9711307 Devine The Southfriere Hills Volcano in Montserrat began erupting on 18 July 1995, creating an urgent need for volcanic hazard assessment. normal components of hazard monitoring (seismicity, ground deformation, etc.) have been complemented by near real-time petrologic studies of eruption products in order to provide estimates of pressure and temperature conditions, and melt volatile content, in the magma storage region beneath the volcano, as well as the rate of magma ascent form that reservoir to the surface. Such information is critical because volatile content and magma ascent rate influence the eruptive style of a volcano. Rapid ascent of water-rich magmas leads to explosive eruptions, whereas slow ascent leads to passive degassing and effusive eruptive behavior. On 17-18 September 1996, the volcano changed briefly from effusive to explosive eruptive style. The change in eruptive behavior resulted from an increase in magma ascent rate. Funding is requested to allow the P.I. to continue petrologic studies that provide estimates of the likelihood of a transition from effusive to explosive eruption behavior.