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- Title
Oscillatory nature of the Okmok volcano's deformation.
- Authors
Walwer, Damian; Ghil, Michael; Calais, Eric
- Abstract
The time-dependent deformation of volcanic edifices can help one understand the dynamics of pre-eruptive overpressure build-up in magma chambers. Thus, geodetic time series recorded at the Okmokvolcano, in Alaska, show a pattern of fast and short inflations — referred to as "pulses" — followed byeither slower and longer deflations, or time intervals with no deformation. This pattern is superimposedonto a longer-period inflation. A rapid inflation occurred just before the 2008 eruption, which suggeststhat the underlying process may lead to eruptions. It is crucial to understand whether such a behavioris driven by external forcing, such as melt supply variations, or whether it can develop spontaneouslywithin the volcano's plumbing system. Here we model the observed oscillations (2004–2008) as resultingfrom the hydraulic interaction between two shallow magma chambers fed by a deeper source region, ageometry that is consistent with geochemical, petrological, and geophysical data. The model shows thatepisodes of periodic fast inflations occur (i) when a viscosity gradient is present in the vertical pipe, forinstance as the result of a temperature gradient; and (ii) when the flux supplying the shallower chamberlies between two bounds that we derive analytically. The deformation pulses observed at Okmok can,therewith, be fully explained by the internal variability of the magmatic system and do not require time-variable external forcing. The proposed model can also be seen as an improvement upon the classichydraulic models regularly used to explain a commonly observed pattern of volcanic deformations, i.e.exponential inflation.
- Subjects
ALASKA; VOLCANOES; VOLCANIC eruptions; TIME series analysis; MAGMAS
- Publication
Geophysical Research Abstracts, 2019, Vol 21, p1
- ISSN
1029-7006
- Publication type
Article