Share facts or photos of intriguing scientific phenomena.

Vital Information About the Abyssal Plains That is Worth Reading

Information About the Abyssal Plains
Just like a mountain and a plateau on the land, our deep ocean surfaces also have different landform features. Abyssal plains are one of those deep sea features. This ScienceStruck article informs you about their characteristics.
Rujuta Patil
Last Updated: May 7, 2018
Echo Sounding
It is a type of SONAR (Sound Navigation And Ranging), which uses sound pulse to gauge the depth of water. The time period between the sound pulse sent and received back is used to determine the ocean bottom.
As the name suggests, abyssal plains are the really deep, unfathomable, less known about, flat expanses below the sea level. These hidden expanses cover around 50% of the Earth. They may not be as rich in biodiversity as the tropical regions, but definitely are a habitat for some exclusive species of fauna, some of which are even today unknown to mankind.
Definition and Formation of Abyssal Plain
Deep underwater plains at the bottom of the ocean floor are known as the Abyssal Plains. They are the flattest areas of the Earth, found between approximately 3000 to 6000 meters under sea. Usually located at the base of the continental rise on one end, they stretch up to the mid-oceanic ridges (divergent plate boundary) on the other. An Abyssal plain is basically the uneven oceanic crust or the oceanic bottom that is leveled by fine sediments accumulating over millions of years together.
Ocean floor showing Abyssal plain
Heavy loads of sediments are carried by the rivers up to the oceans; sometimes even forming huge fan-shaped deltas like the Mississippi river. However, very less amounts of these sediments actually reach the ocean bottom. Finer clay and silt is transported straight down through submarine canyons (huge, deep, and long channels) on to the ocean floor. This process is facilitated by the turbidity currents, which are rapid downflow of sediment carrying, high-density water. Sediments like the remains of biotic marine life, called pelagic deposits, also eventually sink to the deep waters. Volcanic ash, dust particles, and precipitates left of minerals, etc., constitute the rest of the depositions on the plains.
Examples of abyssal plains in the Atlantic Ocean include the Madeira, Nares, Iberia, and Gamba abyssal plains.
Interesting Facts About the Abyssal Plains
Temperature: This zone, being deep down away from any source of light, has a temperature range between approximately 0° - 4°C or 32° - 39°F.

Hydrothermal Vent: Cold sea water seeps down into the oceanic crust through fissures, gets heated, and erupts out in the form of hydrothermal vents. The hot water may reach temperatures of over 300º Celsius, but it still does not boil because of the very high pressures existing at such depths. Sulfide minerals are formed due to the mixing of extremely hot water with the freezing cold water.

Black Smokers: Chimney like structures are formed after cooling of these minerals. Iron sulfide is emitted, giving them the black color.

White Smokers: These are white structures due to the cooling of minerals like calcium, barium, and silicon.

Cold Seeps: These are zones on the sea floor where reduced compounds of methane and sulfide emerge from sediments. The first seep was discovered in the Gulf of Mexico in 1984.

Sea Mount: Mountains on the sea floor rising to a height of about 1000 meters and more, are sea mounts. They are believed to be formed due to volcanic eruptions. Hawaiian Island has an active volcanic sea mount.

Guyot: It is a flat top hill, that is around 200 meter high. Also known as a tablemount, they are formed due to the lava flowing out from volcanic vents.
Metallic nodules of iron, nickel, copper, cobalt, and especially manganese nodules, are also found scattered over these plains due to precipitation of minerals from the ocean water. They can be as small as a pea and as big as a potato. They make the plains resource rich. The International Seabed Authority monitors the licensing for exploitation of these resources.
Marine Life in the Abyssal Plains
Firstly, very little is known about this region of the Earth. Thus, many species of invertebrate organisms discovered here are quite new to science. Holothuroids, rosea, echinoids are a few deposit feeder varieties to name. Hydrothermal vents are also home to some marine life like anemones, tubeworms, clam and other such fish species. For the biotic life under sea, dead remains of phytoplankton and hydrogen sulfide is the only food. Tubeworms, mussels, and clams are found in the Pacific and Atlantic ocean cold seeps too.
The abyssal ecosystem is characterized by limitation of food sources. The detritus matter (also termed as POC or particulate-organic-carbon) sinking from the ocean surface is thus very significant. The bacteria, in absence of sunlight, use the hydrogen sulfide from the vents in the process of chemosynthesis. This is the first and primary link of the food chain. Other creatures depend on these bacteria. Considering the extreme hot temperatures and toxicity of some of the vent fluids, it is a wonder how life exists here. However, apart from the marine life near the vents and seeps, survival of the species elsewhere on the plains is a big concern.
The health of the Abyssal plain ecosystem is in danger when deep oceanic sites become the dumping grounds for human waste, especially radioactive waste. Thus, the biodiversity and the response of the marine life to the changing environment, including climate change impacts, should be considered as something worth paying attention to.