Before undertaking any hike in the Grand Canyon, it is extremely important to note that a hike of any length is not to be taken lightly, even on routinely maintained and patrolled trails which have been constructed with visitor safety in mind. Grand Canyon National Park offers a variety of hiking options reachable from the North Rim which are managed according to backcountry use area. Each use area has a limited overnight capacity based upon the size of the area, the number of suitable and available campsites, its ecological sensitivity, its management zoning, and its use history. To camp below the rim in a backcountry use area you must obtain a backcountry permit. Of the trails that I will describe in this field trip (2A), the North Kaibab Trail, the longest rim-to-river trail in the park, lies within the “Corridor” use area. The Corridor Zone is recommended for hikers without previous Grand Canyon experience. The trails are well groomed and make for pleasant hiking, they receive routine maintenance and are consistently patrolled by rangers, and they boost purified water stations, toilets, signage, emergency phones, and ranger stations. While this is generally true, the North Kaibab Trail is not to be taken lightly, as it is long and much of its length is exposed to the afternoon sun and heat of the day. I recommend breaking up any trek on the North Kaibab Trail into two days, with an overnight stay at Cottonwood Campground. The other three trails described in this section are rim trails, still deserving of your preparedness, but all are relatively level and can be hiked out and back in hours rather than days. The Cape Final Trail and the Widforss Trail offer an opportunity to camp in the backcountry at Cape Final and near Widforss Point (with an overnight backcountry permit of course); the sunrises and sunsets are marvelous. The Uncle Jim Trail offers a family-friendly hike of a few miles at provides great views of upper Bright Angel Canyon.
It is, of course, best to hike during the fall or spring hiking seasons when precipitation is least likely and temperatures within the canyon are generally cool, but not cold. The park service recommends that you “take appropriate precautions depending on seasonal variations in trail [i.e. weather] conditions.” During the winter season, the upper portions of many trails can be dangerously icy because the wintertime sun never reaches into the confines of the side canyons where most trails are found, and ice can remain on the trails long after a snowstorm passes. In-step crampons and hiking poles are recommended. The relative tranquility of weather in summer can be very misleading. From May to September, it is critical that hikers (especially backpackers) have the discipline to begin hiking well before dawn, or in the late afternoon and early evening; heat exhaustion, over-exposure, and dehydration are constant threats! The park service strongly recommends that “hikers should plan on reaching either their destination or a place where they might take a shaded siesta before 10 in the morning (average descent time from rim to river is between 4 and 6 hours).” Similarly, when ascending from river-level during hot weather it is important to reach the relatively shaded canyon head areas by 8-10 in the morning. It is definitely not a good idea to hike between noon and 4pm. I would add that unless you are greatly accustomed to the rigors of the canyon, it is shear folly to attempt a rim-to-river-to-rim hike in a single day (I caution against out and back hikes of any kind that are more than 6-8 miles in length, unless you start and end early, are in shape, and can maintain a speedy pace). So let’s get hiking!
North Kaibab Trail (Tr2A.2)
The North Kaibab trailhead is located at mileage point 43.2 of the Entrance Road route description (43.2 miles south of Jacob Lake on Highway 67 or about 1 mile north of the North Rim Campground and 2 miles north of Grand Canyon Lodge) (Figure 2A.2.1). A small parking area offers limited parking, but there is more parking near Grand Canyon Lodge and transportation is available from there twice each morning (check at the lodge for times and fares). For those staying at North Rim Campground, it is a half-mile walk to the trailhead. Hikers on a rim-to-rim hike and who have only one vehicle often use the private Trans-Canyon Shuttle (928-638-2820), which provides service between the North Rim (departs around 6 a.m.) and the South Rim (departs around 1 p.m.) daily from May 15 to October 15. North Rim park facilities close on October 15, but Highway 67 often remains open to vehicle traffic into November (when winter conditions obstruct access to the trailhead), and then it is not possible to reach the trailhead by vehicle before May 15 of the following spring.
The North Kaibab Trail is definitely the least visited and most difficult of the three maintained “Corridor” trails at Grand Canyon National Park. Its trailhead begins almost a thousand feet higher than its South Rim equivalents, and because Bright Angel Canyon is deeply incised back into the Kaibab Plateau, the trail is just that much longer. Masterfully built during the 1920s to match the quality and grade of the South Kaibab Trail, and upgraded over the years to include only six present-day bridge crossings of Bright Angel Creek, it is still unwise to assume that the apparent ease and convenience of the trail’s grade and gradient does not come without its challenges. The trail is the longest rim-to-river descent in the park, and once out of the relatively shady upper canyon, much of the trail is exposed to the sun and the lower canyon can become quite hot during the heat of the day. If your intention is to descend all the way to the Colorado River (or ascend from the Colorado River), be sure to start well before sunrise, the 14-mile trek is unrelenting.
This is a beautiful trail, offering a wide, relatively smooth (for Grand Canyon trails), and for the most part gradually descending tread with both dramatically sweeping views of the landscape and intimate access to the geology. Hikers are rewarded with a number of unique experiences. Its descent passes through every ecosystem to be found between Canada and Mexico; at the rim, hikers travel through a forest of fir trees and aspen, ferns and wildflowers, but farther down, the ecology progresses through a blend of riparian and desert vegetation. The trail passes Roaring Springs, the entire perennial stream that is Bright Angel Creek seeming to issue from caves at the base of the Muav Limestone that also happens to provide all of the water to both rims of the canyon. Past Cottonwood Campground’s shady comfort, the oasis of Ribbon Falls descends to the valley floor and offers a rewarding side trip in hot weather that is wonderfully juxtaposed against a backdrop of sheer, varicolored canyon walls. And the geology! The North Kaibab Trail first passes through the entire Paleozoic sequence, the contacts between rock units conveniently signed by the park service (the only trail in the park providing this little bonus). Once past the steep headwall section and the Tapeats Sandstone narrows, hikers are treated to a unique display of rarely exposed Late Proterozoic Unkar Group sedimentary rocks and mafic intrusive igneous rocks from the lower part of the Grand Canyon Supergroup before descending into Middle Proterozoic crystalline basement of the Grand Canyon Metamorphic Suite exposed in lower Bright Angel Canyon. And here is your last geological treat: the confining walls of the narrow Inner Gorge reveal rare Rama Schist, inferred to be the metamorphic equivalent of mafic igneous rocks formed in a 1.8-1.7 billion-year-old volcanic arc partially subducted and accreted to the continent.
