This field trip route leaves Grand Canyon National Park entirely (Figure 1.1), heading south on AZ Hwy 64 to Red Butte, an isolated knob of rock preserving just a tiny smidgen of Mesozoic sedimentary rocks capped by resistant Tertiary basaltic lavas and offering a spectacular 360º panoramic view from a fire tower perched on its summit.  The hike to the top of Red Butte is a comparatively easy stroll (when stacked up against your average trek in the Grand Canyon) of only about two and one-half miles round trip through a pleasant stretch of pinyon-juniper forest.  On your climb, several outcrops provide an extremely rare opportunity to view Triassic age Moenkopi and Chinle Formation sedimentary rocks, as well as the basaltic lavas capping the butte.  From the top, the surrounding Kaibab Plateau rises gently to the northeast, while the more distant mountains of the San Francisco Volcanic Field lay to the south.

 

On your drive to the base of Red Butte, you cross Kaibab Limestone, the resistant, Late Permian sedimentary rock that comprises the uppermost Paleozoic “bathtub ring” within the confines of the Grand Canyon, as well as virtually all of the material capping the North and South Rim plateaus.  It may seem hard to believe, but that rock unit was not the last to be deposited in the Grand Canyon region; in fact as much as 4000 feet of Mesozoic sedimentary rock once covered the area, only to be removed by pervasive lateral stripping of the strata during the warm, moist conditions of the early Tertiary, leaving the dense Kaibab Limestone to buttress the canyon rims.  Geologists know that Mesozoic sedimentary rocks once blanketed the region from thick sequences left behind to the north and east, and from sparse clues like those of Red Butte (and Cedar Mountain near Desert View) preserved on the Kaibab Plateau itself.  Erosion would have removed Red Butte’s Mesozoic rocks if a resistant lava flow from the San Francisco Peaks to the south had not entombed them.  Red Butte itself is so named for the reddish hued, tidal-flat derived mudstones of the Moenkopi Formation that underlie a thin slice of sandstones from the basal Shinarump Member of the Chinle Formation; both rock units representing the basal Triassic portion of the Mesozoic Era.

 

The San Francisco Volcanic Field is a collection of several hundred small cinder cones and lava domes interspersed among roughly a dozen larger volcanic peaks.  Volcanic eruptions began near Williams, AZ in the Late Tertiary about 9 million years ago, but the center of active volcanism migrated slowly eastward, with the most recent activity generating the cinder cone of Sunset Crater some 900 years ago.  Much of the volcanism was basaltic, forming the maze of cinder cones and their associated lava flows that represent the bulk of the San Francisco Volcanic Field, but less commonly, large pods of viscous andesitic and dacitic magma erupted to create large composite volcanoes like Mount Humphreys (San Francisco Mountain), and small lava domes such as Elden Mountain near Flagstaff, AZ.  Several eruptions produced copious rivers of basaltic lava that travelled many miles from their source; the lavas capping Red Butte are all that remains of one of the older flows.

 

Route Description

0.0 (0.0)       Refer to Map 1C.1.  Intersection of Grand Canyon National Park entrance road (U.S. Hwy 180) and Desert View Drive (AZ Hwy 64).  Head south onto U.S. Hwy 180 toward the park entrance.

 

1.3 (1.3)       Intersection of Grand Canyon National Park entrance road (U.S. Hwy 180) and Center Road.  Continue south onto U.S. Hwy 180 toward the park entrance.  Center Road offers an alternate entrance to the Grand Canyon Village area that avoids the traffic congestion around the park’s Visitor Center.

 

4.3 (3.0)       Refer to Map 1C.2.  Grand Canyon National Park boundary and entrance station; continue south on US Hwy 180 toward Tusayan, AZ.

 

5.7 (3.0)       Round-about at the north end of Tusayan, AZ.  The road drops into a small, NE-SW oriented, normal-faulted graben here.  Although the structural feature is fairly subtle at this end, it is readily distinguished on Map 1C.3.  Rain Tank Wash drains from the southern end of the valley created by the graben and exploits the fault-induced zone of weakness in the Kaibab Limestone trending to the southwest.

 

6.3 (0.6)       Refer to Map 1C.3.  Round-about at the south end of Tusayan, AZ.  Shortly, the road climbs the southeast flank of the graben.

