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 intense pressure and the lack of light 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 exceeds 1,100 standard atmospheres (110 MPa; 16,000 psi).
Read more about this topic: Hadal Zone
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