Imaging a growing lava dome with a portable radar.

The tiny Caribbean island of Montserrat has been in a state of crisis since the Soufrière Hills Volcano (SHV) began its current eruption in July 1995. With its main town, Plymouth, destroyed by pyroclastic flows in 1997, the islanders who have remained have had to rebuild their society on the northern half of the island under varying degrees of threat from the volcano to the south. During this time, the Montserrat government continues to receive advice on the volcanic hazards from the Montserrat Volcano Observatory (MVO). The continuing eruption has provided a wealth of research opportunities for many international groups who sought to study the growth and repeated partial destruction of a Peléean andesitic lava dome. There have been three episodes of dome growth: November 1995 through March 1998, November 1999 through July 2003, and August 2005 to present. Pyroclastic flows and explosions have been the main source of hazard. The pyroclastic flows have been generated mainly by gravitational collapse of the lava dome, but also by collapse of explosive ash columns. The dome collapses tend to occur from the area of the dome where new lava is being added. Similarly, collapses are more likely when the rate of lava extrusion varies. Also, the propensity of explosive evacuation of the magma in the conduit is partly controlled by the magma supply rate, with high rates favoring explosions