Thermal characterization of the Vulcano fumarole field

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.

[1]  A. Tabbagh,et al.  Measuring and interpreting heat fluxes from shallow volcanic bodies using vertical temperature profiles: a preliminary test , 1999 .

[2]  Stuart Robson,et al.  Oblique photogrammetry with visible and thermal images of active lava flows , 2006 .

[3]  G. Chiodini,et al.  Reactions governing the chemistry of crater fumaroles from Vulcano Island, Italy, and implications for volcanic surveillance , 1993 .

[4]  A. Harris,et al.  Thermal observations of degassing open conduits and fumaroles at Stromboli and Vulcano using remotely sensed data , 1997 .

[5]  L. Nikitina,et al.  Temperature increase and chemical change of fumarolic gases at Momotombo Volcano, Nicaragua, in 1982–1985: Are these indicators of a possible eruption? , 1986 .

[6]  J. Dozier.  A method for satellite identification of surface temperature fields of subpixel resolution , 1981 .

[7]  F. D'amore,et al.  A genetic model for the crater fumaroles of Vulcano island (Sicily, Italy) , 1984 .

[8]  K. Kazahaya,et al.  Mass and heat flux of volcanic gas discharging from the summit crater of Iwodake volcano, Satsuma-Iwojima, Japan, during 1996–1999 , 2003 .

[9]  A. McGonigle,et al.  H2S fluxes from Mt. Etna, Stromboli, and Vulcano (Italy) and implications for the sulfur budget at volcanoes , 2005 .

[10]  B. Raco,et al.  Diffuse emission of CO2 from the Fossa crater, Vulcano Island (Italy) , 1996 .

[11]  M. Lawrence.  The relationship between relative humidity and the dewpoint temperature in moist air - A simple conversion and applications , 2005 .

[12]  H. Pinkerton,et al.  Factors affecting the accuracy of thermal imaging cameras in volcanology , 2006 .

[13]  A. Paonita,et al.  Geochemical modeling of mixing between magmatic and hydrothermal gases: the case of Vulcano Island, Italy , 1999 .

[14]  F. Italiano,et al.  The evolution of a dynamic geological system: the support of a GIS for geochemical measurements at the fumarole field of Vulcano, Italy , 1997 .

[15]  A. Tabbagh,et al.  Determination of sensible heat flux in volcanic areas from ground temperature measurements along vertical profiles: The case study of Mount Etna (Sicily, Italy) , 1987 .

[16]  Athanassios Ganas,et al.  Testing satellite and ground thermal imaging of low-temperature fumarolic fields: The dormant Nisyros Volcano (Greece) , 2007 .

[17]  G. Chiodini,et al.  Origin of the fumarolic fluids of Vulcano Island, Italy and implications for volcanic surveillance , 1995 .

[18]  G. Chiodini,et al.  Carbon dioxide diffuse degassing and estimation of heat release from volcanic and hydrothermal systems , 2005 .

[19]  H. C. Hardee,et al.  Permeable convection above magma bodies , 1982 .

[20]  D. Stevenson.  Physical models of fumarolic flow , 1993 .

[21]  G. Piccardi,et al.  Geochemical surveillance of active volcanoes: data on the fumaroles of Vulcano (Aeolian Islands, Italy) , 1980 .

[22]  Vincent J. Realmuto,et al.  The use of multispectral thermal infrared image data to estimate the sulfur dioxide flux from volcanoes: A case study from Mount Etna, Sicily, July 29, 1986 , 1994 .

[23]  M. Favalli,et al.  Surface hydrothermal alteration mapping at Vulcano Island using MIVIS data , 2001 .

[24]  Gaetano Giudice,et al.  Chemical mapping of a fumarolic field: La Fossa Crater, Vulcano Island (Aeolian Islands, Italy) , 2005 .

[25]  Anthony Finizola,et al.  Double origin of hydrothermal convective flux variations in the Fossa of Vulcano (Italy) , 2008 .

[26]  C. Terranova,et al.  Thermal monitoring of hydrothermal activity by permanent infrared automatic stations: Results obtained at Solfatara di Pozzuoli, Campi Flegrei (Italy) , 2007 .

[27]  M. Ranaldi,et al.  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? , 2006 .

[28]  D. Tedesco.  Fluid geochemistry at Vulcano island: A change in the volcanic regime or continuous fluctuations in the mixing of different systems? , 1995 .

[29]  M. Aubert.  Practical evaluation of steady heat discharge from dormant active volcanoes: case study of Vulcarolo fissure (Mount Etna, Italy) , 1999 .

[30]  M. Carapezza,et al.  Genesis and evolution of the fumaroles of vulcano (Aeolian Islands, Italy): a geochemical model , 1981 .

[31]  Andrew J. L. Harris,et al.  Thermal surveys of the Vulcano Fossa fumarole field 1994–1999: evidence for fumarole migration and sealing , 2000 .

[32]  M. Martini.  Variations in surface manifestations at vulcano (Aeolian Islands, Italy) as a possible evidence of deep processes , 1983 .

[33]  A. Harris,et al.  Magma budgets and steady‐state activity of Vulcano and Stromboli , 1997 .

[34]  Mitsuru Sekioka,et al.  Heat flux estimation in geothermal areas based on the heat balance of the ground surface , 1974 .