The Sonoran Desert is the third largest
North American desert and extends from the California-Nevada border
south to the tip of Baja
California and much of the state of Sonora.
Two thirds of this desert lies in Mexico.
The surface is a mix of volanic and metamorphic rock. Northern
region is marked with craters and lava fields - volcanic activity
is as recent as 1,300 years ago.
the Pinacate Biosphere Reserve - Ron Mader