The South Rim of Grand Canyon National Park affords many opportunities to explore the rich diversity of the canyon’s geology without the intense planning, preparation, and physical exertion of hiking below the rim. Probably the most comfortable, and most “green” way to get around on the South Rim is by using the shuttle service to many classic South Rim locations. Combining the shuttle service with biking on the Greenway Trail and/or hiking on the Rim Trail is an ideal way to experience the beauty of the canyon and its storied geology; and a bit of exercise just seems more natural. The two trails wind their way along the South Rim in the vicinity of Grand Canyon Village, often overlapping with each other and with the transit routes. The paved Greenway Trail provides an excellent bike-riding tour, with many scenic overlooks; however, several segments of the Greenway veer inland from the rim. Only by hiking the Rim Trail in combination with the Greenway can one take in the totality of the South Rim’s views; the trail sticks to the rim like glue, and it offers many unparalleled viewpoints, some only available on foot. I recommend breaking up your excursions into two segments; take a shuttle to Yaki Point for a gorgeous sunrise, and then hike back to Grand Canyon Village from that end on one day, then hike from Grand Canyon Village to Hermits Rest and return via shuttle on the next. Each day hike is roughly 7.5 miles in length, enough to keep even the most avid hiker and geology enthusiast busy. Since the park service shuttles stop at many overlapping locations, and are equipped to carry bikes, there are ample opportunities for older folks and families with younger children to bike and hike portions of the Greenway and Rim Trails and catch a bus when the need arises.
Descriptions in this geological guide correspond to linked segments of the Greenway and Rim Trails, as if you were planning to hike from Yaki Point in the east to Hermits Rest in the west. Numerous locations overlap with shuttle stops, so there is some parallel detail between the auto-touring route described in Field Trip 1A of my website; however, some stops described here can only be reached on foot or bike. Any time spent wandering the South Rim of the Grand Canyon exposes the keen-eyed observer to almost two billion years of earth’s history. A rich story of geology comprised of a thick Paleozoic sedimentary rock sequence, the Great Unconformity (as much as 1.2 billion years of missing rock), graben-filling Middle to Late Proterozoic sedimentary rocks of the Grand Canyon Supergroup, and Early Proterozoic crystalline basement rocks of the Granite Gorge Metamorphic Suite and Zoroaster Plutonic Complex, as well as a multitude of faults and folds related to crustal deformational events in the Neoproterozoic, Late Cretaceous to Early Tertiary, and ongoing Basin and Range tectonism. Although the intimacy of actually touching the many expressions of the canyon’s geology may be lacking without a rim-to-river hike, there is much that can still be learned from the many rimside viewpoints, and any good plunge (physical or intellectual) into the depths of the Grand Canyon’s geology should begin with the broad-brush strokes of a South Rim tour.
It may help to familiarize yourself with some basic Grand Canyon geology first. Figure 1A.4.1 displays a geologic cross-section showing the general topographic expression and age of the rock units found in the eastern Grand Canyon. Figure 1A.4.2 makes the geology more intimate, with a view from Maricopa Point on the Rim Trail just west of Grand Canyon Village, chosen for the diversity of the geology on display. To begin, look to the Grand Canyon’s Inner Gorge nearest the Colorado River; the darker rocks seemingly shot through with nearly vertical, lightly colored ribbons form the foliated metamorphic crystalline basement rocks of the Grand Canyon Metamorphic Suite intruded by granitic rocks of the Zoroaster Plutonic Complex. Stacked above are the flat-lying, multihued layers of Paleozoic-age sedimentary rocks in a range of pastels, starting with the brown cliffs of the Cambrian Tapeats Sandstone, lowermost rocks of the Paleozoic. The rocks most difficult to recognize are the subtly northeast-tilted, brick-red rock layers sandwiched in between; the sedimentary rocks of the Grand Canyon Super Group. Paleozoic sedimentary rocks rest on the uneven top of both dark crystalline basement and reddish Super Group rocks; this contact marks the Great Unconformity.
Figure 1A.4.1. A schematic diagram presenting the suite of sedimentary, metamorphic, and igneous rocks exposed by the downcutting of the Colorado River in Grand Canyon National Park.
Figure 1A.4.2. The geology-packed view from Maricopa Point; three bodies of rock can be identified, dark, foliated crystalline basement of the Inner Gorge, multihued, horizontally layered Paleozoic age sedimentary rocks stacked above, and tilted sedimentary layers of the Grand Canyon Supergroup sandwiched in between.
A brief synopsis of regional geologic history provides context for the rocks shown in Figure 1A.4.1 and Figure 1A.4.2. Between 1.8 and 1.6 billion years ago several volcanic island arcs collided with the southeastern edge of the proto-North American plate. Crystalline basement rocks exposed in the Grand Canyon record formation of volcanic island chains off the continent’s southeast margin, northwest tectonic movement, collision of these island arcs with the continent, and the igneous and metamorphic processes associated with subduction and collisional mountain building. Tectonic and isostatic uplift induced erosion that stripped away the mountain belts over the next several hundred million years to expose their crystalline basement cores on a gently undulating peneplain near sea level. Beginning about 1.2 billion years ago and lasting about 500 million years, thousands of feet of sedimentary rocks accumulated in coastal and shallow marine environments across a seaway that invaded the peneplain’s gradually subsiding surface during a period of back-arc extension associated with the Grenville Orogeny and assembly of the supercontinent of Rodinia. Deposition in the Grand Canyon region formed the Grand Canyon Supergroup, five Mesoproterozoic formations (the Unkar Group) from 1255-1100 million years ago, and four Neoproterozoic formations (the Nankoweap Formation, Chuar Group, and Sixtymile Formation) from about 900-742 million years ago. Later, Rodinia broke up and the continental crust of the Grand Canyon region was stretched and fractured along extensive NW-SE oriented normal faults, offsetting crustal blocks by as much as two vertical miles to form a series of parallel basins and ranges. Subsequent erosion for the next 200 million years removed most of the Supergroup rocks and more of the underlying crystalline basement, leaving only wedge-shaped remnants of tilted Supergroup rocks preserved in large structural grabens below the Great Unconformity. As uplift and erosion waned by 545 million years ago, western North America formed a mature, gradually westward sloping passive continental margin adjacent to the proto-Pacific Ocean. Changes in sea level throughout the Paleozoic and Mesozoic Eras caused periods of marine transgression and regression on the continental margin, depositing a thick sequence of sedimentary rocks across Colorado Plateau; although by present-day, erosion had removed most Mesozoic Era sedimentary rocks from the Grand Canyon region. Dynamic geological events continued, and from roughly 80-40 million years ago, the region was subject to a second tectonic upheaval caused by subduction and compressional mountain building during the Laramide Orogeny, reactivating basement faults and generating broad scale crustal upwarps, monoclinal folding, and erosion across the Colorado Plateau. Subduction ceased along the southwest margin of the North American plate as a mid-ocean ridge collided with the subduction zone beginning about 17 million years ago to be replaced by right-lateral shear at a transform boundary. In the Grand Canyon region, these tectonic motions produced progressive eastward collapse of the Colorado Plateau by crustal extension and reactivation of basement faults to produce ongoing Basin and Range normal faulting. This overview is just a warmup, we will return many times from many angles to flesh out the details of this geologic story. Refer back often as you succumb to your wanderlust and immerse yourself in the geology of this amazing place.
