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'''Hadal zone''' (or ''Hadopelagic zone'') is the delineation for the deepest trenches in the ocean. This zone is found from a depth of around 6000m (19,700 ft) to the bottom of the ocean. ‘Hadal’ means Hades-like.

Contents

Conditions

Notes and references

Conditions

In 1960, Jacques Piccard and Don Walsh reached the Marianas Trench, the deepest trench on Earth, and observed life.^[1] 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 these conditions. 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.
The pressure here can reach over 1100 atmospheres (about 16,200 psi). Creatures removed from this zone will die in the lower-pressure areas above.^[2] The most common creatures include jellyfish, viperfish, tube worms, clams, and the deep sea angler fish.^[3] The hadal zone can reach far below 6,000 meters (20,000 feet) deep; the deepest known is at 10,911 m.

Notes and references

1. ThinkQuest. February 1, 2007.
2. Death of a Hadal Deep-Sea Bacterium After Decompression. February 1, 2007.
3. Meeresboden - down under. February 1, 2007.