An ocean bank, sometimes referred to as a fishing bank or simply bank, is a part of the seabed which is shallow compared to its surrounding area, such as a shoal or the top of an underwater hill. Somewhat like continental slopes, ocean banks slopes can upwell as tidal and other flows intercept them, resulting sometimes in nutrient rich currents.[how?] Because of this, some large banks, such as Dogger Bank and the Grand Banks of Newfoundland, are among the richest fishing grounds in the world.
There are some banks that were reported in the 19th century by navigators, such as Wachusett Reef, whose existence is doubtful.
Ocean banks may be of volcanic nature. Banks may be carbonate or terrigenous. In tropical areas some banks are submerged atolls. As they are not associated with any landmass, banks have no outside source of sediments. Carbonate banks are typically platforms, rising from the ocean depths, whereas terrigenous banks are elevated sedimentary deposits.
Seamounts, by contrast, are mountains rising from the deep sea and are steeper and higher in comparison to the surrounding seabed. Examples of these are Pioneer and Guide Seamounts, west of the Farallon Islands. The Pioneer Seamount has a depth of 1,000 meters, In other cases, parts of a bank may reach above the water surface, thereby forming islands.
The largest banks in the world are: