Hadal zone

"Hadal" redirects here. For the album by Velcra, see Hadal (album).

Aquatic layers
	Pelagic
	Photic
	Epipelagic
	Aphotic
	Mesopelagic
	Bathyalpelagic
	Abyssopelagic
	Hadopelagic
	Demersal
	Benthic
Stratification
	Pycnocline
	Isopycnal
	Chemocline
	Halocline
	Thermocline
	Thermohaline
Marine habitats
Lake stratification
Aquatic ecosystems
Wild fisheries

The hadal zone is the deepest part of the marine environment

The hadal zone (named after the Greek god, Hades, god of the 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 6,000 metres (20,000 ft) to the bottom of the ocean.

Conditions

In 1960, Jacques Piccard and Don Walsh reached the bottom of the Mariana Trench, the deepest known trench on Earth and observed life. It is believed that most life at this depth is sustained by marine snow 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 creatures have adapted with reduced eyesight, having very large eyes for receiving only bioluminescent 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, viperfish, tube worms and sea cucumbers. The hadal zone can reach far below 6,000 meters (20,000 feet) deep; the deepest known 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 1,100 standard atmospheres (110 MPa; 16,000 psi).

External links

• Forscher filmen lebende Fische in Rekordtiefe (In German) from Spiegel 10/09/2008 about an expedition filming fish at a depth of more than 7,000 m