November 19-21, 1993
The geology of Central Arizona is rich and varied. On this trip, we studied many different landforms that might not be unique to Earth, including volcanoes and erosional features.
The Superstition Mountains just east of Phoenix are a complex set of eruption calderas. Topics in this area were volcano explosion mechanics, pyroclastic and flow deposits, mechanics of caldera collapse, chemistry and origin of magmas, and igneous emplacement mechanisms. Other igneous highlights included stops at the Catalina Granite Pluton (Tortolita Mtns) and the Payson Ophiolite (former ocean crust pushed up onto the continent).
The more prominent erisional features on this trip were river terraces, which exhibited themselves along Campbell Avenue, the Canada del Oro wash, and in the fabled Tonto Basin. We also discussed the geology of the region between the Colorado Plateau and the Basin and Range (sometimes called the "transition zona") and the Precambrian and cenozoic rocks of the central area.