 

6.6 (0.3)       The northern entrance to Grand Canyon Airport lies on the right-hand (northwest) side of the road; the airport runway follows the axis of the graben to the southwest.

 

7.2 (0.6)       The southern entrance to Grand Canyon Airport lies on the right.  From here, U.S. Hwy 180 follows the gently undulating back of the Kaibab Limestone, gradually descending into a topographic basin near Valle, AZ which is floored by red mudstones of the lowermost Mesozoic Moenkopi Formation.

 

15.0 (7.8)     Refer to Map 1C.4.  U.S. Hwy 180 passes FS Rd 305 on the left (east).  This location offers your first good view of Red Butte lying to the southeast.

 

16.5 (7.8)     FS Rd 347 lies on the right-hand (west) side of the road here.  The green-gray “bumps” on the horizon are volcanoes of the San Francisco Volcanic Field.  In contrast, Red Butte is not a volcano, although it is capped by an erosional remnant of an ancient lava flow originating from those distant volcanoes.

 

17.8 (1.3)     Intersection of U.S. Hwy 180) and FS Rd 320.  Turn left (east) onto FS Rd 320.  As you proceed Good views of Red Butte’s southwestern flank open up, notice the exposures of red Moenkopi Formation mudstones which provide the isolated knob its name.

 

18.0 (0.2)     FS Rd 320 first ascends a low rise, than drops into a distinctive NE-SW trending swale here, likely controlled by erosion along a fault trace more readily observed on Map 1C.4.

 

19.2 (1.2)     Refer to Map 1C.5.  Intersection of FS Rd 320 and FS Rd 340 on the left (north).  Turn onto FS Rd 340; great views of Red Butte lay off to your right.  Careful observation from here should reveal the butte’s complete stratigraphy which is well exposed in its southwest flank (Figure 1C.1).  Slope-forming, red mudstones of the Triassic Moenkopi Formation overlain by a thin, buff-colored, cliff-forming, sandstone of the Triassic Chinle Formation’s basal Shinarump Conglomerate Member form the base, while the summit is capped by much younger, Tertiary age grayish, basaltic lava flows.  The lavas provided a resistant cap rock that ultimately preserved this small patch of weaker Mesozoic sedimentary rocks.

Figure 1C.1 Red Butte copyrighted

Figure 1C.1.  Red Butte, observed from the intersection of FS Rd 320 and FS Rd 340; note the red-colored sedimentary rocks (capped by gray basalts) exposed in your near view, perhaps not butte’s name isn’t terribly creative, but it is accurate.

 

20.1 (0.9)     Intersection of FS Rd 340 and FS Rd 340A.  Turn right (east) onto FS Rd 340A for the final leg of your drive.

 

20.5 (0.4)     Trailhead parking area for the Red Butte Trail; park anywhere, but please don’t block the road (see the Red Butte Trail – Tr 1C.1 described in the Optional Hiking Trails section).  When you return, it’s only a short drive back to the park; but you may wish to take a short detour in Tusayan, AZ for souvenirs and supplies.
 

Road Route Maps

Phantom Ranch, AZ (Map 1B.1, 1C.1)

Map 1C.1.  Color shaded-relief map of the Phantom Ranch 7.5” Quadrangle containing segments of Field Trip 1B and Field Trip 1C.

 

Tusayan East, AZ (Map 1B.2, 1C.2)

Map 1C.2.  Color shaded-relief map of the Tusayan East 7.5” Quadrangle containing segments of Field Trip 1B and Field Trip 1C.

 

Tusayan West, AZ (Map 1C.3)

Map 1C.3.  Color shaded-relief map of the Tusayan West 7.5” Quadrangle containing a segment of Field Trip 1C.

 

Red Butte SW, AZ (Map 1C.4)

Map 1C.4.  Color shaded-relief map of the Red Butte SW 7.5” Quadrangle containing a segment of Field Trip 1C.

 

Red Butte, AZ (Map 1C.5)

Map 1C.5.  Color shaded-relief map of the Red Butte 7.5” Quadrangle containing a segment of Field Trip 1C.

