Submarine canyons form the deepest parts of the ocean basins. The average height of the continents above sea level is greater than the average depth of the ocean basins below sea level.
Abyssal plains with sediments covering the seafloor igneous rocks are more extensive in the central Pacific basin than in North Atlantic. The west coast of South America and the east coast of North America have very different continental margins.
An atoll is a low, coral reef island typically surrounding an interior lagoon. Submarine canyons form the deepest parts of the ocean basins. The average height of the continents above sea level is greater than the average depth of the ocean basins below sea level.