Scientists say they've discovered a magma buildup near a New Zealand town that explains a spate of recent earthquakes and could signal the beginnings of a new volcano—although they're not expecting an eruption anytime soon. Geophysicist Ian Hamling said that since 1950, enough magma to fill 80,000 Olympic-size swimming pools has squeezed up beneath the surface near the coastal town of Matata, about 200 kilometers (120 miles) southeast of Auckland. A paper published Saturday in the online journal Science Advances outlines the findings. Hamling, the paper's lead author, said that while other parts of New Zealand have active volcanoes, there have been none near Matata for at least 400,000 years. Please Register or Log in to view the hidden image! http://phys.org/news/2016-06-scientists-magma-buildup-zealand-town.html Paper: http://advances.sciencemag.org/content/2/6/e1600288
If my maths is good this is about 0.6 cubic km of magma - a fairly respectable accumulation. As I understand it, around subduction zones you get magma ascending from the descending slab in the form of diapirs. I presume this is what is happening here. I see the magma is said to be at a depth of 10km, which is quite shallow. I do not know what depth the top of the subducted slab would be at this location. Maybe Ophiolite could comment on this - it is his speciality I think......
