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Strait of Gibraltar

The Strait of Gibraltar as seen from space
(North is to the left: Spain is on the left and Africa on the right)

A view across the Strait of Gibraltar taken from the hills above Tarifa, Spain

The Strait of Gibraltar (Arabic: ???? ??? ????, Spanish: Estrecho de Gibraltar) is the strait that connects the Atlantic Ocean to the Mediterranean Sea and separates Spain from Morocco. The name comes from Gibraltar, which in turn originates from the Arabic Jebel Tariq (??? ????) meaning mountain of Tariq. It refers to the Ummayad Berber general Tariq ibn-Ziyad who led the Islamic conquest of Hispania in 711.^[1] It is also known as the Straits of Gibraltar or STROG (Strait Of Gibraltar), the latter being in naval use.^[2]

There are 13 km (8 miles) of ocean separating Europe from Africa at the strait's narrowest point. The strait depth ranges between 300 and 900 meters.^[3] A ferry commutes between the two continents. The Spanish part of the strait is protected under the El Estrecho Natural Park

Location
Geology
Communications

Tunnel across the strait

Inflow and outflow
Resources
See also
External links
References and notes

Location

Europe and Africa from Gibraltar

On the northern side of the Strait is Spain and Gibraltar, while on the southern side is Morocco and Ceuta, a Spanish exclave in North Africa. Its boundaries were known in antiquity as the Pillars of Hercules. There are several small islands, such as the disputed Isla Perejil, that are claimed by both Spain and Morocco.^[4].

Due to its location, the strait is widely used for illegal immigration from Africa to Europe.

Geology

About 6 million years ago, the Strait closed, effectively turning the Mediterranean into a huge salty lake that eventually dried up, in what is known as the Messinian Salinity Crisis. At the Miocene/Pliocene boundary, approximately 5.33 million years ago, the Strait opened up for the last time, and has remained open since.^[5]

Communications

The Straits are an important shipping route from the Mediterranean to the Atlantic. There are ferries that operate between Spain and Morocco across the strait, as well as between Spain and Ceuta and Gibraltar to Tangier.

Tunnel across the strait

In December 2003, Spain and Morocco agreed to explore the construction of an undersea rail tunnel to connect their rail systems. The gauge of the tunnel would be 1435 mm to match the proposed construction and conversion of significant parts of the existing broad gauge system to standard gauge. ^[6]

Inflow and outflow

Internal waves (marked with arrows) caused by the Strait of Gibraltar

On a net basis, water continually flows eastward into and through the Strait of Gibraltar, due to an evaporation rate within the Mediterranean basin higher than the combined inflow of all the rivers that empty into it. The sill of the Strait of Gibraltar acts to limit mixing between the cold, less saline Atlantic water and the warm Mediterranean waters. The latter are so much saltier that they sink below the constantly incoming Atlantic water and form a highly saline (thermohaline, both warm and salty) bottom water, called the Mediterranean outflow. A density boundary separates the layers at about 100 m depth. It flows out and down the continental slope, losing salinity, until it equilibrates after mixing at a depth of about 1000 meters. The Mediterranean outflow water can be traced for thousands of kilometers before losing its identity.

Internal waves (waves at the density boundary layer) are common in the strait. Like traffic merging on a highway, the water flow is constricted in both directions because it must pass over a shallow submarine barrier, the Camarinal Sill. When large tidal flows enter the Strait, internal waves are set off at the Camarinal Sill as the high tide relaxes. The waves?sometimes with heights up to 100 m?travel eastward. Even though the waves occur at great depth and the height of the waves at the surface is almost nothing, they can be traced in the sunglint because they concentrate the biological films on the water surface, creating slight differences in roughness. The waves flow eastward, refract around coastal features; can be traced for as much as 150 km, and sometimes create interference patterns with refracted waves.^[7]

Resources

Cetacea in the strait

The place is very interesting for eolic power production, windsurfing and cetacea seeing.

External links

Climate Control Requires a Dam at the Strait of Gibraltar — American Geophysical Union, 1997. Accessed 26 February 2006.
Project for a Europe-Africa permanent link through the Strait of Gibraltar — United Nations Economic and Social Council, 2001. Accessed 26 February 2006.
Map of Morocco — Multimap.com, 2006. Accessed 26 February 2006.
Estudios Geogr�ficos del Estrecho de Gibraltar — La Universidad de Tetu�n and La Universidad de Sevilla. Accessed 26 February 2006.