TEMPERATURE OF AN ACTIVE LAVA CHANNEL FROM SPECTRAL MEASUREMENTS, KILAUEA VOLCANO, HAWAII

A narrow band spectroradiometer was used to determine the characteristic temperatures of a very active channeled lava flow for the phase 50 eruption of Pu'u 'O'o on the East Rift Zone of Kilauea Volcano, Hawaii. During the twilight of 19 February 1992, 14 spectra of this activity were acquired over a 51 minute interval [18.29 to 19.20 Hawaiian Standard Time (HST)], from which the thermal distribution of energy of two 18 m2 areas, one near the center and one near the margin of the flow, may be investigated. A two-component thermal mixing model applied to the data taken of the center of the channel gave, in the most powerful instance (1.8 x 10(5) W/m2), a crust temperature of 940-degrees-C, a hot component temperature of 1120-degrees-C and a hot radiating area of 60% of the total area. A simultaneous spectrum acquired near the channeled flow margin yielded a crust temperature of 586-degrees-C and a hot area of only 1.2% of the total area radiating at 1130-degrees-C. Average radiant flux densities recorded for the center of the lava channel (1.3 x 10(5) W/m2 average) are much greater than previous measurements of lava lakes (4.9 x 10(3) W/m2) or recently emplaced lava flows (maximum of 7.2 x 10(4) W/m2). The energetic nature of this eruption is shown by satellite measurements made at 02.33 HST on 22 February 1992 by the Advanced Very High Resolution Radiometer in Band 2 (0.72-1.10 mum). These show the utility of using existing satellites with moderate resolution (1 km x 1 km pixels) and high temporal coverage (eight overpasses each day for Hawaii) as potential thermal alarms for rapidly assessing the hazard potential of large volcanic eruptions.