We explain what an abyssal plain is in an ocean, what living beings inhabit it and other characteristics. Also, examples from around the world.
What is an abyssal plain?
In geology and oceanography, certain areas are known as the abyssal plain. flat expanses of land found at the bottom of seas and oceans, in the underwater region known as the abyssal zone (from the Latin abyssus, “abyss”). This is the deepest and darkest region of the known seas, where the least amount of sunlight penetrates and therefore life is scarce, arduous and different from the surface regions.
However, abyssal plains are different from deep ocean depressions (such as trenches) in that they are flat, submerged expanses of land close to continental expanses. They are usually found at depths of several kilometers below the surface and spread out over vast dimensions.
The geological study of these plains reveals that they have a sedimentary origin, that is, they are the result of the accumulation of sediments and substrates from nearby continents, which accumulate over thousands or millions of years until the terrain is smoothed and standardized. submarine. Some abyssal plains are composed of up to a kilometer of sediment accumulated and densified in this way.
Characteristics of the abyssal plains
The abyssal plains are characterized by the following:
- They are flat extensions of underwater terrain, located between 3,000 and 6,000 meters below the sea surface, and in the adjacencies of the continental shelf.
- They can be extremely extensive, stretching hundreds of kilometers in width and thousands of kilometers in length.
- They usually have irregular but elongated shape conforming to the margins of the continental shelf.
- They consist of an abundant sedimentary layer installed on the oceanic crust, generally composed of magnesium silicates (basalt), the result of underwater volcanic eruptions, or the accumulation of materials from the continental shelf and the surface.
- They are regions of little or no luminosity, given the absence of sunlight, and therefore lacking in photosynthetic organisms. Life down there is very different than on the surface.
- They are much more common in the Atlantic Ocean, less common in the Indian Ocean and quite rare in the Pacific. In total, they represent 70% of the ocean floor.
Life on the abyssal plain
Life on the abyssal plain lies adapted to the enormous pressures resulting from the body of water that separates it from the surface, as well as to the lack of sunlight which makes photosynthesis impossible. Furthermore, the temperatures are particularly low, so that vital metabolisms tend to be slow and patients.
Much of life in this region is microscopic, made up of autotrophic bacteria that survive through chemosynthesis, taking advantage of the resources that seismic activity releases on the seabed. There are also small crustaceans, worms and simple-living organisms, many of which survive thanks to the rain of organic matter (waste) that comes from the surface regions.
However, the abyssal plain is often interrupted by occasional hills and elevations (such as mid-ocean ridges), and in these places life flourishes more than in its surroundings, although it does so in dark, deep and poorly productive ecosystems, at least compared to those on the surface.
As to abyssal fish are characterized by a solitary way of life, adapted to extreme conditions. They have a long, slender body, with large jaws that facilitate the capture of the occasional prey.
It is a rare fauna with terrifying features. Many of them are endowed with bioluminescence (that is, the ability to generate light), but not to illuminate their path, since most of them do not depend too much on sight, but as a way to attract their prey.
Examples of abyssal plains
Among the main known abyssal plains, the following stand out:
- The Argentine abyssal plain, located in the deepest region of the Argentine basin, about 6212 meters below sea level and barely 800 km from the Falkland Islands.
- The abyssal plain of Vizcaya, located deep in the Bay of Biscay, off the Spanish coasts of Cantabria, Asturias, Galicia and the Basque Country. This plain is about 2,789 meters deep, separating the two continental shelves of the gulf.
- The abyssal plain of Somalia, part of the so-called Somali basin in the Indian Ocean, east of Africa. Its relief is interrupted by several underwater mountains, which reach the surface forming the islands of the Aldabra group in the Seychelles.
- The Aleutian Abyssal Plains, located in the Aleut Basin in the Bering Sea of the Pacific Ocean, about 3,900 meters below the surface. The region is characterized by deep depressions (trenches) and enormous seismic activity.
- The abyssal plain of Bellingshausen, located in the Antarctic Ocean, south of the final coasts of Chile and close to Antarctica, is a plain that runs along the continental shelf of the latter, and whose name honors the Russian Admiral Fabián Gottlieb von Bellingshausen, who explored the area in the 19th century.