Causes of unrest at silicic calderas in the East African Rift: new constraints from InSAR and soil-gas chemistry at Aluto volcano, Ethiopia - Hutchison, W; Biggs, J; Mather, T; Pyle, D; Lewi, E; Yirgu, G; Caliro, S; Chiodini, G; Clor, L; Fischer, T (Geochemistry Geophysics Geosystems, 2016)