0.00 miles (Trailhead)
Yaki Point (Stop #3 on the Orange Shuttle Route). This scenic vista lies on a promontory at the head of Cedar Ridge which separates Cremation Canyon on the east from Pipe Creek Canyon on the west. It is one of the South Rim’s premier viewpoints, and not to be missed. To reach this location in summer (May through October), you must take an Orange Route bus. This location serves as my trailhead for the 14.5-mile length of the Greenway and Rim Trails, the “unofficial” beginning starting at the southwest edge of the parking area. If you plan an excursion to Yaki Point, include a sunrise in your itinerary. In spring, the sun rises through a gunsight notch immediately north (east) of flat, Wotans Throne, an isolated remnant of the North Rim’s Walhalla Plateau, while the isolated pinnacle of Vishnu Temple rises just to the right.
Yaki Point lies opposite of Zoroaster Temple, a spectacular North Rim monolith, with Brahma Temple just behind (Figure 1A.4.3). The long ridgeline capped by these buttes divides Ottoman Amphitheater, containing the Clear Creek drainage, on the east (right) from Bright Angel Canyon of Bright Angel Creek fame, on the west (left). Both tributary canyons are deeply incised into the North Rim and are a product of a regional southward dip and higher, moisture catching elevations of the Kaibab Plateau, as well as fault-controlled stream erosion. Close examination of the walls of Ottoman Amphitheater and the main river canyon below Zoroaster Temple reveals a typical cliff-slope pattern to the rock formations exposed within the Grand Canyon caused by differential erosion. Cliff-forming rock units are dense, well-indurated, and resistant to erosion, while slope-formers are composed of weak materials. Using Figure 1A.4.1, it should be relatively easy to pick out the rock formations; cliff-formers such as the buff-colored Coconino Sandstone and distinctly reddish Redwall Limestone, from slope-formers such as the brick-red Hermit Formation and greenish-gray Bright Angel Shale are excellent examples. Fill in the remaining units; the outcrop pattern of these formations is observed throughout the Grand Canyon and will become like an old familiar friend.
Below you, a wide topographic bench known as the Tonto Platform (Figure 1A.4.3), slopes gradually away to the edge of the deep, narrow defile of Upper Granite Gorge cut by the Colorado River. A similar bench occupies the north side of the river between the Redwall cliffs and Inner Gorge. These broad, undulating slopes are underlain by rocks of the Middle Cambrian Tonto Group, hence the platform’s name. Below the Redwall Limestone cliffs, the ledgy, yellowish-green slopes of Muav Limestone occur, followed downslope by the gentler topography of the Bright Angel Shale, its greenish-gray mudrocks spread over most of the Tonto Platform, and finally, the brown, cliff-forming layer of the Tapeats Sandstone lying atop the Great Unconformity and darker rocks of the crystalline basement. The platform is a product of rapid weathering and erosion of the weak mudstones of the Bright Angel Shale, a backwasting process which undercuts the more resistant cliffs above, causing them to destabilize and erode faster than normal. The Tonto Group was deposited in successive, conformable, and intercalated layers, during an overall rise in sea level. Initially, Tapeats beaches and nearshore settings deposited sandy to pebbly material in wave-agitated water as the coastline advanced landward. Simultaneously, Bright Angel muds accumulated in deeper, quieter waters offshore, while the Muav’s muddy limestones formed in the calm, deeper waters of a warm-water marine shelf teaming with biological productivity. As the marine transgression progressed, Bright Angel muds were stacked on Tapeats sands, while Muav carbonates were stacked on the previous two layers. Cremation Canyon, to the right of the point and below you, like many of the Colorado River’s tributary canyons, has been notched into the landscape along a fault-controlled lineaments (Figure 1A.4.4), and Cremation Canyon is no exception. Cremation Creek carved its canyon along the northwest-southeast trending Cremation Fault; fracturing of the rocks having generated a ready-made zone of weakness exploited by stream erosion. Careful observation of the valley floor reveals up-to-the-southwest displacement of rock layers associated with reverse movement on the Cremation Fault caused by crustal compression during the Late Cretaceous – Early Tertiary Laramide Orogeny (Figure 1A.4.4). The Tapeats Sandstone is folded over and partially ruptured by the fault and red Hakatai Shale of the Late Proterozoic Grand Canyon Supergroup overlies the Tapeats on the west side of the fault. To the left lies Pipe Creek Canyon, its western wall formed by Cedar Ridge. Sweeping down from your left and onto the Tonto Platform are the multihued cliffs and slopes of the Paleozoic sedimentary rock sequence. Part of the South Kaibab Trail can be observed from your vantage point where it passes around the east flank of O’Neill Butte and descends from Cedar Ridge through the Redwall and Muav Limestones. Follow the trail’s descent; the contact between the red Supai Group and gray Redwall Limestone occurs just before the notch at the end of Cedar Ridge, while the Redwall – Muav contact occurs at trail level below the Redwall cliff, right at the break in slope.
