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Roger Weller, geology instructor

San Francisco Peaks
David Berlin

Physical Geology
Spring 2005
note: First picture loads slowly due to large size.

The San Francisco Peaks
Flagstaff, Arizona Area



Satellite View of San Francisco Peaks
Photo taken by NASA Earth Observatory

         This paper is a consolidation of ideas from my personal history, as well as research by me and others cited.  Growing up in Flagstaff, AZ, I grew to love the magnificence of the San Francisco Peaks (SFP), and of course the warmth of other areas.  I recall times when my family left the area, on the return trip I would always look for the peaks in the back ground.  As I was growing up I always questioned the type of weather we had in the area.  I was always told that the weather was caused by the SFP.  However, this class has given me some indications the terrains features and how the climate interacts have direct effects on the weather.  Further, how the management of our natural resources is a critical importance to the very existence of mankind.




          Over the past several hundred years’ people have observed and taken part of shaping the use of our natural resources and development of the San Francisco Peaks.  This conflict has been the opinion and contradictions to a variety of people from all parts of the world and walks of life. These uses range from religion to the study of the land for future predictions.


          The San Francisco Peaks are located north of Flagstaff, Arizona and 80 miles south of the Grand Canyon.  The San Francisco Mountain is an eroded stratovolcano, which includes Mt. Humphreys, 12,670 ft, Mt. Agassiz, 12340 ft, and Mt. Fremont 11,940.


          The stratovolcano is a composite volcano made of alternating layers of ask and lava, intermediate in composition.  This is created over a period of time when a volcanic ash is covered with hot molten lava.  With other materials collecting and depositing over the top of the ash, then later covered along with the ash by the lava.  The material being deposited on the rims of the volcano, this creates the steepness of the volcano.  The process of this activity occurring over a long period of time, between the overlying lava, ash and other materials being pilled up on the surface, causing pressure with the increased weight and the heat from the magma below creates this type of rock formation.  Within this rock formation there are chances of some of the most beautiful and precious minerals are created.



wpe1.jpg (19117 bytes)

Sunset Crater, Arizona

Photo by Sunset Crater Volcano National Monument National Park Service



         Even though my family owned large portions of land close to the Sun Set Crater, approximately 25 miles north of Flagstaff, AZ., it was un-imaginable, as a small child, to grasp the concept of the Volcano fields spanning out over 5,000 square miles, with over 600 individuals vents.


         The San Francisco Lava fields ranging in composition from basalt to rhyolite, erupted through Precambrain rock and overlying kilometer-thick cover of nearly horizontal sedimentary rocks.  These eruptions are believed to have occurred between 6 million years to less than 1,000 years.  Although Sunset Crater is the last volcano to erupt Northern Arizona, it is believed


         This mountain range also includes lava domes, created by the magma pushing upward and causing the ground to swell.  The pressures of the magma being pushed up ward help to cause small fractures in the ground.  These fractures causes fumaroles and flank eruptions.  As the flank eruptions and escape of the magma thought other channels, releasing the pressure on the ground, the lava domes may have subsided causing additional eruptions.




         During the time when the early Anglo settlers arrived 1880’s in Northern Arizona the uses of the land included grazing for their livestock and herds and the logging industry.  The foresters and logging industry view the extensive use of the forest for economic uses.  This caused an overuse the forests and over killed specific type of trees.  With the area becoming the center of the logging industry and the extensive logging and natural beauty of the area, this caused an increase of the use of the lands resources.  Accommodations were made for the increased usage and with the resources being taken from the land without being replenished.


         The addition of the Arizona Snow Bowl was allowed to be built in the 1930’s.  The provided a ski lodge and a road leading up through the wilderness.  These additions have continued to offer an excellent location for winter sports sitting on the side of the San Francisco Peaks at a summit of 12,633 feet.  With the development of the ski lifts and lodging, this brings people into the area from all parts of the state as well as the world.  Although this brings business into the surrounding area, Flagstaff, this only addresses the issues of the economic value of the land.


         For instance these developments have been made under the objection of the Hopi and Navajo Tribes.  With the continued expansion of the resort area the Hopi Tribe warned “If the ski resort remains or is expanded, our people will not accept the view that this is the sacred home of the Kachinas.  The basis of our existence will become a mere fairy tail”.  These developments have been challenged, without being able to convince the courts the Peaks were indispensable to their religions.


          Earliest Clovis people, whom are now the survivors, are now referred to as the Western Apache, Messier Apaches, and Navajo Native Americans. It is believed that between 1000 to 9000 BC, these people migrated south from Canada,


          After the arrival in the Northern America these people separated into smaller groups and established their traditions, there manner of lives and religions.  However, they were nomads and constantly moving, which made the practice of farming difficult.  The traditions of these people have been handed down from generation to generation, some by word of mouth and others by writings and paintings of the walls of caves.  These traditions have been a very strong part of the culture of these people.  However, with the introduction of other people who also migrated into the area, the way of life for the Native Americans changed.


          This countries history and ongoing conflict are good examples of how single government agencies have undertaken contradictory positions and the potential influence of community pressure.  Government agencies (i.e. the Forest Service in the area of the San Francisco Peaks, has gone from encouraging skiing outright to nominating the area for permanent protected status to considering expansions.


          This class has given me more insight to the importance of better management of our natural resources.  Without the management if these resources by individuals who have the knowledge and forethought about futuristic needs, we will have more and more shortages of these resources.   It’s so important to at the very lease allow the land time to repair itself.  This can be illustrated by the over farming of lands, to the point they would not produce.  The farmers learned they would have to rotate their crops between several fields or plow the fields under to make the soil richer for the next growing seasons.


          It is critical to all mankind to consider all the elements and effects of their decisions before using the resources available.  When placing the importance of financial superiority over management of our limited resources this in turn creates limited availability to individuals.  Even if the product could make the developers and manufactures tons of money, with the people to buy those products it will still fail and then mankind will be even worse than before.