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Below this zone, the deep sea consists of the abyssal zone which occurs between the ocean depths of 3000 and 6000 meters [14] and the hadal zone (6000 – 11,000 meters). [ 15 ] [ 16 ] Food consists of falling organic matter known as ' marine snow ' and carcasses derived from the productive zone above, and is scarce both in terms of spatial and ...
At much greater depths, breathing gases become supercritical fluids, making diving with conventional equipment effectively impossible regardless of the physiological effects on the human body. Air, for example, becomes a supercritical fluid below about 400 metres (1,300 ft). For some recreational diving agencies, "Deep diving", or "Deep diver ...
By August 1982, less than 700 metres of the tunnel remained to be excavated. First contact between the two sides was in 1983. [20] The Tsugaru Strait has eastern and western necks, both approximately 20 km (12 mi) across. Initial surveys undertaken in 1946 indicated that the eastern neck was up to 200 metres (656 feet) deep with volcanic geology.
It is defined by light, and begins at the depth where only 1% of incident light reaches and ends where there is no light; the depths of this zone are between approximately 200 to 1,000 meters (~656 to 3,280 feet) below the ocean surface. [1]
Height above mean sea level is a measure of a location's vertical distance (height, elevation or altitude) in reference to a vertical datum based on a historic mean sea level. In geodesy, it is formalized as orthometric height. The zero level varies in different countries due to different reference points and historic measurement periods.
The foot (standard symbol: ft) [1][2] is a unit of length in the British imperial and United States customary systems of measurement. The prime symbol, ′, is commonly used to represent the foot. [3] In both customary and imperial units, one foot comprises 12 inches, and one yard comprises three feet. Since an international agreement in 1959 ...
A nautical mile is a unit of length used in air, marine, and space navigation, and for the definition of territorial waters. [2] [3] [4] Historically, it was defined as the meridian arc length corresponding to one minute ( 1 / 60 of a degree) of latitude at the equator, so that Earth's polar circumference is very near to 21,600 nautical miles (that is 60 minutes × 360 degrees).
Legua nautica (nautical league): Between 1400 and 1600 the Spanish nautical league was equal to four Roman miles of 4,842 feet, making it 19,368 feet (5,903 metres or 3.1876 modern nautical miles). However, the accepted number of Spanish nautical leagues to a degree varied between 14 1/6 to 16 2/3, so in actual practice the length of a Spanish ...