What's the world like under the ocean?

We stand in front of the globe and see a world with a smooth surface. In fact, the surface of the earth is not smooth, but uneven. There are towering peaks on the earth; Depression with depression; A fractured valley; And rolling hills. So is the bottom of the sea. The seabed is not a flat Yuan Ye, but a rugged and hilly world. There are many mountains, rivers, hills and volcanoes, as well as various animals and plants. This is a colorful world.

Pacific seabed exploration

The earliest humans thought that the sea had no bottom. With the gradual deepening of human understanding of the ocean, people gradually found that the sea is not only bottomless, but also the seabed is not Ma Pingchuan, which is as changeable as land. The seabed of the ocean is more complicated than land topography where people live, and the complexity is shocking. There is a grand canyon at the bottom of the sea, called the trench, and the most famous Mariana trench is 10000 meters deep. If you remove the whole Himalayas from the land and throw them into this grand canyon, the grand canyon will not be filled. What is even more amazing is that there is a unique mountain range at the bottom of the ocean, which is tens of thousands of kilometers long. It winds through the Atlantic Ocean, the Pacific Ocean, the Indian Ocean and the Arctic Ocean like a giant snake. Because it resembles the huge "backbone" of the seabed, scientists call it the "mid-ocean ridge".

Submarine volcanic eruption

There are not only ridges, hills, canyons, but also volcanoes in the ocean. Not only mountains, but also rivers. In the east of Taiwan Province Province, China, there is a huge ocean current and a huge warm current flowing from south to north. Ocean current exists not only on the surface of the ocean, but also in the depths of the ocean. The "Brazilian Warm Current", "Mexican Warm Current" and "Taiwan Province Warm Current" that we often hear are all rivers in the ocean.

The sea floor is uneven. Suppose we go from the mainland to the deep sea, what route will we take? First, we have to cross the intertidal zone. Intertidal zone refers to the zone submerged by seawater at high tide and surfaced at low tide, which is the dividing line between mainland and ocean. Then, we will walk into the continental shelf. The depth of the continental shelf is usually less than 200 meters. Connected with the mainland is the continental slope. The gradient of continental slope is relatively large, generally around 4 ~ 7. The continental slope is also uneven and fluctuates greatly. The continental slope lies between the continental shelf and the ocean. After walking through the continental slope, you will find a relatively flat area, that is, the ocean basin. The ocean basin is surprisingly flat, with an average inclination of less than half a degree, and its area is surprisingly large, accounting for 77.7% of the whole ocean area. Of course, we can't go into the deep sea alone without any carrier, because we will be crushed to pieces by the pressure of seawater before reaching the main body of the ocean. List of main parameters of seabed topographic features Name Depth range (m) Average depth (m) Dip area (106km2) accounts for the total ocean area (%) Continental shelf 0 ~ 200 is about 50 1 ~ 2 27.57.6 Continental slope 200 ~ 2,50012704. 4200 24 ′ ~ 0 40 ′ 283.777.7 Trench > 6,0006,100—1.22.8 The oceans are not all blue.

When it comes to the ocean, people always think of blue. In fact, the blue ocean is only for most oceans, and some oceans in the world show other colors. The world's oceans are rich and colorful. In the same sea area, the color of seawater at different depths is different, because seawater absorbs and scatters sunlight projected into the ocean to different degrees. In addition, different sea areas have different colors of the sea. For example, the Yellow River in China rushed into the East China Sea with a lot of sediment, and the water in the East China Sea turned yellow and blue, and gradually turned green; In the South China Sea, the sea is blue; In the distant Red Sea, because many underwater plants have red algae, the sea water is red; In the Black Sea, the sea water is black because pieces of brown algae grow in the sea water. In the Arctic Ocean, seawater is olive. In a word, the color of the sea depends not only on the depth of the sea, but also on the creatures in the sea.

Underwater world

Deep under the sea, you can't see your fingers. This is because sunlight decays quickly in water. When the light reaches the depth of 100 m, only about 1% remains. So 1, the water depth below 700 meters is a dark world.

