In a new study, scientists suggest that a seamount found previously west of Peru could represent a completely new type of seafloor volcanism, fueled by a hidden, shallow reservoir of magma. Evidence of isolated volcanism such as this could provide a unique window into Earth’s interior.
Most of Earth’s 1500 active volcanoes are located underwater. The vast majority of these form at the boundaries of tectonic plates: either seafloor spreading centers, where newly erupted lava drives plates apart, or at subduction zones, where plates dive beneath one another, leading to melting of the mantle beneath that can trigger eruption.
However, none of these existing theories can explain the new seamount, which is nowhere near any known mantle plumes and is located hundreds of kilometers from the Nazca plate boundaries on which it sits.
By using data from previous studies that used seismic techniques to image Earth’s upper mantle, the researchers found an unusually high concentration of magma at about 70 km beneath this part of the Nazca plate. Seafloor spreading centers often contain magma reservoirs at such relatively shallow depths, but it was surprising to find magma at this depth in the region under study.