Abyssal Plains

Abyssal Plains

Flat, generally featureless plains that form large areas on the seafloor. In the Atlantic Ocean, abyssal
plains form large regions on either side of the Mid-Atlantic Ridge, covering the regions from about 435–620 miles (700–1,000 km), and they are broken occasionally by hills and volcanic islands such as the Bermuda platform, Cape Verde Islands, and the Azores. The deep abyssal areas in the Pacific Ocean are characterized by the presence of more abundant hills or seamounts, which rise up to 0.6 miles (1 km) above the seafloor. Therefore, the deep abyssal region of the Pacific is generally referred to as the abyssal hills instead of the abyssal plains. Approximately 80–85 percent of the Pacific Ocean floor lies close to areas with hills and seamounts, making the abyssal hills the most common landform on the surface of the Earth. Many of the sediments on the deep seafloor (the abyssal plain) are derived from erosion of the continents and are carried
to the deep sea by turbidity currents, wind (e.g., volcanicash), or released from floating ice. Other sediments, known as deep-sea oozes, include pelagic sediments derived from marine organic activity. When small organisms die, such as diatoms in the ocean, their shells sink to the bottom and over time can create significant accumulations. Calcareous ooze occurs at low to middle latitudes where warm water favors the growth of carbonate-secreting organisms. Calcareous oozes are not found in water that is more than 2.5–3 miles (4–5 km) deep, because this water is under such high pressure that it contains dissolved CO2 that dissolves carbonate shells. Siliceous ooze is produced by organisms that use silicon tomake their shell structure.