Volcanoes are thought to form in three settings: where tectonic plates are diverging (for instance at mid-ocean ridges); where tectonic plates are converging (in island arcs, for example); and in "hotpots" (a generic term for volcanic activity that cannot be attributed to plate tectonic movements. Hotspots are generally thought to be formed by hot, buoyant plumes rising rapidly from the boundary between Earth's core and the mantle.
The "new" volcanoes, which are actually between one and eight million years old, are not at plate boundaries. But neither were they formed by deep plumes. The team thinks the mini-volcanoes were created when cracks formed in the Earth's crust during the elastic bending of the northwestern Pacific plate, which is diving under the Kuril and Japan trenches. They think partially melted material from the upper mantle squeezed out of the cracks, to form the volcanoes.
(Story credit: Emma Young, New Scientist Online,
Click here to read the complete article.
(Journal reference: Science (DOI: 10.1126/science.1128235 and 1131298)