Strait of Gibraltar

Last updated
Strait of Gibraltar
STS059-238-074 Strait of Gibraltar.jpg
The Strait of Gibraltar as seen from space.
The Iberian Peninsula is on the left and North Africa on the right.
Location Atlantic Ocean   Mediterranean Sea
Coordinates 35°58′N5°29′W / 35.967°N 5.483°W / 35.967; -5.483 Coordinates: 35°58′N5°29′W / 35.967°N 5.483°W / 35.967; -5.483
Type Strait
Native nameمضيق جبل طارق  (Arabic)
Estrecho de Gibraltar  (Spanish)
Basin  countries
Min. width14.3 km (8.9 mi)
Max. depth900 metres (2,953 ft)

The Strait of Gibraltar (Arabic : مضيق جبل طارق, romanized: Maḍīq Jabal Ṭāriq; Spanish : Estrecho de Gibraltar) is a narrow strait that connects the Atlantic Ocean to the Mediterranean Sea and separates Gibraltar and Peninsular Spain in Europe from Morocco in Africa.


The two continents are separated by 14.3 kilometres (8.9 mile s; 7.7 nautical mile s) of ocean at the Strait's narrowest point. The Strait's depth ranges between 300 and 900 metres (980 and 2,950 feet ; 160 and 490 fathom s) [1] which possibly interacted with the lower mean sea level of the last major glaciation 20,000 years ago [2] when the level of the sea is believed to have been lower by 110–120 m (360–390 ft; 60–66 fathoms). [3] Ferries cross between the two continents every day in as little as 35 minutes. The Spanish side of the Strait is protected under El Estrecho Natural Park.

Names and etymology

The name comes from the Rock of Gibraltar, which in turn originates from the Arabic Jabal Ṭāriq (meaning "Tariq's Mount"), [4] named after Tariq ibn Ziyad. It is also known as the Straits of Gibraltar, the Gut of Gibraltar (although this is mostly archaic), [5] the STROG (STRait Of Gibraltar) in naval use, [6] and Bāb al-Maghrib (Arabic: باب المغرب), "Gate of Morocco". In the Middle Ages, Muslims called it Az-Zuqāq (الزقاق), "the Passage", the Romans called it Fretum Gaditanum (Strait of Cadiz), [7] and in the ancient world it was known as the "Pillars of Hercules" (Ancient Greek : αἱ Ἡράκλειοι στῆλαι, romanized: hai Hērákleioi stêlai). [8]


Europe (left) and Africa (right) Detroit Gibraltar 2007.jpg
Europe (left) and Africa (right)

On the northern side of the Strait are Spain and Gibraltar (a British overseas territory in the Iberian Peninsula), while on the southern side are Morocco and Ceuta (a Spanish autonomous city in northern Africa). Its boundaries were known in antiquity as the Pillars of Hercules.

Due to its location, the Strait is commonly used for illegal immigration from Africa to Europe. [9]


The International Hydrographic Organization defines the limits of the Strait of Gibraltar as follows: [10]

On the West. A line joining Cape Trafalgar to Cape Spartel.
On the East. A line joining Europa Point to P. Almina.


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

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. [11] 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, [12] 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, [12] and such an event would lay down mineral deposits like the salt deposits now found under the sea floor all over the Mediterranean.

After a lengthy period of restricted intermittent or no water exchange between the Atlantic Ocean and Mediterranean basin, approximately 5.33 million years ago, [13] the Atlantic-Mediterranean connection was completely reestablished through the Strait of Gibraltar by the Zanclean flood, and has remained open ever since. [14] The erosion produced by the incoming waters seems to be the main cause for the present depth of the Strait (900 m (3,000 ft; 490 fathoms) at the narrows, 280 m (920 ft; 150 fathoms) at the Camarinal Sill). The Strait is expected to close again as the African Plate moves northward relative to the Eurasian Plate,[ citation needed ] but on geological rather than human timescales.


