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 degreesC. This means that eruption cessation is simple to detect using satellite infrared data, where a sudden, irrecoverable decline in thermal radiance, occurring over a period of hours, is characteristic of termination. AVHRR data acquired during and after 5 eruptions at Krafla (Iceland) illustrate this. In all cases the 3.9 mum spectral radiance in the first image following the known time of eruption cessation is markedly reduced compared to that recorded during the eruption, and subsequently remains at persistently low levels.