The origin of the ocean

After the formation of the primitive earth, the surface temperature rose slowly. Therefore, the earth began to warm from the surface. During this period, the temperature of the earth gets higher as it gets closer to the outside. As the temperature continues to rise, the surface substances begin to melt.

These molten materials are similar to volcanic magma and cover the earth's surface. With the increase of magma cover, the volatile substances in it escape and form the primitive atmosphere. This kind of atmosphere is mainly composed of water and carbonic acid gas, and its air pressure is more than 100 times of the current one. Later, the atmospheric temperature dropped, and the water vapor in the atmosphere turned into water and fell to the ground, forming a primitive ocean.

In the primitive ocean, seawater is not salty, but acidic and anoxic. Water is constantly evaporating, repeatedly forming clouds and causing rain, and then falling back to the ground, dissolving salt in rocks on land and under the sea, and constantly collecting it in seawater.

After hundreds of millions of years of accumulation and integration, it has become a generally uniform salt water. At the same time, because there was no oxygen and ozone layer in the atmosphere at that time, ultraviolet rays could reach the ground directly. With the protection of seawater, life was first born in the ocean.

Extended data

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 the heat conduction of surface current and other regional characteristics such as upwelling. The temperature of the vast ocean ranges from below-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℃. According to the total amount, about 50% of the ocean water temperature is between 65438 0.3 ~ 3.8℃. The salinity of the surface layer of seawater-that is, the proportion of dissolved salt in seawater-is changing, which mainly depends on the comparison between evaporation loss of local seawater and rainfall.

The average salinity of the ocean is 34.7. In areas where rivers inject a lot of fresh water or a lot of icebergs melt, the salinity of seawater will be slightly lower; In areas where the amount of evaporated water is extremely high, the salt concentration will be higher.

Baidu encyclopedia-the sea