Subsurface Detection

Satellites can measure the elevation of the sea level surface with astonishing precision. Because their path crosses the same place on Earth over and over again, the effects of waves and tides can be accounted for, and the actual variations in the elevation of sea level can be determined. These variations are most often the result of relief on the ocean floor. Where there is a mountain on the ocean floor, its additional mass draws extra water toward it, which will elevate the level of the sea above it. Where a trench exists on the ocean floor, the absence of mass attracts less water and a depression in the elevation of sea level will occur above it. Many of the detailed maps of the sea floor were obtained indirectly in this way.