<Dd> "Seamount chain" redirects here; for a broader coverage related to this topic, see Undersea mountain range . </Dd> <P> 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 . </P> <P> 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 . </P> <P> 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 . </P>

What is a chain of underwater mountains called