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. The Thunder River-Deer Creek Loop is the only trail I will describe in this field trip (2D); of the three use area designations in Grand Canyon National Park (“Corridor”, “Thershold”, and “Primitive”), this trail lies wholly within “Primitive” use areas. Essentially, what this means is that this loop hike occurs on trails that are not maintained and only rarely patrolled and are recommended only for highly experience Grand Canyon hikers with proven route-finding skills. Hiking on trails in Primitive use areas is not recommended during the summer because of high temperatures and/or because they lack reliable water sources. In contrast, trails in the Corridor Zone are recommended for hikers without previous Grand Canyon experience, while trails within Threshold use areas are recommended for hikers with some previous Grand Canyon experience. Corridor 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. Threshold trails only receive occasional maintenance (if severely damaged by a landslide for example) and are irregularly patrolled by backcountry rangers.
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 and are a speedy, and in shape hiker). So let’s get hiking!
Thunder River-Deer Creek Loop (Tr2D.1)
Backcountry hikers originally accessed Thunder River, Tapeats Creek, and Deer Creek via the trail from Indian Hollow, but the newer Bill Hall Trail east of Monument Point offers a 2.5 mile shortcut and has become the primary trailhead for the Thunder River Trail and Deer Creek Trail. These latter two trails can be connected along a route that follows the Colorado River between each drainage to make a loop hike unparalleled among Grand Canyon backcountry treks known informally as the Thunder River-Deer Creek Loop. The loop hike as described here begins at the Bill Hall trailhead located at the very end of FS Rd 292A (Map 2D.1.1); mileage point 32.1 of Field Trip Route 2D or 32.1 miles from where I have described the driving route initially leaving Highway 67 (on FS Rd 22) a few miles north of the park entrance station. FS Rd 22 can also be accessed from Highway 67 by taking FS Rd 461 just south of its junction with Highway 89A (from the end of Field Trip 2D at mile marker 66.7). Follow the route maps for Field Trip 2D from either end; all roads leading to the trailhead from Highway 67 are gravel, but all are in excellent condition and suitable for most any vehicle. A third access point for FS Rd 22 lies a few miles east of Fredonia off of Highway 89A, which links to mile marker 57.1 of Field Trip 2D; this alternative allows passage all the way to the Bill Hall Trailhead from a lower elevation drive, and may be open later into the fall, or earlier in the spring.
This trek offers some of the most unique geology and scenery in the park and should be enjoyed at your leisure. I recommend making it a six-night backpacking trip if you really want to take it all in, and that is how I have described it. From the eye-popping, colossal Surprise Valley mega-landslide complex and the voluminous outpourings of water at Thunder River and Deer Spring, to a rare traverse of the Esplanade Platform, and the more subtle debris-filled former channel of the Colorado River perched on the north wall of the inner canyon near the entrance to Lower Granite Gorge, these varied natural wonders provide attractions beyond compare. Taken as whole, the loop hike provides access to one of the most geologically diverse areas the Grand Canyon has to offer, its multiple landslides, channel fills, and strath terraces associated with Surprise Valley clearly define the dynamic nature of canyon forming processes.
Be aware that for obvious reasons, the crystal clear water of Thunder River and Deer Creek, emerging from mysterious caves as full-fledged streams, only to transform the harsh desert of the inner canyon downstream into absurdly beautiful green oasis adorned by cool pools complemented with the music of falling water have become exceedingly popular among backcountry hikers and river rafters alike. River trips often stop at the mouth of Tapeats Creek and Deer Creek so hikers should be prepared to encounter large groups of river runners in the general vicinity. You may have to exercise patience obtaining a permit and at the swimming hole. The loop trail is classified as a “route,” but it’s popularity keeps it for the most part in great shape and easy to follow. On the other hand, it is one of the longest rim-to-river descents in the park, taking roughly 12 miles to reach the Colorado River on the Thunder River Trail, the first 8 or more miles being waterless and over potentially hot trails well-exposed to the sun. It should be hiked only by the experienced Grand Canyoner. In the event that you plan to descend all the way to the Colorado River (or ascend from the Colorado River) in one day, I recommend reconsidering your course of action. The Esplanade Platform offers many shady spots to wait out the midday sun or even spend a night if you get a late start. I describe spending a night on the Esplanade Platform going in and coming out, chiefly to provide the time to properly explore the geology of this awesome place. Also plan for two nights in both Tapeats Creek Canyon and Deer Creek Canyon, you won’t regret it.
