Chiricahua National Monument was established in 1924 to preserve the mountain range, homeland of the Chiricahua Apache. The Chiricahua Mountains rise above the grasslands of southeastern Arizona. Dramatic rocky pinnacles were formed 27 million years ago when eruptions of the Turkey Creek Volcano spewed ash over 1200 square miles. These superheated ash particles melted together forming layers of grey rhyolite rock. Cooling and subsequent uplifting created joints and cracks in the rock. Eventually weaker rocks washed away, leaving innumerable spires, balanced rocks and other shapes.