A COMPARISON OF THE THERMAL-CHARACTERISTICS OF ACTIVE LAVA FLOWS AND FOREST-FIRES

Landsat TM data of active lava flows from Kilauea Volcano Hawaii (7/23 /91) and forest fires within Yellowstone National Park (9/8/88) are co mpared to show the differences in the spectral and spatial distributio n of radiance. At visible wavelengths, smoke from forest fires obscure s terrain features, while active eruptions show little degassing at br eakouts (ruptured lava tubes). Lava flows exhibit a gradual increase i n infrared radiance (>2 mu m) from the edge of an emplaced flow to the central breakout. The hottest parts of the forest fire (which radiate similar amounts of energy to flow breakouts) are located within 90 m of the edge of the burn scar with the interior portions exhibiting sha rp decreases in infrared radiance. The radiance measured at 10.4-12.4 mu m relative to that at near-infrared wavelengths (2.08-2.35 mu m) su ggests that the surface cracks exposing molten lava anneal proportiona tely with the progressive thickening of the flow crust, while burn sca rs, produced by forest fires, cool to pre-burn background temperatures rapidly with only small areas of high-temperature embers remaining. T hese differences will be important for the implementation of an automa tic thermal-anomaly detection system using satellite data.