They were unsure if the organisms in the sample were from the bottom or were the dead remnants of shallower animals. The HMS Challenger expedition from 1873 to 1876 was the first to physically sample the hadal zone, when members collected a small sediment grab at about 8,000 meters (about 26,000 feet) in the Japan Trench. The important thing is not the exact depth or which is the deepest, but the fact they are really deep.ģ. Four other trenches also exceed 10,000 meters in depth: the Tonga, Kuril-Kamchatka, Philippine, and Kermadec. On March 24, 1995, the Japanese ROV Kaiko descended to 10,911 meters (35,797 feet) and placed a plaque to mark the trench as the deepest point on Earth. Since 1951, it has been measured by researchers from Britain, the U.S.S.R., Japan, and the United States with results that vary from a minimun depth of 10,599 meters (34,774 feet) to a maximum of 10,971 meters (35,994 feet). This method was used to sound the depths of the Middle America, Tonga, Peru-Chile, Japan, and Mariana trenches, but the exact depth of the deepest point in the ocean, currently located in the Mariana Trench, is rather difficult to determine. The extreme depths of the hadal trenches were discovered using “bomb sounding,” whereby someone threw a half-pound block of TNT off a ship and the echo of the explosion off the seafloor was recorded on board the ship via a transducer amplifier. Trenches (black), plunging to more than 10,000 meters deep, make up a small proportion of the total seafloor but constitute a vast habitat for organisms able to adapt to the very high pressure and other challenges of life at such great depth.Ģ. The abyssal plains (yellow), ranging from about 4,500 to 6,500 meters deep, make up nearly half the seafloor. Slightly more than half the seafloor (gray) is shallower than 4,500 meters deep. Hades was also renowned for his overwhelming wrath towards anyone who tried to leave, which might be analogous to the effects of decompression on organisms specifically adapted to high pressure if they are removed from the trench. It is interesting to note that, although he was also once considered more altruistic than he is now, he was known to strictly forbid the inhabitants of his dominion to leave, which is a rather apt analogy for hadal fauna, as the species inhabiting hadal depths are often confined to one or more trenches and rarely capable of leaving. The term can also be loosely translated as “the unseen,” “abode of the dead,” or “the dominion of Hades.” In modern days, Hades is seen as evil, but in mythology he was often portrayed as more passively angry than actively malicious. According to myth, the three brothers defeated the Titans and claimed dominion over the Underworld, air, and sea, respectively. The term “hadal” comes from “Hades ,” which refers both to the Greek kingdom of the Underworld and the god of the Underworld himself, Hades (son of Cronus and Rhea and brother of Zeus and Poseidon). (Photo by Ken Kostel, Woods Hole Oceanographic Institution)Īlan Jamieson, biologist from the University of Aberdeen and author of the upcoming book The Hadal Zone, provided his Top 10 Random Trench Anecdotes:ġ. University of Aberdeen biologist Alan Jamieson prepares bait for a lander, a device he uses to lure deep-sea fish within range of a camera.
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