Dike swarms are emplaced along ring fractures and fault zones at the southwest edge of the caldera. Near the dying stages of the volcano, magma surged upward and arched the roof of the magma chamber into a broad dome with relief of about .
Along the ring fractures and fault zones on the southwest side of the caldera, dike swarms are emplaced. As the volcano approached its end, magma rose and formed a broad dome atop the magma chamber, rising to an elevation of approximately.