The saltiest sea in the world, would you like to have a taste?

Produced by: Science Popularization China

Author: Blue Ocean Team

Producer: China Science Expo

Between northern Africa and the Arabian Peninsula, there is a bright red sea, the Red Sea. It is a subsidiary sea of ​​the Indian Ocean. The Red Sea is like a crocodile with its mouth wide open, lying diagonally from northeast to southeast. The northern section is connected to the Mediterranean Sea through the Suez Canal, and the southern end is connected to the Gulf of Aden through the Bab el-Mandeb Strait. The red algae in the sea will reproduce seasonally, turning the entire sea water reddish brown. Sometimes even the sky and the coast are reflected in bright red, which makes a deep impression on people, so it is called the Red Sea. In fact, under normal circumstances, the sea water is blue-green.

(Photo source: Xinhuanet)

After the opening of the Suez Canal in 1869, the Red Sea became the main route between the Indian Ocean and the Mediterranean Sea and an important international shipping route; it shortened the original route around the Cape of Good Hope by 9,000 kilometers.

The Red Sea is a young sea. About 20 million years ago, the Arabian Peninsula separated from Africa, giving birth to the Red Sea. It can still be seen that the shapes of the two banks are very similar, which is the trace left by the continent being torn apart. The rift between the African plate and the Arabian plate passes through the middle of the Red Sea bottom. In the past 3-4 million years, the two plates have continued to separate, and the two banks have expanded outward at an average rate of 2.2 cm per year. The Red Sea is constantly widening and may become a new ocean in the future.

The geometric discontinuity of the coastlines on both sides of the Afar Triangle region on the edge of the Red Sea is very telling. About 25 million years ago, today's Yemen was exactly between Laobia and Somalia. After the central expansion and separation, the crustal fragments on both sides of the Danakil horst were formed, forming the Afar Triangle region.

In 1947, the Swedish survey ship "Albatross" visited the Red Sea and discovered several heat sources in the seafloor rift. Later, the American "Atlantis II" and the British "Discoverer" also came here to investigate and confirmed the existence of these heat sources. They measured the water temperature here as high as 56°C and the salinity as high as 74-310. Under normal circumstances, the water temperature of tropical sea surface is generally only 30°C at most, and the deep water is generally only 4°C. The salinity of seawater is generally around 35. In the rift of the Red Sea, the water temperature is more than ten times higher and the salinity is 2-9 times higher, which is really surprising. Therefore, the Red Sea is the saltiest sea area known so far.

Why did such an abnormal situation occur? Scientists have argued that due to the continuous expansion of the rift valley, the lava from the mantle flowed out, heating the seawater that seeped down along the cracks; a large amount of minerals and dissolved salts also took the opportunity to dissolve into the seawater. In these hot seawaters, there are rich polymetallic minerals such as iron, manganese, zinc and lead, which are called hydrothermal deposits. After the results of the investigation were announced, they attracted the attention of the world; the Sudanese government first proposed the ownership of these seabed minerals. However, it is not easy to mine these minerals 2,000 meters underwater, so it is still a paper plan.

(Photo source: China Daily)

The Red Sea is located in a tropical desert climate zone. The annual rainfall in the north is only 28 mm, which is really pitiful, and in the south it is only 127 mm. Every drop of water is as precious as oil. However, the evaporation here is very large, with an annual average of about 2100 mm, which is much greater than the precipitation. In addition, there are no rivers flowing into the Red Sea, which makes the Red Sea water inadequate. It must be supplemented by the water flow from the Indian Ocean; the Gulf of Aden has become a "large reservoir" to regulate the water level of the Red Sea. The water entering the Gulf of Aden from the Indian Ocean flows northward and enters the thirsty Red Sea to supplement its insufficient water source. The high temperature and high salt water of the Red Sea also continuously passes through the bottom of the Bab el-Mandeb Strait and flows to the Gulf of Aden, becoming an important source of high temperature and high salt water in the Indian Ocean.