The average depth of the ocean is about 3.7 kilometers (2.3 miles). Starting from the continental shelf slope with a general depth of 100 ~ 200 meters, the continental slope was reduced to a vast deep-sea plain.
About 75% of the seabed is between 3 and 6 kilometers deep, only about 1% deeper. The deepest waters are distributed in narrow trenches, and most of them are related to the Pacific island arc. At present, the deepest water is Mariana Trench11.034m..
2, the characteristics of the ocean
Many important features of the ocean are determined by the temperature and salinity of seawater. In addition, the pressure determines the density of seawater. The heat of seawater mainly comes from the solar energy absorbed by its surface, and the water temperature on the surface will be obviously different with the latitude.
However, the distribution of surface temperature is obviously influenced by other regional characteristics such as heat conduction and upwelling of surface ocean currents. The temperature of the vast ocean ranges from-1℃ to 28℃ (30 ~ 82 ℉).
In tropical and temperate latitudes, the most obvious drop in ocean seawater temperature is thermocline (below the surface layer where seawater is fully mixed, the depth is about 100 m). When the water depth exceeds 1 km, the water temperature changes slowly and tends to the bottom water temperature below 2℃.
3, the material in the ocean
Seawater contains all kinds of dissolved inorganic substances, organic substances, gases and organic substances. In addition to the above dissolved components, it also contains suspended particles (such as plankton). Besides water, the most abundant inorganic components are chloride, sodium, sulfate, magnesium, calcium, potassium and bicarbonate.
Unlike many trace substances, the concentrations of these main components are different, but they are almost fixed in proportion to salinity. Marine seawater is slightly alkaline, and its pH value is close to 8. Geochemists believe that despite the continuous increase and decrease of substances, the main composition characteristics of seawater have remained basically unchanged for at least the past 600 million years.
Extended data:
In fact, the sea was formed by too much water vapor during the first volcanic eruption in the history of the earth, and then it rained heavily for thousands of years and merged into the sea.
Studies have proved that some large and small nebulae were separated from the solar nebula about 5 billion years ago. They revolve around the sun while rotating. In the process of movement, they collided with each other, and some lumps combined with each other, from small to large, and gradually became the original earth.
During the collision of nebula clusters, they shrink sharply under the action of gravity, and the radioactive elements in them degenerate, which makes the primitive earth heat up continuously. When the internal temperature reaches high enough, underground substances, including iron and nickel, begin to melt. Under the action of gravity, the weight sinks and tends to concentrate in the center of the earth, forming the core; Lighter ones float to form the crust and mantle.
At high temperature, the water inside evaporates, rushes out with the gas and rises into the air. But because of gravity, they will not run away, but will only turn around the earth and become a circle of air and water.
In the process of cooling and condensation, the crust on the earth's surface is constantly impacted and squeezed by the violent movement inside the earth, so it becomes uneven and sometimes crushed, forming earthquakes and volcanic eruptions, spewing magma and hot gas. At first, this kind of situation often happens, and then it gradually decreases and tends to be stable. This division of light and heavy substances led to great turmoil and reorganization, which was completed about 4.5 billion years ago.