Saguaro National Park guide · 2 min read
A Metamorphic Core Complex Beneath the Cacti
The oldest rock in the park is Pinal Schist, about 1.7 billion years older than the Basin and Range Province that the park belongs to.
It appears in the Rincon Mountain District, where a dry wash runs off Cactus Forest Loop Drive. Catalina gneiss is the rock you will meet most often across the Rincons, and you can see it at Javelina Rocks beside that same drive. Tanque Verde Ridge is made largely of altered granites that are about 1.4 billion years old.
Far more recently, roughly 600 million years ago, the land around present-day Tucson sat under shallow seas. Sediment settling there eventually hardened into limestone, sandstone and shale. In the late 1800s, limestone was mined to make mortar, and the ruins of lime kilns still stand beside the Cactus Forest Trail.
The park takes its name from the saguaro, a big cactus found naturally nowhere outside the Sonoran Desert. The park is made of two separate areas. Saguaro West lies about 15 miles west of the Tucson city center, and Saguaro East sits about 20 miles east of it. The western Tucson Mountain District has denser cacti, while the eastern Rincon Mountain District holds fewer cacti but rises above 8,000 feet into forest. Rincon is Spanish for corner and refers to the shape of the range.
Cactus Forest Loop Drive passes Javelina Rocks and has trailheads at Cactus Forest North and Cactus Forest South. Starting from either one, you can follow the Cactus Forest Trail for roughly 2.5 miles, passing the old kilns on the way. At a junction along the way, a side wash leads to Lime Falls, which holds water only after rain.
Other users are common here, since the path is open to hikers, mountain bikers and people on horseback. Much of the tread is firm desert soil, though three wash crossings bring soft sand. Anyone wanting a longer outing will find miles of backcountry trails in the Rincon Mountain District.
