The cooling of frontal flow ramps: a calorimetric study on the Rocche Rosse rhyolite flow, Lipari, Aeolian Islands, Italy

Relaxation geospeedometry using differential scanning calorimetry (DSC) has been applied to quantify the cooling history across the glass transition of flow ramps at the front of the calc-alkaline rhyolite Rocche Rosse flow of Lipari, Aeolian Islands, Italy. Modelled cooling rates for the obsidian retrieved from two profiles range between 0.2 and 0.03 K min(-1). Cooling at the flow front appears to be dominated by conductive heat loss of individual flow ramps forming individual cooling units. Cooling rates of tens of Kelvins per day appear to have controlled the last stage of viscous deformation before the entire flow came to rest. It is inferred that cooling rates slower than those modelled are required to sustain flow in highly viscous rhyolitic lavas.