Discovery of a new type of seamount chain in the Pacific Ocean

Nature Geoscience article reports a new kind of volcanic chain that might link plate tectonic events around the margins of the Pacific to the unique bend in the Hawaiian–Emperor seamount chain.

05/01/2015 | 4:10 PM

Ocean islands, seamounts and volcanic ridges are thought to form above mantle plumes – hot upwellings that probable rise from the core-mantle boundary. Yet, this mechanism cannot explain many volcanic features on the Pacific Ocean floor and some might instead be caused by cracks in the oceanic crust linked to the reorganisation of plate motions. 

An international team that includes visiting researcher John O’Connor, and researcher Jan Wijbrans (Geology and Geochemistry cluster), has found a new type of seamount chain with a geochemical signature that is surprisingly unlike typical ocean island basalts and instead resembles mid-ocean ridge basalts. The authors conclude in their paper that the chains are unrelated to mantle plume activity and probably formed in an extensional setting due to deformation of the Pacific Plate.

Subduction zones are active around the margins of the Pacific causing the ‘Ring of Fire’, the most seismically and volcanically active zone in the world. A major reorganisation of Pacific subduction zones could have deformed the Pacific plate and triggered the chains, while at the same time the Hawaiian–Emperor seamount chain was developing a major 60° bend.

Hawaii-Emperor-bend
Hawaii-Emperor bend - Image reproduced from the GEBCO world map 2014, www.gebco.net

The origin of such a distinctive bend in the Hawaiian–Emperor seamount chain has long puzzled Earth scientists and is explained by changes in the direction of motion of the Pacific Plate or the movement of the Hawaiian plume, or a combination of both.

The research team speculates that the Hawaiian-Emperor bend was formed by a change in the motion of the Hawaiian plume caused by a major reorganisation of the plate-mantle system that was potentially triggered by a series of subduction events at the Pacific Plate margins.