HR: 08:24h
AN: V31D-03    [Abstracts]
TI: Can Satellite-Based Sensors, Hand-Held Thermal Imagers and Thermal Infrared Radiometers Calculate Reliable Eruption Rates at Active Lava Flows, Domes and Lakes?
AU: * Harris, A J
EM: harris@higp.hawaii.edu
AF: HIGP/SOEST, University of Hawaii, 2525 Correa Road, Honolulu, HI 96822 United States
AB: Thermal data provide viable means of extracting eruption rates at active lava flows, domes and lakes. The initial algorithm, developed since 1994, uses total heat flux (Q), extracted from satellite-sensor-derived thermal images of the active lava body to extract eruption rate (E) using E = Q / $\rho$ [c $\Delta$ T + f L]. Here $\rho$ and c are lava density and specific heat capacity, $\Delta$T is lava cooling, f is fractional crystallization and L is latent heat of crystallization. Later it was shown that this reduces to a linear relationship: E = a Q + b, where a and b are defined by values assumed for $\rho$, c, $\Delta$T, f, and L. We present three case studies that: (1) demonstrate the variety of thermal data and activity styles that can be used in this approach, and (2) validate the approach through cross-checks with independent, field-based data: {\it(I) Stromboli: Satellite and thermal imager-based lava flow eruption rates.} A safe, easy and rapid method to calculate lava effusion rates using hand-held thermal image data was developed in June 2003 at Stromboli (Italy). FLIR data were used as input to the thermal effusion rate model, previously applied to satellite data, allowing automated effusion rate extraction. A comparison between a thermally-derived (0.2 - 0.9 m$^{3}$/s) and dimensionally-derived (i.e. channel depth x width x velocity) effusion rate (0.6 m$^{3}$/s) showed excellent agreement. In addition, the comparison between FLIR-derived effusion rates and satellite (AVHRR) derived values showed a good correlation (R = 0.9). {\it(II) Santiaguito: Satellite-derived eruption rates for a lava dome} A time series of 21 Landsat ETM+ and TM images acquired during 1986-2003, were used to calculate eruption rates at Santiaguito dome (Guatemala) to yield a time-averaged effusion rate of 0.4 m$^{3}$/s. Field-based flow dimension and velocity measurements during 1987 and 2000-03 yielded a values of 0.6$\pm$0.3 and 0.5$\pm$0.2 m$^{3}$/s which compared with an ETM+ derived values of 0.7$\pm$0.1 and 0.5$\pm$0.1 m$^{3}$/s, respectively. {\it(III) Erta Ale: Thermal infrared thermometer derived eruption rates} Using the typical surface temperature recorded by a thermal infrared thermometer targeted at the center of the Erta Ale lava lake (Ethiopia), a flux of ~1-4 x 10$^{7}$ W, to give a mass flux of 30-110 kg/s. These compare with satellite-based (TM) estimates of 40-100 kg/s. At Etna (Italy) 657 effusion rate measurements were made from combined thermal and field-based sources during 1999-2004. These all show excellent cross-data-set agreement. We have achieved a calibration of a and b in E = a Q + b. Suitable values for $\rho$, c, f, and L show that $\Delta$T is consistently in the range of 150 to 250 $\deg$C.
DE: 8400 VOLCANOLOGY
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2004 AGU Fall Meeting