Hypsography of the continents and ocean floor       Hypsometry is the measurement of land elevation (relative to mean sea level). Bathymetry is the underwater equivalent. A hypsometric curve is a histogram or cumulative distribution function of elevations in a geographical area.         Continental margin Continental margin, the submarine edge of the continental crust distinguished by relatively light and isostatically high-floating material in comparison with the adjacent oceanic crust. It is the name for the collective area that encompasses the continental shelf, continental slope, and continental rise. Continental margins are about 28% of the oceanic area. A continental shelf is a portion of a continent that is submerged under an area of relatively shallow water known as a shelf sea. Much of these shelves has been exposed during glacial periods.           The continental shelf (approx 0.1°), steep continental s...