At-large camping is not permitted on the North Kaibab Trail (no matter how tired and sweaty you become); all visitors must camp in either of two designated campgrounds: Cottonwood Campground (CCG) located near the trail’s halfway point 7 miles from the North Kaibab trailhead, or Bright Angel Campground (CBG) located just downstream from Phantom Ranch and near to the Colorado River at the bottom of the canyon, 14 miles from the North Kaibab trailhead. I strongly encourage you to break the hike up with an overnight at Cottonwood Campground, especially if ascending from the river. Potable water is generally available at the North Kaibab trailhead, Supai Tunnel, Roaring Springs, the Pumphouse Residence, Cottonwood Campground and Bright Angel Campground, but all of these locations are seasonal except Bright Angel Campground and are turned off in the fall depending on the arrival of freezing temperatures. Unforeseeable water pipeline breaks can occur do the rockfalls, so potable water stations should not be relied upon. Be sure to check trailhead signage prior to descending and always bring a form of water treatment. The trail is never far from Bright Angel Creek once hikers reach Roaring Springs, and water can be filtered or treated if reserves run low. Be aware that you may share the trail with mule riders between the rim and Roaring Springs. If you should encounter a mule train, step to the inner side of the trail in a safe location and follow the wrangler’s instructions.
Let’s begin the descent! The North Kaibab trail begins its initial downward climb toward the Colorado River along Roaring Springs Canyon. This side canyon is notched into the Kaibab Plateau at an angle to its master stream, Bright Angel Canyon where stream erosion has preferentially incised along the Roaring Springs Fault, a subsidiary to the Bright Angle Fault. The trail descends via numerous switchbacks and sweeping traverses through a forest of spruce, pine, fir, aspen, and Gambel’s oak, with occasional outcrops of Permian Kaibab Limestone and Toroweap Formation, providing grand views southward to the darkly silhouetted peaks of the San Francisco volcanic field (Figure 2A.2.1). The prominent contact between the cliff-forming, Permian Coconino Sandstone and overlying slopes of Toroweap Formation, primarily composed of mudstones is never far from view. A careful examination of the Coconino cliffs reveals distinctive large-scale crossbeds, the product of sand dune migration in the vast desert erg formed during Coconino time. At about 0.40 miles (Map 2A.2.1), the trail rounds a gentle left-hand bend to offer a good view through Ponderosa stands of the Coconino and your views begin to suggest something unusual, that this sandstone formation sits higher on the east and west canyon walls than it does here in the center where you are walking. The trail reaches the aptly named Coconino Overlook at 0.68 miles (Map 2A.2.1). Here, atop the Coconino, it quickly becomes apparent that your position is lower than the Toroweap-Coconino contact to right or left; the explanation being that the Roaring Springs Fault consists of two splays at the head of this valley forming either side of a small graben, the block you are standing on having been dropped downward in between (Figure 2A.2.2). The sheer cliffs of Coconino seen here are an easy reminder of the importance of breakdown slopes formed by faults to navigation below the rim; without the shattering effects of faults, rock units like the Coconino would be nearly impossible to pass through.
Figure 2A.2.1. The uppermost North Kaibab Trail presents many spectacular views downcanyon and past the South Rim; framed by the varicolored slopes of Roaring Springs Canyon, one can see all the way to the dark cones of the San Francisco volcanic field.
Figure 2A.2.2. The view from Coconino Overlook; note that your position atop the Coconino is at a lower level than the surrounding cliffs, a sure sign of faulting.
As you descend tight switchbacks through the break in the Coconino and the slopes of Hermit Shale below, the conifer forest gradually thins (although is remains more persistent on the north-facing, shadier slopes). A wide variety of shrub thickets abound here, including Gambel’s oak, New Mexican locust, elderberry, cliffrose, and Rocky Mountain maple, as Ponderosa pine give way to juniper. The offset in the Coconino is readily observed at 0.79 miles (Map 2A.2.1) if you look back up valley from the first switchback beyond the Coconino Overlook; and at 1.03 miles (Map 2A.2.1), a right-hand switchback and a gap between the Coconino cliffs and a large boulder affords a good look at the Coconino Sandstone – Hermit Shale contact (Figure 2A.2.3), distinctly lower here than on the valley side walls around you. The trail reaches the base of the Coconino breakdown slope and greets the Coconino – Hermit contact face-to-face at 1.21 miles (Map 2A.2.1), where buff-colored sandstone rests directly on red-brown mudstone. Note the presence of vertically oriented fractures in the top of the Permian Hermit Shale filled with contrasting Coconino sandstone (Figure 2A.2.4). These features represent rapid desiccation of the Hermit’s muddy sediments at the onset of Coconino deposition, a testament to the quickness with which extreme aridity took over the regional depositional environment.
Figure 2A.2.3. First view of the readily discernable Coconino Sandstone – Hermit Shale contact.
Figure 2A.2.4. Vertically oriented fractures formed in the top of the Hermit Shale resulted from rapid desiccation of the Hermit’s muddy sediments at the onset of extreme aridity during deposition of the Coconino Sandstone.
After your rapid descent through the Coconino Sandstone, the trail now slackens its downhill pace, making a gradual downward traverse through more open slopes of Hermit Shale. Once in the open, take a quick break to look back in the direction you have come, there are ample views of the down-faulted Coconino block from here. Continue your downward tread. After passing through a large gully, you reach a metal sign at 1.55 miles (Map 2A.2.1) and your first thick bed of reddish sandstone; sign and sandstone mark the contact between the Hermit Shale and Esplanade Sandstone, uppermost unit of the lower Permian to Pennsylvanian Supai Group. The Supai consists of four red-brown rock formations, oxidized under predominantly arid conditions; in descending order they are the Esplanade Sandstone, Wescogame Formation, Manakacha Formation, and Watahomigi Formation. They generally form ledgy sandstones and interbedded mudstones, but the first and third units are comprised of more uniformly resistant cliff-forming sandstones, while the second and forth units are mainly slope-forming mudstones. See if you can pick them out as you descend.
Civilization returns briefly at 1.7 miles into your descent with the appearance of a faucet (and seasonally available water) plus toilets just this side of the Supai Tunnel (Map 2A.2.1). Take a quick break here, but don’t teary too long; it’s an often-congested spot without a view and you still have miles to go! After passing through the tunnel bored through the Esplanade Sandstone, the North Kaibab Trail makes an unusual quick descent via tight switchbacks through much of the Supai Group. Unusual in the sense that most rim-to-river trails in the Grand Canyon make a lengthy traverse along the top of the Supai Group before descending further. The normally well-bedded rock layers of the Supai have been scattered by movement on the Roaring Springs Fault here, once again offering a convenient avenue of descent. The unobstructed views along this section of moderately steep trail offer an awe-inspiring (if not a little intimidating) display of Roaring Springs Canyon and your trail ahead (Figure 2A.2.5). The effects of differential erosion are on display and it is not difficult to pick out the formations of the Supai Group.
Figure 2A.2.5. The view of Roaring Springs Canyon from just below the Supai Tunnel is spectacular and educational; here, it is easy the effects of differential erosion on the canyon’s rock units, cliff-formers comprised of resistant sandstones and limestones alternate with weak, slope-forming mudstones.
The sandstone cliffs hemming you in are the Esplanade, and just below lie the slopes of the Wescogame Formation. A distinctive cliff-band further down is the Manakacha, and the slopes just above the bridge crossing the wash below form the Watahomigi Formation. As you continue onward, the desert-like climate of the Inner Canyon begins to make its presence felt. Gone are the moisture loving fir and Ponderosa. The more sun-baked slopes of red rock here support a pinon-juniper woodland, with scattered small trees of redbud and box elder, as well as shrubs of Utah serviceberry, Apache plume, and cliffrose.
