[1] Thirty interferometric synthetic aperture radar (InSAR) images, spanning various intervals during 1992–2000, document coeruptive and posteruptive deformation of the 1992–1993 eruption on Seguam Island, Alaska. A procedure that combines standard damped least squares inverse methods and collective surfaces, identifies three dominant amorphous clusters of deformation point sources. Predictions...

Understanding the mechanisms that control the start-up of volcanic unrest is crucial to improve the forecasting of eruptions at active volcanoes. Among the most active volcanoes in the world are the so-called persistently degassing ones (e.g., Etna, Italy; Merapi, Indonesia), which emit massive amounts of gas during quiescence (several kilotonnes per day) and erupt every few months or years. Th...

Measurements of CO2 fluxes from open-vent volcanos are rare, yet may offer special capabilities for monitoring volcanos and forecasting activity. The measured fluxes of CO2 and SO2 from Mount St. Helens decreased from July through November 1980, but the record includes variations of CO2/SO2 in the emitted gas and episodes of greatly increased fluxes of CO2. We propose that the CO2 flux variatio...

By using recently determined experimental phase equilibria we show that the viscosity of granitic magmas emplaced atupper crustal levels is approximately constant a -• 104.5 Pa s, irrespective of their temperature and level of emplacement. Magmas crystallizing as granitic plutons are not water-poor and thus not more viscous than their extrusive equivalents. Instead, comparison between pre-erupt...

The Hapaimamo flow contains xenoliths of gabbronorites, troctolites, dunites, websterites and periodotites. Composition of cumulate olivines ranges from Fo78-86, clinopyroxenes ranges from En47-53Wo37-40Fs8-12, and orthopyroxenes ranges from En71-83Wo2-5Fs13-25. Most xenoliths display an intergranular, subpoikilitic or poikilitic texture. Petrologic and compositional information point towards a...

One of the greatest remaining problems in modern volcanology is the process by which volcanic eruptions are triggered. It is generally accepted that eruptions are preceded by magma intrusion [Sigurdsson and Sparks, 1978]. The degree of interaction between previously ponded magma in a chamber and newly intruded magma determines the nature and rate of eruption and also the chemistry of erupted la...

Intrusions of magma induce thermal aureoles in the country rock. Analytical solutions predict that the thickness of an aureole is proportional to the thickness of the intrusion. However, in the field, thermal aureoles are often significantly thinner or wider than predicted by simple thermal models. Numerical models show that thermal aureoles are wider if the heat transfer in the magma is faster...

Ground deformation often precedes volcanic eruptions, and results from complex interactions between source processes and the thermomechanical behaviour of surrounding rocks. Previous models aiming to constrain source processes were unable to include realistic mechanical and thermal rock properties, and the role of thermomechanical heterogeneity in magma accumulation was unclear. Here we show ho...

[1] Volcanic eruptions are often accompanied by spatiotemporal migration of ground deformation, a consequence of pressure changes within magma reservoirs and pathways. We modeled the propagation of pressure variations through the east rift zone (ERZ) of K ılauea Volcano, Hawai‘i, caused by magma withdrawal during the early eruptive episodes (1983–1985) of the ongoing Pu‘u ‘ O‘ o-Kupaianaha erup...

The emplacement of the Mesoproterozoic Götemar Pluton into Paleoproterozoic granitoid host rocks of the Transscandinavian Igneous Belt is re-examined by microfabric analysis, including cathodoluminescence microscopy. Field data on the pluton-host rock system are used to strengthen the model. The Götemar Pluton, situated on the Baltic Shield of SE Sweden, is a horizontally zoned tabular structur...