This beautifully illustrated guide provides a geologist¿ s eye view into the geologic setting and history of the Santa Catalina Mountains. With this text in hand, the reader will peer into the window that Sabino Canyon offers into the core of the Santa Catalina Mountains. Photographs of granite, gneiss, schist and other rocks will enrich your visit. A simplified geologic map places the geology in context, while block diagrams and cross-sections illustrate how the mountains formed and how major faults, complemented by weathering and erosion, shape and sculpt the range. For those ascending Catalina Highway to the summit of Mt. Lemmon, this guide points out major geographic features, roadsite rock outcrops, and discusses how geologic processes, still operating today, shape and reshape the mountain¿s flanks and summit.