Magma supply dynamics at Westdahl volcano, Alaska, modeled from satellite radar interferometry

Abstract

[1] A group of satellite radar interferograms that span the time period from 1991 to 2000 shows that Westdahl volcano, Alaska, deflated during its 1991-1992 eruption and is reinflating at a rate that could produce another eruption within the next several years. The rates of inflation and deflation are approximated by exponential decay functions having time constants of about 6 years and a few days, respectively. This behavior is consistent with a deep, constant-pressure magma source connected to a shallow reservoir by a magma-filled conduit. An elastic deformation model indicates that the reservoir is located about 6 km below sea level and beneath Westdahl Peak. We propose that the magma flow rate through the conduit is governed by the pressure gradient between the deep source and the reservoir. The pressure gradient, and hence the flow rate, are greatest immediately after eruptions. Pressurization of the reservoir decreases both the pressure gradient and the flow rate, but eventually the reservoir ruptures and an eruption or intrusion ensues. The eruption rate is controlled partly by the pressure gradient between the reservoir and surface, and therefore it, too, decreases with time. When the supply of eruptible magma is exhausted, the eruption stops, the reservoir begins to repressurize at a high rate, and the cycle repeats. This model might also be appropriate for other frequently active volcanoes with stable magma sources and relatively simple magma storage systems.

A two‐magma chamber model as a source of deformation at Grímsvötn Volcano, Iceland

“…It is difficult to distinguish between these two components, such that most of the models that are used to interpret deformation measurements can be classified into two end-members. The first set of models considers a magma reservoir surrounded by an elastic homogeneous medium and fed or drawn out through a hydraulic connection [Lu et al, 2003[Lu et al, , 2010Mastin et al, 2008], thus favoring a complex pressure evolution within the magma reservoir. In contrast, the second set of models usually considers a more simplistic pressure scenario, most often as a sudden pressurization that acts over a viscoelastic or poroelastic medium.…”

“…However, these time constants are significantly smaller than those obtained for other basaltic volcanoes. Lengliné et al [2008] reported = 1.13 years for Kilauea Volcano and = 7.3 years for Mauna Loa Volcano, and Lu et al [2003] reported = 6 years for Westdahl Volcano. This difference can easily be explained either by a stronger hydraulic connection between the two reservoirs (a larger conduit with a smaller vertical extension) or by less viscous magma.…”

“…Usually, the inflation rate is greater just after eruptive events and then it decreases with time [Lu et al, 2003[Lu et al, , 2010Sturkell et al, 2006]. This behavior with exponentially decaying uplift following an eruption was monitored by interferometric synthetic aperture radar (InSAR) measurements after the 1991 Westdahl eruption [Lu et al, 2003] and after the 1997 eruption at Okmok Volcano [Lu et al, 2010].…”

Caldera-scale inflation of the Lazufre volcanic area, South America: Evidence from InSAR

“…8 is a compilation of selected recent works at volcanic areas subject to inflation larger than 5 km in diameter. We retrieve approximate diameters from previous geodetic studies (Amelung et al, 2000;Feigl et al, 2000;Lu et al, 2000Lu et al, , 2002aPritchard and Simons, 2002;Masterlark and Lu, 2004;Pedersen and Sigmundsson, 2004;Newman et al, 2006;Lundgren and Lu, 2006;Wicks et al, 2006) and add also the dimension of the Lazufre area for the four observed periods shown in Fig. 3.…”

Volcano deformation monitoring using GPS

“…Around the vent of the New Trident volcano in Alaska, a 7-9cm uplift was observed over a 2-year period by Lu et al (1997). Other case studies were reported by Rosen et al (1996), Amelung et al (2000), Lu et al (2003) and Furuya (2004). Due to its high degree of spatial coverage and completeness (spatial resolution of a few 10m over an image size of 100km × 100km), its cost-effectiveness and ability to penetrate clouds, the use of InSAR is certainly a beneficial option in complex and inaccessible terrain.…”