No trigger required

Most volcanoes need some kind of external event to trigger an eruption.  Often an earthquake on a fault will create a weakness that allows the pressure to escape.  Supervolcanoes, whose eruptions can be cataclysmic, were always a bit of a puzzle when it came to working out what set them off.  However a team of Swiss geologists have discovered that they don't need a trigger.  Their size alone is enough to generate enough pressure in the magma to generate an eruption.  Though this may be a little worrying, supervolcanoes have long time gaps between eruptions - roughly 100,000 years.  Of course we don't know exactly when in that time period the big bang will happen....