Hadal zone
Overview
 
The hadal zone was the ancient Greek god of the underworld. The genitive , Haidou, was an elision to denote locality: "[the house/dominion] of Hades". Eventually, the nominative came to designate the abode of the dead.In Greek mythology, Hades...

"—in other words "unseen" or "underworld"), also known as the hadopelagic zone and trench zone, is the delineation for the deepest trenches in the ocean.
Encyclopedia
The hadal zone was the ancient Greek god of the underworld. The genitive , Haidou, was an elision to denote locality: "[the house/dominion] of Hades". Eventually, the nominative came to designate the abode of the dead.In Greek mythology, Hades...

"—in other words "unseen" or "underworld"), also known as the hadopelagic zone and trench zone, is the delineation for the deepest trenches in the ocean. This zone is found from a depth of around 6000 metres (19,685 ft) to the bottom of the ocean.

Conditions

In 1960, Jacques Piccard
Jacques Piccard
Jacques Piccard was a Swiss oceanographer and engineer, known for having developed underwater vehicles for studying ocean currents. He was one of only two people, along with Lt...

 and Don Walsh
Don Walsh
Don Walsh is an American oceanographer, explorer and marine policy specialist. He and Jacques Piccard were aboard the bathyscaphe Trieste when it made a record maximum descent into the Mariana Trench on 23 January 1960, the deepest point of the world's ocean...

 reached the bottom of the Mariana Trench
Mariana Trench
The Mariana Trench or Marianas Trench is the deepest part of the world's oceans. It is located in the western Pacific Ocean, to the east of the Mariana Islands. The trench is about long but has a mean width of only...

, the deepest known trench on Earth and observed life. It is believed that most life at this depth is sustained by marine snow
Marine snow
In the deep ocean, marine snow is a continuous shower of mostly organic detritus falling from the upper layers of the water column. It is a significant means of exporting energy from the light-rich photic zone to the aphotic zone below. The term was first coined by the explorer William Beebe as he...

 or the chemical reactions around thermal vents. The lack of light and intense pressure create hostile living conditions and few species are adapted to exist here. As no sunlight reaches this layer of the ocean, deep sea
Deep sea
The deep sea, or deep layer, is the lowest layer in the ocean, existing below the thermocline and above the seabed, at a depth of 1000 fathoms or more. Little or no light penetrates this part of the ocean and most of the organisms that live there rely for subsistence on falling organic matter...

 creatures have adapted with reduced eyesight, having very large eyes for receiving only bioluminescent
Bioluminescence
Bioluminescence is the production and emission of light by a living organism. Its name is a hybrid word, originating from the Greek bios for "living" and the Latin lumen "light". Bioluminescence is a naturally occurring form of chemiluminescence where energy is released by a chemical reaction in...

 flashes. Most of the bottom-dwelling creatures lack any pigmentation, since coloration is not useful in an environment with no light.

Organisms from this zone will die in the zones where pressure is lower. The most common organisms include jellyfish
Jellyfish
Jellyfish are free-swimming members of the phylum Cnidaria. Medusa is another word for jellyfish, and refers to any free-swimming jellyfish stages in the phylum Cnidaria...

, viperfish
Viperfish
A viperfish is a saltwater fish in the genus Chauliodus, with long, needle-like teeth and hinged lower jaws. They grow to lengths of 30 to 60 cm . Viperfish stay near lower depths in the daytime and shallow at night. Viperfish mainly stay in tropical and temperate waters...

, tube worms
Giant tube worm
Giant tube worms, Riftia pachyptila, are marine invertebrates in the phylum Annelida related to tube worms commonly found in the intertidal and pelagic zones...

 and sea cucumbers. The hadal zone can reach far below 6,000 meters (20,000 feet) deep; the deepest known
Mariana Trench
The Mariana Trench or Marianas Trench is the deepest part of the world's oceans. It is located in the western Pacific Ocean, to the east of the Mariana Islands. The trench is about long but has a mean width of only...

extends to 10,911 meters (35,814 ft). At such depths- for example at 36,000 feet below sea level- the pressure in the Hadal zone will reach over 1100 atm (111.5 MPa; 16,165.5 psi).

External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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