 Calabozos lies in an area between thick and thin continental crust , and its eruptions are probably fed from a pool of andesitic and rhyolitic magma that sits just under its caldera . The caldera is underlain by a layer of volcaniclastic sedimentary rock from the Mesozoic era coalesced with intrusive and volcanic rocks of Tertiary age , over a layer of Precambrian @-@ Triassic sedimentary and metamorphic rock formed from later plutons ( magma intrusions ) . Under its northeast edge , Calabozos is cut by a north @-@ south trending segment of sedimentary rock that includes gypsiferous and carbonates . 
