still Water Mixing (Simplified).jpg
Camarinal Still Water Mixing (Simplified).jpg
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