Ocean Topography: Four zones are distinguished at the bottom of the oceans.
The first zone is the underwater edge of the continents. The underwater outskirts of the continents is the outskirts of the continents flooded by the waters of the ocean. It, in turn, consists of a shelf, a continental slope and a continental foot. The shelf is a coastal bottom plain with rather shallow depths, in essence, a continuation of the marginal plains of the land. Most of the shelf has a platform structure.
How Does The Ocean Floor Look Like: 5 Ocean Topography
On the shelf, residual (relict) landforms of surface origin are quite common, as well as relict river and glacial deposits. This means that during the Quaternary retreats of the sea, vast expanses of the shelf turned into land.
Typically, the shelf ends at depths of 100-200 m, and sometimes at large rather sharp inflection, the so-called shelf edge. Below this edge, the continental slope extends toward the ocean — a narrower than the shelf zone of the oceanic or seabed with a surface gradient of several degrees.
Often the mainland slope has the form of a ledge or series of ledges with a steepness of 10 to several tens of degrees.
The second – transitional – zone was formed at the junction of continental blocks and oceanic platforms. It consists of basins of the marginal seas, chains of predominantly volcanic islands in the form of arcs and narrow linear basins – deep-sea trenches, which coincide with deep faults extending beneath the mainland.
On the outskirts of the Pacific Ocean, in the Mediterranean, Caribbean, and Scotia seas, the underwater margins of the continents do not contact directly with the ocean bed, but with the bottom of the basins of the marginal or Mediterranean seas. In these basins, suboceanic-type crust. It is very powerful mainly due to the sedimentary layer.
From the outside, these pools are surrounded by huge underwater ridges. Sometimes their peaks rise above sea level, forming a garland of volcanic islands (Kuril, Marian, Aleutian). These islands are called island arcs.
On the oceanic side of the island arcs there are deep-sea troughs – there is no grand continental crust. Instead, earthly, narrow, but very deep (6–11 km deep) depressions are developed here.
The third – the main – the zone of the bottom of the oceans – the bed of the ocean, it is characterized by the development of the earth’s crust exclusively oceanic type.
The ocean bed occupies more than half of its area at depths of up to 6 km. On the bed of the ocean there are ridges, plateaus, hills that divide it into hollows. Bottom sediments are represented by various silts of organogenic origin and red deep-sea clay, arising from thin insoluble mineral particles, cosmic dust and volcanic ash. At the bottom there are many ferromanganese nodules with impurities of other metals.
How does the World Ocean Floor look Like?
Ocean ridges are quite clearly divided into two types: arch-block and block. Vault-block structures are based on vaulted, linearly elongated uplifts of the oceanic crust, usually broken by transverse faults into separate blocks (the Hawaiian ridge, which forms the underwater base of the archipelago of the same name).
The fourth zone stands out in the central parts of the oceans. These are the largest relief forms of the ocean floor – mid-ocean ridges – giant linearly oriented arch elevations of the earth’s crust. When the arch is formed, the greatest stresses arise not at its top, here faults are formed, along which part of the arch is lowered, grabens are formed, the so-called rift valleys. In these weakened zones of the earth’s crust, mantle material rushes up. #How Does The Ocean Floor Look Like: 5 Ocean Topography