The Strait has been identified as an Important Bird Area by BirdLife International because of the hundreds of thousands of seabirds which use it every year to migrate between the Mediterranean and the Atlantic, including significant numbers of Scopoli's and Balearic shearwaters, Audouin's and lesser black-backed gulls, razorbills, and Atlantic puffins. [15]

A resident killer whale pod of some 36 individuals lives around the Strait, one of the few that are left in Western European waters. The pod may be facing extinction in the coming decades due to long term effects of PCB pollution. [16]


Historic map of the Strait of Gibraltar by Piri Reis Strait of Gibraltar by Piri Reis.jpg
Historic map of the Strait of Gibraltar by Piri Reis

Evidence of the first human habitation of the area by Neanderthals dates back to 125,000 years ago. It is believed that the Rock of Gibraltar may have been one of the last outposts of Neanderthal habitation in the world, with evidence of their presence there dating to as recently as 24,000 years ago. [17] Archaeological evidence of Homo sapiens habitation of the area dates back c.40,000 years.

The relatively short distance between the two shores has served as a quick crossing point for various groups and civilizations throughout history, including Carthaginians campaigning against Rome, Romans travelling between the provinces of Hispania and Mauritania, Vandals raiding south from Germania through Western Rome and into North Africa in the 5th century, Moors and Berbers in the 8th–11th centuries, and Spain and Portugal in the 16th century.

Beginning in 1492, the Strait began to play a certain cultural role in acting as a barrier against cross-channel conquest and the flow of culture and language that would naturally follow such a conquest. In that year, the last Muslim government north of the Strait was overthrown by a Spanish force. Since that time, the Strait has come to foster the development of two very distinct and varied cultures on either side of it after sharing much the same culture for over 300 years from the 8th century to the early 13th century.[ citation needed ]

On the northern side, Christian-European culture has remained dominant since the expulsion of the last Muslim kingdom in 1492, along with the Romance Spanish language, while on the southern side, Muslim-Arabic/Mediterranean has been dominant since the spread of Islam into North Africa in the 700s, along with the Arabic language. For the last 500 years, religious and cultural intolerance, more than the small travel barrier that the Strait presents, has come to act as a powerful enforcing agent of the cultural separation that exists between these two groups.[ citation needed ]

The small British enclave of the city of Gibraltar presents a third cultural group found in the Strait. This enclave was first established in 1704 and has since been used by Britain to act as a surety for control of the sea lanes into and out of the Mediterranean.

Following the Spanish coup of July 1936 the Spanish Republican Navy tried to blockade the Strait of Gibraltar to hamper the transport of Army of Africa troops from Spanish Morocco to Peninsular Spain. On 5 August 1936 the so-called Convoy de la victoria was able to bring at least 2,500 men across the Strait, breaking the republican blockade. [18]


3-d rendering, looking eastwards towards the Mediterranean. Hercules3D.jpg
3-d rendering, looking eastwards towards the Mediterranean.

The Strait is 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 across the Strait. The gauge of the rail would be 1,435 mm (4 ft 8.5 in) to match the proposed construction and conversion of significant parts of the existing broad gauge system to standard gauge. [19] While the project remains in a planning phase, Spanish and Moroccan officials have met to discuss it as recently as 2012, [20] and proposals predict it could be completed by 2025.

Special flow and wave patterns

The Strait of Gibraltar links the Atlantic Ocean directly to the Mediterranean Sea. This direct linkage creates certain unique flow and wave patterns. These unique patterns are created due to the interaction of various regional and global evaporative forces, tidal forces, and wind forces.

Inflow and outflow

The Strait of Gibraltar with the Mediterranean Sea in upper right. Internal waves (marked with arrows) are caused by water flowing through the Strait (bottom left, top right). InternalWaves Gibraltar ISS009-E-09952 54.jpg
The Strait of Gibraltar with the Mediterranean Sea in upper right. Internal waves (marked with arrows) are caused by water flowing through the Strait (bottom left, top right).