At-large camping is permitted on the Esplanade Platform (AY9) and Surprise Valley (AM9) Use Areas, but camping is limited to the designated campsites in the Tapeats Creek and Deer Creek Use Areas. The designated campsite at Deer Creek (AX7) accommodates two groups per night. Upper Tapeats (AW7) campsite accommodates a maximum of three groups per night and Lower Tapeats (AW8) can take two. Thunder River, Tapeats Creek, Deer Creek, and the Colorado River are permanent water sources along this hiking route, and the sections of trail in the Tapeats Creek and Deer Creek drainages, as well as along the Colorado River are generally never far from water (which can be filtered or treated if reserves run low). Many hikers choose to cache water on the Esplanade or in Surprise Valley for the return trip. Caches should be dated, hidden from view, and carried out at the end of the hike. During or immediately after wet weather temporary pools might be found in sandstone potholes along the Esplanade Platform. I strongly encourage you to break the hike up with an overnight on the rim of the Esplanade Platform, especially if ascending from the river. The sunset and sunrise views into Surprise Valley are reward enough, but you’ll be thankful for the shade from the midday sun.
The short hike to Monument Point has been covered elsewhere (see mile marker 32.1 of this field trip), but I have incorporated a slightly altered version of it here for continuity’s sake. To begin your thunderous undertaking, start walking west from the parking area on the Bill Hall Trail (Map 2D.1.1); through a first saddle and to a high point ahead. At the saddle, a left-hand fork in the trail can be taken to a nice rim viewpoint of Tapeats Amphitheater and a plaque commemorating Ward “Bill” Hall for which the trail is named. Bill Hall was a seasonal park ranger on the North Rim who was killed in the line of duty (automobile accident) in 1979. Stick to the right fork which is the main trail. It traverses rather unassuming ground near the canyon rim through the skeletal remains of a recently burned pinon-juniper woodland. Only grasses and brush like Gambles Oak have recolonized, leaving the area devoid of trees except a few nearest the rim that escaped the blaze. You are almost immediately treated to a great view of the Tapeats Amphitheater (Figure 2D.9). The view from here skirts along the rim to the west toward Monument Point and the pencil-thin ridge of Coconino Sandstone forming Bridgers Knoll below, and swings eastward into the western part of the Tapeats Amphitheater. Steamboat Mountain lies in shadow at the left edge of the photograph, while the deeply entrenched canyon of lower Tapeats Creek takes center stage to the south as you look down the axis of its tributary eroded along the trace of the Tapeats Fault. Tapeats Canyon itself flows slightly northwest across this fault and then bends southwest before its confluence with the Colorado River. The Inner Gorge of the Colorado lies below the prominent cliffs of Great Thumb Mesa on the Grand Canyon’s South Rim, which can be seen behind Bridgers Knoll.
Continue walking along the rim past the high point and through a second, smaller saddle. Nearing the next high point, you reach the rock cairn and signage for the Bill Hall Trail at 0.70 miles (Map 2D.1.2). Drop your backpack here for a few moments and stroll passed the trail junction to the obvious promontory a couple hundred feet ahead. When you reach Monument Point, you are immediately drawn to Bridgers Knoll which lies directly below your perch (Figure 2D.10). The knoll is capped by a fin of Coconino Sandstone that points like an arrow almost directly to the mouth of Tapeats Canyon and the east end of Great Thumb Mesa. The inner gorge of the Colorado River, flowing in a northerly direction toward you, lies just east of Great Thumb Mesa. Tapeats Canyon can be seen cutting deeply through Supai Group rocks, Redwall Limestone, and Muav Limestone to the southeast of Bridgers Knoll (Figure 2D.11). Perhaps the most striking view from Monument Point lies to the west. Here, the panorama takes in the mountains of the Mount Trumbull Volcanic Field on the Uinkaret Plateau in the distance, as well as an enormous shallow basin floored by the broad expanse of the Esplanade Platform in the foreground (Figure 2D.12). The deeper canyons draining this part of the platform north of the Colorado River constitute the Deer Creek watershed (Figure 2D.12). The Bill Hall Trail descends to the Esplanade Platform, then joins the Thunder River Trail coming in from Indian Hollow to the west. The Thunder River Trail then skirts to the right (east) around the canyons of upper Deer Creek, eventually dropping over the edge of the Esplanade rim near the photograph’s center.