A noticeably reduced gradient occurs where the trail enters gentler slopes underlain by the Watahomigi Formation. A final right-hand switchback above the bridge spanning the dry wash at the bottom of Roaring Springs Canyon brings you to the contact between Supai Group and Redwall Limestone at 2.35 miles (Map 2A.2.1). The top of the Redwall was subaerially exposed for several million years after its deposition, and during this time, the limestone was eroded by streams and pockmarked with sinkholes and caves, forming a karst landscape similar to that of present-day Mammoth Caves National Park. Loose debris was deposited within these stream valleys and karst features and preserved as a limestone breccia, its discontinuous cover on the Redwall forming the upper Mississipian Surprise Canyon Formation. Just left of the trail near this location, one can observe a jumble of limestone blocks imbedded in a reddish, limey mudstone matrix, an exposed portion of Surprise Canyon Formation known as a breccia pipe.
Cross the bridge just ahead, and be sure to examine the bed and lower walls of the wash. Here the polished rock surfaces portray the true properties of the Redwall, a typically fine-grained, dull gray limestone. It is the muddy slope wash from the overlying Supai Group and Hermit Shale draped over the massive cliffs of Mississippian Redwall Limestone that gives this unit its distinctive color at a distance (and name of course). From the bridge, your route climbs briefly back up through the Watahomigi Formation slopes and tops out at the base of the sandstone cliffs of the overlying Manakacha Formation. Once you reach the base of the Manakacha at 2.63 miles (Map 2A.2.1), the reason for your upward climb becomes apparent; below you, a large gully has eroded back into the valley sideslope, requiring this bit of circumnavigation. You have reached the highpoint in this section of trail; be sure to look back upcanyon. Evidence of rock deformation and displacement can easily be observed at the canyon head where layers of the resistant Coconino and Esplanade Sandstones have been ruptured and dropped downward along two splays of the Roaring Springs fault (Figure 2A.2.6).
Figure 2A.2.6. Layers of resistant Coconino and Esplanade Sandstone exposed in the headwall of Roaring Springs Canyon are shattered and offset by two splays of the Roaring Springs Fault; faulting has dropped a central block down relative the the same layers on either side.
The trail now crosses the aforementioned gully, and abruptly descends back through the slope-forming Watahomigi Formation and into the upper Redwall Limestone. Here begins a long stretch of the trail that has been blasted out of the limestone cliffs, for the most part forming a sort of half tunnel for the next three quarters of a mile. The Redwall section of the North Kaibab Trail is less strenuous than most trails because of its craftiness, but its awe-inspiring in every way. A plethora of fantastic views mingle with daring exposures in an awesome blend of natural and engineering marvels. The opposing canyon wall provides an unobstructed view of the Paleozoic sedimentary sequence from Coconino Sandstone down through the Redwall Limestone, which you have plenty of time to contemplate. As you take it all in, be sure to note that on your side of the canyon, the Redwall Limestone appears somewhat lower than on the east side; more evidence of the offsetting effects of the Roaring Springs Fault. When you reach 3.18 miles (Map 2A.2.1), the trail makes an abrupt and rapid descent through a notch in the remaining Redwall, the breakdown slope here indicates the trace of the western splay of the Roaring Springs Fault (the limestone block tilting outward from the main canyon wall here, called The Needle, lies east of the splay on the downthrown side of the fault) (Figure 2A.2.7).
Figure 2A.2.7. The Redwall traverse on the North Kaibab Trail ends abruptly with a rapid descent through fault-induced breakdown slope in the resistant limestone.
Proceeding through the notch, the trail offers its first good views of the olive-drab ledgy slopes of the Muav Limestone, uppermost formation of a three-tiered sequence of middle Cambrian sedimentary rocks formed during a major, global-wide marine transgression. The middle unit of the sequence is the Bright Angel Shale, and the basal unit of the sequence is the Tapeats Sandstone. All rim-to-river trails wind there way downward through limestone, shale, and sandstone units, taking the marine transgression in reverse order; the Muav Limestone representing deposition on the distal, deep-water portion of a tropical continental shelf, the Bright Angel Shale the proximal, shallower shelf, and the Tapeats Sandstone the nearshore to beach transition. This makes the three rock units time transgressive, that is, the formations are older in the western part of the Grand Canyon than in the eastern part because they were deposited west to east as marine conditions invaded the passive continental margin.
Reaching the base of the Redwall Limestone, the trail enters a deep defile cut into the canyon’s west wall. After passing through the head of the amphitheater-like, dry tributary, you descend a series of wooden crib steps to reach a metal sign posted at 3.79 miles (Map 2A.2.1). This location marks a very rare feature of Grand Canyon stratigraphy, an outcrop of the Devonian Temple Butte Formation (Figure 2A.2.8a). This unit forms a thin, discontinuous layer comprised of lens-shaped bodies sandwiched between Redwall above and Muav below and is bounded by disconformities representing millions of years of subaerial exposure and erosion. It is preserved where muddy limestones were deposited in tidal channels deeply scoured into the Muav Limestone. Here, thin, wavy beds of purple-hued limestone contrast sharply with the gray Redwall Limestone and yellowish Muav Limestone (Figure 2A.2.8b). The wavy pattern was formed by the passage of tidally-induced ripple marks. Numerous small, tubular-shaped features in the limestones are trace fossils produced by burrowing worms.
Figure 2A.2.8. Rare outcrops of the purplish, thinly bedded limestones and shales of the Temple Butte Formation (A) and (B) greet you at trailside near mile 4.79 on the North Kaibab Trail.
In a short distance of about 100 yards, the trail passes another sign indicating the contact between Temple Butte Formation and Muav Limestone. From here, you make a long, gradually descending transit of the olive-drab, ledgy slopes of the Muav dappled with pinon and juniper. Near 4.04 miles (Map 2A.2.1), a second grotto-like tributary is entered. Several small springs emerge from near the contact between the Muav and Redwall, a not uncommon occurrence in the Grand Canyon. Many canyons tributary to the Colorado begin at large amphitheater-like headwall basins formed by processes known as groundwater sapping. Water percolating down through porous sandstone and limestone encounters a less permeable clay-rich layer and is forced to flow laterally. Where is emerges on a slope at springs, the moisture can cause frost action to rapidly weather exposed rock, and when combined mass wasting and gully erosion where flow is concentrated enough, erosion and undercutting of overlying layers can occur. The amphitheater formed here is a small representation of those processes.
