What is a seamount?

A seamount is an underwater mountain with steep sides rising from the seafloor.

This ~4,200-meter (~13,800-foot) high seamount, dubbed

This ~4,200-meter (~13,800-foot) high seamount, dubbed "Kahalewai," was mapped during the Mountains in the Deep: Exploring the Central Pacific Basin expedition and was found to be almost 1,000 meters taller than previously thought. Image courtesy of the NOAA Office of Ocean Exploration and Research, Mountains in the Deep: Exploring the Central Pacific Basin. Download larger version (jpg, 254 KB).

Seamounts are often remnants of extinct volcanoes and come in a variety of shapes and sizes. By definition, seamounts are geological structures that rise more than 1,000 meters (3,300 feet) above the surrounding the seafloor, but most are much taller than that, rising upwards of 5,000 meters (16,400 feet), sometimes to within a few hundred meters of the ocean surface.

Seamounts can be found in every world ocean basin. While it is difficult to know just how many seamounts there are, they seem to be quite abundant. Using data from satellite altimetry and radar, as well as bathymetric data obtained from survey ships, estimates of the number of seamounts range from 14,700 to more than 33,000 total. Despite their abundance, remarkably, less than one-tenth of a percent of the seamounts in the world have been explored.

Studies conducted over seamounts indicate that seamounts function as “oases of life,” with higher species diversity and biomass found on the seamount and in the waters around it than on the flat seafloor. Seamounts rise up high in the water column, creating complex current patterns influencing what lives on and above them. Seamounts also provide substrate (a location for attachment) where organisms can settle and grow. These organisms provide a food source for other animals. Scientists have found that seamounts often provide habitat to endemic species, or species found only in a single location.