The ocean floor is one of the most intriguing and least explored places on the planet. It hides tons of minerals, the deepest depressions and hollows, underwater ridges. Amazing organisms live here and mysteries that we have not yet solved are hidden.
World Ocean
All land areas of our planet cover an area of 148 million km2, but this is negligible compared to the area of the ocean. It accounts for 361 million km², that is, almost 71% of the entire surface of the Earth.
The World Ocean is a continuous body of water that surrounds 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 are 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 depressions, valleys, ridges, rocks, plateaus and basins. It has its own unique flora and fauna.
The depth of the seabed is the least near 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 deepest is the Pacific Ocean, with an average depth of 3726 meters, the shallowest is the Arctic Ocean with an average of 1225 meters.
Oceanic crust
Like the mainland, the seabed is formed by the earth's crust. However, there are significant differences in their structure and geology. Thus, the oceanic crust is completely devoid of the granite layer, which often comes to the surface on land. In addition, it is much thinner - its thickness varies from 5 to 15 kilometers.
The crust of the seabed consists of three main layers. The very first, lower, level is composed of gabbro and serpentinite rocks. They may consist of quartz, apatite, magnetite, chromite, contain impurities of dolomite, talc, garnet and other minerals. Above is the bas alt layer, and even higher is the sedimentary one.
The uppermost level of the seabed, 4-5 kilometers thick, is deposits of metal oxides, deep-sea clays, silt and carbonate skeletal remains. Precipitation does not accumulate on the ridges and slopes, so the bas alt layer comes to the surface in these places.
Bottom relief
The ocean floor is by no means flat and level. As you move away from the coast of the continents, it gradually decreases, forming a kind of depression or bowl. Conventionally, this reduction is divided into three parts:
- Shelf.
- Mainland slope.
- Bed.
The underwater margins of the continents begin with shelves - flat or slightly inclined shallows, only 100-200 meters deep. Only sometimes they fall to 500-1500 meters. As a rule, they are rich in oil, natural gas and other minerals.
Shelves end in bends (brown), after which continental slopes begin. They are represented by ledges and hollows, strongly dissected by basins and canyons. The angle of inclination in this part of the ocean sharply increases, ranging from 15 to 40 degrees. At a depth of 2500-3000 meters the slope turns into a 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 hills and depressions. Its largest formations are mid-ocean ridges. This is a huge underwater mountain system that stretches for 70 thousand kilometers, skirting all the continents of the planet.
The ridges don't look like they do on land. They look like huge shafts, in the middle of which there are faults and deep gorges. Here the lithospheric plates move apart and magma comes out. On the slopes of the ridges there are flat volcanoes and transverse faults that appeared from their activity.
In places where the oceanic crust moves under the continental, longitudinal depressions of the seabed, or trenches, are formed. They stretch for 8-11 kilometers in length and about the same in depth. The mostdeep trench - the Mariana Trench in the Pacific Ocean. It descends about 11,000 meters and stretches along the Mariana Islands.
Bottom biology
The organic world of the seabed is more diverse the closer it is to the surface of the ocean. The shelves are considered the richest in organisms. They are inhabited by all kinds of crabs, shrimps, octopuses, squids, sponges, starfish, corals. Flounders and skates usually burrow into the upper layer of the bottom, perfectly camouflaging themselves under the silt. In addition to them, gobies, dog-like, sucker species, catfish, eels, loaches, unusual chimeras and bitite fish live below.
The poorest are gorges and depressions, as well as deep sections of the sea bed. Cold water, high pressure, high salinity and lack of sunlight make them not very habitable. However, there is life here too. So, at great depths, near hydrothermal springs, entire colonies of mussels, shrimps, crabs and other organisms were found, many of which have not yet been studied. The water here is very hot, creating conditions for life even in such cold and desert areas of the ocean.