Further on, near 4.35 miles (Map 2A.2.1), you pass beautiful step-like cliffs of Muav Limestone; look for worm burrow trace fossils in slabs of muddy limestone along the trail side; you’ll see more as you descend through the Muav and Bright Angel Shale. Continue your downward tread, the day is now growing hot as you near the confluence of Roaring Springs Canyon and the flatter bottom of Bright Angel Canyon. A spur trail on the left at 4.70 miles provides a worthy detour to Roaring Springs. Across the canyon, water gushes directly out of the cliffs, cascading over rock, moss, and fern through thickets of riparian vegetation to form the headwaters of Bright Angel Creek (Figure 2A.2.9). The water emerges from the base of the Muav Limestone where groundwater is forced to flow laterally above the impermeable mudstones of the Bright Angel Shale. The water passes downward from the Redwall Limestone along prominent joints in the Muav. This giant spring provides drinking water for every visitor and resident within Grand Canyon National Park. The water is delivered to the South Rim via a pipeline buried beneath the North Kaibab Trail (installed 1965-1970). The pipeline is buried beneath the trail and sections of it are occasionally visible; it stretches across the Colorado River on the underside of the Bright Angel Trail’s Silver Bridge which you can see near Bright Angel Campground at the end of the North Kaibab Trail. It is only a 15 minute out and back stroll down to the Roaring Springs oasis, if you are not pressed for time, drop your backpack here and make the quick side trip; it’s a pretty and freshening little stop, great for lunch and a there’s even a toilet. The brief descent does offer a good outcrop of Bright Angel Shale.
Figure 2A.2.9. Roaring Springs as viewed from the North Kaibab Trail; note the emergence of the springs and their relationship to the intercalated contact of the Muav Limestone – Bright Angel Shale transition.
Grab your pack and move onward. You are still within the Muav Limestone at the Roaring Springs spur trail juncture, but just 50 yards or so down the main trail, you return to the Bright Angel Shale. Your cross-canyon view presents an excellent exposure of the Muav to Bright Angel transition (Figure 2A.2.9); the contact between rock units is indistinct and is described as a gradational, intercalated contact by geologists. This means that layers of the Bright Angel Shale fade out gradually to be replaced by layers of the Muav Limestone, indicating that the change from shallower to deeper water conditions was gradual and fluctuating, one set of depositional conditions giving out to the other only grudgingly. Further down canyon, you may notice the same type of contact separating the Bright Angel Shale from the Tapeats Sandstone. Recall that all three formations were deposited on the same continental shelf under different, but laterally adjacent, depositional environments. The intercalated layers at the gradational contacts was the product of minor fluctuations in sea level during an overall marine transgression and geologists describe this three-fold sequence as a transgressive, fining-upward depositional sequence.
Continue your traverse of the exposed Bright Angel slopes, now only sparsely covered in stunted pinon and gnarled juniper, scrub live oak, and manzanita. As you round the bend and drop into Bright Angel canyon, pretty views open up to the east, up the main canyon of Bright Angel Creek surrounded by soaring cliffs and capped by evergreen forests of the North Rim (Figure 2A.2.10). The transition to Tapeats Sandstone occurs near the 5.04 mile mark (Map 2A.2.1), and you remain in Tapeats all the way to the valley floor near its confluence with the dry wash of Manzanita Creek. Shortly, as you enter the sandstone gorge of the Tapeats narrows, you pass the pipeline pumphouse operator’s residence and reach a seasonal water faucet just beyond. Passing the pumphouse residence and faucet is a welcome sign for the descending backpacker because it signals a trail milestone, you have reached the relative ease of the valley floor and a general slackening of the trail’s gradient, Cottonwood Campground’s shade (and rest) is fast approaching. In another 100 yards, the trail crosses to the left side of Bright Angel Creek on a steel footbridge at 5.41 miles (Map 2A.2.2). The bridge lies just below the stream’s confluence with the dry wash of Manzanita Creek. At the bridge, Bright Angel Creek is already a sizable, vigorous stream and not easily crossed unaided. You’ll follow within feet of the stream’s course for the remainder of your trek on the North Kaibab Trail.
Figure 2A.2.10. As you round the bend into Bright Angel Canyon, your view to the left extends to the head of the canyon along the Bright Angel Fault and to the fringing evergreen-covered Walhalla Plateau beyond.
Take a few moments to rest at the bridge. Look downstream to the left bank, where the creek meanders to the right, and observe the wall of Tapeats Sandstone above. The left side of this cliff is sharply truncated by a rubble-strewn saddle; the shattered sandstone of the saddle marks the trace of the Bright Angel Fault (Figure 2A.2.11). Bright Angel Creek follows the trace of the fault, carving a valley through overlying rock along a path of least resistant, like all good streams will do if given the chance. This fault has a very long history. In the late Proterozoic, roughly 750 million years ago, normal faulting in the region associated with NW-SE extension ensued as the Rodinian supercontinent began to break up further to the west. The Bright Angel Fault formed at this time. Continued normal faulting substantially offset crustal blocks to form a series of parallel basins and ranges, while erosion simultaneously stripped Supergroup rocks from the area. By the beginning of the Paleozoic (about 545 million years ago), only wedge-shaped remnants of Supergroup rocks were preserved in large grabens bounded to the east by the now inactive normal faults and the western North America formed a mature passive continental margin. The Bright Angel Fault and its brethren remained quiescent throughout the Paleozoic and much of the Mesozoic as a layercake of sedimentary rocks accumulated on the continent’s edge. Faulting activity was renewed between about 70 and 40 million years ago during the Rocky Mountain-building Laramide Orogeny, but this time, faulting was related to a compressional tectonic regime causing the Bright Angel Fault to return to life as a reverse fault. Mild deformation over the Colorado Plateau caused upwarping of the crust, formation of generally N-S oriented monoclinal folding (such as a Kaibab Plateau), and stripping of much of the Mesozoic age sedimentary rocks from the Grand Canyon area at this time. Most recently, beginning roughly 17 million years ago and continuing today, E-W extensional tectonics resumed producing the Basin and Range. Old faults such as the Bright Angel were once again reactivated as normal faults as Basin and Range tectonics has gradually crept eastward across the western Colorado Plateau. As you make your way toward the Colorado from here, watch for telltale signs of deformation related to the Bright Angel Fault.
Figure 2A.2.11. The trace of the Bright Angel Fault is readily observed as a saddle of crushed and broken Tapeats Sandstone as you enter the Tapeats narrows just downstream of the steel bridge where it crosses Bright Angel Creek below the Pumphouse Residence.
Beyond the bridge, the Bright Angel Trail rounds to the right around the cliff of Tapeats Sandstone and onto the northwestern side of the Bright Angel Fault. If you look across Bright Angel Creek, you’ll see layers of interbedded reddish mudstones and sandstones lying below the brownish layers of Tapeats Sandstone. Oddly, these lower layers are tilted to the east at an angle relative to the flat-lying sandstones above. You have arrived at the Great Unconformity, here forming an angular unconformity between the Late Proterozoic Dox Formation below and Cambrian Tapeats Sandstone above. The Dox Formation is part of the Mesoproterozoic Unkar Group (formed between 1255-1100 million years ago); its interbedded mudstones and sandstones represent tidal flat deposition associated with a shallow seaway and zone of back-arc extensional tectonics and crustal thinning that stretched diagonally NE-SW across Laurentia (the ancestral North American continent) during the 1.2 to 1 billion-year-old Grenville Orogeny. The eastward tilt of the Dox layers was produced later by the same crustal extension and normal faulting that broke up the supercontinent of Rodinia and created the Bright Angel Fault about 750 million years ago. The fault forms the eastern side of a half-graben and you are literally standing where the eastward tilted Supergroup rocks meet the faulted edge of the graben.