Figure 1A.4.3. Zoroaster and Brahma Temples lay nearly opposite Yaki Point along a ridge separating the Ottoman Amphitheater from Bright Angel Canyon; both tributary canyons are fault-controlled, and their walls expose the common pattern of cliff and slope caused by differential erosion of resistant vs. weak rock formations.
Figure 1A.4.4. Yaki Point affords an excellent view of fault-controlled Cremation Canyon; the dashed line indicates the approximate position of the Cremation Fault offsetting Proterozoic and Paleozoic sedimentary rocks by up-to-the-southwest motion (the Hakatai Shale is juxtaposed against the Tapeats Sandstone).
Hiking south from Yaki Point offers good views into Pipe Creek Canyon. As you approach the South
Kaibab Trailhead, a promontory viewpoint above the trailhead looks down onto the upper part of the South Kaibab Trail as it descends snake-like through the Kaibab Limestone and into Pipe Creek Canyon. Near the trail, stringers of chert nodules formed parallel to bedding in the limestone can be observed; the nodular chert often contains siliceous sponge spicules indicating deposition of this unit on a warm, shallow seafloor. The walls of the canyon are gorgeous, providing one of many opportunities to examine the influence of differential erosion more closely on the pattern of rock exposure in the Grand Canyon. Here, distinctly contrasting cliff-slope-cliff-slope exposures in the four upper Paleozoic rock units formed in response to alternating resistance to weathering and erosion (Figure 1A.4.5): the cliffs of Kaibab Limestone and Coconino Sandstone are stronger than the slopes of Toroweap Formation and Hermit Formation. The pattern continues downward through the visible layers of the Supai Group and Redwall Limestone.
Just ahead, your route briefly connects with the South Kaibab Trail (Tr1A.6), one of three “Corridor” trails designated by the park service; meaning that the trail is regularly patrolled by rangers and that it receives routine maintenance. It does suffer from large crowds of day-hikers and the occasional mule train, but the trail is unique in that it follows an eye-popping, ridgeline descent for much of its length (most trails in the park are confined to canyons) and it offers awesome scenery at every turn. The South Kaibab Trail connects the North Kaibab Trail and the Bright Angel Trail (via the connecting River Trail) at river level.
Follow the trail to the South Kaibab Trailhead parking area (Stop #3 on the Orange Shuttle Route), then take the crosswalk to the left toward the southwest edge of the short loop road.
Figure 1A.4.5. Upper Pipe Creek Canyon from a vantage point above the South Kaibab Trailhead; the canyon walls offer a gorgeous display of differential erosion’s influence on the exposure pattern of sedimentary rocks.
The official beginning of both the Greenway Trail and Rim Trail starts here, at the southwest edge of the South Kaibab Trailhead parking area. As part of the Greenway Trail, the route ahead is paved, with relatively gentle grades from here to the park Visitor Center and offers a pleasant biking opportunity.
1.13 and 1.30 miles
Two back-to-back promontories jut prominently from the rim and provide great views into Pipe Creek Canyon; the second one offers the better view of the South Kaibab Trail where it clings to the eastern edge of the canyon and the upper portion of Cedar Ridge. Shortly, the trail passes the first of two Pipe Creek Vista pullouts on AZ Hwy 64. Continue ahead to the second pullout for a better view into Pipe Creek Canyon.
Pipe Creek Vista (Stop #4 on the Orange Shuttle Route). The view lies more-or-less along the axis of the canyon, and it is not difficult to observe its linear shape, a product of erosion along subsidiary faults related to the northwest-southeast trending Cremation Fault. Below, a sharp V-notch at the head of Pipe Creek Canyon occurs where water has exploited the fault trace to form sheer walls of Redwall Limestone. As with many rim views, this is a good place to observe differential erosion by focusing your attention on the stair-stepped nature of the upper Paleozoic sequence (Figure 1A.4.6). However, a discerning eye may note that the Coconino forms less of a distinctive cliff here compared to most locations because it has been highly fractured by faulting (compare this rim section to its counterpart on the west side of Pipe Creek Canyon observed in Figure 1A.4.5. Careful observation of the eastern headwall will reveal the trace of the South Kaibab Trail as it first comes into view ascending ledgy outcrops of interbedded red Supai Group and Hermit Shale sandstones and mudstones along Cedar Ridge, then through the much-subdued, fault-shattered cliffs of Coconino Sandstone, and finally along a lengthy traverse through slopes of Toroweap Formation mudstones, eventually disappearing back into the recesses of the canyon where it will climb tight switchbacks in rapid succession up through the imposing, banded cliffs of Kaibab Limestone.
Evidence of ongoing erosion at work in the Grand Canyon is also on display within the confines of upper Pipe Creek Canyon. Figure 1A.4.7 focuses your attention on two large blocks of Redwall Limestone that have become detached from the eastern headwall; these blocks are not uncommon where a resistant rock unit like the Redwall overlies weaker rocks like the muddy Muav Limestone and the Bright Angel Shale below it. Mudrocks are easily weathered and eroded, even in the relatively dry climate of the Grand Canyon region, and they tend to backwaste more rapidly than resistant limestones and sandstones. Here, backwasting of the weaker Bright Angel Shale and overlying Muav Limestone has destabilized the massive Redwall Limestone causing blocks to break lose and slide downward and outward over the underlying mudrock slopes. The blocks can be seen to lean back (they are back-tilted) into the main Redwall cliff from which they originated.
From this location, you can rejoin the transit route on a westbound orange shuttle and eventually make your way to Mather Point; or you can bike or hike the one and half paved miles to Maher Point instead, enjoying wonderful views of Pipe Creek Canyon and Cedar Ridge enroute.
Figure 1A.4.6. Pipe Creek Canyon’s eastern headwall is adorned by a layer cake of Paleozoic sedimentary rocks whose alternating cliff-slope topography is a product of differential erosion, while in the distance, the Grand Canyon’s North Rim displays a similar banded pattern; look more closely at the nearby cliffs, you may notice that the Coconino appears crumbly, an expression of the “shattering” influence of the Cremation Fault.
Figure 1A.4.7. Slump blocks formed in the Redwall Limestone cliffs of upper Pipe Creek Canyon; the normally dense, resistant Redwall has become unstable and fractured into large slabs that are gradually sliding downslope due to rapid weathering and erosion of the weaker Muav Limestone and Bright Angel Shale which lie below it.