Detect the depth of the ocean

How did early humans measure the depth of the ocean? They use the heavy hammer method. The heavy hammer method is simple: hang a heavy object at one end of a long rope and then throw it into the sea. People can judge whether a heavy object touches the seabed by their own feelings and the tightness of the rope. Once the weight touches the bottom of the sea, the length of the rope entering the water is the depth of the sea. The ancients used the heavy hammer method to measure the water depth. Usually two people row a boat and throw a heavy hammer into the sea with the rope on the boat. In order to increase the specific gravity of the heavy hammer, their heavy hammer is made of lead, and a hollow is prefabricated at the bottom of the heavy hammer, and the hollow part is filled with grease so as to stick to the sediment on the seabed. Tie a knot on the rope every other length, and finally calculate the water depth according to the number of knots of equal length. While measuring the water depth, I also have a certain understanding of the soil layer on the seabed, which really kills two birds with one stone.

Submarine detector

However, the measurement of seawater depth by heavy hammer method is limited by the length of rope and influenced by waves and currents, so the measurement results are not very accurate, and generally only shallow water areas can be measured. With the progress of science and technology, especially the development of acoustic technology, people begin to use sound waves to detect the depth of the ocean. 19 1 1 year, an engineer invented the technology of measuring water depth by using acoustic pulse. In this technology, the acoustic pulse generator is first installed on a moving ship. When the sound pulse is transmitted from the ship to the bottom of the sea, it is bound to reflect. If the sea is deep, it takes a long time for the sound waves to reflect back. On the contrary, sound waves reflect back for a short time. Record the time of sending and receiving sound pulses, and know the time difference and the propagation speed of sound pulses in water, so that the water depth can be calculated quickly. In the 1920s, the German research ship Meteor used echo sounder to measure the seabed topography in the South Atlantic for the first time.

In recent years, American scientists have developed a new sonar navigation detector. This detector is very sensitive, even if it is only a few centimeters high, it can detect the ups and downs of the seabed. With it, scientists can detect many underwater worlds that humans have not yet detected.

China has four sea areas from north to south. Of these four sea areas, Bohai Bay is the shallowest, with an average water depth of only 18m and a maximum water depth of only 70m. The Yellow Sea is next, with an average water depth of 44m and a maximum water depth of140m. The East China Sea is slightly deeper, with an average water depth of 370 meters and a maximum water depth of 27 19 meters. The South China Sea is the deepest, with an average water depth of 1, 21.2m and a maximum water depth of 5559m.. These data show that China's four sea areas are getting deeper and deeper to the south. China has one of the widest continental shelves in the world, on which both the Yellow Sea and the Bohai Sea are located. China's continental shelf with a water depth of 200 meters covers an area of 6,543,800 square kilometers.

In addition to measuring the depth of the ocean at sea, there are people who are keen on the theoretical research of this problem. An astronomer once calculated the depth of the ocean. His calculation theory is to calculate the depth of the sea according to the fluctuation of tides. It is calculated that the maximum depth of the ocean is 37,000 meters. However, this calculation result was quickly overturned by facts.

Is the mountain high or the sea deep?

Is the mountain high or the sea deep? Let's look at a set of data. The average depth of the world's oceans is less than 4000 meters; The deepest sea area in the world is in the Pacific Ocean, with a depth of about 10 and 0 13 meters. The deepest part of the Indian Ocean can reach 7000 meters; The maximum depth of the Atlantic Ocean can reach more than 8000 meters.

Deep seabed

The South China Sea is the largest sea area around China, with an area of over 3.6 million square kilometers, equivalent to the area of more than 30 Bohai Seas. The South China Sea is not only the largest sea area in China, but also the deepest sea area. The depth of the South China Sea is much deeper than that of the Bohai Sea and the East China Sea. Its average depth is 1, 2 12 meters, and the deepest point can reach 5559 meters, which is higher than the average height of the Qinghai-Tibet Plateau on the roof of the world.

