We use uncrewed-aerial-system-derived optical and infrared data, mineralogical and geochemical analyses of rock samples, and surface degassing measurements to analyze degassing and hydrothermal alteration at the fumaroles of the La Fossa cone, Vulcano island, Italy. We give a detailed view of associated structures and dynamics, such as local alteration gradients, diffuse active units that significantly contribute to the total activity, or effects of permeability reduction and surface sealing.