 The formation of the older lava domes may have been influenced by buried faults or the supply systems of the older Pissis and Bonete Chico volcanoes . Isotope and composition data suggest that the magma of Incapillo forms at relatively constrained depths of c . 65 – 70 kilometres ( 40 – 43 mi ) above the shallow slab . A focus of seismic activity is found at Incapillo . 
