The Strait of Gibraltar

The Strait of Gibraltar connects the Atlantic Ocean with the Mediterranean Sea and separates Spain on the European continent from Morocco on the African continent. It is 36 miles (58 km) long and narrows to 8 miles (13 km) in width between Point Marroquí (Spain) and Point Cires (Morocco). The strait’s western extreme is 27 miles (43 km) wide between the capes of Trafalgar (north) and Spartel (south), and the eastern extreme is 14 miles (23 km) wide between the Pillars of Heracles—which have been identified as the Rock of Gibraltar to the north and one of two peaks to the south: Mount Hacho (held by Spain), near the city of Ceuta, a Spanish exclave in Morocco; or Jebel Moussa (Musa), in Morocco. The strait is an important gap, averaging 1,200 feet (365 metres) in depth in the arc formed by the Atlas Mountains of North Africa and the high plateau of Spain.

The winds in the strait tend to be either easterly or westerly. Shallow cold-air masses, invading the western Mediterranean from the north, often stream through as a low-level, high-speed easterly wind, known locally as a levanter. There is also a significant exchange of water through the strait. A surface current flows eastward through the centre of the channel, except when affected by easterly winds. This surface movement exceeds a westward flow of heavier, colder, and more saline water, which takes place below a depth of about 400 feet (120 metres). Thus, only the existence of the strait prevents the Mediterranean from becoming a shrinking salt lake.

The seabed of the Strait is composed of synorogenic Betic-Rif clayey flysch covered by Pliocene and/or Quaternary calcareous sediments, sourced from thriving cold water coral communities.[14] Exposed bedrock surfaces, coarse sediments and local sand dunes attest to the strong bottom current conditions at the present time.

Around 5.9 million years ago,[15] the connection between the Mediterranean Sea and the Atlantic Ocean along the Betic and Rifan Corridor was progressively restricted until its total closure, effectively causing the salinity of the Mediterranean to rise periodically within the gypsum and salt deposition range, during what is known as the Messinian salinity crisis. In this water chemistry environment, dissolved mineral concentrations, temperature and stilled water currents combined and occurred regularly to precipitate many mineral salts in layers on the seabed. The resultant accumulation of various huge salt and mineral deposits about the Mediterranean basin are directly linked to this era. It is believed that this process took a short time, by geological standards, lasting between 500,000 and 600,000 years.

It is estimated that, were the Strait closed even at today’s higher sea level, most water in the Mediterranean basin would evaporate within only a thousand years, as it is believed to have done then,[15] and such an event would lay down mineral deposits like the salt deposits now found under the sea floor all over the Mediterranean.

Editorial Desk