Volcanic activity can be broadly divided into two types: effusive, which is generally not dangerous and consists of the production of lava domes and flows, or explosive, which is far more dangerous and produces eruption columns, ash fall, pyroclastic flows and ballistics.
Many people have worked on aspects of each type of activity and some models consider the transition between the two styles. Volcán de Colima has increased in its activity since 1998. Since then, it has switched several times from effusive to explosive and back, and during certain periods has produced both types of activity simultaneously. This makes it an excellent laboratory to study the transition.
Various data sets are being integrated to define a model to explain the transitions. The complex nature of eruption dynamics can imply that a relatively small variation in one parameter, such as the volatile contents of the magma, ascent velocity in the conduit, magma permeability or crystallisation could lead to a switch in eruption style. It is difficult to quantify many of these variables, but by observing the relationship between different measurable parameters a model is being produced.
Lava dome from crater rim, Nov. 2001
Dome from South, January 2002
Explosion 29th of January 2005