The geomorphic processes forming the Esplanade Platform are very similar to those of the Bright Angel Shale resting on Tapeats Sandstone which forms the Tonto Platform in the eastern Grand Canyon. However, here, much further west, the Hermit Shale and Esplanade Sandstone (the uppermost formation of the Supai Group) are both comparatively thick, the shale forming a weak, easily eroded unit similar to the Bright Angel Shale and the Esplanade forming a resistant sandstone layer similar to the Tapeats Sandstone. As the Colorado River carved downward through Permian rock formations, it passed through resistant layers to eventually encounter the weak Hermit Shale, allowing the river to switch from a canyon-cutting to a meandering regime. This stream-erosion-induced lateral widening of the river valley, combined with rapid weathering and mass wasting of the mud-rich Hermit Formation lying directly above of the Esplanade Sandstone allowed undermining and backwasting of the overlying rock units in a process known generally as slope retreat, a process that quickly exposed the Esplanade Sandstone over a considerable area. A return to a canyon-cutting regime ensued as the river continued carving downward into the resistant Esplanade Sandstone, thus forming and accentuating the extensive benchland of the Esplanade Platform.
As you look west, notice that the Inner Gorge of the Grand Canyon has changed considerably from the classic North and South Rim viewpoints well to the east (Figure 2D.12). Now the TontoPlatform is gone and the Redwall Limestone closes in to very near the river because the Bright Angel Shale is much thinner here and doesn’t play as much of a role in canyon widening as it does upriver. Look closely at the inner gorge near the center of the photograph, hopefully you can make out the grayish dome peeking above the Esplanade rim from within the gorge. This dome is Cogswell Butte on the north side of the river, comprised of an isolated remnant of Redwall Limestone with a thin veneer of lowermost Supai Group rocks. The butte sits at the outer edge of Surprise Valley, nearest the river. Surprise Valley may have formed as a fault graben now hidden by a massive landslide complex produced by multiple collapses of huge slabs of Supai Group and Redwall Limestone the peeled away from the cliff face of the inner gorge long ago. The Thunder River Trail drops into Surprise Valley, traversing the landslide debris, and then heads east (upriver) and into Tapeats Canyon, passing Thunder River along the way, a perennial stream that originates from a continuously gushing torrent of groundwater issuing from the base of the Muav Limestone. The Deer Creek Trail splits from the Thunder River Trail in Surprise Valley and heads west (downriver) and into lower Deer Creek. The two trails can be connected by a river route to form the exceptional Thunder River-Deer Creek Loop you are about to traverse. When you have seen enough, return to the trail junction and your backpack; let the real adventure begin!
The Bill Hall Trail leaves the rim east of Monument Point and drops steeply through the Kaibab and Toroweap Formations toward Bridgers Knoll, then contours northwest within the Toroweap to a breakdown slope west of Monument Point and a quick descent through the Coconino Sandstone and Hermit Shale (Map 2D.1.2). It is worth noting that the Permian rock formations exposed here in the western part of the Grand Canyon are noticeably different from the same units in the eastern canyon. These formations were deposited on a passive continental margin and the primary control over their deposition was a fluctuating sea level and the relative position of the coastline. The Permian sea invaded landward from the west, so in general, marine conditions prevailed in the west, with terrestrial conditions more prevalent eastward. Marine- and shoreline-dominated rock units tend to be thicker in the west and thin eastward, while terrestrial-dominated rock units tend to be thinner in the west and thicken to the east. In this area, the Early Permian Esplanade Sandstone is considerably thicker and more pervasively comprised of sandstone layers formed in a coastal eolian setting. The Early Permian Hermit Shale is also much thicker here than in the east, consisting of mudstones formed in coastal deltaic and floodplain environments. On the other hand, the Early Permian Coconino Sandstone in much thinner here than it is to the east, probably owing to its predominantly eolian origins, sands having been blown in from continental sources to the east. The Late Early Permian Toroweap Formation is thicker and consists mainly of more resistant, cliff-forming limestones deposited on a shallow marine tropical shelf transgressing from the west, while the Middle Permian Kaibab Limestone forms resistant cliffs of nearly pure, fossil-rich carbonates representing a pervasive marine invasion of the passive continental margin.
As you descend through the many broken, step-like layers of the Kaibab Limestone exposed along the trail, keep a sharp eye out for your footing and for the abundant fossils weathered out along bedding planes; brachiopods, crinoid stems, and bryozoan fossils are particularly well-preserved (Figure 2D.1.1). You can readily identify the brachiopods by their distinctive “D” shape, while the crinoid stems are circular in cross-section. At 0.98 miles (Map 2D.1.2), the trail bends sharply to the right off the main ridge and makes several switchbacks down the southwest flank of Monument Point. Here, the trail crosses the contact between resistant, cliff-forming layers of Kaibab Limestone, and softer, slope-forming mudstones of the upper part of the Toroweap Formation (Figure 2D.1.2). The trail soon begins an undulating, northwesterly traverse of the Toroweap near the transition (and break in slope) between its upper mud-rich portion, and the thick, resistant limestones making up much of the formation below. The mudstones were deposited in shallow tidal flat settings and the limestones formed in deeper open marine shelf environments. Prominent, but discontinuous patches of whitish evaporite deposits are found within the mudstones along this segment of trail. The evaporites are mainly alabaster gypsum, indicating the concentration of salts by high rates of evaporation along an arid shoreline. Some gypsum outcrops display distinctive “chickenwire” structure (Figure 2D.1.3), formed when concentrations of gypsum crystals grow within a muddy shoreline substrate, pushing the mud matrix aside to form whitish nodules separated by the original dark mud they grew within.
