Thermal characterization of the Vulcano fumarole field
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Ground-based thermal infrared surveys can contribute to complete heat budget inventories for fumarole fields. However, variations in atmospheric conditions, plume condensation and mixed-pixel effects can complicate vent area and temperature measurements. Analysis of vent temperature frequency distributions can be used, however, to characterise and quantify thermal regions within a field. We examine this using four thermal infrared thermometer and thermal image surveys of the Vulcano Fossa fumarole field (Italy) during June 2004 and July 2005. These surveys show that regions occupied by low temperature vents are characterised by distributions that are tightly clustered around the mean (i.e., the standard deviation is low), highly peaked (positive kurtosis) and skewed in the low temperature direction (negative skewness). This population is associated with wet fumaroles, where boiling controls maximum temperature to cause a narrow distribution with a mode at 90–100°C. In contrast, high temperature vent regions have distributions that are widely spread about the mean (i.e., the standard deviation is high), relatively flat (negative kurtosis) and skewed in the high temperature direction (positive skewness). In this dry case, fumaroles are water-free so that maximum temperatures are not fixed by boiling. As a result greater temperature variation is possible. We use these results to define two vent types at Vulcano on the basis of their thermal characteristics: (1) concentrated (localized) regions of high temperature vents, and (2) dispersed low temperature vents. These occur within a much larger region of diffuse heat emission across which surfaces are heated by steam condensation, the heat from which causes elevated surface temperatures. For Vulcano's lower fumarole zone, high and low temperature vents occupied total areas of 3 and 6 m2, respectively, and occurred within a larger (430 m2) vent-free zone of diffuse heat emission. For this lower zone, we estimate that 21–43 × 103 W of heat was lost by diffuse heat emission. A further 4.5 × 103 W was lost by radiation from high temperature vents, and 6.5 × 103 W from low temperature vents. Thus, radiative heat losses from high and low temperature vents within Vulcano's lower fumarole zone respectively account for 10% and 15% of the total heat lost from this zone. This shows that radiation from open vents can account for a non-trivial portion of the total fumarole field heat budget.
KeywordsFumarole Vulcano Thermal image Infrared thermometer Heat flux
We are extremely grateful to Natalie Yakos for extracting the statistical data from the FLIR regions of interest. This manuscript was greatly improved by the suggestions of Giovanni Chiodini, Toby Fischer, Mike James and an anonymous reviewer.
- Aubert M, Diliberto S, Finizola A, Chebil Y (2008) Double origin of hydrothermal convective flux variations in the Fossa of Vulcano (Italy). Bull Volcanol, in pressGoogle Scholar
- Barberi F, Neri G, Valenza M, Villari L (1991) 1987–1990 unrest at Vulcano. Acta Vulcanol 1:95–106Google Scholar
- Bukumirovic T, Italiano F, Nuccio PM, Pecoraino G, Principio E (1996) Evolution of the fumarolic activity at La Fossa crater of Vulcano. Acta Vulcanol 8:210–212Google Scholar
- Chiodini G, Cioni R, Guidi M, Marini L, Raco B, Taddeucci G (1992) Gas geobarometry in boiling hydrothermal systems: a possible tool to evaluate the hazard of hydrothermal explosions. Acta Vulcanol 2:99–107Google Scholar
- Chiodini G, Cioni R, Marini L, Raco B, Taddeucci G (1993b) Fumarolic gases geochemistry. Acta Vulcanol 3:280–282Google Scholar
- Chiodini G, Cioni R, Marini L, Panichi C, Raco B, Taddeucci G (1994) Fumarolic gases geochemistry (Vulcano). Acta Vulcanol 6:43–46Google Scholar
- Chiodini G, Granieri D, Avino R, Caliro S, Costa A. (2005) Carbon dioxide diffuse degassing and estimation of heat release from volcanic and hydrothermal systems. J Geophys Res 110:B08204, doi: 10.1029/2004JB003542
- Chiodini G, Vilardo G, Augusti V, Granieri D, Caliro S, Minopoli C, Terranova C (2007) Thermal monitoring of hydrothermal activity by permanent infrared automatic stations: results obtained at Solfatara di Pozzuoli, Campi Flegrei (Italy). J Geophys Res 112:B12206, doi: 10.1029/2007JB005140 CrossRefGoogle Scholar
- Granieri D, Carapezza ML, Chiodini G, Avino R, Caliro S, Ranaldi M, Ricci T, Tarchini L (2006) Correlated increase in CO2 fumarolic content and diffuse emission from La Fossa crater (Vulcano, Italy): evidence of volcanic unrest or increasing gas release from a stationary deep magma body? Geophys Res Lett 33:L13316, doi: 10.1029/2006GL026460 CrossRefGoogle Scholar