Global Positioning System geodesy was used to measure surface deformation on Soufriere Hills volcano, Montserrat from October 6, 1995 to July 1, 1997 during initial dome growth and gravitational collapse. Our data from this period show non-axially symmetric horizontal displacements, and decreasing subsidence as a function of radial distance from the former topographic high of the volcanic edifi...

The Ma&tan alnijite contains a rich and varied megacryst suite of unprecedented compositional range. We have undertaken trace element and isotope modeling in order to formulate a petrogenetic scheme which links the host alniiite to its entrained megacrysts. This requires that a proto-alntiite magma is the product of zone refining initiated by diapiric upwelling (where the initial melt passes th...

The very high temperature contrast between magma/lava and water ice commonly leads to the assumption that significant melting will take place immediately upon magma/lava ice contact, yet observations of active flows show little evidence of voluminous melting upon contact. We use analytical thermal models to reassess the efficiency with which heat can be transferred from magma to ice in three si...

Millisecond fluctuations in length of day over multiple decades may induce fluctuations in flow of magma to the surface. We propose that the same magmatic volatiles that greatly amplify volcanic eruptions can also amplify these minute magmatic fluctuations sufficiently to be detected in sea surface temperature.

Three syenite dike sets, named the Santa Cruz dikes, are coeval with the 627 ± 13 Ma old porphyritic calc-alkalic Princesa Izabel granitoid, northeastern Brazil. Dike set 1 is up to 1.5 m wide, strike 030 e040 Az, roughly parallel to the regional foliation. Dike set 2 strikes 120 e130 Az and consists of xenolith-bearing syenites and is roughly parallel to dike set 3, which is up to 1.5 m wide a...

A volcanic crust may be produced as a result of magma ocean processes. Solidification of a magma ocean naturally produces a silicate mantle with denser layers near the surface, therefore unstable to gravitational overturn. The mantle is predicted to rapidly flow in the solid state to gravitational stability. Hot buoyant silicate mantle rising from depth will melt through depressurization and er...

The Neoproterozoic rocks of the Bir Madi area, south Eastern Desert, comprise a metagabbrodiorite complex (GDC) and a tonalite-granodiorite suite (TGrS). The GDC has a weak tholeiitic to strong calc-alkaline character and is made up of olivine gabbro, hornblende gabbro, diorite and monzodiorite. The olivine gabbro is characterized by abundance of augite and labradorite with pseudomorphic serpen...

[1] We explore physical mechanisms controlling formation of a confining conduit plug using 1D, steady-state numerical models of magma ascent. Model results for the welldocumented 1997 Vulcanian explosions at Soufrière Hills volcano were compared against subsurface conditions constrained by geophysical and petrologic analysis. We suggest that, if magma is permeable and overpressured and rock sur...