At this location, the Greenway Trail splits from the Rim Trail and heads to either the Visitor Center or Yavapai lodge and Market Plaza; if you are hiking, remain on the Rim Trail (the Greenway Trail briefly rejoins the Rim Trail at Mather Point and at the western end of Grand Canyon Village).
Pass several water tanks on the left, then swing right and onto a rimside promontory here offering a great view of the narrow fin of Kaibab Limestone that forms Mather Point (Figure 1A.4.8). Many such “fins” project from the rim; these, and the hoodoos (isolated pinnacles) which often accompany them are caused by weathering and erosion along joints in the limestone. The joints form naturally in response the removal of loading pressure and deformation and they act as conduits water to work its way into the rock and slowly widen the fractures over time through physical and chemical processes such as frost action and dissolution.
Figure 1A.4.8. Mather Point as viewed from the Rim Trail; fins of limestone such as this commonly project from the rim and are produced by weathering and erosion along joints.
Here, short jog to the right carries you down to the end of the limestone fin forming Mather Point and truly “immense” views of the Grand Canyon. Otherwise, a left turn offers a relatively short walk or ride to either the Visitor Center where you can pick up the Greenway Trail toward Market Plaza and Grand Canyon Village, or to Stop #5 on the Orange Route. The Visitor Center also serves as the hub from all transit routes (Stop #1 on the Orange, Blue, and Purple Routes). But first, let’s explore what Mather Point has to offer.
This wonderful vista is named for Stephen Mather, the first director of the National Park Service. Few locations more splendid than this one could serve as a reminder of Mather’s contributions to conservation of our nation’s most uniquely spectacular places, both as an advocate for the creation of the National Park Service, and then as manager of the fledgling agency for its first dozen years of operation. Because of its location nearest the south entrance to Grand Canyon National Park, as well as its proximity to the new park Visitor Center and its attendant parking lots, Mather Point tends to draw huge crowds. However, the overlook is well chosen, offering scenic beauty, especially at sunrise or sunset, and wide-open views both up and down canyon, making it worth the amusement park feel; and I admit that I do take pleasure in hearing those first gasps and exclamations of awe from many a Grand Canyon initiate here.
Mather Point is an ideal location to experience the oft-mentioned array of shifting colors and patterns comprised of rock and sky, sunlight and shadow as the sun advances through its day. Dawn and dusk are especially resplendent. The up-canyon view of Wotans Throne and Vishnu Temple at sunset (Figure 1A.4.9) exemplifies the true grandeur of this Grand Canyon phenomenon. You really must experience it for yourself. Standing at Mather Point, gazing into the canyon and basking in its immensity, a first experience for many, can elicit a multitude of responses; but surely nearly universal among them is an appreciation for the vastness of time. Questions come to mind, such as how much time did it take to accumulate all those rock layers, and the Grand Canyon is so huge, how much time did it take to carve this landscape?
Returning to our geological roots, perhaps this is a good time to recall that nearly two billion years of earth’s history are exposed within the walls of the Grand Canyon, including an impressive array of Paleozoic sedimentary rocks, the Great Unconformity, and the more ancient sedimentary rocks of the Grand Canyon Supergroup and crystalline basement, plus faults and folds related to several phases of ancient and ongoing regional tectonism. Most visitors peering into the Grand Canyon from Mather Point can readily distinguish the layer-cake arrangement of rocks within by their color, thickness, and stair-step-like exposure pattern (Figure 1A.4.1), patterns remarkably well displayed in Figure 1A.4.9. Identifying faults and folds can be more challenging, but it is a good bet that most tributary canyons are dissected along the traces of ancient faults. Many of the isolated pinnacles and buttes within your field of view (and common throughout the canyon) are a product of the gradual erosion and wastage of larger mesas first separated from the main canyon rims along faults. Vishnu Temple, Wotans Throne, and the Walhalla Plateau present a living example of this latter process (Figure 1A.4.9); Vishnu Temple, lying farthest to the south and closest to the canyon axis, has been isolated from the main North Rim for the longest time and is eroded to a mere pinnacle, while Wotans Throne has separated more recently in time and forms a butte, with the massive Walhalla Plateau lying farthest to the north and at the greatest distance from the canyon axis.
Mather Point lies on the east side of a major South Rim promontory separating Pipe Creek Canyon from Garden Creek Canyon. A pleasant three-quarter mile walk on the Rim Trail brimming with excellent views will take you to the end of the promontory at Yavapai Point. Doubling that distance completes a short loop that takes you along the west side of the Yavapai promontory for equally gorgeous down canyon vistas, where you can join a short trail back to the Shrine of the Ages and a shuttle on the eastbound Blue Route back to the Grand Canyon Visitor Center. Yavapai Point can’t be reached by bicycle because the Greenway Trail cuts westward and passes through Market Plaza and westward to Grand Canyon Village.
Figure 1A.4.9. Sunset on Wotans Throne and Vishnu Temple; viewed from Mather Point; the interplay of multihued rocks, blue shy, sunlight, and shadow create an unforgettable landscape; and the geology is quite fascinating too!
Yavapai Point and Geology Museum (Stop #4 on the Orange Shuttle Route). Yavapai Point is easily accessed by foot, private vehicle, or transit bus, and is a popular South Rim overlook. The presence of a small museum specializing in Grand Canyon geology, plus the fantastic 180º panorama of the inner canyon and North Rim, ideal for observing many of the geologic features common to the Grand Canyon, make this site a first-rate destination. One such view unfolds to the northwest across the Inner Gorge of the Colorado River where Trinity Canyon can be followed to its sources on the North Rim at Shiva Temple (Figure 1A.4.10). Granite Gorge in the depths of the inner canyon snakes darkly across your panoramic view, its walls comprised of dense Early Proterozoic crystalline basement, here mainly Vishnu Schist intruded by pinkish ribbons of Zoroaster Granite. The Vishnu basement consists of sediments derived from a growing volcanic island arc, metamorphosed and folded tightly into nearly vertical layers called foliation, then intruded by silicic magma; rocks formed deep within the earth’s crust, grafted to the proto-North American continent at the site of collisional mountain building long ago. The resistance of these crystalline rocks forces the Colorado River to expend much of its erosive energy on downcutting, there is little energy left over for meandering about, hence explaining the deep V-notch of the Grand Canyon’s Granite Gorge.
