Red Sea

The Red Sea is one of Earth's most dynamic and interesting geological features. Its location and continuing geological activity make it essential in the geological history and development of both Africa and Asia and an important source of information about geological processes and their impacts.

General Description and Location

The Red Sea is one of several important seas associated with the Indian Ocean. It is almost totally landlocked by the Sinai Peninsula to the north; Egypt, Sudan, Eritrea, and Djibouti to the west; and Saudi Arabia and Yemen to the east. The southern end connects via Bab el-Mandeb, a thirty-two-kilometer strait that divides Yemen from Djibouti to the Gulf of Aden, leading to the Arabian Sea and thence to the Indian Ocean. The northern end splits into two small gulfs, the relatively shallow Gulf of Suez to the west and the much deeper Gulf of Aqaba to the east. In the north, the Gulf of Suez connects to the Mediterranean Sea via the Suez Canal, completed in 1869 after a ten-year effort that included the innovative use of three natural lakes and a set of canals.

The Red Sea is recognized as the major divide between the continents of Africa and Asia. Several islands, many of them exposed coral reefs, lie within its waters, particularly at the southern end. In the north, the Gulf of Aqaba is also bordered by Israel and Jordan; in the south, beyond Bab el-Mandeb, the Gulf of Aden is also bordered by Somalia.

A body of water with a brilliant blue-green hue, the Red Sea likely takes its name from the occasional blooms of the red algae Trichodesmium erythraeum, which, upon death, give the surrounding waters a reddish-brown tint. Other explanations that have been proposed include the reflection of the sun-burnished cliffs in its waters or the reddish skin color of populations living near it. Records of Ancient Egypt, Palestine, and Mesopotamia provide references indicating that the sea was termed “red” by the earliest civilizations within the region. However, at that time, it referred to an area extending all the way to the northwest coast of India (today’s Indian Ocean).

Geology

The Red Sea, technically a graben, is part of the African Rift Valley system or the Great Rift Valley, a major geological depression and fault zone on the surface. This is the point where the African and Arabian tectonic plates have been slowly tearing apart (rifting) under the influence of strong magmatic convection currents in the underlying mantle. Over time, this will eventually split the African continent into two separate landmasses, forming a new sea between them in the process. This large rift valley extends south from the Sinai Peninsula about 3,500 kilometers, reaching as far as Tanzania and north for about 450 kilometers, through the Jordan Rift Valley along the Dead Sea rift. The Red Sea valley itself cuts through a mass of Precambrian igneous (basalt) and metamorphic rocks known as the Arabian-Nubian Massif, the upper portions of which form the rugged mountains, technically known as steep fault scarps, which ring the sea. On top of the Precambrian rock strata sit layers of Paleozoic marine sediments laid down some 544 to 245 million years ago, as well as Mesozoic and Cenozoic sediments as much as 57 million years old.

The thirty-million-year-old Red Sea was created when the Arabian Peninsula began to break away from Africa and moved north in two distinct phases. The northern part of the Red Sea was created over ten million years. Subsequent geological movement commencing about three to four million years ago created the much deeper Gulf of Aqaba and the southern half of the Red Sea. The movement, which continues in the twenty-first century, adds about fifteen millimeters per year to the width of the Red Sea and supports unique forms of marine life among the hydrothermal vents in the deepest parts of the sea, where extensive volcanism and seismic activity occur. There are several active undersea volcanoes at the southern end just south of the Dahlak Archipelago, as well as a recently extinct volcano on the island of Jabal at-Ta’ir.

Five major types of mineral resources are present in the Red Sea region. Oil and natural gas deposits have been extensively tapped near the junction of the Gulf of Suez and the main body of the Red Sea. Evaporites such as halite, sylvite, gypsum, and dolomite are mined along the Sinai Peninsula, although not in proportion to what is available. Sulfur deposits have been extensively mined since the beginning of the twentieth century, while the phosphate deposits are of such a low grade that extraction techniques make them economically unattractive resources. There are extensive and valuable heavy-metal deposits in the deep portions of the Red Sea along the Atlantis II Deep basin, but these deposits are not yet commercially mined. Because they are found in the form of fluid oozes rather than solid rocks, it is believed that they may be able to be pumped up to the surface, although attempts to do so in more than a casual manner have proved elusive.

