Volcanic Eruption Dynamics

Why do volcanoes often show a range of activity, from energetic explosions that emit large amounts of pumice and ash to those that generate lava flows and domes?  Contrasting behaviour at volcanoes is often not just a function of the composition of magma erupted, but may also be due to the physics of magma flowing in conduits and degassing/crystallization processes that stem from decompression and cooling. Prof. Jonathan Castro has initiated several field-based case studies at volcanoes that have recently erupted in both explosive and effusive manners in order to better constrain the controls on eruption style.  The focus of these studies is to make primary field observations of eruption phenomena, document deposit characteristics corresponding to different activities, and to collect samples of fresh lava and tephra. One prime example is Chaitén Volcano, Chile, which erupted rhyolite magma in May, 2008 and continues to effuse lava today.  Collaborators on these projects include the USGS and SERNAGEOMIN volcano hazards teams.