On the other hand, the main portion of Trinity Canyon is confined by walls of sedimentary rock (Figure 1A.4.10). The Tapeats Sandstone, oldest of the Paleozoic layer-cake of sedimentary rocks overlying the crystalline basement (Figure 1A.4.1), forms a distinctive horizontal, brown band capping the igneous and metamorphic rocks below. The Tapeats rests on the Great Unconformity, the gently undulating surface generated by countless millennia of erosion that exhumed the core of ancient mountains. The grayish slopes above the Tapeats are formed of Bright Angel Shale and Muav Limestone (Figure 1A.4.1), the three rock units completing a fining-upward sequence of sedimentary rock generated by worldwide Middle Cambrian marine transgression. Above the gray slopes of Bright Angel and Muav lay the massive red cliffs of resistant Mississippian Redwall Limestone (Figure 1A.4.1), its natural gray marine carbonates coated in red muds derived from oxidized sediments carried down from above. Resting on the Redwall is the distinctively red, stair-stepped bands of the Pennsylvanian and lower Permian Supai Group and Hermit Shale (Figure 1A.4.1), the source of the Redwall’s red adobe texturing. These units are partially terrestrial, deposited along an arid coastline undergoing periodic marine incursions. To complete the picture, follow Trinity Wash upward, its dual arms encircle Shiva Temple, a large butte capped by resistant Permian Kaibab Limestone isolated from the main North Rim beyond. Trinity Canyon and Shiva Temple are framed by the twin pinnacles of Isis Temple to the east and Osiris Temple to the west, both erosional remnants topped by resistant Permian Coconino Sandstone. The Permian Toroweap Formation forms the vegetated, slope-forming unit between the whitish cliffs of Coconino and Kaibab (Figure 1A.4.1). The Coconino formed in a huge coastal desert, while the successive layers of the Toroweap and Kaibab represent a gradual return to marine conditions.
Figure 1A.4.10. The inner gorge of the Colorado River and Trinity Creek Canyon from Yavapai Point; the tributary drainage is headed by Shiva Temple which is framed by the dual Coconino Sandstone-capped spires of Isis Temple (on the right) and Osiris Temple (on the left).
A short walk on the Rim Trail west from Yavapai Point’s Geology Museum offers another educational opportunity that should not be overlooked: the Trail of Time. This stretch of the Rim Trail is marked off in one-meter-per-million-year increments that provide a unique, distance-equals-time view of the rocks exposed in the walls of the Grand Canyon. Continuing westward and into the earth’s past, each rock unit that has been described and mapped in the Grand Canyon is laid out in its proper place along the trail by inferred age (Figure 1A.4.11), covering two billion years, the entirety of the rock record unearthed by canyon carving.
Figure 1A.4.11. The pedestal of Elves Chasm Gneiss marks the beginning of the Trail of Time just west of Yavapai Point; this section of the Rim Trail is marked off in one-meter-per-million-year increments with each rock unit exposed by canyon dissection laid out in its proper place along the trail by age, and offering a uniquely visual display of the immensity of time portrayed within Grand Canyon’s depths.
A highlight on this stretch of trail is the little publicized overlook of Grandeur Point. Situated at the end of upper Garden Canyon’s eastern rim, Grandeur Point offers a stunning spectacle, from its intimate view deep into the confines of Garden Creek, to its broad views of the main Colorado River canyon, Bright Angel Canyon, and the North Rim beyond. On the western side of the promontory and opposite your vantage point, the panorama provides an unparalleled view of the straight-as-an-arrow confines of Bright Angel Canyon where perennially flowing Bright Angel Creek has cut a deep trench back into the North Rim west of Walhalla Plateau (Figure 1A.4.12). The distinctive lineament of this tributary canyon is matched on the South Rim by Garden Canyon, a lineament controlled by the Bright Angel Fault, canyon erosion preferring the path of least resistance as the Colorado River sliced downward, the stream keeping pace with base level lowering. The Bright Angel Fault formed in the Late Proterozoic as a normal fault by extensional tectonics during the breakup of the Rodinian supercontinent, but was reactivated as a reverse fault 80-40 million years ago by a Laramide Orogeny compressional regime. And this major rupture is probably at it again, recently reactivated as a normal fault during ongoing Basin and Range extension. Many faults in the region boast similarly complex histories; the take-away is that old faults never die, they just grumble from time to time.
East of Grandeur Point, turn your gaze toward Garden Canyon’s headwall which offers a superb view of the up-to-the-west displacement of sedimentary rocks related to Laramide compression and reverse movement on the Bright Angel Fault (Figure 1A.4.13). As you examine the headwall area, look for evidence of faulting. Trace the path of the Bright Angel Trail downward from the rim; most rim-to-river trails were developed along faulting-induced breakdown slopes in the Paleozoic strata, and this one is no exception. Faults such as the Bright Angel generally rupture along multiple, closely spaced, subparallel fractures called a fault zone, and only rarely occur along a singular plane; that rupturing produces countless small breaks in the rock layers, weaknesses exploited by weathering and erosion that results in copious amounts of talus, hence the “breakdown slopes”. Notice that the South Rim above Garden Canyon is not level; much of Grand Canyon Village occupies a slight depression in the South Rim at the head of Garden Canyon; the dip indicates fault displacement. Finally, follow any layer of sedimentary rock west to east through the very head of the canyon, the Coconino Sandstone’s massive, buff-colored cliff is one such standout, and you can see that that layer is displaced downward on the nearer, eastern, side (or upward on the western side).
Figure 1A.3.12. Bright Angel Canyon from Grandeur Point; the distinctive linearity of this large tributary to the Colorado is the result of preferential stream erosion along the trace of the Bright Angel Fault.
Figure 1A.4.13. The headwall of Garden Canyon is split by the Bright Angel Fault (dashed line); the readily visible displacement of Paleozoic sedimentary rocks was generated by up-to-the-west motion related to Laramide age compression (although the fault is currently undergoing extension).
