Magma buoyancy and volatile ascent driving autocyclic eruptivity at Hekla Volcano (Iceland)

作者：Hautmann Stefanie^*; Sacks I Selwyn; Linde Alan T; Roberts Matthew J

来源：Geochemistry Geophysics Geosystems, 2017, 18(9): 3517-3529.

DOI：10.1002/2017GC007061

• borehole strainmeter
• reservoir replenishment
• buoyancy-controlled magma migration
• volatile-driven pressurization
• Hekla

Volcanic eruptions are typically accompanied by ground deflation due to the withdrawal of magma from depth and its effusion at the surface. Here, based on continuous high-resolution borehole strain data, we show that ground deformation was absent during the major effusion phases of the 1991 and 2000 eruptions of Hekla Volcano, Iceland. This lack of surface deformation challenges the classic model of magma intrusion/withdrawal as source for volcanic ground uplift/subsidence. We incorporate geodetic and geochemical observables into theoretical models of magma chamber dynamics in order to constrain quantitatively alternative co- and intereruptive physical mechanisms that govern magma propagation and system pressurization. We find the lack of surface deformation during lava effusion to be linked to chamber replenishment from below whilst magma migrates as a buoyancy-driven flow from the magma chamber towards the surface. We further demonstrate that intereruptive pressure build-up is likely to be generated by volatile ascent within the chamber rather than magma injection. Our model explains the persistent periodic eruptivity at Hekla throughout historic times with self-initiating cycles and is conceptually relevant to other volcanic systems.

• 出版日期2017-9