Monitoring General Flashcards
“Today’s volcanologists can….
… ill afford to rely on any one speciality to furnish the necessary tools and information” (Dzurisin, 2003)
What is volcano monitoring?
Volcano monitoring is the regular, long-term, multi-parameter observation of certain manifestations of volcanic activity
It is about identifying the surface expression of processes occurring deep within the Earth’s crust - therefore about finding proxies
What processes have advanced our understanding of volcanic processes?
New technology, advances in computing power and speed, intensive study of several specific volcanic eruptions (e.g. Mt St Helens)
Sparks, 2003
What general methods are there?
Seismology - tracks fracture of moving fluids and deformation of rock
Geodesy - tracks volume changes due to magma input/output, pressurisation etc.
Geochemistry - studies pressurising/depressurising of magma and exsolution of volatiles
Give examples of where monitoring helped to identify diagnostic patterns of behaviour (2)
1) Mt Etna using geochemistry - Auippa et al., 2007 (2006 eruption)
2) Montserrat - Voight et al., 1999 - using seismology and ground deformation to understand dome effusive eruptive cycles
How is the use of monitoring different to studying volcanic stratigraphy and eruption histories?
It involves different methods, timescales and applications
Event history is important for understanding pre-human eruptions (e.g. Yellowstone) and also for studying long dormant volcanoes that have not shown activity for substantial times
Those with recent histories may instead be subject to monitoring
Why may event histories still be helpful?
They can help to understand eruptive patterns
E.g. at Pinatubo geologic reconnaissance and radiocarbon dating helped to create a hazard map in the weeks leading up to the eruption (Newhall et al., 1996)
What is the ideal monitoring situation and why does this not always come to fruition?
The ideal case is to have a well-equipped volcano observatory - with multi-parameter and long-term observations
However due to inaccessibility, limited funding, and (especially in the Global South) political turmoil this is often not the case
Campaign monitoring is the middle case, but often even this is not achievable and many volcanoes remain unmonitored
Sparks et al., 2013
441 active volcanoes in 16 developing countries, of which 384(!!) have rudimentary, or no monitoring - and of these 65 are considered to pose risk to large nearby centres of population
Dzurisin, 2006
Simply because a proxy is useful at indicating that a specific volcanic process may be taking place, the absence of such a measurement does not mean that the process is not happening
Doukas and Gerlach, 1995
E.g. an increase in the flux of SO2 may indicate the recent arrival at shallow depths of a fresh and gas-charged magma, but the absence does not mean no magma has arrived
SO2 is very soluble in water and therefore scrubbing by groundwater may have occurred
At Mt Spurr, Alaska (1992) groundwater scrubbing of SO2 was so effective that no precursors increase in SO2 flux was detected prior to the series of eruptions
Lipman, 1981
Mt St Helens (1980) eruption actually occurred in a lull in activity, which was later shown to be related to pressurisation
What percentage of periods of unrest actually led to a volcanic eruption?
64% of 220 volcanoes that experienced unrest since the year 2000 culminated in eruptive events
Phillipson et al., 2013
THIS HIGHLIGHTS THE IMPORTANCE OF MULTIPROXY APPROACH - especially as false alarms can be costly (e.g. Gaudeloupe, Fiske, 1984)
Alone, any single volcanic monitoring technique provides information that is…
… ambiguous, or subject to alternative explanations
Thus no signal should be used alone
Dzurisin, 2003