If you have enough geology for one day, or if you wish to escape the crowds in the Grand Canyon Village area, the trail junction here offers an escape route of sorts. The trail to the left links up with the east- and westbound blue transit routes at the Shrine of the Ages, providing transport to the park’s Visitor Center, lodging, and campgrounds. Otherwise, remain on the Rim Trail, there is plenty more to see.
Here, you have arrived at the end of the Trail of Time and Verkamp’s Visitor Center. Verkamp’s houses a visitors center and gift shop. A short walk south (left), past Verkamp’s, brings you to optional stops on the westbound Blue Transit Route. Continue on the Rim Trail, but be warned, you have reached the Grand Canyon Village and the most congested section of the Rim Trail with a plethora of lodging, shopping, and dining opportunities at El Tovar Hotel, Kachina Lodge, Bright Angel Lodge, Kolb Studio and Lookout Studio. The village was established at the end of the Grand Canyon Railway (formerly a part of the Santa Fe Railroad) and the major cross-canyon hiking route comprised of the Bright Angel and North Kaibab Trails.
The Bright Angel Trailhead veers off to the right at this location just pass the water filling station and public bathrooms. The Bright Angel Trail (Tr1A.2) is considered by many to be the park’s premier hiking trail, with access to water stations, covered rest houses, vault toilets, camping below the rim, gorgeous scenery, and geological wonders beyond compare, who could say otherwise? It is one of the Park Service-designated “Corridor” trails, and although it is 9.4 miles from rim to river, it is well maintained and regularly patrolled by rangers, and so it is ideally suited for a beginning backpacking experience in the Grand Canyon.
The Rim Trail briefly reencounters the Greenway Trail here at the Hermits Rest Transfer Station on the Red Route. From this location, you can also catch a connecting Blue eastbound transit bus by walking over to the nearby Hermit Route Transfer Station. The Greenway follows the same route on the old West Rim Drive initially, but you will see it again later. It offers a low traffic volume biking opportunity with access to all the transit stops. If you are hiking, continue west on the Rim Trail to any number of spectacular overlooks (returning on the eastbound Red Route at several opportunities). Ahead, the Rim Trail circles around the uppermost portion of Garden Canyon and strikes out for Maricopa Point along Garden Canyon’s western rim, ascending past the upthrown side of the Bright Angel Fault. Look for outcrops of Kaibab Limestone exhibiting fossil crinoids, brachiopods, and sponge spicule bearing chert nodules.
Trail View Overlook (Stop #2 on the Red Shuttle Route). Looking back to the southeast form this viewpoint, the Grand Canyon Village can be seen lying in a natural depression along the South Rim at the head of Garden Canyon. The dip in the rim here is related to down-to-the-east displacement on the Bright Angel Fault, as well as preferential weathering and erosion caused by fault-induced weaknesses in the limestone cap rock. The view is difficult at this angle, but a discerning eye may notice that the Coconino Sandstone on this side of the fault is higher than on the southeast side. Trace the Bright Angel Trail as it zigzags down through the rock formations in upper Garden Canyon. The trail briefly crosses onto the Bright Angel Fault near the contact between the slope-forming Toroweap Formation and the cliff-forming Coconino Sandstone, and then makes a series of tight switchbacks on a colluvial wedge of talus deposited along the fault where it has completely fractured and offset the Coconino. The trail passes through the Coconino cliffs at a fault-related breakdown slope, a common feature of Grand Canyon rim-to-river trails.
Here, the Rim Trail reaches Maricopa Point (Stop #3 on the Red Shuttle Route), the first of three spectacular overlooks in quick succession offering similar views into the Grand Canyon. All three viewpoints are connected to the Red Route and Greenway Trail. Figure 1A.4.2 provides a view from Maricopa Point across the Grand Canyon, focusing on Cheops Pyramid and Buddha Temple to the west of Bright Angel Canyon. The basic geology of this view is described in the introduction.
A half-mile walk to the west from Maricopa Point brings you to Powell Point (Stop #4 on the Red Shuttle Route). This stop hosts a memorial to John Wesley Powell, the leader of the first two scientific expeditions through the Grand Canyon in 1869 and 1872, who later became the first director of the U.S. Geological Survey. The viewpoint occupies a needle-like fin of Kaibab Limestone projecting from the rim into upper Horn Creek Canyon, the eastern toe of a multipronged promontory just west of Grand Canyon Village. Horn Creek Canyon is bordered by ridges of Supai Group forming The Battleship on the right and a long buttress of Redwall Limestone extending to Dana Butte on the left, its panoramic view spreads along the North Rim northeast of Bright Angel Canyon to northwest of Trinity Canyon. Vertically foliated crystalline basement rocks of Early Proterozoic Vishnu Schist intruded by Zoroaster granite are exposed within the Inner Gorge nearest the river (Figure 1A.4.14). Stacked above, the variegated colors of the flat-lying, Paleozoic sedimentary rocks stand in sharp contrast. The contact between these major rock bodies is fairly obvious, the Great Unconformity, a nonconformity here readily identified where the horizontal, buff-colored Tapeats Sandstone rests on the vertically foliated igneous and metamorphic rocks at the lip of Upper Granite Gorge.
However, not all the rocks in your field of view comprise Paleozoic sediments and crystalline basement. A prominently paired cliff and slope of red sandstone and shale are exposed at the base of Cheops Pyramid, running from Bright Angel Canyon southward to near the position of Isis Temple (Figure 1A.4.14). A second, thinner, brown-colored cliff-forming unit is also exposed below the Hakatai nearer Bright Angel Canyon. These distinctive rock layers are the Shinumo Sandstone, Hakatai Shale, and Bass Limestone, Mesoproterozoic sedimentary rocks of the Unkar Group, the lowermost units of the Grand Canyon Supergroup. What is more difficult to see from this rim view is that the Supergroup rocks dip to the northeast within a large fault-bounded graben formed during crustal extension associated with Neoproterozoic rifting of the Rodinian supercontinent (Figure 1A4.14). The Shinumo Sandstone best exhibits the northeastward dip. Now focus on the area just below and to the fore of Cheops Pyramid. A NW-SE trending normal fault bounding the southwest side of the graben is exposed at either end of a table-like feature capped by Tapeats Sandstone (the fault passes beneath the “table,” and is older than the undeformed Tapeats Sandstone above). Vishnu basement rocks are exposed on the southwest upthrown side of the fault nearer the Inner Gorge.