Physical Features and Climate

The Red Sea extends some 2,000 kilometers from north to south and is about 350 kilometers across at its widest point, near the southern end. Its maximum depth is about 3,000 meters, although there is an extensive continental shelf around the periphery of the entire sea that is no more than a few hundred meters deep.

The Red Sea contains some of the world’s hottest and saltiest waters, with an average temperature of 25 degrees Celsius (77 degrees Fahrenheit) and an average salinity of 40 parts per thousand. Little precipitation occurs in the area, although evidence exists that more significant precipitation occurred during some past periods. A remarkable circulatory system maintains the water level in the face of very high evaporation rates of more than two meters per year along its length and breadth. The denser, saltier water of the north sinks and flows south along the lower depths, while winds drive less dense and less salty waters (about 36 parts per thousand) above it northward from the shallow southern end of the strait of Bab el-Mandeb. This results in a complete replacement of the sea’s water about every twenty years. Underneath this exchange of saltwater, very deep in the central trough, brine with an average temperature of almost 60 degrees Celsius and a salinity of 257 parts per thousand rises from underground sources. This upward movement adds to the general circulation within the Red Sea and measurably increases its overall salinity.

Fierce windstorms can arise suddenly on the Red Sea, especially coming off the desert sands to the northwest, called the Egyptian winds. Daily air temperature ranges from 8 to 28 degrees Celsius during the fall, winter, and spring, with scorching highs of up to 40 degrees Celsius in July and August, accompanied by intense relative humidity.

Scientific and Economic Importance

The Red Sea provides scientists with a glimpse of geologic processes that likely occurred in the early stages of the formation of the Atlantic and Pacific Ocean basins during the breakup of Pangaea some 250 million years ago. The continuing movement of the Arabian plate northward adds to the width of the Red Sea each year in a small but measurable way. It provides a living laboratory to observe ongoing volcanic and seismic activity associated with the evolution of crustal margins, along with the action of hydrothermal vents. The Red Sea’s complex water chemistry and geology have been the focus of many scientific expeditions in the modern era, including those conducted in such submersibles as the Swedish Albatross (1948) and the American Glomar Challenger (1972), the latter of which drilled and removed core samples from some of the sea’s deepest locations.

The undersea vents and the extreme saltiness of the Red Sea support a unique and varied marine life, including spectacular coral reefs, notably the Protector Reef near Port Sudan, Ras Muhammad at the southern tip of the Sinai (one of the top ten diving spots in the world), and the Daedalus Reef parallel with Aswan, Egypt. Vibrantly colored exotic fish and an abundance of rare and endangered species of marine life found nowhere else in the world attract visitors from all over the globe.

Thousands of species of fish and invertebrates and hundreds of types of coral have been identified within its teeming waters. Its natural beauty has been a lure for divers since ancient times, and it has recently become a popular subject of nature films and a playground for underwater photography enthusiasts. Scientists continued to study marine life in the Red Sea in the twenty-first century. In 2022, one of the most extensive studies of marine life in the Red Sea was released, highlighting the waters' biodiversity and the coral reefs' brilliance. Though some areas were in dire condition, the study found many thriving plants and animals in the waters.

The Red Sea has been important since ancient times as a commercial and cultural waterway that provides access to and from Africa, Arabia, and the Indian subcontinent. This is despite the danger posed by its many reefs that lie just below the surface and the need to keep the southern channel open at Bab el-Mandeb Strait by blasting and dredging regularly. From the time of Seti I (d. 1279 Before the Common Era BCE) and Ramses II (ca. 1303 BCE–1213 BCE), the Egyptians used shallow canals to connect the Red Sea to branches of the Nile River delta and permit the easy passage of goods via sea rather than by an arduous land route through blistering desert sands. The Greek, Roman, and early Muslim empires continued this practice until the end of the eighth century Common Era (CE).

