19. Analysis of Lava Flow Effusion Rate Using High Spatial Resolution Infrared Data

Remote sensing thermal data of active lava flows allow for the evaluation of instantaneous effusion rates. This is made possible by simple formulae relating the lava effusion rate to the power energy radiated per unit time from the surface to the flow. The most questionable assumption is probably the constancy of the surface temperature. Due to the assumptions of the model, this formula implies that heat flux, surface temperature and lava temperature varies as a function of the flow thickness. These relationships, never verified or validated before, have been used by several authors as a proof of the weakness of the model. Herein, MIVIS (Multispectral Infrared and Visible Imaging Spectrometer) high spatial resolution (5–10 m) thermal data acquired during Etna’s 2001 eruption were used to investigate down-flow heat-flux variations in the lava flow emitted from a vent located at 2,100 m a.s.l. A high correlation between the down-flow heat-flux and the lava flow thickness (measured from a pre-existing digital elevation model) was found. According to this relationship, observed changes in the surface temperature would be the expected consequence of differences in the down-flow lava flow thickness due to topographic variations.