From here to Cottonwood Campground, it is not difficult to trace the position of the Great Unconformity which rises gradually higher on the western wall of the canyon. Near mile 5.95 (Map 2A.2.2), after passing through the Tapeats narrows, a look back up canyon offers a good view of the angular unconformity where Tapeats Sandstone cliffs overlie slopes of dipping Dox Formation (Figure 2A.2.12). Looking down canyon in your direction of descent provides a stunning view of Bright Angel Canyon. The length of the valley appears straight as a arrow as it follows the trace of the Bright Angel Fault. The desert exerts an ever stronger influence as you descend toward your day’s destination, with scrub live oak, yucca, Mormon tea, Engelmann prickly pear, sacred datura, and a variety of bunchgrasses common to the Lower Sonoran Zone becoming increasingly common. After crossing a rubble-strewn dry wash, a sign posted at 6.75 miles (Map 2A.2.2) marks the upper entrance to Cottonwood Campground; hopefully, with prior arrangements, your rest stop for the night. The campground provides seasonal running water, toilets, and an emergency phone, in addition to campsites surrounded by clumps of scrub live oak that offer a modicum of shade and reasonable privacy. A seasonally staffed ranger station at the lower end of the campground is shaded by the only grove of Fremont cottonwoods in the area.
Figure 2A.2.12. The Great Unconformity exposed on the west wall of Bright Angel Canyon below the Tapeats narrows; note the horizontal layers of Tapeats Sandstone resting on eastward tilted layers of Dox Formation.
Those fortunate to overnight at Cottonwood Campground can enjoy a dip in Bright Angel Creek; the water is cool, but very relaxing after your 7-mile descent. The late afternoon to early evening light and shadows playing across the canyon’s varicolored multitude of cliffs, slopes, spires, and alcoves is a gift beyond reckoning for your toils. A few moments of contemplation should be ample time to pick out many of the Paleozoic rock units you have passed through on your way here: the cliffs of the Kaibab Limestone, the Coconino Sandstone, the Supai Group, the Rewall Limestone, and Tapeats Sandstone are especially distinct in the late afternoon sunlight (Figure 2A.2.13). The campground lies just across the stream from the mouth of The Transept, the deep canyon flanking the west side of Bright Angel Point; in fact, the point itself is easily observed atop the Kaibab Limestone cliffs overlooking your resting place (Figure 2A.2.13). The Transept parallels Roaring Springs canyon, but oddly, it has no known faults to control its deep, but narrow incision into the Kaibab Plateau. Engrossed in your evening meal preparation and other camp chores, do take time to note that Cottonwood Campground is nestled deep within slopes comprised of Dox Formation mudstones and sandstones and good views of the Great Unconformity lie just across the valley to the west.
Figure 2A.2.13. Bright Angel Point, the highest location on the right-hand side of the photo) and the mouth of The Transept (the canyon just left of the point) offer a gorgeous late afternoon view while basking in the shade at Cottonwood Campground.
Be on your way early, you still have half the distance to Bright Angel Campground and the Colorado River. Initially, your tread undulates between creek-side views and the lower rubble-strewn slopes on the east side of the valley floor, crossing occasional outcrops of more resistant Dox sandstones. Desert yucca, Mormon tea, Apache plume, various cacti, and rabbitbrush take dominance of trailside slopes, while downcanyon views stretch to the South Rim. Nearly three-tenths of a mile below Cottonwood Campground, a series of diabase dikes and sills intrude the Dox Formation. The intrusions are distinctly dark green to black in color; a close examination reveals small, interlocking crystals indicating fairly rapid cooling at shallow depths. These dikes and sills intrude Unkar Group rock units and formed at the close of Dox Formation deposition. They have been interpreted by geologists as part of the plumbing system that feed the Cardenas Basalt (not observed in Bright Angel Canyon), lava flows extruded at the earth’s surface 1100 million years ago. Taken together, the outpourings of flood basalts and their subterranean feeder system were formed by continued back-arc rifting during the same Grenville Orogeny that generated the seaway in which Supergroup rocks accumulated.
The Bright Angel Trail climbs briefly to a bench above the stream, but returns to the valley floor after making a 180 bend at 7.29 miles (Map 2A.2.2) near a diabase sill. At the bend, a look across the stream to the west offers your first view of buff-colored ledges of Shinomo Sandstone dipping eastward toward stream level. Shortly, after dropping from the bench, outcrops of pinkish sandstones appear at trailside. The quartz-rich Shinomo Sandstone formed in nearshore and beach environments of the “Grenville” seaway that later accumulated the Dox Formation sediments you’ve become hiking through. You reach perennial Wall Creek at 7.50 miles (Map 2A.2.2) as you trend down-section, deeper into the Shinomo. Observation of the west side of the canyon reveals more diabase dikes and sills intruding the Shinomo Sandstone. As you continue, the canyon gradually widens, and your early morning views of the surrounding heights really open up.
At 8.00 miles into your trek (Map 2A.2.2), about 1.2 miles below Cottonwood Campground, a trail junction offers an opportunity you don’t want to miss. To the right, a spur trail and bridge takes you across Bright Angel Creek to offer either of two options: a lower trail to the base of Lower Ribbon Falls, or an upper trail to Upper Ribbon Falls. Both destinations are worth it, offering good opportunities to examine outcrops of Shinomo Sandstone and intruding diabase, but if you are cramped for time, you don’t want to miss the half-mile out and back excursion to explore the oasis of the lower falls, a true gem of the North Kaibab Trail. Hikers caught in the heat of the day should consider taking a siesta here until late afternoon.
Lower Ribbon Falls is located in a shady grotto at the base of towering red cliffs of Shinomo Sandstone (Figure 2A.2.14). After crossing the bridge, the trail heads downstream passed a sign noting the Shinomo Sandstone cropping out nearby, and then bends abruptly right into the tributary of Ribbon Creek. A close examination of the Shinomo reveals a crystalline texture, indicating that it has been mildly metamorphosed to a quartzite (indeed, the older geologic literature names the unit the Shinomo Quartzite). As you approach the waterfall, you pass a “Day Use Only” sign; directly behind the sign is a beautiful outcrop of diabase intruding sandstone. The diabase is relatively weak and easily eroded compared to the Shinomo, forming a trough-like feature in the sandstone. Further into the grotto, you first see Lower Ribbon Falls plunging 120 feet from a narrow slot cut into 300-foot high walls of sandstone (Figure 2A.2.15). Willow and other water-loving, riparian vegetation such as scarlet monkeyflower, golden columbine, and maidenhair fern thrive in the cool, misty microclimate of the grotto. The water does not fall into a plunge pool as is typical, but instead splashes over an oddly conical-shaped mound centered under the falls. This moss-draped cone is formed of travertine, a carbonate rock crystallized from salty ions carried in the stream water. During times of low flow, the normally hot, arid conditions of the canyon concentrate the ions in solution, allowing them to chemically bond and form crystals of calcium carbonate (calcite); the crystals precipitate onto the surface of the cone causing it to grow steadily skyward over time. It is possible that the roaring waters of a future flash flood, or a debris flow will tear the cone down (and past ones probably have), but for now, it is a truly unique feature of Bright Angel Canyon (and standing on the cone under a cool shower isn’t so bad either) (Figure 2A.2.16).