Through the Strait, water generally flows more or less continually in both an eastward and a westward direction. A smaller amount of deeper saltier and therefore denser waters continually work their way westwards (the Mediterranean outflow), while a larger amount of surface waters with lower salinity and density continually work their way eastwards (the Mediterranean inflow). These general flow tendencies may be occasionally interrupted for brief periods by temporary tidal flows, depending on various lunar and solar alignments. Still, on the whole and over time, the balance of the water flow is eastwards, due to an evaporation rate within the Mediterranean basin higher than the combined inflow of all the rivers that empty into it.[ citation needed ] At the Strait's far western end is the Camarinal Sill, the Strait's shallowest point which limits mixing between the cold, less saline Atlantic water and the warm Mediterranean waters.

The Mediterranean waters are so much saltier than the Atlantic waters that they sink below the constantly incoming water and form a highly saline ( thermohaline , both warm and salty) layer of bottom water. This layer of bottom-water constantly works its way out into the Atlantic as the Mediterranean outflow. On the Atlantic side of the Strait, a density boundary separates the Mediterranean outflow waters from the rest at about 100 m (330 ft; 55 fathoms) depth. These waters flow out and down the continental slope, losing salinity, until they begin to mix and equilibrate more rapidly, much further out at a depth of about 1,000 m (3,300 ft; 550 fathoms). The Mediterranean outflow water layer can be traced for thousands of kilometres west of the Strait, before completely losing its identity.

Simplifed and stylized diagram of currents at the Camarinal Sill Camarinal Still Water Mixing (Simplified).jpg
Simplifed and stylized diagram of currents at the Camarinal Sill

During the Second World War, German U-boats used the currents to pass into the Mediterranean Sea without detection, by maintaining silence with engines off. [21] From September 1941 to May 1944 Germany managed to send 62 U-boats into the Mediterranean. All these boats had to navigate the British-controlled Strait of Gibraltar where nine U-boats were sunk while attempting passage and 10 more had to break off their run due to damage. No U-boats ever made it back into the Atlantic and all were either sunk in battle or scuttled by their own crews. [22]

Internal waves

Internal waves (waves at the density boundary layer) are often produced by the Strait. Like traffic merging on a highway, the water flow is constricted in both directions because it must pass over the Camarinal Sill. When large tidal flows enter the Strait and the high tide relaxes, internal waves are generated at the Camarinal Sill and proceed eastwards. Even though the waves may occur down to great depths, occasionally the waves are almost imperceptible at the surface, at other times they can be seen clearly in satellite imagery. These internal waves continue to flow eastward and to refract around coastal features. They can sometimes be traced for as much as 100 km (62 mi; 54 nmi), and sometimes create interference patterns with refracted waves. [23]

Territorial waters

Except for its far eastern end, the Strait lies within the territorial waters of Spain and Morocco. The United Kingdom claims 5.6 km (3.5 mi; 3.0 nmi) around Gibraltar on the northern side of the Strait, putting part of it inside British territorial waters. As this is less than the 22.2 km (13.8 mi; 12.0 nmi) maximum, it means, according to the British claim, that part of the Strait lies in international waters. The ownership of Gibraltar and its territorial waters is disputed by Spain. Similarly, Morocco disputes Spanish sovereignty over Ceuta on the southern coast. [24] There are several islets, such as the disputed Isla Perejil, that are claimed by both Morocco and Spain. [25]

Under the United Nations Convention on the Law of the Sea, vessels passing through the strait do so under the regime of transit passage, rather than the more limited innocent passage allowed in most territorial waters. [24] [26]

Power generation

Some studies have proposed the possibility of erecting tidal power generating stations within the Strait, to be powered from the predictable current at the Strait.

In the 1920s and 1930s, the Atlantropa project proposed damming the Strait to generate large amounts of electricity and lower the sea level of the Mediterranean by several hundreds of meters to create large new lands for settlement. [27] This proposal would however have devastating effects on the local climate and ecology and would dramatically change the strength of the West African Monsoon.

See also

Related Research Articles

Atlantic Ocean Ocean between Europe, Africa and the Americas

The Atlantic Ocean is the second largest of the world's oceans, with an area of about 106,460,000 square kilometers. It covers approximately 20 percent of Earth's surface and about 29 percent of its water surface area. It separates the "Old World" from the "New World".

