Sources: PowerPoint, Web

1. Large volcano collapses and forms Caldera. Crustal extension causes Detachment Fault that moves Tucson Mt. Caldera 20 miles to the southwest (to approximately where Tucson Mountains are today). Further crustal extension (the Basin and Range Disturbance) produces a series of normal faults, dropping down Tucson Valley and lifting up Tucson and Catalina Mountains. Erosion has resulted in current form of Tucson Mts., Tucson Basin, and Santa Catalinas.