 

Optional Hiking Trails for Field Trip 1C

Red Butte Trail (Tr 1C.1)

Trail Description

The trail begins at an interpretive sign found at the south edge of the parking area (Map 1C.1.1).  Red Butte is clearly visible and the ascent is obvious.  The cliffs of gray lava and buff-colored Shinarump sandstone stacked on ledgy slopes of red Moenkopi mudstones exposed on the butte’s right side can be seen through the pinyon-juniper forest as you proceed.  Note the red soils covered in coarse fragments of basalt and the occasional chunk of sandstone as you climb; here the trail has been worn into well weathered Moenkopi mudstones, through a thin veneer of slope colluvium and residual debris washed down from above.  Expect to get muddy on this section of trail if it has rained recently.

The trail passes through several switchbacks and then gradually ascends the western flank of the butte to reach a broad bench on its northwest side at just under nine-tenths of a mile (Map 1C.1.1).  Just ahead, Red Butte’s summit cap of basaltic lavas, where they lay on Shinarump sandstone can be observed.  After passing through a broad swale cut into the Red Butte’s northwest slope, the trail climbs southeast to a switchback at just under one and one-tenths of a mile (Map 1C.1.1).  Here the trail skirts left to avoid a prominent cliff of red Moenkopi Formation on the butte’s southern flank.  This location offers a wonderful view of the volcanic peaks of the San Francisco Volcanic Field to the south.  A short detour down slope to the right from this switchback brings you to the base of the Moenkopi cliff and provides an excellent opportunity to explore sedimentological characteristics of the formation.  The cliff is dominantly comprised of thick sandstones interbedded with thin mudstones (Figure 1C.1.1); the slope at the base of the cliff is formed on mudstones.  The cliff exposure extends for several hundred yards eastward and the interbedded mudstones thicken in that direction. Near the west end of the outcrop (at your location), a gray mud-pebble and sand filled channel can be observed, cut disc-like into, and buried by massive sandstone (Figure 1C.1.2).  The alternating layers of sandstone and mudstone exposed here likely formed in associated with low-gradient, coastal, meandering river systems around 240 million years ago, in a setting much like the Gulf Coast today.  The sandstones represent broad, shallow migrating stream channels, while the mudstones preserve evidence of associated floodplain deposition.

Figure 1C.1.1 Prominent Moenkopi cliff on the Red Butte Trail copyrighted

Figure 1C.1.1.  A prominent cliff of red Moenkopi sandstones with thin interbedded mudstones lies within feet of the trail near a left-hand switchback at one and one-tenths of a mile; the base of the outcrop exposes gorgeous laminated shales interbedded with massive sandstones.

Figure 1C.1.2 Channel Fill in Moenkopi Formation copyrighted

Figure 1C.1.2.  A superb little mud-pebble and sand filled channel is cut into underlying massive sandstone near the western (closer) end of the cliff-forming outcrop.

 

Return to the Red Butte Trail at your leisure.  From this left-handed switchback, the trail climbs steadily upward on the butte’s narrowing upper portion through several progressively tighter traverses (Map 1C.1.1); each left-handed switchback offering good views of the cliffs on Red Butte’s southern flank.  As you climb, notice that the chunks of basaltic rubble increase in size and frequency.  The massive sandstone cliff at the next left-hand switchback exposes the Shinarump Conglomerate Member of the Chinle Formation overlying the Moenkopi; and the next left-hand switchback (fourth from the Moenkopi exposure) provides an opportunity to examine Shinarump outcrops up close.  At this switchback, now just over one and three-tenths of a mile into your hike (Map 1C.1.1), take the short detour to your right; but be careful, the slope is steep and covered in scree.  The Shinarump here is comprised of coarse, quartz-rich sandstone, with too low of a gravel fraction to be considered a conglomerate.  The outcrops display gorgeous small-scale, low-angle cross bedding characteristically generated by high-energy streams (Figure 1C.1.3).  The alternate bleach white and rusty red-orange outcrops and covered in pretty, bright orange lichens, all contrasting pleasantly with the crystal-clear blue skies above.

