Rates of Magmatic Processes
The rates at which magmatic processes take place and thus their influence on volcanic activity are still quite poorly constrained. In part, this
is due to the difficulty in acquiring long term time series data sets at sampling rates appropriate to those of the processes in question. For
example, gas exsolution and episodic formation/collapse of a shallow gas-rich foam layer may occur over a period of hours to months leading to
frequent Strombolian eruptions, whereas a system may be quiescent for 100s-1000s of years and reactivate with little if any warning in a very
short period of time. Sporadic geophysical monitoring, such as time-lapse microgravity, have been used effectively on volcanoes for decades to
characterise the subsurface changes in volcanic systems. However, this monitoring, which involves punctual measurements during surveys typically
lasting a few days to weeks, and repeated annually, sacrifices temporal resolution for good spatial resolution. We have recently initiated a
number of continuous gravity studies (measurements a 1 Hz with 1-2 instruments operating for a short period of time, 2 to 3 weeks) that have
provided compelling evidence of very rapid changes in the volcanic plumbing system at Masaya and Kilauea volcanoes. An example of the importance
of these short-term changes was documented at Mt. Etna, Italy, where precursory signals were detected that led to eruptive activity. In order to
study these rapid subsurface processes, we will be taking part in a multi-parameter USGS-sponsored study of Kilauea volcano, which will involve
the integration of numerous continuously-recording gravity meters with seismic, continuous GPS, FLYSPEC and MultiGAS sensors. The aim of this
study will be to gain an understanding of the physical relationships between activity at the summit caldera and that at the downrift vent.
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A synergy of remote sensing with ground-based geochemical (gas flux, initial volatile content) and geophysical (gravity/deformation) measurements should make it possible to characterise the "masking" effect of near-surface processes, thus enabling better modeling of the deeper magmatic processes (e.g., magma mixing, volatile exsolution) that may be responsible for triggering eruptions. The long time series (over 10 years with near global coverage) high temporal and spatial resolution data sets that are now available from remote sensing platforms such as GOES (thermal), MODIS (multi-spectral) and RADARSAT-2 (deformation), offer the opportunity to statistically investigate the possibility that non-volcanic processes such as Earth tides may, in some cases, be trigger mechanisms for volcanic eruptions . The target volcanoes are persistently active and occur in equatorial regions where tidal forcing would be greatest (e.g., Arenal, Colima). |