Knowledge about the seabed?

Seabed refers to the contact surface between sea water and land under deep water. The ocean area is about 362,000,000 square kilometers (65,438+040,000,000 square miles), accounting for nearly 765,438+0% of the earth's surface area. The ocean contains more than1350 million cubic kilometers of water, accounting for about 97% of the total water of the earth. The global ocean is generally divided into several oceans and smaller oceans.

It was not until 1950s that geographers were able to map the underwater world with advanced technology. The results of surveying and mapping show that there is a towering ocean "ocean ridge" on the seabed, forming an underwater "mountain range", which stretches for about 83,683.6 kilometers and passes through all the oceans in the world. The "sea ridge" at the bottom of the ocean is also called the fault valley.

Magma keeps pouring out of the fault valley, and after cooling, a series of new submarine mountains are created at the bottom of the ocean. This process is called submarine spreading, and these new submarine mountains are called seamounts. As new rocks are added to the fault valley, the rocks on both sides of the fault valley gradually move away from the center of the ocean ridge. So the farther away from the "mountain", the older the rock is.

When seamounts and new submarine plains are formed, the magma in the fault valley will continue to gush out, playing the role of "conveyor belt", pushing the new seamounts out of the crustal rocks, and at the same time slowly pushing them down from the crustal rocks and remelting them into the mantle, thus achieving the balance of rebirth and growth.

submarine volcano

Volcanoes are formed in shallow seas and the seabed. Including extinct volcanoes and active volcanoes.

Volcanic activities on the earth are mainly concentrated in plate boundaries, while submarine volcanoes are mostly distributed in mid-ocean ridges and island arcs in edge of the ocean.

There are sometimes some volcanic activities inside the plate, but the number is very small.

Submarine volcanoes can be divided into three types, namely marginal volcanoes, ocean ridge volcanoes and ocean basin volcanoes, which are significantly different in geographical distribution, lithology and genesis.

When submarine volcanoes erupt, spectacular explosions often occur when the water is shallow and the water pressure is not high. When this explosive submarine volcano erupts, it will produce a lot of gas, mainly water vapor, carbon dioxide and some volatile substances from the deep part of the earth, as well as a lot of pyroclastic materials and hot lava, which will condense into volcanic ash, volcanic bombs and pyroclastic rocks in the air. "Volcanic Island" once appeared in the Mediterranean with the help of volcanic ash.