"Well No. 4 in this area was being drilled at this site here when suddenly an underground steamexplosion managed to get its way to the surface, " he explains.
Furthermore, it would take a combination of extreme events to make things dangerous in Tokyo (nuclear re-criticality, steamexplosion) etc all of which are being rendered less and less likely as time passes and the heat decay process progresses.
Institute Director Renato Solidum said the explosion early Tuesday was "steam-driven" and is considered "normal" activity for a volatile volcano like Mount Mayon.