article_snippet: Dr Lowell Miyagi also said the stiff upper part of the lower mantle may explain different magmas seen at two different kinds of seafloor volcanoes.
article_snippet: Recycled crust and mantle from old slabs eventually emerges as new seafloor during eruptions of volcanic vents along mid-ocean ridges - the rising end of the conveyor belt.
article_snippet: The magma in this new plate material has the chemical signature of more recent, shallower, well-mixed magma that had been subducted and erupted through the conveyor belt several times.
article_snippet: But in island volcanoes like Hawaii, created by a deep hotspot of partly molten rock, The magma in this new plate material is older, from deeper sources and less well-mixed.
article_snippet: Dr Lowell Miyagi said the viscous layer in the lower mantle may be what separates the sources of the two different magmas that supply the two different kinds of volcanoes.