The earth's surface is divided by the mainland into vast interconnected waters called oceans, with a total area of about 360 million square kilometers, accounting for about 7 1% of the earth's surface area, with an average water depth of about 3795 meters. The ocean contains more than1350 million cubic kilometers of water, accounting for about 97% of the total water of the earth, and only 2% is available for human consumption.
The four oceans of the earth are the Pacific Ocean, the Atlantic Ocean, the Indian Ocean and the Arctic Ocean, and most of them are bounded by land and seabed topographic lines. So far, only 5% of the seabed has been explored by humans, and 95% of the seabed is unknown.
Extended data:
Explore the ocean
The science that studies the ocean is oceanography. As early as prehistoric times, human beings have been traveling on the ocean, fishing from the ocean, making a living from the ocean and exploring the ocean. Before the development of aviation, navigation was the main mode of intercontinental transportation and travel. The exploration of the deep seabed didn't really begin until the middle of the 20th century. Although people use diving balls and submarines to explore the ocean today, they still know little about the deep sea.
The ocean deep in the earth
Through laboratory simulation, geologists found water at a depth of more than 0/000 kilometers below the surface. In mineral rocks with a temperature higher than 1000℃ and under high pressure, the water content may be five times that of all oceans on earth. In addition, this discovery may help to understand how the earth formed and developed.
650 km to 2900 km below the surface, there are high temperature and high pressure substances around the iron-rich core. Experts from Tokyo Academy of Sciences in Japan estimate that this mineral called the lower mantle may contain water with its own mass of 0.2. According to the existing planetary theory, the amount of water, carbon dioxide and other early evaporation substances that appeared at the beginning of its formation is inferred. This discovery shows that the amount of mixed substances in the initial stage of the earth may have exceeded previous expectations.
A strange ocean
For millions of years, the mantle is like a pot full of hot soup, which is in a state of intense agitation and turbulence, making the tectonic belt of the mantle move and mixing the chemical components of the mantle. The greater the viscosity, the faster the speed of mantle agitation and turbulence. The water formed by minerals in the lower mantle may also affect the tectonic belt of the mantle, making it difficult to sink deeper into the stratum. When tectonic belts sink, are heated and are squeezed, the water released by them may soften the surrounding mantle and relax their sinking channels.
In the slightly higher mantle, that is, about 400 km to 650 km below the surface, it is called the transition zone, because it is located between the upper mantle and the lower mantle, and there may be water equivalent to several oceans here. Scientists have found that the minerals in the lower mantle may have about one tenth of the mass of the upper mantle, but because the volume of the lower mantle is much larger than that of the transition zone, it has quite a lot of water.
Geologists at the University of Bristol in the United Kingdom believe that this discovery will help advance the debate on how much water is in the mantle. He said that until now, most people still insist that there is not much water in the mantle. In addition, in another similar study conducted two years ago, it was concluded that there was not much water under the mantle.
Japanese scientists simulated the lower mantle in the laboratory, and they used three minerals that make up most of the area for research. They designed and applied a special multi-anvil experimental device to reproduce the harsh conditions under the mantle, while squeezing and heating minerals with hard teeth.
At about 1600℃ and 250000 atmospheric pressure, they used secondary ion mass spectrometry technology to make the ion beam hit the mineral and detect the ions released on the surface of the mineral, thus measuring the amount of hydrogen. Other research results show that any hydrogen obtained in these mineral rocks comes from the water stored in them. Finally, the experts detected much more hydrogen than expected in the experiment, thus reaching the present conclusion. ?
The color of the sea
When we open the world atlas, the Yellow Sea, the Red Sea, the Black Sea and the White Sea will come into our eyes. Sunlight looks white; But it is made up of seven kinds of visible light: red, orange, yellow, green, cyan, blue and purple. These seven kinds of light have different wavelengths, and seawater with different depths will absorb beams with different wavelengths.
Long-wavelength beams such as red, orange and yellow are gradually absorbed after they enter seawater, while short-wavelength beams such as blue and blue will be scattered and reflected in all directions when they meet seawater molecules or other tiny floating bodies hanging in the ocean. In particular, seawater absorbs less blue light, but reflects more, and the deeper it goes, the more blue light is reflected back to the water surface. Therefore, the sea water we see in the ocean is blue.
Since the sea scatters blue light, no matter which sea is blue, it is full of red, yellow, blue, white and black. This is because when the discoloration factor of some seawater is stronger than the blue produced by scattering, the seawater will be deformed and become colorful.
The factors that affect the color of seawater are suspended solids, ions, plankton and so on. There are few suspended solids and tiny particles in the ocean, and its water color mainly depends on the optical properties of seawater, so the seawater is mostly blue; Offshore seawater, due to the increase of suspended solids, particles become larger, mostly light blue; In coastal or estuarine cities, seawater turns yellow due to the color of sediments; In some sea areas, when red plankton multiply in large numbers, the seawater is often red.
The Yellow Sea in China, especially the offshore waters, is mostly khaki and muddy. Because the Huaihe River, Biliuhe River, Yalu River, Han River, Datong River and Qingchuan River on the Korean peninsula pour into the Yellow Sea, the river water carries a lot of sediment, which makes the near sea water yellow, so it is named the Yellow Sea.
