From the BLM site:
"The Wilderness consists of 26,243 acres. Small, narrow steep-walled canyons wind throughout, creating a natural maze within this badlands labyrinth. Sandy washes divide this area and contain stands of ironwood, smoke tree and palo verde, while scattered stands of ocotillo grow on the gentler slopes and mesa tops. Uniquely faulted and folded geologic formations are the result of the San Andreas Fault, making the Mecca Hills one of the most unusual geological sites of its kind in the world. Entire regions expose eroded layers of rock, providing important information to scientists about the impact of earthquakes on the earth's crust. Bighorn sheep have been observed crossing into the Mecca Hills from the Orocopia Mountains where they water. Prairie falcon, desert tortoise and spotted bat have also been seen here."