Figure 1C.1.3 Crossbedded Shinarump Sandstone on Red Butte copyrighted

Figure 1C.1.3.  Fluvial sandstones of the Shinarump Conglomerate Member of the Chinle Formation; here the Shinarump is comprised of coarse sandstone organized into small-scale crossbeds intersecting at low angles, an indication of deposition by fast-flowing streams.

 

Once again on the main trail, head upslope to the left.  In about 100 yards, at the next right-hand switchback, you reach the base of the Tertiary basaltic lava flows capping Red Butte.  Although typically a dull, dark gray, the basaltic outcrops on the butte are covered in a profusion of neo-green lichens.  The next left-hand switchback (sixth from the Moenkopi cliff exposure) offers an expansive view of the lava flows exposed in Red Butte’s southern cliffs with their distant source, the volcanic peaks of the San Francisco Volcanic Field, as a backdrop (Figure 1C.1.4).

Figure 1C.1.4 Basaltic lava flows capping Red Butte copyrighted

Figure 1C.1.4.  Tertiary basaltic lavas form the resistant cap-rock on Red Butte; their source was a now long eroded cinder cone associated with the San Francisco Volcanic Field (seen in the background).

 

From this switchback, it is just a short ascent to Red Butte’s summit.  The outcrops of basalt become continuous and readily accessible from trailside.  Take a few moments to examine this volcanic rock; Red Butte is the only place close to Grand Canyon National Park’s South Rim where you can so easily do so.  Note the dark gray, dense mass of fine crystals and the abundance of tiny, rectangular surface pits.  The pits once held crystals of the mineral feldspar which are susceptible to weathering and alteration to clay even in this relatively arid environment.  The table-like surface of the butte is also worth noting, its flatness a product of the relatively fluid lava flow of which it is formed.

The base of the fire tower is reached in about one and six-tenths of a mile from the trailhead (Figure 1C.1.5).  The fire tower is pretty cool, with its own rainwater harvesting system and solar powered electrical supply.  When I visited the site, the lookout’s stairs could be climbed to a balcony that offered stunning 360° views of your surroundings, well worth the short hike.  As you absorb your heightened perspective, consider the seeming oddity of your current perch; how is it that Red Butte came to be?  Try to imagine the landscape of roughly nine million years ago.  Rather than standing on this isolated butte, you would likely have been standing in a shallow stream valley cut into the Chinle’s Shinarump Conglomerate.  Eventually, pa hoe hoe lavas extruded from a nearby cinder cone would force you from the wash, only to solidify at your feet into the dark gray basalts you so recently observed on your climb.  Hopping onto the lava flow and taking a ride through geologic time, the adjacent land not protected by your basaltic blanket would be gradually lowered some 900 feet by erosion, once again leaving you high, dry, and ready to contemplate your “odd” situation.

Figure 1C.1.5 Red Butte Fire Lookout copyrighted

Figure 1C.1.5.  Red Butte Fire Lookout.

 

Now take a look around.  The Grand Canyon lies to the north, although you won’t see much of it, appearing as it does from your location like a shallow brown gash in the broad, gently undulating plateau’s which encircle it.  In fact, from ground level, the canyon cannot be observed until you are literally upon it, so your view here is a bit more three-dimensional.  This is one of the Grand Canyon’s most unusual features, the presence of a deeply carved canyon contained within an expansive, beveled landscape is baffling to many (by contrast, canyons carved in mountainous terrain make more sense).  The surrounding plateaus are impressive landscape elements in their own right (Figure 1C.1.6), their sheer size is remarkable.  They isolate the canyon, and make it stand out; in essence, they define the Grand Canyon.  The Kaibab and Coconino Plateaus form the opposing rims of the Grand Canyon in the immediate region, and they were once connected as the larger, elongated, north-south oriented Kaibab upwarp, but are now dissected by the Colorado River’s magnificent gorge.  Very subtly, the two plateaus dip southward at 1-2º with the Paleozoic sedimentary rock layers, the river cutting across the southern margin of the upwarp (Figure 1C.1.6).  Plateaus usually represent mature landscapes because their formation requires extensive lateral removal of thousands of feet of strata, and in all likelihood, that very scenario played out here on the southwest edge of the Colorado Plateau.

