Between 3000 and 6000 meters below the ocean surface, over 50% of the earths surface is covered by what formations

An abyssal plain is an underwater plain on the deep ocean floor, usually found at the depths between 3000 and 6000 m. Lying generally between the foot of a continental rise and a mid-ocean ridge, abyssal plains cover more than 50% of the Earth's surface. They are among the flattest, smoothest, and least explored regions on Earth.