What methods do scientists use to determine the bathymetry of the ocean floor, and how do they work?

Answer 1

?Scientists use information from many different sources to get a clearer idea of the details of the ocean floor. Echo sounders are used to bounce sound waves off the seafloor. Sound waves are emitted from a ship at the surface and as they hit the bottom, the sound waves are reflected back to the ship. The depth is determined by D=V (T/2), where V is the velocity of the sound waves, T is time it takes for the sound waves to travel away from and back to the ship.
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Another method is called a multibeam echo sounder system, which uses many beams (up to 121 ) that radiate from a ship. When the ship moves along a transect pattern, like mowing the lawn, information from all the beams combined gives scientists a fairly accurate map of greater areas of the ocean floor. A third system uses satellites to gather information about the ocean floor. Since satellites cannot measure the ocean floor directly, they measure small variations in the elevation of the surface water. Subtle irregularities in the sea surface are caused by differences in the pull of gravity depending on the nearness of massive parts of the earth-such as an undersea mountain or ridge. Although these elevation variations cannot be seen with the unaided eye, satellites can detect them.