Figure 1C.1.6 Plateaus of Grand Canyon region

Figure 1C.1.6.  A satellite image of the Grand Canyon region showing the unusually broad, flat plateaus which surround and define it, plateaus formed by uplift and lateral stripping of a thick section of Mesozoic and Cenozoic sedimentary rocks between 80 and 30 million years ago during prevailing moist, subtropical conditions.

 

Warm, moist, subtropical climatic conditions prevailed in the southwest between about 80 and 30 million years ago, which tended to produce flatter, more subdued landscapes through enhanced chemical weathering.  Slope retreat kept pace with stream downcutting and broad scale, lateral erosion removed thick sheets of strata from the Grand Canyon region (Mesozoic and Cenozoic sedimentary rocks are still observed further north in the Grand Staircase area).  Landscape-wide planar erosion gradually gave way to localized vertical erosion as intensifying aridity and pervasive, cool, dry climatic conditions between 30 and 15 million years ago caused weathering and erosion to be limited to vertical dissection along stream corridors, creating the deeply incised canyons with broad, intervening plateaus and mesas of today.  Early Grand Canyon geologist Clarence Dutton was the first to recognize and distinguish two cycles of erosion on the Colorado Plateau; an early period he named the “Great Denudation” in which lateral stripping of Cenozoic and Mesozoic strata overlying the Grand Canyon region created the plateau county there and the Grand Staircase (he named) to the north, and a later period he named the “Great Erosion” which caused deep channel incision across the plateaus.

Looking to the south, you are treated with a grand array of volcanoes, the strato-volcanoes, cinder cones, volcanic domes, and associated lava flows of the San Francisco Volcanic Field near Flagstaff, AZ (Figure 1C.1.7).  Volcanic activity began over 6 million years ago and has continued into recent times (from a geologist’s stand point, it is likely ongoing), generating predominantly basalts, although compositions range from basalt to andesite, with several significant eruptive centers of dacite to rhyolite.  Volcanism in the 4800 square kilometer field mainly produced monogenetic (single event) eruptions that evolved and migrated over time in an easterly direction, increasing in both magma production and eruption frequency; and the field dips northeast between ½ and 2° toward the Little Colorado River drainage.  San Francisco Mountain, a large composite volcano that began erupting roughly 2 million years ago, dominates your view (Figure 1C.1.7).  Impressive though it is, this mountain lost much of its summit to collapse during an eruption about half a million years ago.  Although not apparent from here, the large depression on its eastern side is ample evidence of its violent eruptive history.  Much like Mount St. Helens, San Francisco Peak blew out its northeastern slope in a flank eruption, that probably also caused its summit to collapse into the lopsided, amphitheater-like caldera formed on its northeast face.  A veritable maze of hills dot the terrain around San Francisco Mountain, the relative relief associated with greater moisture contributing to a dark cloak of ponderosa pine at higher elevations, with pinyon-juniper woodlands similar to those of Red Butte dominating lower elevations.  Most of the smaller dimples are basaltic cinder cones, but several larger edifices are lava domes which erupted as viscous dacitic to rhyolitic lavas.  The prominence left of San Francisco Mountain, O’Leary Peak, is one such lava dome, while the major hump immediately to the right of San Francisco Mountain is Kendrick Peak, another lava dome (appearing larger than O’Leary because it is closer to your position).

Figure 1C.1.7 The San Francisco Volcanic Field from the Red Butte Fire Lookout copyrighted

Figure 1C.1.7.  The cinder cones, lava domes, and composite volcanoes of the San Francisco Volcanic Field are nicely displayed to the south as you ascend the Red Butte Trail.

 

The San Francisco Volcanic Field is not the only concentration of volcanoes in the region.  Further to the southwest lies the Mount Floyd Volcanic Field, actively erupting about 8 million years ago, and to the northwest, on the western margin of the Grand Canyon’s North Rim, lies the Uinkaret Mountains.  Mount Trumbull, a moderate-sized shield volcano, is the largest peak in the range, which is mainly comprised of overlapping basaltic cinder cones and lava flows.  Copious volcanic activity in the Uinkaret Mountains within the past 3 million years has repeatedly generated lava flows that poured into the lower Grand Canyon, temporarily damming the Colorado River more than a dozen times.

 

Hiking Trail Map

Red Butte, AZ (NW quarter) (Map 1C.1.1)