The Tapeats Sandstone capping crystalline basement at the lip of Granite Gorge pinches out against the Shinumo Sandstone, especially below the pyramid, but note that the Tapeats reappears brimming the crystalline basement of Bright Angel Canyon to the northeast (Figure 1A.4.14). Geologists believe that resistant rocks such as the tilted Shinumo would have formed a ridge-like “island” during deposition of the Tapeats Sandstone; thus, during the Middle Cambrian marine transgression the Shinumo Sandstone was not immediately inundated, instead the unit temporarily protruded above sea level, consistent with the lack of Tapeats Sandstone over the tilted red cliffs here which are instead overlain by the Bright Angel Shale.
Figure 1A.4.14. The inner canyon of the Colorado below Powell Point exposes Mesoproterozoic Supergroup rocks preserved within a back-tilted half-graben stacked on Early Proterozoic crystalline basement comprised of the dark-colored, vertically foliated Vishnu Schist intruded by stringers of pinkish-colored Zoroaster Granite.
Hopi Point (Stop #5 on the Red Shuttle Route). This rim’s edge overlook is perched on the middle appendage of the three-toed promontory jutting into the canyon west of Grand Canyon Village. It lies due south of Dana Butte and the ridge separating Horn Creek Canyon from Salt Creek Canyon, and it is almost directly opposite and closest to the twin spires of Osiris and Isis Temples north of the river, standing as sentinels to Shiva Temple herself at the head of Trinity Canyon. Both pinnacles are capped by Coconino Sandstone, but Shiva Temple retains her crown of Kaibab Limestone. This large, flat-topped temple is isolated from the North Rim by erosion along the Phantom Fault which trends NW-SE behind the edifice and then down Phantom Creek Canyon. A walk from the eastern to the western terminus of Hopi Point offers a 180º of the main canyon. At its western end, you are treated with the first view of the Colorado River on the Rim Trail (Figure 1A.4.15), a particularly gorgeous vantage point and one of the most prized sunset locations in the park. West of Hopi Point, the Rim Trail circumnavigates Salt Creek Canyon to offer superb views into its shadowy depths enfolded by protruding arms of stone. The canyon’s western wall is observed first, capped by a distinctively red, extended platform of Esplanade Sandstone called “The Alligator” (Figure 1A.4.16). Recall that the Esplanade Sandstone forms the uppermost unit within the Supai Group (Figure 1A.4.1); its four formations are easily distinguished by the cliff-slope-cliff-slope pattern that their composition and relative resistance forces upon them. Continuing to the canyon’s far side, a look back reveals the long, narrow Redwall arm of Dana Butte projecting far to the north. Examine any map of the Grand Canyon and you will observe this pattern because the Redwall is such a thick, massive, dense limestone, its breakdown is quite slow compared to most of the other Paleozoic rock units (simply put, its hard to get rid of it).
Figure 1A.4.15. A down-canyon view from the western end of Hopi Point, come back and enjoy the show at sunset, Hollywood could never do it better!
Figure 1A.4.16. The Alligator, capped by the Esplanade Sandstone, forms the western arm enfolding deep, narrow Salt Creek Canyon west of Hopi Point.
Roughly three-quarters of a mile later, you arrive at Mohave Point (Stop #6 on the Red Shuttle Route). This overlook perches at the northwestern end of the Great Mohave Wall, a particularly steep section of the upper Paleozoic sedimentary rock sequence forming the eastern side of Monument Canyon, offering another spectacular 180º vista (Figure 1A.4.17). Erosion of Monument Canyon is controlled by the NW-SE trending Monument Fault which runs parallel to the central part of the inner canyon. A careful observer can even identify the canyon’s namesake, “The Monument”, a spire of Tapeats Sandstone perched on Zoroaster Granite at the confluence of the primary stream channel and its largest western tributary. All the usual suspects are on eminent display, with an impressive view into the main canyon’s Inner Gorge and its exposure of crystalline basement, as well as the many layered and multihued soaring cliffs and ramparts comprised of Paleozoic sedimentary rocks. Down canyon, you are teased by the first exciting views of the Colorado River. As you approach the next shuttle stop, look for tell-tale signs of rock falls from the Coconino Sandstone cliff along the canyon headwall (Figure 1A.4.18). These features appear as fresh scars where unweathered sandstone is now exposed on the cliff face, accompanied by a downslope runner of bouldery scree, evidence that weathering and erosion is alive and well in the Grand Canyon.
Figure 1A.4.17. The downcanyon view from Mohave Point offers up deeply carved Monument Canyon and an exciting opportunity to see the rushing waters of the Colorado River; look carefully near the confluence of the canyon’s two major tributaries for The Monument, a pedestal of Tapeats Sandstone resting on a base of Zoroaster Granite.
Figure 1A.4.18. Recent rockfalls at the head of Monument Canyon attest to active processes of weathering and erosion that have gradually sculpted much of the scenery arrayed before you.
The Abyss (Stop #7 on the Red Shuttle Route). A brief stop here is worth it just for the sheer adrenaline rush of looking over the edge of the rim into Monument Canyon. The canyon forms a deeply carved reentrant into the South Rim, bounded by incredibly high, steep cliffs that drop some 3000 feet to the base of the Redwall Limestone. Let your eyes wonder out to Mohave Point and be sure to gape appropriately at the Great Mohave Wall that soars skyward along the eastern and most sheer side of the canyon.
Monument Creek Vista (Stop #8 on the Red Shuttle Route). This stop offers another amazing look into Monument Creek’s depths and its view is worthy of its name as it looks directly down the axis of Monument Creek Canyon. Eagle eyes (or a trusty pair of binoculars) can pick out The Monument where east and west tributaries meet. This location also brings together the Rim Trail and the Greenway Trail and an opportunity to bike on a paved trail out to Pima Point, approximately 1.7 miles distant.
