#oceanography notes

Pacific -- area (millions) = 166.2 km² or 64.2 mi² -- average depth = 4,188 meters or 13,741 feet -- deepest place = Marianas Trench

Atlantic -- area (millions) = 86.5 km² or 33.4 mi² -- average depth = 3,736 meters or 12,258 feet -- deepest place = Puerto Rico Trench

Indian -- area (millions) = 73.4 km² or 28.3 mi² -- average depth = 3,872 meters or 12,704 feet -- deepest place = Java Trench

Arctic -- area (millions) = 9.5 km² or 3.7 mi² -- average depth = 1,330 meters or 4,364 feet -- deepest place = Molloy Deep

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-- dead zone = an area of water where oxygen levels have become very low

-- hypoxic = where oxygen is present in a very low concentration

-- dead zones have insufficient oxygen for respiration

-- organisms die or must move

-- occur near coastlines where there are high levels of nutrients washing off agricultural land

-- first one reported in the early 20th century

-- sources:      -- chemical fertilizers      -- sewage waste

-- can form naturally if nutrients are brought up from deep water by wind or current

-- Gulf of Mexico dead zone is the second largest

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