They are found within the bounds of the ocean floor and in the transitional zone and are divided into two morphological typesâflat, or subhorizontal, and hilly. Flat abyssal plains are confined to the margins of ocean basins or to the centers of the basins of epicontinental seas. Hilly abyssal plains occupy a large part of the bottom of the ocean floor. The surface of the flat abyssal plain is characterized by exceptional evenness, with floor gradients of less than 0.001. Starkly contrasting solitary seamounts, evidently of volcanic origin, are also found.
The first person to do so ever was as early as the 3rd century BC by Aristarchus of Samos. Unfortunately, his notion gained only few supporters and was summarily rejected. Later in the 16th century, Nicholas Copernicus presented a mathematical model. In the next century, Johannes Kepler made inclusions of elliptical orbits, and Galileo Galilei presented supporting observations made using a telescope.
In 1444 Nicholas of Cusa again argued for the rotation of the Earth and of other heavenly bodies, but it was not until the publication of Nicolaus Copernicusâs De revolutionibus orbium coelestium libri VI (âSix Books Concerning the Revolutions of the Heavenly Orbsâ) in 1543 that the heliocentric system began to be reestablished.