The La Reforma caldera has a diameter of , and the height of its rim ranges from . It is a semicircular structure around Cabo Virgenes, which reaches the Gulf of California at La Reforma in the northwest and Punta Las Cuevas in the southeast. A tectonic block inside the caldera rises above the rim of the caldera; it is a resurgent dome formed by welded tuff. The highest point of the dome is .