hadalzonen

Hadalzonen are the deepest parts of the world's oceans, extending from about 6,000 meters (roughly 19,700 feet) to the ocean floor in the deepest trenches. The term derives from Hades, the Greek god of the underworld, reflecting the extreme depth, darkness, and inaccessibility of these waters.

Environmental conditions in the hadal zone include hydrostatic pressures exceeding 1,000 atmospheres, near-freezing temperatures of about 1–4°C, and complete darkness. Food is scarce, and organisms rely on marine snow, detritus, and occasional chemosynthetic inputs.

Biota in hadal zones are highly specialized and often small in number but can be diverse in their adaptations. Common groups include amphipods and isopods, along with hadal snailfishes of the Liparidae family. Species show adaptations to high pressure, such as altered membranes and enzymes.

Distribution and depth: Hadal zones occur in ocean trenches worldwide, including the Mariana, Tonga, Japan, Izu-Bonin, Kuril-Kamchatka, and Peru-Chile trenches. The deepest point on Earth lies in the Mariana Trench's Challenger Deep, at about 10,900–11,000 meters.

Exploration and research: The hadal zone first yielded direct observations during the 1960 Trieste descent. Since then, deep-diving submersibles and remotely operated vehicles have increased sampling and imaging. Modern expeditions continue to map trenches and study their unique communities, ecology, and biogeography, despite ongoing technological challenges.