Gates Pass

The route you are traveling began in 1883 as one man's search for a shortcut.
Thomas Gates (local pioneer, saloon keeper, and rancher) wanted a quicker route to his carbonate mine in Avra Valley.
While exploring these mountains, he found this natural canyon, marked by "bubbling springs, streams, and lush growth." Gates paid $1,000 to clear and grade the winding road over this pass, which now bears his name.

You are standing near the center of what was a massive volcanic crater that exploded 70 million years ago, forming this mountain range. This colossal upheaval was 100 to 1,000 times more powerful than the 1980 eruption of Mount St. Helens. The volcano took the form of a caldera, or great pit, about 15 miles in diameter.
The rock and cliffs towering around you were formed in the bottom of the crater. Most of the material was made of volcanic ash fused by its own heat, forming a rock called tuff. Massive blocks of rhyolite broke from the caldera wall and slid into the center of the pit where they were welded to the tuff. The remnants of the caldera wall can be seen below in the large white blocks of rhyolite on your right. Erosion of the crater's rim and sinking of the adjacent valley left the mountain tops that you see here.

Desert Adaptations
The plants and animals of the Sonoran Desert have developed remarkable physical characteristics and behaviors that allow them to thrive in this challenging environment.

Desert Survival
The Sonoran Desert offers an array of habitats, from rocky mountain slopes to expansive valleys and verdant riparian corridors. The plants and animals that thrive in this land of scant rainfall and temperature extremes make efficient use of energy and resources.

Water Conservation
Using water resources efficiently and minimizing water loss from evaporation are vital for survival in the desert.

Adaptive Use
Using an underground burrow or the strategic placement of a web are ways that animals make good use of features in their environment to avoid the heat of a summer day or the chill of a desert night.

Timing
Sonoran Desert plants and animals rise to the demands of their habitat by adjusting daily or seasonal periods of activity.

Desert Tortoise
Gopherus morafkai
During the summer rainy season, the desert tortoise drinks large amounts of available water. It gorges on succulent cactus fruit and green grasses, which it also converts to water. The tortoise's shell and leathery skin provide insulation and reduce surface evaporation. The desert tortoise hibernates through the cool winter months.

Banner-tailed Kangaroo Rat
Dipodomys spectabilis
The kangaroo rat gets all the moisture it needs from the seeds and insects it eats. It has efficient kidneys that conserve water by producing highly concentrated urine.

Gopher Snake
Pituophis catenifer
One of the most common snakes in North America thrives in a wide range of desert habitats. The patterns and colors of the gopl or snake mimic somespecies of rattlesnake. The non-venomous gopher snake will even vibrate its tail when threatened. The gopher snake slips down a hole in search of its prey and spends the cool winter months in the shelter of a burrow or rocky crevice.

PIMA COUNTY
Bats
Many species of bats navigate the summer night skies using echo-location.
Most of Arizona's 28 species of bats eat insects. They time their forays to coincide with moderate temperatures and peak numbers of moths and other flying insects. Two species of bats feed on the nectar of plants, such as saguaros and agaves. The nectar-feeding bats are also known to visit hummingbird feeders at night during the summer months.

Triangle-leaf Bursage
Ambrosia deltaidea
In times of drought, this hardy plant drops its leaves and goes dormant. Bursage is quick to respond to rain, producing leaves, flowers, and seeds in al matter of days. The hard, spiny seedpods, or burrs, are distributed by attaching to the fur of animals..Read more