[Triumf-seminars] TRIUMF Colloquium today at 14:00

[postmaster at admin.triumf.ca]

Date/Time: Thu 2009-02-05 at 14:00

Location:  Auditorium          

Speaker:   Glyn Williams-Jones (SFU)

Title:     Big Bangs - Geophysics and Active Volcanoes

Abstract: Although considerable progress has been made in characterising volcanic eruptions, a more complete understanding of the physical processes responsible for volcanic activity will only be possible through the integration of multi-temporal and multi-spatial geophysical and geochemical studies. The intrusion of fresh, gas-rich magma into a reservoir is thought to be essential to the occurrence of an eruption and to cause the latter by interacting with the ponded magma. However, the extent of this interaction and the rate at which it occurs (these control the nature of an eruption) are still poorly understood. Only through time series studies involving multi-parameter multi-temporal baseline data sets is it possible to accurately model these interactions which occur on time scales of seconds to decades. Our main objective is therefore to gather geochemical and geophysical data aimed at determining the depth and physical properties of magma chambers and associated hydrothermal systems as well as investigate conduit processes beneath persistently active volcanoes and long-lived calderas in a state of unrest. This data is then used to develop integrated models relating ground deformation and changes in potential fields (e.g., gravity, magnetism, electrical) to changes in the volume and volatile composition of a magma reservoir.

A problem in studies of this type is that changes in the upper edifice of active volcanoes (e.g., hydrothermal systems) can “mask” changes occurring at depth. Hydrothermal systems, which may or may not be well developed, are directly related to the heat, gas and fluids coming from the shallow magma chamber and plumbing system.We therefore attempt to constrain the spatiotemporal influence of these near-surface effects by collecting time series data at persistently active volcanoes through gas emissions monitoring, geodetic and passive geoelectrical responses at Masaya (Nicaragua) and Kawah Ijen (Indonesia). Recent technological advances in the development of low-cost continuously-recording sensors (e.g., GPS, seismometers, scanning volcanic gas sensors) integrated into wireless networks now makes it possible to perform detailed time-series analysis of surficial volcanic activity and gain insight into sub-surface processes. By integrating ground-based geochemical (melt inclusions/gas flux) and geophysical (gravity/deformation/self-potential) measurements which allow for characterization of the near-surface processes involved in persistent volcanism (e.g., convection within a conduit), it becomes possible to better model the deeper magmatic processes (e.g., magma mixing) that are likely responsible for triggering eruptions.

Stimulants available 15 minutes before the talk.

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