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Roger Weller, geology instructor

wellerr@cochise.edu

San Bernardino Valley
by Mollie Hobbs
Physical Geology
Fall 2011    

     The San Bernardino valley is not commonly hike or a tourist attraction to most.   The desire to seek adventure and new things is not commonly found among the dust and mountainous terrain that is established on this land. Underneath the surface of the dirt and Arizona heat lays an historic story of the past volcanic activity that has occurred here.  Two newly minted geology students searched for an entrance to the beautiful San Bernardino Valley in an attempt to walk were no one has and find treasures only a new geologist would appreciate.  The two conquered various tasks in order to come face to face with the dormant volcano and basaltic lava. The geology of the San Bernardino Valley is comprised of three distinct elements. Paleozoic and Mesozoic sedi­mentary rocks and mid-Tertiary volcanic most likely form the bedrock floor of the basin. The field covers some 850 km and consists of olivine basalt flows, tuff rings and maars with 130 identified volcanic vent areas and cinder cones.  Maars are craters created by a steam blast.  Paramore crater is the largest of these, about 1 km by 1.5km and about 60 m deep.

The journey began with attempting to find an entrance into the valley.  The land was owned by several different ranchers who carefully guarded their land against illegal immigrants and drug cartels.  Over 24.3% of land is private. Most private land is interspersed with state owned land. The largest portions of contiguous private land are near the communities of Cazador Bernardino and Chiricahua. Primary land uses are domestic and grazing of cattle.

Dangers Among us:

The mission continued once a kind rancher allowed us to occupy his land in order to learn the geology. The owner warned us of the dangers of hiking on his land. He explained that they have several issue with illegals traveling through his land and warned us against talking to any one seen on the land.  If someone was to look as they are hurt to run back to the car. There had been a murder recently of one of the ranchers Robert Krentz, who walked upon a man that looked to be injured. The supposed injured man gun down the local rancher and took his clothes and left him for dead.

volcanoes:

     The land was full of volcanic bombs and years of lava flows.  This adventure had brought new meaning of Volcanoes in Arizona’s own backyard. Limited radiometric dating indicates the exposed rocks of the San Bernardino volcanic field had erupted between 750,000 and 260,000 years ago.

     To continue the trip we hiked to various other dormont volcanoes.  They appeared to be close but once the hike began we found that to be very different. The total trip was approximentaly six hours with about an hour drive to the site and an hour back.

The Rocks Among Us
 

     The mountains surrounding the valley are composed of igneous, metamorphic, and sedimentary rocks (Cooper, 1959) . The sights most commonly seen are those of Cinder cones, with varying amounts of bombs, vent lava, and agglutinate breccia.