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The hadal zone, also known as the hadopelagic zone, is the deepest region of the ocean, lying within oceanic trenches.The hadal zone ranges from around 6 to 11 km (3.7 to 6.8 mi; 20,000 to 36,000 ft) below sea level, and exists in long, narrow, topographic V-shaped depressions.
In British and Canadian military argot it equates to a range of terms including slit trench, or fire trench (a trench deep enough for a soldier to stand in), a sangar (sandbagged fire position above ground) or shell scrape (a shallow depression that affords protection in the prone position), or simply—but less accurately—as a "trench".
A trench of the Änäkäinen fortification in Lieksa, Finland. A well-developed trench had to be at least 2.5 m (8 ft) deep to allow men to walk upright and still be protected. There were three standard ways to dig a trench: entrenching, sapping, and tunneling. Entrenching, where a man would stand on the surface and dig downwards, was most ...
In trench warfare, soldiers occupy trenches to protect them against weapons fire and artillery. Trenches are dug using manual tools such as shovel and pickaxe or heavy equipment such as backhoe, trencher, and excavator. For deep trenches, the instability of steep earthen walls requires engineering and safety techniques such as shoring.
The early phase of trench exploration reached its peak with the 1960 descent of the Bathyscaphe Trieste to the bottom of the Challenger Deep. Following Robert S. Dietz ' and Harry Hess ' promulgation of the seafloor spreading hypothesis in the early 1960s and the plate tectonic revolution in the late 1960s, the oceanic trench became an ...
The final zone includes the deep oceanic trenches, and is known as the hadal zone. This, the deepest oceanic zone, extends from a depth of 6,000 metres down to approximately 11,034 meters, at the very bottom of the Mariana Trench, the deepest point on planet Earth.
But trenches were very soon extended to avoid this; they were dug deeper and connected by deep or even underground passages to bunkers far behind the lines, where defenders could safely wait out bombardments. When the bombardment stopped, this signalled the start of the attack to the defenders, and they quickly moved back to their forward ...
The ocean floor is not all flat but has submarine ridges and deep ocean trenches known as the hadal zone. [6] For comparison, the pelagic zone is the descriptive term for the ecological region above the benthos, including the water column up to the surface.