Last erupted in the Oligocene (27.3- 27.1 Ma), the volcano is composed mostly of trachyte, rhyolite pyroclastic flows, lava dome fragments, and lahars, which all erupted from numerous vents around a main central caldera near the central of the Bofecillos Mountains.
The formation of the Leyva Canyon Volcano began with the eruption of rhyolite along a small fissure near the central vent, flowing south to southwest.
Near the Guale Mesa, Cerro de las Burras, and Three Dike Hill, this ash flow tuff was 24 to 27.5 meters thick.
Based on this, it was estimated to have erupted with 1 km^3 of ejecta volume, presumably rating 3–4 on the volcanic explosivity index.
Along Bofecillos Canyon, ash flow and lahar deposits were 37 meters thick with some lapilli measuring 60 cm across.