The modern Suez Canal has assured the Red Sea a critical place in world commerce. However, hostilities among Arab nations, Israel, and African nations sometimes led to the complete closure of this important sea artery during the twentieth century. The Israel-Palestine conflict, which began with Hamas' attack on Israel on October 7, 2023, has had dire consequences for the Red Sea. In solidarity with Palestinians in Gaza, the Yemen-based Houthis have launched attacks on shipping vessels tied to Israel in the Red Sea. This has caused significant disruption to global trade as traffic in the Red Sea has decreased by 40 percent since the outbreak of the conflict. This issue prompted the United States to launch Operation Prosperity Guardian to protect Red Sea shipping routes. Finally, due to the ability of the Red Sea to connect many nations in the region, fears surrounding the proliferation of the conflict beyond Israel and Palestine have been voiced. 

Major seaports in the Red Sea include Suez and El Suweis in Egypt, Jiddah in Saudi Arabia, Elat in Israel, Al Aqabah in Jordan, Massawa in Eritrea, and Bur Sudan and Suakin in Sudan. Fishing, a major regional industry producing more than eight thousand metric tons per year, is supported by the extensive reefs that plunge thousands of meters to the ocean floor.

Principal Terms

asthenosphere: the layer of the mantle immediately beneath the lithosphere; the asthenosphere exists in an almost “plastic” state and therefore behaves like a very thick liquid

continental shelf: the gentle slope that extends from the coast into the ocean, generally to a depth of about 500 meters at the continental slope

graben: a down-thrown block of rock between two steeply angled normal faults

hydrothermal vent: an undersea location where superheated liquid and gases are released because of volcanic activity

Pangaea: the supercontinent that geologists hypothesize existed about 280 million years ago, when all the landmasses of the world were one

rift: a graben on a very large scale that results in a massive depression in the ground surface with steep sides; the most famous is the Great Rift Valley, which extends from Turkey in Asia to Mozambique in Africa

salinity: the amount of dissolved salts present in seawater, usually expressed in parts per thousand

seismic activity: movements occurring within the crust that often cause various other geological phenomena to occur

Bibliography

Al-Goidi, Faozi, and Oumeyma Chelbi. “Conflict in the Red Sea Makes Economic Waves.” Middle East Council on Global Affairs, 22 Feb. 2024, mecouncil.org/blog‗posts/conflict-in-the-red-sea-makes-economic-waves. Accessed 22 July 2024.

Ambraseys, N. N., C. P. Melville, and R. D. Adams. The Seismicity of Egypt, Arabia and the Red Sea: A Historical Review. New York: Cambridge UP, 1994.

Bland, Archie. “Israel-Gaza War: Will the Red Sea Crisis Lead to a Wider Middle East Conflict?” The Guardian, 2 Jan. 2024, www.theguardian.com/world/2024/jan/02/israel-gaza-war-risk-wider-conflict-us-iran-houthi-ships-red-sea. Accessed 22 July 2024.

Coleman, Robert G. Geologic Evolution of the Red Sea. New York: Oxford UP, 1993.

Edwards, Alasdair J., and Stephen M. Head. Red Sea. New York: Pergamon, 1987.

Ehteshami, Anoushiravan, and Emma C. Murphy. The International Politics of the Red Sea. New York: Routledge, 2011.

“Red Sea Crisis, Gaza Conflict Pose Threat to Progress, Stability in Yemen, Speakers Tell Security Council.” Meetings Coverage and Press Releases, 15 Apr. 2024, press.un.org/en/2024/sc15661.doc.htm. Accessed 22 July 2024.

Silva, Luis. “Largest Environmental Study of the Red Sea Coast Sets New Standard.” The Maritime Executive, 10 Nov. 2022, maritime-executive.com/editorials/largest-environmental-study-of-the-red-sea-coast-sets-new-standard-1. Accessed 15 Apr. 2023.

Speakman, Simon. “Have the Houthi Red Sea Attacks Hurt Israel's Economy?” Al Jazeera, 13 Jan. 2024, www.aljazeera.com/news/2024/1/13/have-the-houthi-red-sea-attacks-hurt-israels-economy. Accessed 22 July 2024.

Taylor, Leighton R. The Red Sea. Woodbridge: Blackbirch, 1998.

Tregenza, Leo Arthur. The Red Sea Mountains of Egypt & Egyptian Years. 1955, 1958. Cairo: American U in Cairo P, 2004.

Zahran, M. A. Climate-Vegetation: Afro-Asian Mediterranean and Red Sea Coastal Lands. Edited by F. Gilbert. New York: Springer, 2010.