Figure 2A.2.14. Lower Ribbon Falls is tucked into a grotto at the base of soaring cliffs of Shinomo Sandstone and offer a welcoming oasis during the heat of the day (the photo is taken from a location downstream of the trail junction at 8.00 miles).
Figure 2A.2.15. Ribbon Falls; the cone at its base is comprised of travertine, a carbonate rock precipitated from salts concentrated in the water of Ribbon Creek under the hot, arid climate of the canyon.
Figure 2A.2.16. The “showering” platform atop the travertine cone at the base of Lower Ribbon Falls; note the overhang of massive Shinomo Sandstone resting on thin beds of mudstone undercut by groundwater sapping and frost action.
Returning the same way you entered the waterfall’s amphitheater, a shortcut can be taken downstream to a ford across Bright Angel Creek, but this route is only passable during low flow conditions (it is better to take the established trail). Upper Ribbon Falls can be visited from a higher trail that leaves the Lower Falls trail on the left, just before reaching the bridge over Bright Angel Creek. The trail is not hard to follow on Google Earth, but there is some exposure on steep slopes, and I must admit I have not made the hike myself.
Back on the main path, head to your right up a few steep switchbacks. Bright Angel Trail climbs to a high bench composed of landslide debris perched on a resistant knob of Shinomo Sanstone that provides great views of the western wall of the canyon near the mouth of Ribbon Creek. The cliffs are comprised of buff-colored Shinomo Sandstone, which in this area is intruded by a dark green diabase dike that pinches out to the east (Figure 2A.2.17a). Further along the bench, the same line of Shinomo cliffs is intruded by a sill of dark green diabase (Figure 2A.2.17b). A spectacular downcanyon view unfolds at the lower edge of the bench, exposing yet another layer of the Unkar Group where the brick-red slopes of the Hakatai Shale can be seen to extend from the base of the overlying Shinomo Sandstone (Figure 2A.2.18). The mudstones of the Hakatai Shale were deposited in a predominately tidal flat environment associated with the “Grenville” seaway. Notice that the layers of Shinomo Sandstone and Hakatai Shale dip upcanyon, generally to the east and against the Bright Angel Fault.
Figure 2A.2.17. From a high bench of landslide debris formed opposite the mouth of Ribbon Creek, the Shinomo cliffs of Bright Angel Canyon’s western wall can be seen to be intruded by dark green diabase dikes (A) and sills (B).
Figure 2A.2.18. This downcanyon view provides an excellent look at the Hakatai Shale and overlying Shinomo Sandstone adorning the western side of Bright Angel Canyon; the dark green blob on the right is a diabase sill intruding layers of Shinomo which pinches out downcanyon.
Descending the far side of the bench, you begin a long traverse in an open valley floored by the Hakatai Shale. A careful assessment of each side of the canyon should tell you that the Hakatai layers extend much higher on the left-hand side than on the right, indicating back-tilting down to the east against the Bright Angel Fault. At 8.38 miles (Map 2A.2.2), another signed trail for Ribbon Falls enters from the left. This trail is the lower end of the aforementioned “shortcut” and can be used as an alternate route to Lower Ribbon Falls. However, Bright Angel Creek must be forded on slippery boulders, and the stream crossing is only accessible during low water conditions. Turn around here to look upcanyon once more, this is a good place to observe the lobate-shaped debris pile from the ancient landslide you just traversed.
The main trail now ambles down a spectacularly wide canyon, sticking to a shrubby bench above the creek. At 8.66 miles (Map 2A.2.2), you cross a dry wash and encounter the first of many Tapeats Sandstone boulders, broken lose from the cliffs above in a long ago rockfall. Look to the right here across the valley to the slopes of Hakatai Shale, an obvious dark green diabase dike cuts nearly vertically up through red mudstones. Moving forward, the trail threads its way through the boulder field; be sure to examine trailside boulders, some of which preserve nice examples of crossbedding formed by ripple migration along a wave-agitated shoreline in the middle Cambrian. Near 8.96 miles (Map 2A.2.2), your tread parallels the mouth of a dry tributary entering on the west side of the canyon. A large diabase sill crops out beside the trail immediately to your left (Figure 2A.2.19a) which you follow downcanyon for roughly a tenth of a mile, well past the confluence of the western tributary with Bright Angel Creek. At 9.08 miles (Map 2A.2.2), look across the stream to the lower slopes on the western side of the valley (Figure 2A.2.19b), the dark green diabase sill forms a resistant cliff that can be seen to thicken downcanyon for some distance.
Figure 2A.2.19. A close examination of the diabase intrusive igneous rock reveals its crystalline texture formed by cooling from magma (A); a dark green diabase sill intruding Hakatai Shale forms cliffs exposed on the lower western wall of the main canyon near 9.08 miles.
As you continue a steady downcanyon pace, gazing into the distance ahead, it soon becomes apparent that the canyon narrows to a defile (Figure 2A.2.20). Difficult to pick out at first, this “narrows” is where Bright Angel Creek begins to cut its way through the crystalline basement of the Middle Proterozoic Grand Canyon Metamorphic Suite; much of the stream’s energy is required to incise downward through the extremely resistant rock, lateral meandering of the channel is reserved for weaker materials like the sedimentary rocks of the Grand Canyon Supergroup you have been hiking through since the Pumphouse Residence, hence the wide valley in your current location. Now turn your gaze to the rock layers above and to the immediate left of the defile (Figure 2A.2.20); these layers are the Bass Limestone, lowermost unit of the Mesoproterozoic Unkar Group and first to be deposited above the crystalline basement. Notice that the Bass Limestone layers are flat-lying nearest the stream, but they curve sharply upward just to the east (and are somewhat overturned), only to return to a horizontal position again where they disappear beneath the thick Tapeats Sandstone cliffs. This Z-shaped fold forms a monocline, and the Bright Angel Fault passes right through its center. Recall that the Bright Angel Fault has a long history of reactivation. The flat-lying rocks east of the fold axis were uplifted nearly 600 feet relative to the flat-lying rocks to the west when the Bright Angel Fault was behaving as a reverse fault during compression associated with the Laramide Orogeny about 80-40 million years ago.
Figure 2A.2.20. As you approach the nine and a quarter mile-mark, the canyon ahead can be seen to narrow into a deep defile where Bright Angel Creek begins downcutting through resistant Vishnu basement; just east (left) of the stream, the Bass Limestone is folded in a tight “Z” called a monocline due to displacement on the Bright Angel Fault.