Mediterranean Sea Sea connected to the Atlantic Ocean between Europe, Africa and Asia

The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Southern Europe and Anatolia, on the south by North Africa and on the east by the Levant. Although the sea is sometimes considered a part of the Atlantic Ocean, it is usually referred to as a separate body of water. Geological evidence indicates that around 5.9 million years ago, the Mediterranean was cut off from the Atlantic and was partly or completely desiccated over a period of some 600,000 years before being refilled by the Zanclean flood about 5.3 million years ago.

Geography of Morocco

Morocco spans from the Mediterranean Sea and Atlantic Ocean on the north and the west respectively, into large mountainous areas in the interior body, to the Sahara desert in the far south. Morocco is a Northern African country, located in the extreme north west of Africa on the edge of continental Europe. The strait of Gibraltar separates Spain off Morocco with a 13 kilometres (8.1 mi) span of water. Morocco borders the North Atlantic Ocean to the west, and the west Mediterranean Sea to the north.

North Atlantic Deep Water deep water mass formed in the North Atlantic Ocean

North Atlantic Deep Water (NADW) is a deep water mass formed in the North Atlantic Ocean. Thermohaline circulation of the world's oceans involves the flow of warm surface waters from the southern hemisphere into the North Atlantic. Water flowing northward becomes modified through evaporation and mixing with other water masses, leading to increased salinity. When this water reaches the North Atlantic it cools and sinks through convection, due to its decreased temperature and increased salinity resulting in increased density. NADW is the outflow of this thick deep layer, which can be detected by its high salinity, high oxygen content, nutrient minima, high 14C/12C, and chlorofluorocarbons (CFCs).

Endorheic basin Closed drainage basin that allows no outflow

An endorheic basin is a limited drainage basin that normally retains water and allows no outflow to other external bodies of water, such as rivers or oceans, but converges instead into lakes or swamps, permanent or seasonal, that equilibrate through evaporation. Such a basin may also be referred to as a closed or terminal basin or as an internal drainage system or interior drainage basin.

Physical oceanography The study of physical conditions and physical processes within the ocean

Physical oceanography is the study of physical conditions and physical processes within the ocean, especially the motions and physical properties of ocean waters.

Thermohaline circulation A part of the large-scale ocean circulation that is driven by global density gradients created by surface heat and freshwater fluxes

Thermohaline circulation (THC) is a part of the large-scale ocean circulation that is driven by global density gradients created by surface heat and freshwater fluxes. The adjective thermohaline derives from thermo- referring to temperature and -haline referring to salt content, factors which together determine the density of sea water. Wind-driven surface currents travel polewards from the equatorial Atlantic Ocean, cooling en route, and eventually sinking at high latitudes. This dense water then flows into the ocean basins. While the bulk of it upwells in the Southern Ocean, the oldest waters upwell in the North Pacific. Extensive mixing therefore takes place between the ocean basins, reducing differences between them and making the Earth's oceans a global system. The water in these circuits transport both energy and mass around the globe. As such, the state of the circulation has a large impact on the climate of the Earth.

Indonesian Throughflow Ocean current that provides a low-latitude pathway for warm, relatively fresh water to move from the Pacific to the Indian Ocean

The Indonesian throughflow (ITF) is an ocean current with importance for global climate since it provides a low-latitude pathway for warm, fresh water to move from the Pacific to the Indian Ocean and this serves as the upper branch of the global heat conveyor belt. Higher ocean surface topography in the western Pacific than in the Indian Ocean drives upper thermocline water from the North Pacific through the western route of the Makassar Strait to either directly exit through the Lombok Strait or flow eastward into the Banda Sea. Weaker flow of saltier and denser South Pacific water passes over the Lifamatola Passage into the Banda Sea, where these water masses are mixed due to tidal effects, Ekman pumping, and heat and fresh water flux at the ocean surface. From the Banda Sea the ITF exits Timor, Ombai, and Lombok passages.

