Oceanography is the study of all aspects of, and phenomena associated with, the oceans and seas. The major sub-disciplines of oceanography include marine geology (see plate tectonics), marine biology, marine meteorology, and physical and chemical oceanography.
Most modern maps of the seafloor are compiled by use of echo sounders, the vessel's position at sea being accurately determined by radar or otherwise. Water sampling, in order to determine, for example salinity and oxygen content, is also important. Sea-floor sampling, to determine the composition of the sea-floor, is carried out by use of dredges, grabs, etc., and especially by use of hollow drills which brings up cores of rock.
Ocean currents can be studied by use of buoys, drift bottles, etc., and often simply by accurate determinations of the different positions of a ship allowed to drift. Further information about the sea bottom can be obtained by direct observations, by study of the deflections of seismic waves (see earthquake) or by satellite.
History of oceanography
The science of oceanography dates from the Challenger expedition (1872–76). Jacques Cousteau's invention of the scuba aided human exploration of the seas. In 1948, the bathyscaphe, invented by August Piccard, was first used. The Deep Sea Drilling Project is a long-term investigation of the evolution of ocean basins.