The volcano is composed from basalt and dacite and there is no evidence of Holocene activity.[3] Below 1000m, several parasitic cones lie on the southwest flank of the volcano.[4]
^D'Orazio, M.; Tamponia, M.; Tonarinib, S.; González-Ferránd, O.; Lahsend, A.; Omarinie, R. (August 2003). "The Quaternary calc-alkaline volcanism of the Patagonian Andes close to the Chile triple junction: geochemistry and petrogenesis of volcanic rocks from the Cay and Maca volcanoes (not, vert, similar45°S, Chile)". Journal of South American Earth Sciences. 16 (4): 219–242. Bibcode:2003JSAES..16..219D. doi:10.1016/S0895-9811(03)00063-4.
^M D'Orazio; F Innocenti; P Manetti; M Tamponi; S Tonarini; O González-Ferrán; A Lahsen; R Omarini (August 2003). "The Quaternary calc-alkaline volcanism of the Patagonian Andes close to the Chile triple junction: geochemistry and petrogenesis of volcanic rocks from the Cay and Maca volcanoes (~45°S, Chile)". Journal of South American Earth Sciences. 16 (4): 219–242. Bibcode:2003JSAES..16..219D. doi:10.1016/S0895-9811(03)00063-4.