In geomorphology, an outburst flood — a type of megaflood — is a high-magnitude, low-frequency catastrophic flood involving the sudden release of a large quantity of water. During the last deglaciation, numerous glacial lake outburst floods were caused by the collapse of either ice sheets or glaciers that formed the dams of proglacial lakes. Examples of older outburst floods are known from the geological past of the Earth and inferred from geomorphological evidence on Mars. Landslides, lahars, and volcanic dams can also block rivers and create lakes, which trigger such floods when the rock or earthen barrier collapses or is eroded. Lakes also form behind glacial moraines, which can collapse and create outburst floods.

Jebel Musa (Morocco) mountain

Jebel Musa is a mountain in the northernmost part of Morocco, on the African side of the Strait of Gibraltar. It is part of the Rif mountain chain. The mountain is generally identified as the southern Pillar of Hercules, Abila Mons.

Alboran Sea The westernmost portion of the Mediterranean Sea, lying between the Iberian Peninsula and the north of Africa

The Alboran Sea is the westernmost portion of the Mediterranean Sea, lying between the Iberian Peninsula and the north of Africa. The Strait of Gibraltar, which lies at the west end of the Alboran Sea, connects the Mediterranean with the Atlantic Ocean.

The Messinian Salinity Crisis (MSC), also referred to as the Messinian Event, and in its latest stage as the Lago Mare event, was a geological event during which the Mediterranean Sea went into a cycle of partly or nearly complete desiccation throughout the latter part of the Messinian age of the Miocene epoch, from 5.96 to 5.33 Ma. It ended with the Zanclean flood, when the Atlantic reclaimed the basin.

Norwegian Current A current that flows northeasterly along the Atlantic coast of Norway into the Barents Sea

The Norwegian Current is a water current that flows northeasterly along the Atlantic coast of Norway at depths of between 50 and 100 metres through the Barents Sea Opening into the Barents Sea. It contrasts with the North Atlantic Current because it is colder and contains less salt, having most of its tributary water coming from the slightly brackish North and Baltic seas, as well as the Norwegian fjords and rivers. It is, however, considerably warmer and saltier than the Arctic Ocean, which is freshened by the ice in and around it. Winter temperatures in the Norwegian current are typically between 2 and 5 °C whereas the temperature of the Atlantic water exceeds 6 °C.

Strait of Gibraltar crossing railway tunnel

The Strait of Gibraltar crossing is a hypothetical bridge or tunnel spanning the Strait of Gibraltar that would connect Europe and Africa. The governments of Spain and Morocco appointed a joint committee to investigate the feasibility of linking the two continents in 1979, which resulted in the much broader Euromed Transport project.

El Estrecho Natural Park

El Estrecho Natural Park is a natural park in Spain, located on the northern side of the Strait of Gibraltar.

Camarinal Sill

The Camarinal Sill is the sill separating the Mediterranean Sea and the Atlantic Ocean. This threshold is the shallowest seafloor pass between the Iberian Peninsula and Africa. It is located approximately 25 km west of the narrowest section of the Strait of Gibraltar and 20km east of the Espartel Sill, at 35°56′N5°45′W, at an elevation of −280 m.

Atlantropa proposed German megaproject

Atlantropa, also referred to as Panropa, was a gigantic engineering and colonisation idea devised by the German architect Herman Sörgel in the 1920s and promoted by him until his death in 1952. Its central feature was a hydroelectric dam to be built across the Strait of Gibraltar, which would have provided enormous amounts of hydroelectricity and would have led to the lowering of the surface of the Mediterranean Sea by up to 200 metres (660 ft), opening up large new lands for settlement, for example in the Adriatic Sea. The project proposed four additional major dams as well:

Estuarine water circulation is controlled by the inflow of rivers, the tides, rainfall and evaporation, the wind, and other oceanic events such as an upwelling, an eddy, and storms. Estuarine water circulation patterns are influenced by vertical mixing and stratification, and can affect residence time and exposure time.

Orlando Fernández, a.k.a. "The Puerto Rican Aquaman", is the first Puerto Rican swimmer to cross the Strait of Gibraltar.

Zanclean flood Theoretical refilling of the Mediterranean Sea between the Miocene and Pliocene Epochs

The Zanclean flood or Zanclean deluge is a flood theorized to have refilled the Mediterranean Sea 5.33 million years ago. This flooding ended the Messinian salinity crisis and reconnected the Mediterranean Sea to the Atlantic Ocean, although it is possible that even before the flood there were partial connections to the Atlantic Ocean. The reconnection marks the beginning of the Zanclean age.