The deepest part of the ocean is mostly located in the trench, which is distributed on the edge of the ocean or island. The deepest trench in the world is the Mariana Trench in the western Pacific Ocean, which is 2550 kilometers long and about 70 kilometers wide. If the height of one floor is 3.5 meters, the depth of Mariana Trench is equivalent to the height of 3000 floors, reaching more than 1 1000 meters. The Oriental Pearl and Jinmao Tower in Shanghai are world-famous, but compared with Mariana Trench, their heights are less than 1/20 of the depth of Mariana Trench.

Schematic diagram of ditch

For many years, many explorers have longed to come to the Mariana Trench. Later, a submarine named "Quster" came to the seabed with a water depth of more than 65438+100000 meters. This is the submarine of US Navy Colonel Walsh and George W. Pickart. The names of Walsh and George W. Pickart will remain in the history of human deep-sea exploration forever, because they were the first pioneers to open the door of this 10,000-meter abyss.

Among the many sea areas that have been investigated, the deepest sea area is the trench east of the Philippines, with a depth of 1 1, 515m. This is the measured data of British "Cook" in 1962. Based on the sea level, the distance from the deepest seabed in the world to the sea level is more than 2600 meters from the peak of the highest mountain in the world.

People often like to use "higher than the mountain and deeper than the sea" to express their deep feelings. In fact, it is enough to say "deeper than the sea", because deeper than the sea will definitely be higher than the mountain.

Who changed the map of the world

Some small islands in the world will be swallowed up by sudden waves in an instant, and all the creatures on the islands will be spared. They have since disappeared from the map of the world. It was the tsunami that directed this human tragedy. The most serious marine disaster is the tsunami.

Tsunamis are mainly caused by submarine earthquakes, submarine volcanic eruptions, land subsidence or typhoons. When there is an earthquake at the bottom of the sea, the drastic change of the seabed crust causes the great change of the water level. At the same time, the strong seismic wave at the rupture hit the seabed, causing the water body to vibrate violently and causing big waves on the sea surface. Big waves are like wild horses that are out of control. Everywhere they go, houses are destroyed and people are killed. Besides earthquakes, typhoons can also cause tsunamis. Typhoon was born on the ocean surface in tropical areas, because the weather there is very hot and the hot air is rising. Hot air tends to form a rotating air vortex on its way up. When this vortex rotates at a high speed in a large range, it is possible to form a typhoon. The typhoon moves outward while rotating, forming huge waves on the ocean surface of Wan Li, which are powerful and can destroy all obstacles that hinder its progress.

Earthquake/tsunami

What people remember most is the tsunami that happened in the Indian Ocean at the end of 2004. Thousands of lives were swallowed up by the sea.

In addition to the tsunami, sea level rise also threatens some island countries, coastal cities and villages. Due to the development of modern industry, a large number of coal and oil are burned, and the greenhouse gases such as carbon monoxide and carbon dioxide emitted are increasing day by day, and the earth is warming day by day. The warming of the weather has brought two major consequences: first, it has caused the melting of Antarctic and Arctic glaciers, and some polar iceberg shelves are disintegrating; Second, the temperature of seawater is also rising, which will cause seawater to expand. These two consequences make the average water level of the ocean rise continuously.

Creatures in the underwater world

In the global greenhouse gas emissions, the United States ranks first, and its greenhouse gas emissions are a quarter of the world. It is reported that the sea level has risen at an average annual rate of 3.9 mm in the past decade. Due to the continuous improvement of industrialization, the speed of sea level rise is also accelerating. It is speculated that the global average sea level will rise by 0.3 ~ 0.5 meters by 2050 if human beings cannot effectively control this rising speed. By then, most of the coastline of the United States will be submerged by seawater, and some urban and rural areas along the eastern coast of China will also be submerged.

There are more than 30 island countries in the world. The Maldives in the Indian Ocean is a country composed of more than 2,000 coral reefs, with an average elevation of only 1.2 meters. No wonder the President of Maldives lamented: "The rising sea level means that the Maldives as a country will disappear into the sea of Wang Yang." If mankind continues to increase greenhouse gas emissions without taking any effective measures to control greenhouse gas emissions, then the lament of the Maldivian President will become a reality and the ocean will change today's world map.