About world geography

The Sahara desert is the largest desert in the world. Sahara means "big desert" in Arabic. Located in the south of Atlas Mountains and Mediterranean Sea, it is about 14(250mm isohyet) north latitude, starting from the Atlantic coast in the west and the Red Sea coast in the east. Spanning the northern part of the African continent, it is 5,600 kilometers long from east to west and 1.600 kilometers wide from north to south, covering an area of about 9.6 million square kilometers, accounting for about 32% of the total area of Africa.

There are many types of arid landforms in the Sahara desert. It consists of rocky desert (rocky desert), gravel desert and desert. Rocky deserts are mostly distributed in the high-lying areas in the central and eastern Sahara, and are mainly composed of large sandstone, limestone, chalk and basalt, or bare rocks or only a thin layer of rock debris. For example, the stony desert in TinHeurte, the stony desert in Chamra and the stony desert in Shafia, and the Nubian desert east of the Nile is mainly stony desert.

Gravel desert is mostly found between rocky desert and desert, and mainly distributed in rocky areas in piedmont alluvial fan areas such as Libyan desert, Atlas mountain and Kuxishan mountain, such as Tibesti gravel desert, Kalancho gravel desert and Getousai gravel desert. Desert is the most extensive, except for a few mountains and plateaus, which are widely distributed everywhere.

The famous deserts are Libyan Desert, Leibuyanai Desert, Obari Desert, Eastern and Western Algerian Desert, Shesh Desert, Zhu Fu Desert, Alvana Desert and Bilma Desert. The larger area is called "sand sea", which consists of complex and regular sand dunes with complex and diverse shapes, including tall fixed sand dunes, low flowing sand dunes and large areas of fixed and semi-fixed sand dunes. Fixed dunes are mainly distributed in the south near grasslands and Atlantic coast. From Libya to Algeria, it is a quicksand area. The flowing sand dunes are constantly moving with the wind. In the Sahara desert, it is observed that mobile sand dunes move 9 meters every year.

The Sahara region is vast and sparsely populated, with an average of less than 1 person per square kilometer. Mainly Arabs, followed by Berbers, etc. Residents and agricultural production are mainly distributed in the Nile valley and oasis, and some are mainly nomadic. Since 1950s, abundant minerals have been found in the desert, such as oil, natural gas, uranium, iron, manganese and phosphate. With the large-scale exploitation of mineral resources, the economic outlook of some countries in this region has changed. For example, Libya and Algeria have become the world's major oil producers, and Niger has become a famous uranium producer. Road networks, air lines and new settlements have also appeared in the desert.

The earliest subway

The earliest subway in the world was built in 1863 in London, England, with a trunk line length of 6 kilometers. Because the electric locomotive had not come out at that time, the locomotive traction was still steam locomotive. Despite the smog in the tunnel, people are still scrambling to sit, and more than 9.5 million passengers were transported that year.

The country with the longest subway.

There are subways in eight cities in Britain, with a total length of nearly 1000 km and 458 stations, which is the longest country at present.

The shortest subway

The total length of Istanbul subway in Turkey is only 0.6 kilometers, with two and a half stations.

The subway with the largest passenger flow

The San Francisco subway is the most modern subway in the world today. The running speed of subway is128km, which is the highest in the world.

The deepest subway

Due to geological reasons, the subway in Pyongyang, North Korea is 70 to 80 meters deep from the ground.

The most convenient subway

The subway in Moscow is the most convenient, with long operation time, frequent departure, fast running speed, comfortable ride, low fare and convenient transfer, which is world-class.

The most luxurious subway

The subway station in Paris, France is famous all over the world. It is built under the railway station, with exquisite architectural design and advanced technology and equipment, and is known as the "underground palace".