The scale of summit collapse during the April 2007 eruption of Piton de la Fournaise volcano, Réunion Island, western Indian Ocean, was evaluated using before-and-after differential digital elevation models (DEMs) derived from nadir and backward-looking images from the Advanced Spaceborne Emission and Reflection radiometer (ASTER) instrument. The dimensions of horizontal length and width, volume and depth of the depression were estimated as 1,100 × 800 m, 9.6 × 107 m3 and 320 m, respectively. These estimates show excellent agreement with field survey data. A ring shaped thermal anomaly (diameter of about 500 m) was found at Dolomieu Crater during or just after the collapse on nighttime ASTER SWIR image. It may correspond to the high temperature areas associated with the cross section of a hydrothermal zone at a constant altitude inside the crater. Our analysis of ASTER orbital data documents topographic and related thermal changes as a result of the 2007 eruption and demonstrates the power of ASTER as a volcanological tool.