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The Colorado Plateau

The Vast and the Intimate
Suspended in Time
A Textbook of Geomorphology


New Mexico


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Arches NP, Utah
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Upper Gunnison Basin, Colorado
Kaibab Plateau, Arizona
La Sal Mountains, Utah
Lees Ferry, Arizona
Little Colorado River, Arizona
Mesa Verde, Colorado
Mogollon Rim, Arizona
San Francisco Peaks, Arizona
White Mountains, Arizona
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Zion NP, Utah

PlacesSan Francisco Peaks, Arizona (Page 1 of 2)


peaks1.jpg (31753 bytes)

Winter view of the San Francisco Peaks.
Photo by Sarah R. Jacobs.

Rising more than a mile above the surrounding pine forests and grasslands of northern Arizona, the San Francisco Peaks are a prominent feature of the southern Colorado Plateau. Thought by some geologists to be the remains of a large strato-volcano similar to Mt. St. Helens in Washington State, the Peaks rise in dramatic isolation to over 12,000 feet. They are often visible from more than one hundred miles away.

The Peaks and much of the surrounding Coconino National Forest are managed by the United States Forest Service. Traditional land uses of the area have included grazing of livestock, logging, and mining of cinders and pumice. Today, recreation and tourism, including downhill skiing at the Arizona Snowbowl, have become the most prominent land-uses of the Peaks. The mountain's caldera, known as the Inner Basin, contains an aquifer that supplies much of the municipal water for the city of Flagstaff, the largest city on the Colorado Plateau. Water is piped southward to the city from a series of wells tapping the basin's aquifer, which is recharged by seasonal snowmelt.

The Inner Basin

The Inner Basin of the San Francisco Peaks, looking west. Photo courtesy USGS.

The San Francisco Peaks are well known as the place of origin of C. Hart Merriam's Life Zones concept, developed in a study done on the slopes of the volcano in the late 19th century. Several distinct biotic communities can be observed from the base of the peaks to their summit, including pinyon-juniper woodlands, ponderosa pine, mixed conifer, aspen, and spruce-fir forests, and finally alpine tundra atop the two highest peaks, Mt. Humphreys and Mt. Agassiz.

Grazing and Logging

Grazing and logging on the flanks of the peaks have occurred since Anglo settlement in the late 1800s. Although the San Francisco Mountain Forest Reserve was created in 1898, pre-existing timber contracts remained valid, and timber cutting continued on the mountain. Early foresters primarily viewed the extensive forests of the region exclusively for their economic value; "mixed use" management of forests was still decades away. The creation of the transcontinental Atlantic and Pacific railroad along the 35th parallel just south of the Peaks in the early 1880s had profound effects on the economy and development of northern Arizona. During the course of a few years, towns along the railroad such as Flagstaff and Williams rapidly expanded from tiny railroad camp origins. These towns became the hubs for lumber processing, first for laying the railroad tracks themselves, then for shipping prolific timber harvests across the country via the train. The trains also brought hundreds of thousands of sheep and cattle to the area to be grazed on the grasslands and meadows of the larger region.

Logging remained intense on and around the San Francisco Peaks well into the twentieth century. Ponderosa pine regeneration was poorly understood at this time, with foresters mistakenly believing that several mature trees left intact per acre would quickly regenerate these forests. In 1908, the Fort Valley Forest Experimentation Station was established at the base of the peaks to determine the causes of poor forest regeneration and to improve management. Years of research helped foresters to piece together a picture of poor forest management based on a lack of knowledge of the ponderosa pine ecosystem. A combination of factors including the rarity of natural ponderosa propagation except during intermittent bumper years, livestock grazing, and fire suppression were acting to create an unnatural and less-healthy forest.

In the 1960s, the United States Forest Service began incorporating a policy of sustained planning and multiple use management in an effort to balance grazing, logging and recreation interests. Today, experimental restoration treatments are underway in the ponderosa pine forest at the base of the San Francisco Peaks, and larger-scale treatments are being planned. The Forest Service, recognizing the radical change in the health and structure of the region's pine forests over the last century, is thinning and burning certain areas in an attempt to restore ecosystem health and lessen fire danger. Grazing continues only on private landholdings. The Navajo Nation holds much of the grazing allotments on the north side of the mountain, but does not actively graze animals there.

Follow these links to:
Page 2 - Sacred Lands, Controversial Uses
Page 2 - Research on the Peaks