Vulcano's Fumaroles and
Geochemical Monitoring of Volcanoes

Volcanism Seminar
Christoph Moder
2004-05-25

Abstract

Since gas plays an important role in volcanic activities, geochemical monitoring is crucial for understanding the processes in the magma chamber. However, a precise prediction of eruptive events solely based on chemical analysis is not possible, but requires additional geophysical methods. Furthermore, the chemical setting differs between the volcanoes and can also vary with time, so conclusions cannot be drawn from a single measurement. Stand-alone monitoring stations provide the necessary continuous recordings; thus, they are an important means to recognize trends and developments.

What Are Fumaroles?

holes in the ground where hot gas comes out

gas comes out of the magma chamber (where differentiation occurs)

fumarole + groundwater = geyser

Gas Composition

H2O (35%-90%) (from magma or ground water, can be distinguished by isotope ratio)

CO2 (5%-50%)

SO2 (2%-30%)

HCl

H2S

Influences on Solubility

solubility in the magma depends on pressure, temperature, viscosity and chemical structure

saturated magma  gas is released

release order: CO2, S, Cl, H2O, F

Geochemical Monitoring: Why?

to understand what happens in the magma chamber

eruption warnings

volcanic gas itself can be a danger

Geochemical Monitoring: How?

Continuous Monitoring:

only few types of gas

shortage of energy (clouds, ash covering solar panels)

maintenance required

measuring interval must be short

Laboratory Analysis:

more exact

not realtime

not regularly

somewhat dangerous

Measuring Methods

gas chromatography, ion chromatography

mass spectrometer

chemically selective sensors

optical methods:

COSPEC (COrrelation SPECtroscopy): SO2 measurement by UV absorption

FTIR (Fourier Transform InfraRed spectroscopy): CO2 measurement with an interferometer

LIDAR (light detection and ranging): measurement of light scattering with different wavelengths (DIAL, DIfferential Absorption Lidar)

Patterns for Volcanic Activity

appearance of fumaroles in general

rising gas temperature

shift of the chemical equilibrium

other atypical things like oscillation of concentration

Examples for Monitoring

Colombia: Galeras

Indonesia: Merapi (Java)

France: Soufrière (Guadeloupe), Pelée (Martinique), Piton de la Fournaise (Réunion)

USA: Kilauea (Hawaii)

Japan: Mt Mihara

References

Hans-Ulrich Schmincke: “Vulkanismus”, Wissenschaftl. Buchgesellschaft, Darmstadt 2000

Jacques-Marie Bardintzeff: “Vulkanologie”, Ferdinand Enke Verlag, Stuttgart 1999

Ollier Cliff: “Volcanoes—An Introduction to Systematic Geomorphology”, MIT Press, Cambridge MA (USA) and London (UK) 1975

http://volcanoes.usgs.gov/About/What/Monitor/Gas/continuous.html + sample.html

http://www.volcanolive.com/gases.html

http://www.dgg.tu-berlin.de/tagungen/dgg2002/abstracts/VU/Faber_P.htm

http://www.seismo.com/msop/nmsop/13%20volcano/volcano5/volcano5.html#13.5.3

http://homepage.ntlworld.com/volcano/gas.htm

http://www-volcano.geog.cam.ac.uk/research/degassing.html

Christoph Moder

2004-05-13T20:11:17