The ocean floor is one of the most intriguing and least explored places on the planet. It hides tons of minerals, the deepest hollows and hollows, underwater ridges. Amazing organisms live here and mysteries that we have not yet uncovered lurk.
World Ocean
All land areas of our planet occupy an area of 148 million km 2, but this is negligible compared to the area of the ocean. It accounts for 361 million km², that is, almost 71% of the entire Earth's surface.
The oceans of the world are called the continuous body of water that surrounds the continents and islands. It includes all existing seas, bays, bays and straits, as well as four oceans (Atlantic, Pacific, Indian and Arctic). All these parts represent a single water shell, but their characteristics (salinity, temperature, organic world, etc.) are different.
The seabed is also diverse. It is dotted with all sorts of hollows, valleys, ridges, rocks, plateaus and hollows. It has its own unique flora and fauna.
The depth of the seabed is the least along the coast, in the shelf area. There it reaches no more than 200 meters. Then it gradually increases and reaches 3-6 km, in some areas and up to 11 km. The Pacific Ocean is considered the deepest, with an average depth of 3726 meters, the shallowest is the Arctic Ocean with an average of 1225 meters.
Oceanic crust
Like mainland land, the seabed is formed by the earth's crust. However, there are significant differences in their structure and geology. So, the oceanic crust is absolutely devoid of a granite layer, which on land often comes to the surface. In addition, it is much thinner - its power varies from 5 to 15 kilometers.
The seabed crust consists of three main layers. The very first, lower, level is composed of gabbro rocks and serpentinites. They can consist of their quartz, apatite, magnetite, chromite, contain impurities of dolomite, talc, garnet and other minerals. Higher is the basaltic layer, and even higher is the sedimentary layer.
The highest level of the seabed, with a thickness of 4-5 kilometers, is a deposit of metal oxides, deep clays, silt and carbonate remains of skeletons. Precipitation does not accumulate on ridges and slopes, therefore, in these places the basalt layer comes to the surface.
Bottom relief
The ocean floor is by no means flat and even. As it moves away from the shores of the continents, it gradually decreases, forming a kind of depression or bowl. Conditionally, this decrease is divided into three parts:
- Shelf.
- Mainland slope.
- Bed.
The underwater margins of the continents begin with shelves - flat or slightly sloping shallows, with a depth of only 100-200 meters. Only sometimes they fall to 500-1500 meters. As a rule, they are rich in oil, natural gas and other minerals.
Shelves end in kinks (brow), after which continental slopes begin. They are represented by ledges and hollows, are strongly dissected by basins and canyons. The inclination angle in this part of the ocean increases sharply, ranging from 15 to 40 degrees. At a depth of 2500-3000 meters, the slope passes into the bed. Its relief is the most complex and diverse, and the organic world is poorer than that of other layers.
Ups and downs
The bed of the seabed is formed under the influence of external and internal forces of the Earth, forming all kinds of elevations and depressions. Its largest formations are the mid-ocean ridges. This is a huge underwater mountain system, which stretches for 70 thousand kilometers, enveloping all the continents of the planet.
The ridges do not look exactly like they do on land. They look like huge ramparts, among which are faults and deep gorges. Here, the lithospheric plates move apart and magma comes out. On the slopes of the ridges are flat volcanoes and transverse faults, resulting from their activity.
In places where the oceanic crust moves under the continental, longitudinal depressions of the seabed, or trough, are formed. They stretch for 8-11 kilometers in length and about the same in depth. The deepest basin is the Mariana Trench in the Pacific Ocean. It descends by about 11, 000 meters and stretches along the Mariana Islands.
