Approximately 75 percent of the ocean seafloor is covered in one of three types of sediments: red clay, calcareous ooze or siliceous ooze. These pelagic, or open ocean, "soils" are generated by a variety of sources.
Red clay is comprised of minerals and less than 30 percent of organic material. By contrast, the oozes feature over 30 percent organic matter, differentiated by content. Calcareous ooze is comprised primarily of the shed calcium carbonate exoskeletons of marine life such as plankton and mollusks. This ooze typically only forms above 14,800 feet in ocean depth. Siliceous ooze forms from silica skeletons of organisms such as microscopic diatoms and warm-water protozoa.