Just a short distance beyond, at about 9.38 miles (Map 2A.2.3), an outcrop of Bass Limestone appears to the left of the trail (Figure 2A.2.21). The limestone beds are tilted nearly vertically, indicating that you are on the western, downthrown side of the monoclinal fold and that the Bright Angel Fault lies just to the east under the valley side slope. If you care to step off-trail here to examine the Bass Limestone up close, you will notice a visible wavy pattern on the weathered face of the layers; these wrinkles are 1200-million year-old algal mats, or stromatolite fossils. Lime mud accumulating on a shallow sea bed was bound into thin wavy laminations by gelatinous secretions from cyanobacteria, stacked layer by layer, and lithified into rock. Just ahead, you get an awesome view of the monocline deforming the Bass Limestone (Figure 2A.2.22), you can almost hear the rock groaning as it was subjected to intense compression, reverse faulting, and folding.
Figure 2A.2.21. Vertically tilted beds of Bass Limestone indicate your position relative to the Bright Angel Fault and its monoclinal fold; the position of the folded rock layers just left of the trail means that you are on the west side of the fold axis and fault, the uplifted side lying just east of the tilted layers.
Figure 2A.2.22. A close up view of the monoclinal fold deforming layers of the Bass Limestone.
At 9.76 miles (Map 2A.2.3), the trail rounds the nose of a low hill and you get your first glimpse into the defile carved by Bright Angel Creek’s passage downward through resistant, 1.8 – 1.7 billion-year-old schists. Note the outcrops of horizontally layered Bass Limestone which occur here. Shortly, the trail passes over several springs that emerge from the Bass Limestone to encourage the lush growth of riparian willow, sawgrass, and horsetails. As you make your way around the left-hand side of a large meander, the layers of Bass Limestone become steeply tilted (you are approaching the monoclinal fold axis and the Bright Angel Fault. Circling around to the downstream side of the meander at 9.96 miles (Map 2A.2.3), look back upcanyon to observed the deformed layers of the Bass Limestone to the west of the fault (Figure 2A.2.23). Beds of Bass Limestone are tilted like upright dominos to the east and sweep downward to the west to become flat-lying at the nose of the hill you recently passed.
Figure 2A.2.23. Deformed layers of Bass Limestone dipping steeply on the left, but gradually flattening to the right indicate that your position is just west of the Bright Angel Fault and the axis of its associated monoclinal fold.
However, you’re not done with the Bass Limestone yet. Walls of gray limestone begin to enclose the canyon as the trail takes a wide swing along a left-hand meander and not far ahead at 10.12 miles (Map 2A.2.3) you reach a nonconformity separating the the Hotauta Conglomerate, the basal member of the Bass Limestone, from underlying Rama Schist (Figure 2A.2.24). The unit consists of a mixture of rounded quartz and granitic pebbles in a matrix of sand and oxidized cement, its composition indicating deposition by vigorous streams. The Hotauta formed 1200 million years ago, so this nonconformity represents 500 million years of missing rock, the lesser of the Grand Canyon’s two basal unconformities for sure, but still quite impressive. Notice how the nearly horizontal layers of the Hotauta Conglomerate contrast sharply with the crystalline basement rocks, making this erosional contact easy to trace along the canyon walls.
Figure 2A.2.24. The nonconformity between the Hotauta Conglomerate (basal member of the Bass Limestone) above and the Vishnu Schist below (the point of the trekking pole rests above the contact).
Now turn your gaze upwards as you hike; you can see that the Tapeats Sandstone does not lie far above on the canyon walls, and in a short distance down the trail, the Bass Limestone pinches out against this lowermost Paleozoic unit at the Great Unconformity. Figure 2A.2.25 shows your last view of the Bass Limestone sandwiched between Tapeats Sandstone and faulted Rama Schist at 10.54 miles (Map 2A.2.3). You quickly passed beyond the edge of the faulted graben that trapped and preserved a section of the Unkar Group, the lower four formations of the Grand Canyon Supergroup you have been walking through since Cottonwood Campground. Although it is not obvious from this perspective, the deformation of the Supergroup rocks makes this an angular unconformity, and because the Tapeats Sandstone is roughly 525 million years old, the unconformity here forms a larger gap of almost 700 million years. Of course, where the Great Unconformity lies directly on crystalline basement, it reaches its maximum gap in time of about 1.2 billion years!
Figure 2A.2.25. The Tapeats Sandstone stacked on Bass Limestone and the Bass Limestone stacked on a faulted section of the Vishnu Schist; an angular unconformity lies between Tapeats and Bass (the Great Unconformity), while a nonconformity lies between the Bass and Vishnu (the “greatest” unconformity).
Now begins your descent of the Inner Gorge, a narrow, twisting hallway of a canyon within the Grand Canyon that gradually deepens from here to the river. Walled in completely by Grand Canyon Metamorphic Suite comprised of Rama Schist, Vishnu Schist, and Zoroaster Granite, the dark, contorted cliffs “box” in the trail on either side and amplify the sounds of rushing water from the adjacent stream. This is a hauntingly beautiful part of the trail. The Vishnu Schist and Zoraster Granite comprise the majority of crystalline basement rocks exposed within the Inner Gorge of the Grand Canyon. The Vishnu rocks generally represent the metamorphic equivalent of sediments stripped from the rising volcanic arc that was eventually plastered to the proto-North American continent about 1.8 – 1.7 billion years ago. These rocks were intruded in multiple phases by the Zoroaster Granite during collision and mountain building. What make’s lower Bright Angel Canyon special is the extensive exposures of Rama Schist, a metamorphic rock not found within the Inner Gorge is very many locations (much less such an accessible location as this one). The Rama Schist formed in the same volcanic arc as the Vishnu, but these rocks are considered to be derived from mafic igneous rocks erupted as part of the volcanic islands (of the arc itself) later accreted to the continent.
Although the trail within the confines of The Box, as this section of Inner Gorge is aptly named, is not challenging from the perspective of gradient, roughness, or exposure, you should be aware that it is particularly dangerous during summer months because the trail lies at a low elevation and it commonly becomes extremely hot from mid-morning until late afternoon. The gorge of black rock through which the trail passes becomes like an oven and can be compared to walking through an asphalt parking lot on an August day in Phoenix. There is no water except that which you can readily filter from Bright Angel Creek, so be prepared. Enjoyment of the canyon’s incredible exposures of crystalline basement rocks canbe challenged by the heat. To beat the heat, one normally plans their hike through the Inner Gorge of Bright Angel Canyon for the early morning or evening, unfortunately during which time, deep shadows often make picking details of the geology more difficult. Still, your venture through deep time and tortured rocks is an awesome experience.
