Ocean relief – Concept, forms and characteristics

We explain what the oceanic relief is, its characteristics and what its forms are like. Also, what is the continental relief.

ocean relief
The oceanic relief encompasses all the forms that the seabed acquires.

What is the oceanic relief?

In geography, we speak of oceanic relief or submerged relief to refer to the different forms that the underwater bed acquires, that is, the portion of the lithosphere or earth’s crust that is covered by seas and oceans. In simpler terms, we are talking about the shapes that the seabed takes.

In this it differs from the emerged or continental relief, which deals with the portion of land emerging from the waters, and which in the current geographical configuration of our planet, is the minority. The submerged portion of the lithosphere occupies about 70% of the total surface of the planet, and being isolated by the waters of erosive factors such as wind or rain, it is much less varied in terms of relief than its continental version.

This does not mean that the geological configuration of the seabed is static or immobile, far from it. Like the continental relief, it is in continuous change throughout a very slow process over the centuries, known as the geological cycle, whose manifestations are very difficult to perceive throughout human life.

Characteristics of the oceanic relief

In general, the underwater relief is characterized by the following:

  • It is, as we have said, the portion of the lithosphere that is submerged under the water of the oceans: the seabed. Therefore, it reaches important depths in specific regions: ranges from 0 to 11 km below sea level.
  • They have different margins of volcanic activity, which shed terrestrial materials and modify the underwater soil, sometimes giving rise to volcanic islands. Otherwise, they are subject to much more benevolent erosive forces than on the surface, so that its changes depend on seismic and tectonic activity mainly.
  • It is distributed along the different layers of ocean water, which vary in conditions of pressure, luminosity and presence of life, and which are the bathyal zone, the pelagic zone and the abyssal or abyssopelagic zone.
  • The oceanic relief tends to be flatter where sedimentation is strong, as a consequence of the sedimentary contribution of rivers, the decomposition of marine fauna and flora, the erosive action of salt water on the seabed itself, or the contribution of underwater volcanic matter.

Forms of the oceanic relief

oceanic relief shapes
Each of the oceanic landforms has its own characteristics.

Although the oceanic relief tends to be much more uniform and homogeneous than its emerged counterpart, it presents common and recognizable shapes, such as the following:

  • The continental shelf. Intermediate area between the continent and the ocean, the extension of the first within the second is considered, along the coastline to a depth of no more than 200 meters. It has a variable amplitude, starting from the coast, but it is usually an area with a significant presence of sediments and abundant animal and plant life, which is why it tends towards the plain.
  • The continental slope. It consists of a strong submarine decline that connects the continental shelf with the abyssal plain, and ranges between 200 and 4,000 meters below sea level. It is a more or less irregular fall, with the presence of valleys and submarine canyons, on an inclined plain whose slope usually ranges between 5 ° and 7 °, but can reach 50 °, producing numerous slides of sedimentary material. Natural steps or steps are common in it, and life begins a noticeable decrease with respect to the previous area.
  • The abyssal plain. This is the name given to the deep plain at the bottom of the seas and oceans, between 3,000 and 7,000 meters deep, usually located between the continental slope and some oceanic ridge or, conversely, some abyssal trench. This type of relief constitutes 50% of the ocean floor, and they are the main sedimentation areas of the entire planet. Seismic activity is also frequent, giving rise to small volcanic hills or seamounts (guyots). Being a region that receives little sunlight, life is much scarcer and temperatures are low.
  • The abyssal trenches. Also known as ocean trenches or sea trenches, they are the deepest known depressions on the planet, penetrating from the abyssal plain to 11,000 meters below the sea surface. Sunlight does not penetrate this unknown region of the oceans, whose waters are around 4 ° in temperature and are subjected to crushing pressures. They are usually found in the proximity of the continental edges or volcanic islands, since their origin is clearly tectonic, and contrary to what it seems, they are not free of life, although it is much scarcer and very different from life Of the surface.
  • The ocean ridges. Mid-ocean or mid-ocean ridges are underwater elevations located in the mid-ocean region, which can reach heights between 2,000 and 3,000 meters above the abyssal plain. They have a natural fissure at their top, known as rift, where magma is emitted continuously, forming new rocks and possible new volcanoes. For this reason, the rocks around them tend to be younger, and a new seabed tends to be produced, in a continuous process of renewal of the ocean floor.

Continental relief

The continental relief, unlike the oceanic, corresponds to the emerged portion of the earth’s surface, that is, with the portion of lithosphere that is not submerged under water. Unlike the oceanic relief, which is much more homogeneous, the action of air, rain and other erosive factors typical of the atmosphere (the greater drought, for example) make the continental relief very diverse in its forms.