The Tucson area is a wide desert heavily decorated with mountain ranges. Downtown Tucson is at an elevation of 2,389 feet above sea level, but the town is ringed by mountain ranges. On the north side are the Santa Catalina's, topping out at 9,157 feet. The Santa Ritas, to the south, are just a little taller (9,453 ft.), and the Rincons on the east are a little shorter. Other mountain ranges in or immediately joining the 100-mile circle include the Baboquivaris, the Silverbells, the Sierritas, the Picachos, the Tanque Verdes, the Whetstones, the Galiuros, the Huachucas, the Tucsons, the Dragoons (and the Little Dragoons), the Winchesters, and the Tortolitas. Between these rugged outcrops are wide valleys - river valleys, even though there may not be water in the rivers. The Santa Cruz valley, Avra Valley, Altar Valley and the San Pedro River Valley (a river which actually has flowing water in it) are among the more important. Habitats produced by this topographical mixture are highly variable, as would be expected. Elevation plays an important role, but so do rain-shadow and wind shadow effects, the direction a slope faces, the geology and hydrology of any particular place, as well as its historic (or prehistoric) geology.

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This is a relief map of southern Arizona, with the 100 Mile Circle indicated (approximately) in red. Please note that the actual boundaries of the circle vary a fair amount according to what part of Tucson is chosen for the center point. map generated using Microsoft MapPoint 2004

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© 1996-2003 Tucson Herpetological Society
Revised: 5 October 2003