New research by a team of US and UK scientists into the Soufrière Hills volcano on the Caribbean island of Montserrat shows that they are far more complex than previously thought. While the pattern of eruptions on the surface would lead an observer to believe that magma was produced in fits and starts beneath a volcano, the study found that magma production and eruptions were separate parts of a complex system involving two chambers and some kind of control valve between the deeper magma-producing part and the shallower part that feed the eruption. Geologists previously believed the shallower part of the system controlled the timing of eruptions. The Montserrat study indicates that the shallower chamber is a fairly passive element in the system and that it is the channel between the upper and lower chambers acting like an on/off valve that really controls the eruptions.
Naturally, these results will need to be compared to other volcanoes to see if they are universal or peculiar to that one volcano. At the very least, the study tells us that volcanoes are complicated systems and that dependable long-term predictions of their behavior is still a ways off. In the meanwhile, this points he way to future research. I hear the Discovery institute is working on figuring out how the angels who control the valve decide when bad homosexual behavior downwind from the volcano needs punishing.