Remote infrared detection of the cessation of volcanic eruptions

When an effusive eruption ends lava surfaces initially cool rapidly so that within minutes temperatures across the hottest zones have dropped by 600 d egreesC. This means that eruption cessation is simple to detect using satel lite infrared data, where a sudden, irrecoverable decline in thermal radian ce, occurring over a period of hours, is characteristic of termination. AVH RR data acquired during and after 5 eruptions at Krafla (Iceland) illustrat e this. In all cases the 3.9 mum spectral radiance in the first image follo wing the known time of eruption cessation is markedly reduced compared to t hat recorded during the eruption, and subsequently remains at persistently low levels.