[aerohead]

A year or so ago, PBS' NOVA, or Secrets of the Dead, broadcast a program about the Japanese team which scanned the Egyptian pyramid, using the cosmic particles as the scanning beam. Clever!
Seems like it took a rather long time, for enough particles to stream in, sufficient enough to collect an image.
I'm unsure how a sensor array, large enough to image a volcano's underlying magma chamber could be constructed, or how, an imaging team could receive enough funding to construct and bury it 'underneath.' The single cost might exceed the entire GDP of some nations. And there's thousands of volcanoes to monitor.