Red Sea

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east the Gulf of Aqaba (Eilat). At its southern end is the Bab el-Mandeb ("Gate of Lamentation"), a strait 16mi/26km wide which gives access to the Gulf of Aden and thence to the Indian Ocean.

The Red Sea occupies a tertiary rift valley running from northwest to southeast through the table land of North Africa and Arabia, continued to the north by the Jordan Valley and to the south by the rift system of East Africa. The whole region shows the volcanic phenomena characteristic of recent fault zones. Reflecting its geological origin, the coast falls steeply down, with few intermediate steps or shelves. The coastline is relatively featureless, with only a few inlets usable as harbors. On both sides are mighty mountain ridges rising to 6,560ft/2,000m. The coasts are fringed by long coral banks and reefs which constitute a hazard for shipping.

As a result of the meagre inflow of freshwater and the high rate of evaporation the salt content of the water is considerably higher than in other seas, ranging from 2-4% in the Gulf of Suez to 3-65% off the island of Perim in the Bab el-Mandeb. In general the salt content increases from the surface towards the bottom. An unusual phenomenon, discovered by a scientific expedition in 1964, is a body of water of exceptionally high salinity, 3-6mi/5-10km long and 330ft/100m thick, lying at a depth of over 6,560ft/2,000m in latitude 21°30' north and longitude 38°6' east; the salt content, at a temperature of 140 °F/60 °C, was no less than 33%.

The marine currents in the Red Sea, flowing north on the Arabian side and south on the African side, are subject to the influence of the monsoon. Counter currents at different levels carry highly saline deep water into the Indian Ocean and surface water of low salinity from the Indian Ocean into the Red Sea. There is a tidal movement averaging 24in/0.6m at the north end of the Red Sea, rising to 83in/2.1m at the spring tides.

The Red Sea is the warmest of all seas, with a water temperature on the surface of up to 95 °F/35 °C, with a constant 71 °F/21.5 °C at greater depths. The color of the water normally ranges between deep blue and greenish blue, though there may be variations caused by the presence of minerals or algae.

The climate is hot, with only scanty and sporadic rainfall. The high rate of evaporation produces a relatively high air humidity. At the height of summer temperatures regularly rise above 104 °F/40 °C in the shade, but during the winter months the heat is tempered at the north end of the sea by the strong northerly and north-westerly winds then prevailing in this area. In the south the monsoon winds, blowing from the north in summer and from the south in winter, bring a measure of relief.

The name "Red Sea" (Latin Mare Rubrum, a name found only in the Late Roman period) has been variously interpreted, being explained by reference to the reddish color of the rocks along its shores, or to the reddish coloring imparted to the water at certain points by algae (Trichodesmium erythraeum), or again to the ancient designation of northeast Africa as the land of the "red tribes".

In antiquity the northern part of the Red Sea was the principal route for trade between Asia and North Africa. In the Middle Ages the maritime trade of the great European commercial cities (Venice, Pisa, Genoa, etc.) with the East Indies passed through the Red Sea. After the discovery of America and of new routes to East Asia, however, the importance of the Red Sea route which in any case might on occasion be interrupted by political circumstances suffered a rapid and lasting decline, to recover only with the opening of the Suez Canal in 1869. Although in ancient times the Red Sea was one of the world's most important and busiest seaways, its coasts, with their lack of fresh water, offered little scope for permanent human settlement. Only a few ports and trading posts, mostly quite small, were established in these inhospitable regions where the desert reached right down to the coast. In recent years, however, the Red Sea coast with its beautiful empty beaches and magnificent diving grounds has begun to be cautiously developed for the tourist trade, and modern holiday colonies have been established at Ain Sukhna and Hurghada.