  1. See Robinson, Allan Richard and Paola Malanotte-Rizzoli, Ocean Processes in Climate Dynamics: Global and Mediterranean Examples. Springer, 1994, p. 307, ISBN   0-7923-2624-5.
  2. Würm glaciation [ better source needed ]
  3. Cosquer cave [ better source needed ]
  4. Chisholm, Hugh, ed. (1911). "Gibraltar"  . Encyclopædia Britannica . 11 (11th ed.). Cambridge University Press. p. 938.
  5. Google Books Ngram Viewer results "Strait of Gibraltar/Gut of Gibraltar"
  6. See, for instance, Nato Medals: Medal for Active Endeavor, awarded for activity in the international water of the Mediterranean and STROG.
  7. Pamphlet of the Museum of the Castle of Guzman el Bueno, [El Ayuntamiento de Tarifa] accessed 16 November 2016.
  8. Strabo Geographia 3.5.5.
  9. "Migration Information Source – The Merits and Limitations of Spain's High-Tech Border Control". Retrieved 2011-07-15.
  10. "Limits of Oceans and Seas, 3rd edition" (PDF). International Hydrographic Organization. 1953. Retrieved 7 February 2010.
  11. De Mol, B., et al. 2012. Ch. 45: Cold-Water Coral Distribution in an Erosional Environment: The Strait of Gibraltar Gateway, in: Harris, P.T., Baker, E.K. (Eds.), Seafloor geomorphology as benthic habitat: GEOHAB Atlas of seafloor geomorphic features and benthic habitats. Elsevier, Amsterdam, pp. 636–643
  12. 1 2 Messinian salinity crisis#Evidence
  13. At the Miocene/Pliocene boundary, c. 5.33 million years before the present
  14. Cloud, P., Oasis in space. Earth history from the beginning, New York: W.W. Norton & Co. Inc., p. 440. ISBN   0-393-01952-7
  15. "BirdLife Data Zone". Retrieved 2019-02-23.
  16. editor, Damian Carrington Environment (2018-09-27). "Orca 'apocalypse': half of killer whales doomed to die from pollution". The Guardian. ISSN   0261-3077 . Retrieved 2019-02-23.CS1 maint: extra text: authors list (link)
  17. "Last of the Neanderthals". National Geographic. October 2008. Retrieved 2009-12-29.
  18. Antony Beevor (2006) [1982]. The Battle for Spain. Orion. ISBN   978-0-7538-2165-7.
  19. "Europe-Africa rail tunnel agreed". BBC News.
  20. "Tunnel to Connect Morocco with Europe". February 17, 2012. Archived from the original on 2012-11-04.
  21. Paterson, Lawrence. U-Boats in the Mediterranean 1941–1944. Chatham Publishing, 2007, pp. 19 and 182. ISBN   9781861762900
  22. "U-boat war in the Mediterranean". Retrieved 2011-07-15.
  23. Wesson, J. C.; Gregg, M. C. (1994). "Mixing at Camarinal Sill in the Strait of Gibraltar". Journal of Geophysical Research . 99 (C5): 9847–9878. Bibcode:1994JGR....99.9847W. doi:10.1029/94JC00256.
  24. 1 2 Víctor Luis Gutiérrez Castillo (April 2011). The Delimitation of the Spanish Marine Waters in the Strait of Gibraltar (PDF) (Report). Spanish Institute for Strategic Studies. Retrieved 5 July 2019.
  25. Tremlett, Giles, "Moroccans seize Parsley Island and leave a bitter taste in Spanish mouths", in The Guardian , 13 July 2002.
  26. Donald R Rothwell. "Gibraltar, Strait of". Oxford Public International Law. Oxford University Press. Retrieved 6 July 2019.
  27. "Atlantropa: A plan to dam the Mediterranean Sea". Xefer blog. 16 March 2005. Retrieved on 13 August 2012.