[1] We use 2006–2009 ALOS Interferometric Synthetic Aperture Radar data over the entire west Sunda arc, Indonesia, home of 13% of the world’s active volcanoes, to derive arcwide time-dependent ground deformation data. We present unambiguous evidence of inflation at six volcanoes, three of which erupted after the observation period.We show that these volcanoes have shallow magma reservoirs at 1–...