Continuing your hike on the Greenway/Rim Trail, you pass several unnamed overlooks along Monument Canyon’s western rim offering exceptional views directly across to the Great Mohave Wall and to The Abyss (Figure 1A.4.19). The steep headwall and eastern face of Monument Canyon can be attributed to westward thickening of resistant, cliff-forming units in the Paleozoic sequence, such as the Kaibab and Redwall Limestones, as well as active groundwater sapping at the base of the Redwall. This process occurs when downward percolating groundwater is forced to flow laterally when it reaches an impermeable clay-rich layer (the Bright Angel Shale); the water eventually finds an outlet where the ground surface intersects with the impermeable layer and the concentration of water on the slope causes erosion of the weak clay material to undercut overlying, more resistant layers (the Redwall Limestone). Undercutting creates instability, and the normally resistant rock collapses, breaks up, and is carried away by mass wasting and flash floods.
Figure 1A.4.19. The Rim Trail on the western side of Monument Creek Canyon provides excellent views of The Abyss and the Great Mohave Wall; the exceedingly steep slopes in the upper Monument drainage are related to westward thickening of resistant rock units such as the Redwall Limestone and active groundwater sapping.
Here, the trail veers away from rim and navigates through a small valley cut into the plateau limestone. In its lower reaches, a grove of ponderosa pine enjoys a shady microclimate where thicker soils have formed in the alluvial bottom that retain moisture better than nearby surroundings dominated by pinyon-juniper woodland.
An unnamed viewpoint at this location affords a superb look at lower Monument Canyon and its confluence with the Colorado River where Granite Rapids has formed (Figure 1A.4.20). This is no coincidence. Consider where else you have observed river rapids, and you will likely conclude correctly that they often occur at the confluence of tributary canyons with the Colorado River. Why? The turbulent, frothy flow of water through a rapids corresponds to a significant change in stream gradient, related to the deluge of coarse, rocky debris delivered to the river by periodic flash flooding on its tributary. The Colorado’s energy would quickly remove these obstacles without renewed input of bouldery material by repeated flood events, reoccurring with a frequency of about one in every 50 years (a 2% chance on any given year).
Figure 1A.4.20. Lower Monument Canyon and Granite Rapids observed from an unnamed promontory on Monument Canyon’s west side.
Pima Point (Stop #9 on the Red Shuttle Route). A near perfect view of lower Hermit Creek Canyon and downriver along the inner canyon of the Colorado lies at the western edge of the Pima Point promontory (Figure 1A.4.21). Much of the bowl-shaped lower end of the canyon is comprised of greenish-gray slopes eroded from the Muav Limestone and Bright Angel Shale to form the broad expanse of the Tonto Platform (Figure 1A.4.22). Look closely, you should be able to make out a trail zig-zagging its way down the eastern slopes of the bowl and then across the platform to the Tapeats Narrows of Hermit Creek, this is the Hermit Trail (Tr1A.5). Hermit Creek carved its canyon parallel to and on the downthrown western side of the NE-SW trending Hermit Creek Fault. Several fault splays parallel the main fault and can be observed to cut through Supai Group rocks and Redwall Limestone directly below your position (Figure 1A.4.22). Weaknesses induced by faulting caused slumping and displacement within the Supai and Redwall units (the Hermit Trail exploits the breakdown slope through the Redwall related to these faults).
More distantly, follow the Colorado River’s course downstream where it begins a gentle turn to the northwest; featured in the middle distance of Figure 1A.4.21, a prominent buttress of Redwall Limestone north of the river projects southward toward the Inner Gorge, paralleled on its eastern side by a very linear canyon. The linearity of this rock wall and adjoining canyon are telltale signs of fault-controlled rock deformation and stream erosion. Both features trend parallel to the trace of the Crystal Fault which cuts diagonally from north to south across the upper end of the ridge (just east of the Tower of Ra) from Crystal Canyon to Ninetyfour Mile Canyon through crystalline basement as well as Paleozoic rocks. Looking further afield, shift your attention to the North Rim and skyline (Figure 1A.4.21). Just below the rim, the Coconino Sandstone forms its typical, horizontal white cliff-band. Follow this layer from right to left to the first large V-shaped notch in the rim; this is the Muav Saddle, separating Powell Plateau from the North Rim proper. A notch such as this is often a subtle sign of erosion along a fault, the Muav Fault in this case. As with most faults in the Grand Canyon region, this fault was first active as a normal fault generated by the regional extension during the Late Proterozoic breakup of the Rodinian supercontinent, and more recently, reactivated as a reverse fault during compressional tectonics of the Laramide Orogeny 80-40 million years ago. Evidence of this latter stage of faulting is also exhibited in your view (Figure 1A.4.21). Left of the Muav Saddle, the Coconino cliff-band, and the red layers of Supai Group rocks beneath bend downward as they approach the V-notch. The crustal block on which Powell Plateau sits was uplifted during Laramide compression, and the Paleozoic rocks that had accumulated on earlier faulted crystalline basement were fractured and warped into the Crazy Jug Monocline overlying the fault during Laramide reactivation. Hiking toward Hermits Rest, several locations offer tantalizing views further into Hermit Creek Canyon (but there are no views into its upper basin). The western side of the canyon eventually reveals Dripping Spring amphitheater, a large depression cut by erosion back into the rim. This feature offers another great example of groundwater sapping at work, but this time; it is the weak mudstones of the Hermit Formation that act as the impermeable, but rapidly backwasting layer, while the resistant Coconino Sandstone in being undercut.
Figure 1A.4.21. Your down-canyon panorama from Pima Point looks directly into the wide expanse of lower Hermit Canyon and on down the winding corridor of the Colorado River.
Figure 1A.4.22. Evidence of faulting in Hermit Creek Canyon lies directly below Pima Point where a fault splay cuts through Supai Group and Redwall Limestone causing slumping and a large landslide.
Hermits Rest (Stop #10 on the Red Shuttle Route). The end of the line for the Greenway/Rim Trail; after a look around, there is naught else to do but hike, bike, or ride the bus back to the first stop at the Village Route Transfer Station. The views from Hermits Rest are not much in comparison to what you’ve witnessed on the way here; but Hermits Rest is historically significant, and it does offer a snack bar and gift shop. This location serves as the jump off point for the Hermit Trail (Tr1A.5), a classic rim-to-river trail which connects with the Boucher and Dripping Springs Trail (Tr1A.1) in upper Hermit Canyon, as well as the Tonto West Trail (Tr1A.7) in the lower canyon. This ends the Greenway and Rim Trails.