Seamounts are submarine volcanoes that form when magma is focused in a single location. Most large seamounts are found away from tectonic plate boundaries, where there is no clear magma source. The hotspot hypothesis proposes that intra-plate volcanoes are produced by plumes of hot, low-density material rising up from the deep mantle. Since tectonic plates move over these supposedly stationary plumes, trails of seamounts are formed over time spans of up to 130 million years.

Diagram of how mantle plumes generate age-progressive seamount trails.

Overarching Questions:

  • If magma supply from a plume is constant, why do we get individual seamounts instead of a continuous volcanic ridge?
  • What is the diameter of a plume? Seamount trails such as the Walvis Ridge have coeval volcanism at points more than 200 km apart.
  • What controls the size and shape of a seamount? Does the distribution of lava flow morphologies and the amount of volcaniclastic material play a role?
  • How do axial, near-ridge and fracture-related intra-plate seamounts differ from hotspot seamounts?