Granite Mountain
Arizona

James S. and Susan W. Aber
Jim and Susan Schubert

Table of contents
Introduction Kite aerial photos
Granite Mountain References

Introduction

We have conducted kite aerial photography in Arizona twice before in 2019 and 2020—see
Arizona KAP. We were able to return again in March 2022. We stayed in Prescott Valley with our friends, Jim and Susan Schubert, who hosted us and assisted with KAP at the Williamson Valley Trailhead in the Granite Mountain Wilderness, Prescott National Forest, Yavapai County. An open prairie next to the parking area provided a good place to set up for kite flying.

Entrance to Williamson Valley Trailhead (left) with Granite Mountain in the background. Aerial shot (right) of the trailhead parking area with a storm in the background.

After waiting a few days for suitable weather, we had a small window of good wind and sun before an approaching storm front reached us. Wind was generally from the west at 10-15 miles per hour, but was highly variable with updrafts, gusts, and fickle moments. We flew our large rokkaku kite on our lighter line and without a tail. This required constant attention to the kite, so we utilized our autoKAP Sony camera rig to take pictures continuously while in flight. We also had to keep vigilant for thorny hazards at our flying site.

Kite flyers (left). JSA observes the camera rig with binoculars while SWA handles the kite-line reel. Rokkaku (right) in flight during KAP session. The kite measures 7½ by 6 feet in size. Photos by J. Schubert.
Ground hazards, especially during takeoff and landing, could snag the line, kite, or camera rig, as well as human skin. Cholla (left), Cylindropuntia, is a genus in the cacti family. Prickly pear (right), Opuntia, is also a genus in the cacti family. The spines of both easily puncture boot leather.

Elevation at the trailhead is 5200 feet (1585 m), which certainly qualifies for high-altitude KAP. To the southwest Granite Mountain reaches a maximum height of 7626 feet. This elevation is given on older U.S. Geological Survey (USGS) maps and is repeated in many references. However, newer USGS topographic maps show a maximum height just under 7600 feet (USGS TopoView 2022). To the northeast, Chino Valley drops below 4400 feet, giving an elevation range of some 3200 feet in the vicinity. Finally we should note that our site was just over 5 miles away from the Prescott Municipal Airport, which is an FAA requirement (Aber et al. 2019).

Kite aerial photographs
Looking southwest toward Granite Mountain. Overview (left) and closer view (right). Sparse juniper dots the foreground, and snow is visible on the highest peaks.
Views eastward over Chino and Prescott valleys. A storm front approaches from the north (left) and comes closer (right). We finished our KAP and packed up equipment just as the first raindrops began to fall.
Closer views. Looking toward the southeast (left) over Williamson Valley Road and suburban housing. KAP site (right) with kite flyers at lower right (*). An ephemeral, dry wash crosses the scene (^) and is filled with sand and gravel. Tin Trough Springs Trail (#308) appears on right side (<).

Geology of Granite Mountain

Granite Mountain was once called Mount Gurley after the first governor of Arizona Territory. It is part of the Sierra Prietas, an uplifted fault block of basement crust in the Basin and Range Province. The mountain is made up of the Mint Wash Granodiorite, a hard crystalline rock that varies from granodiorite to granite in composition (Spencer and Young 2012). This rock is dated about 1.7 billion years old. Granite Mountain is part of the Yavapai tectonic province, which extends from northern Arizona across central Colorado, beneath northern Kansas, and all the way to the western Great Lakes (Baldridge 2004).

Ground views of Granite Mountain from our
KAP site. Overview (left) and closer shot (right).

The Basin and Range Province includes most of Nevada, southern Arizona, and parts of adjacent states between the Sierra Nevada and Colorado Plateau. This region underwent tension and was stretched east-west approximately 250-300 km (~150-190 miles) during the past 30 million years; most of this expansion took place within the past 16 million years (Baldridge 2004). Extension of the crust was connected with the North American plate overriding the Farallon Plate and East Pacific Rise along subduction zones on the western margin of the continent.

Two major consequences of crustral stretching were firstly deep-seated faults along which basins (wide valleys) dropped down and intervening ranges of basement rock rose up. The Sierra Prietas is one such uplifted fault block, and the Chino and Prescott valleys to the east occupy a basin. Secondly magma migrated upward along faults and erupted in numerous volcanic centers. For the most part, the magma was derived from the mantle (beneath the crust) and is basaltic in composition. Hyrdothermal fluids from shallow magma led to widespread mineralization including turquoise and copper, for which Arizona is well known.

Young basaltic lava flows in the Chino Valley (Gootee et al. 2010). At Lake Sullivan (left) and in the narrow gorge of the Verde River (right) below the lake. Elevation 4340 feet (USGS TopoView 2022).

Lava flows of Miocene and Pliocene age (23 to 2½ million years old) partly cover the lower flanks of Granite Mountain (Spencer and Young 2012). These lava flows take two forms. Vesicular (bubbly) basalt is dark gray to nearly black in color. Given its high iron content, basalt has a high density and is heavy in spite of its swiss-cheese texture. Scoria has a rust-red (scorched) color and a foamy texture that gives it a lower density. The sand and gravel in ephemeral washes reflect these two sediment sources, namely ancient Granite Mountain and relatively young basaltic lava.

Unnamed wash (left) behind KAP site (see above). Sand and gravel fill the normally dry channel. Close-up shot (right) of coarse sand and gravel including granite, granodiorite, basalt, and quartz pebbles up to about 4 inches long.
Boulders of vesicular basalt (left) and scoria (right). The latter displays flow bands that solidified as the lava cooled. From the unnamed wash at the KAP site; comb is about 5 inches long.

References


All text and images © J.S. and S.W. Aber.

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Last update: March 2022.