Seamounts can be found in every ocean basin in the world, distributed extremely widely both in space and in age. A seamount is technically defined as an isolated rise in elevation of 1,000 m (3,281 ft) or more from the surrounding seafloor, and with a limited summit area, of conical form. There are more than 14,500 seamounts. In addition to seamounts, there are more than 80,000 small knolls, ridges and hills less than 1,000 m in height in the world's oceans.
Most seamounts are volcanic in origin, and thus tend to be found on oceanic crust near mid-ocean ridges, mantle plumes, and island arcs. Overall, seamount and guyot coverage is greatest as a proportion of seafloor area in the North Pacific Ocean, equal to 4.39% of that ocean region. The Arctic Ocean has only 16 seamounts and no guyots, and the Mediterranean and Black seas together have only 23 seamounts and 2 guyots. The 9,951 seamounts, which have been mapped, cover an area of 8,088,550 km2 (3,123,010 sq mi). Seamounts have an average area of 790 km2 (310 sq mi), with the smallest seamounts found in the Arctic Ocean and the Mediterranean and Black Seas, whilst the largest mean seamount size occurs in the Indian Ocean 890 km2 (340 sq mi). The largest seamount has an area of 15,500 km2 (6,000 sq mi) and it occurs in the North Pacific. Guyots cover a total area of 707,600 km2 (273,200 sq mi) and have an average area of 2,500 km2 (970 sq mi), more than twice the average size of seamounts. Nearly 50% of guyot area and 42% of the number of guyots occur in the North Pacific Ocean, covering 342,070 km2 (132,070 sq mi). The largest three guyots are all in the North Pacific: the Kuko Guyot (estimated 24,600 km2 (9,500 sq mi)), Suiko Guyot (estimated 20,220 km2 (7,810 sq mi)) and the Pallada Guyot (estimated 13,680 km2 (5,280 sq mi)).
- "Seamount chain" redirects here; for a broader coverage related to this topic, see Undersea mountain range.
Seamounts are often found in groupings or submerged archipelagos, a classic example being the Emperor Seamounts, an extension of the Hawaiian Islands. Formed millions of years ago by volcanism, they have since subsided far below sea level. This long chain of islands and seamounts extends thousands of kilometers northwest from the island of Hawaii.
Distribution of seamounts and guyots in the North Pacific
Distribution of seamounts and guyots in the North Atlantic
There are more seamounts in the Pacific Ocean than in the Atlantic, and their distribution can be described as comprising several elongate chains of seamounts superimposed on a more or less random background distribution. Seamount chains occur in all three major ocean basins, with the Pacific having the most number and most extensive seamount chains. These include the Hawaiian (Emperor), Mariana, Gilbert, Tuomotu and Austral Seamounts (and island groups) in the north Pacific and the Louisville and Sala y Gomez ridges in the southern Pacific Ocean. In the North Atlantic Ocean, the New England Seamounts extend from the eastern coast of the United States to the mid-ocean ridge. Craig and Sandwell noted that clusters of larger Atlantic seamounts tend to be associated with other evidence of hotspot activity, such as on the Walvis Ridge, Bermuda Islands and Cape Verde Islands. The mid-Atlantic ridge and spreading ridges in the Indian Ocean are also associated with abundant seamounts. Otherwise, seamounts tend not to form distinctive chains in the Indian and Southern Oceans, but rather their distribution appears to be more or less random.
Isolated seamounts and those without clear volcanic origins are less common; examples include Bollons Seamount, Eratosthenes Seamount, Axial Seamount and Gorringe Ridge.
If all known seamounts were collected into one area, they would make a landform the size of Europe. Their overall abundance makes them one of the most common, and least understood, marine structures and biomes on Earth, a sort of exploratory frontier.