Abyssal plains, Earth's most common landform are flat (vary no more than a few meters in depth over their entire area), expanses of layered sediments (ooze) that bury the oceanic basaltic crust. They are found in Atlantic ocean, are less common in the Indian ocean, and are relatively rare in the Pacific where trenches mostly trap terrigenous, turbidity-current delivered, sediments. Abyssal plains account for nearly all of the area of deep, ocean floor that is not part of the oceanic ridge system.

The vast muddy expanses of the abyssal plains occupy about 60 percent of Earth's surface and are important in global carbon cycling.

grenadier fish

calcareous tests of foraminifera (protozoa)

Silica tests of Radiolaria (protozoa) (diameter 0.1–0.2 mm)

manganese nodules

fringing reef barrier reef atoll