Not only sediments can change the color of seawater, but also marine life can change the color of seawater. Between Asia and Africa, one side of the Red Sea is the Arabian Desert, and the other side is the dry wind blowing from the Sahara Desert. The temperature and salt content of seawater are relatively high, so the reddish-brown algae in the sea multiply in large numbers, and the coral and red microalgae in the bay are covered with a layer of red, so the Red Sea is reddish, hence the name "Red Sea".
Due to the blocking effect of thermocline in the Black Sea, a large amount of silt has accumulated on the seabed, which is the factor that causes the black sea water to turn black. In addition, the Black Sea is rainy and cloudy, especially the fierce northeast wind in summer, which sets off gray waves on the sea surface and turns the sea water black, hence its name.
The White Sea is the marginal sea of the Arctic Ocean, which goes deep into the northwest inland of Russia. The weather is extremely cold and the freezing period is as long as six months. The white sea is named because the snow covering the coast has not melted, the thick ice layer has frozen its harbor, and the sea surface is covered with snow. Due to the strong reflection of the white surface, the sea water we see is white. The colorful sea is a masterpiece of nature.
mariculture
Human civilization consists of mainland culture and marine culture. The word "marine culture" first appeared in "Li Er" and "The Birth of a Ship", and was later quoted by academic circles at home and abroad.
Marine culture and mainland culture interact, blend and promote each other. Ancient human civilization was formed by the fusion of mainland culture and marine culture. Fires and stone axes on land created ships, and the water activities of ships promoted the development of mainland culture. Canoe appeared in the Neolithic Age, which is the inevitable product of the development of human culture to a certain extent. It not only reflects the development level of human productive forces, but also reflects the scientific and technological development level of the whole society. It also opened up a brand-new era for the development of human marine culture.
Human beings are characterized by their exploration and desire for the unknown world.
Human beings are so dependent on water. As long as there is water flowing through, human beings will drift with the tide. Nile civilization in ancient Egypt; China ancient civilization of two rivers, the Yellow River and the Yangtze River all came into being. Similarly, in the ocean, as long as there are islands (in people's field of vision), people will leave by boat, thus establishing cultural exchanges between land and sea. In this way, the ancient culture of China spread to all parts of the world step by step.
China is not only a vast mainland country, but also the Yellow River and the Yangtze River, as mother rivers, have nurtured the Chinese nation and made China famous for its ancient civilization. China is also a maritime country with a long coastline and vast oceans. The great Chinese nation, like the Mediterranean countries, is an important birthplace of human marine civilization, and rich marine culture is an important part of human historical civilization.
The Chinese nation not only created a glorious history of navigation as early as 7,000 years ago, but also brought the earliest civilization, ancient culture and science and technology of human beings to America and other parts of the world in the frequent and long voyage of 7,000 years (Introduction to Li Er and China Waterway History).
This is the result of a large number of cultural relics unearthed and excavated around the world, and the study of ancient documents by experts and scholars from all over the world, including the research results of China marine culture in many international academic seminars.
Five wooden paddles were unearthed in Hemudu Site, Yuyao County, Zhejiang Province, China. One of them has a residual length of 62.4 cm and a residual width of 10.8 cm. The other stump is 92 cm long and 9 cm wide. According to carbon 14, the age of five wooden paddles is about 7000 years ago, belonging to matriarchal clan social relics. In the same floor, there are nearly 100 kinds of animals and plants, wood remains and carbonized rice grains used in tenon-mortise and tenon-plate structure housing construction.
This proves that fishing and hunting gathering still played a very important auxiliary role in the economic life at that time. Hemudu site is located in Ningshao Plain on the south bank of Hangzhou Bay. Yaojiang River flows through the west and south of the site, with Siming Mountain in the south, facing Hemudu across the river. The site is only 3-4 meters above sea level. In ancient times, it may be Wang Yang or a low-lying swamp. It is worth noting that at the joint of the handle and blade of the civil propeller, the chord and diagonal are intaglio. This proves that such a finely carved wooden paddle is by no means the most primitive, and it has a long process of development and evolution.
Then the appearance of primitive wooden paddles should be earlier, maybe around 8000 years (Li Er and Chapter 1 of China Waterway History made a bold inference). Coincidentally, also in Hangzhou, Zhejiang, a canoe was unearthed at the Neolithic site of Xiaoshan Lake Bridge. According to the determination of carbon 14, the age of this wooden boat is 7500-8000 years ago, which coincides with our inference in the history of China's water transportation. It should be said that this is an amazing discovery. It is the earliest canoe ever excavated in China (Li Er and the Seven Thousand Years at Sea).
Ocean anecdote
1, Black Sea, which the ancient Greeks called "the sea with a broad mind".
The Dead Sea is just an inland salt lake, not a real sea.
3. Mediterranean, which the Romans called "the sea of the heart of the earth".
The Aegean Sea was named after the ancient king of Athens, Igyus.
Seven Seas, an ancient sailor term, means: Red Sea, Mediterranean Sea, Persian Gulf, Black Sea, South China Sea, Caspian Sea and Indian Ocean.
The sargasso sea, the only ocean in the world without a coast.
References:
Baidu Encyclopedia-Ocean (Geographical Noun)