At 10.65 miles, and again at 10.88 miles (Map 2A.2.3), you cross Bright Angel Creek on steel foot bridges, your third and fourth in quick succession since beginning this backpacking odyssey. Near mile 11.22 (Map 2A.2.3), after crossing a dry wash coming in from the west, the trail navigates a large right-hand bend. The canyon walls around you offer an excellent display of disruption, fracturing, and crushing related to the trace of the Bright Angel Fault. Descending deeper, the confines of The Box offer little room for trail and stream, and the trail is forced to switch from wall to wall several times as its path is often blasted from the protesting crystalline basement over the next several miles. As you tread within the Inner Gorge, take time to examine your passage through the metamorphosed heart of the Grand Canyon. The contorted twists and turns of the trail are primarily forced upon it by the downcutting of the stream as it sought a path of least resistance through vertically foliated dark schists shot through by ribbons of pink Zoroaster Granite (Figure 2A.2.26). The Zoroaster intrusions were generally injected parallel to foliation within the schists indicating that much of the metamorphism was complete by the time of their intrusion. However, pink bands of granitic rock are themselves folded in some areas suggesting a concurrency between magmatic intrusion and continued metamorphism. Look for unusual bands of the Zoroaster that appear to shrink and swell, forming sausage-like stringers of pink granite called boudinage (the French word for sausage). Close examination of the canyon walls as you progress toward Bright Angel Campground and the Colorado River provides numerous opportunities to view metamorphic and intrusive features preserved in the crystalline basement rocks of the Grand Canyon Metamorphic Suite (Figure 2A.2.27). Figure 2A.2.27a shows a close-up of the near to vertical foliation in the Rama Schist (the dark rock), intrusion by the Zoroaster Granite (the stringers of pinkish rock), and offset of both along a small, steeply-oriented shear zone that probably formed by the same compressional regime that produced the foliation in the schists. Figure 2A.2.27b shows a large block of dark Rama Schist completely surrounded by intrusive Zoroaster Granite.
Figure 2A.2.26. A superb exposure of Rama Schist intruded by Zoroaster Granite somewhere in the depths of Bright Angel Canyon’s lower narrows.
Figure 2A.2.27. (A) captures a trailside view of vertically foliated, dark Rama Schist intruded by stringers of pinkish Zoroaster Granite, both of which are offset along a small, steeply-oriented shear zone that probably formed by the same compressional regime that produced the foliation in the schists; (B) shows a large block of Rama Schist completely surrounded by an intrusive blob of Zoroaster Granite.
After enough twists and turns to make your head swim, the Bright Angel Trail brings you abreast of Phantom Creek’s yawning maw (Figure 2A.2.28) at about 12.75 miles (Map 2A.2.4). The large opening and watery passage surrounded by sheer cliffs seems to beckon exploration. Phantom Creek is a perennial stream that drains a significant portion of the Kaibab Plateau west of Bright Angel Point; it can be negotiated for a considerable distance, but its narrow, trailless, rubble-strewn confines, and frequent waterfalls make the trek a real canyoneering adventure. Just ahead, at 12.81 miles, your route crosses Bright Angel Creek on yet another steel bridge (Map 2A.2.4); and at 13.06 miles, you come to your last steel bridge-negotiated crossing of the stream before reaching Phantom Ranch. For frequent hikers on the Bright Angel Trail, these foot bridges serve as convenient reference points for measuring progress.
Figure 2A.2.28. The entrance to Phantom Creek surrounded by towering cliffs of crystalline basement rock capped by the Tapeats Sandstone appears out of nowhere on the west side of Bright Angel Canyon offers a strangely inviting corridor into the “unknown” deeps of the Inner Gorge.
Not long after your last bridge crossing, the North Kaibab Trail emerges from The Box into a wider valley dotted by clumps of brittlebush and arrow weed. Views of the Grand Canyon’s South Rim loom much closer than before; you can even pick out details such as Yavapai Point. In a few tenths of a mile, at mile 13.37 (Map 2A.2.4), you reach a trail junction. The Clear Creek Trail diverges to the left here and climbs steeply to the Tonto Platform, a wide bench of rolling hills and swales formed in the transition zone between the Bright Angel Shale and Tapeats Sandstone; but that trail is a worthy adventure for another day. Continue along a lengthy stretch of more or less straight trail, but at 13.71 miles (Map 2A.2.4) be sure to look back upcanyon toward the entrance to The Box. A large slab of layered rock is perched high on the left (west) wall of the canyon. This slab consists of Supergroup rocks rotated down to the west, the eroded remnants of a large block dropped down-to-the-east against the Bright Angel Fault (Figure 2A.2.29). The slab slide downward to the east into a small graben formed along a parallel normal fault subsidiary to the main Bright Angel Fault; such fault blocks are not an uncommon occurrence along complex faults like the Bright Angel; this is why geologists often refer to them as “fault zones,” implying multiple related faults formed by the same tectonic processes rather than a singular fault.
Figure 2A.2.29. An upcanyon view from a stretch of trail just downstream of The Box (near mile 13.71) reveals a slab of Supergroup rocks clinging to the upper west wall of Bright Angel Canyon; this slab was dropped down-to-the-east against the Bright Angel Fault and back-tilted westward along a parallel subsidiary fault to the Bright Angel Fault.
Fremont Cottonwoods and mesquite begin to appear and you finally arrive at the upper end of the Phantom Ranch complex at mile 13.83 (Map 2A.2.4). A split in the trail lets you head toward Phantom Ranch (to the left); or bypass Phantom Ranch and head straight for Bright Angel Campground (to the right). Assuming that you are camping, take the right-hand fork and continue to a steel foot-bridge crossing of Bright Angel Creek at 14.16 miles (Map 2A.2.4). Cross the stream to enter the upper end of Bright Angel Campground, or if you are continuing to the Colorado River and parts beyond, remain on the main trail to the left side of the stream. You will soon reach another steel foot bridge at 14.44 miles (Map 2A.2.4). This is the end of the North Kaibab Trail. A right turn here takes you across Bright Angel Creek to the lower end of Bright Angel Campground, or a connection with the lower end of the Bright Angel Trail (see Bright Angel Trail, Tr1A.2 in Field Trip 1A for a complete description). A left turn here begins the lower end of the South Kaibab Trail (see South Kaibab Trail, Tr1A.4 in Field Trip 1A for a complete description).
I hope you have made plans to stay at either Phantom Ranch or Bright Angel Campground. A layover day would be even better as there is much to explore in the area (and a cantina to enjoy after your labors). For complete details on the area’s geology, I encourage you to seek out the information provided in the Bright Angel Trail and South Kaibab Trail descriptions referred to above.
Hiking Trail Maps
Map 2A.2.1. Shaded-relief map of the northeast quarter of the Bright Angel Point, AZ 7.5 minute quadrangle.
Map 2A.2.2. Shaded-relief map of the southeast quarter of the Bright Angel Point, AZ 7.5 minute quadrangle.
Map 2A.2.3. Shaded-relief map of the southwest quarter of the Bright Angel Point, AZ 7.5 minute quadrangle.
Map 2A.2.4. Shaded-relief map of the northwest quarter of the Phantom Ranch, AZ 7.5 minute quadrangle.