Figure 2D.1.1. Layers of Kaibab Limestone exposed along the Bill Hall Trail contain numerous large D-shaped fossil brachiopods and smaller circular crinoid stems.
Figure 2D.1.2. The Kaibab-Toroweap contact can be observed at the break in slope between resistant, cliff-forming limestones change abruptly to weak, slope-forming mudstones.
Figure 2D.1.3. Chickenwire structure in alabaster gypsum deposits of the Toroweap Formation; the “wire” forms as gypsum crystals grow in a muddy matrix, pushing the mud outward and eventually squeezing it between adjacent crystals.
Twisted pinon pines and junipers, mixed with sagebrush, Mormon tea, and buffalo berry cling to the steep slopes along your Toroweap traverse, as ample clearings afford numerous spectacular views to the southwest of the forested slopes of volcanic Mount Trumbull and Mount Logan on the far horizon, down the broad trough carved by the Colorado River, and across the expansive tableland of the Esplanade Platform still some 1000 feet below (Figure 2D.1.4). Immediately below your position, the shadowy tendrils of Deer Creek’s tributary canyons seem to creep close. Again, note the topographic differences between the eastern and western Grand Canyon and their relationship to the stratigraphy exposed by canyon dissection. As I have already described, here in the west, a thicker, more sand-rich Esplanade Sandstone and thicker Hermit Shale combine to allow slope retreat to push the Hermit Shale and the upper Permian rock formations resting on it back significantly from the Inner Gorge to create the Esplanade Platform. This platform does not manifest in the eastern canyon because the Esplanade Sandstone in relatively thin and more mud-rich, while the Hermit is thinner too. In contrast, a thin Bright Angel Shale here in the west has had the opposite effect on the overlying Redwall Limestone. The Redwall Limestone occurs much closer to the Colorado River and forms the upper buttress of the canyon’s Inner Gorge, which itself is deeper in the west because slope retreat related to the Bright Angel Shale has not impacted the overlying Redwall Limestone to generate a “Tonto Platform” in the way that it has in the eastern Grand Canyon where the Bright Angel Shale is much thicker. To say it another way, there is no Tonto Platform here because the Bright Angel Shale is relatively thin and not subject to significant slope retreat.
Figure 2D.1.4. A typical view of the Esplanade Platform and Inner Gorge of the Colorado River from the Toroweap traverse along the Bill Hall Trail.
The traverse ends abruptly at 1.53 miles (Map 2D.1.2), near the base of the Toroweap Formation where a 12-foot-high resistant limestone band must be negotiated with care; no rope is required, there are ample hand and foot holds that work quite nicely. Your route quickly leads to the head of a steep, rubbly talus cone and 49 switchbacks that gradually take you down through the Coconino Sandstone and Hermit Shale. At the 5th switchback in rapid succession, the trail comes level with the Toroweap-Coconino contact, well-exposed on the cliff face immediately to the northwest (Figure 2D.1.5). The contact is marked by a distinct color change from yellowish-brown limestones and red mudstones of the Toroweap Formation to the typically buff-colored, quartz-rich Coconino Sandstone. Nearby outcrops of the Coconino exhibit steeply dipping mega-scale crossbedding indicating the rock unit’s origin as eolian, or wind-blown sand dunes. As you descend to the base of the talus cone, note how the rubble pile gradually tapers outward and decreases in slope (Figure 2D.1.6). The cones consist of rubble produced from weathering and erosion of the overlying Kaibab Limestone, Toroweap Formation, and Coconino Sandstone and can be easily observed further afield where olive-drab materials are draped onto the underlying red mudstone slopes of the Hermit Shale (Figure 2D.1.5). The Coconino-Hermit contact is buried beneath the talus, but is visible to the right and left of the debris cone as an abrupt transition from whitish cliff-forming sandstones to brick-red mudstone slopes (Figure 2D.1.6).
Figure 2D.1.5. The Toroweap-Coconino contact seen from the head of the breakdown slope and large talus cone used to reach the Esplanade Platform.
Figure 2D.1.6. Talus cones are a common feature of the Permian cliff-slope transition bordering the Esplanade Platform; the Bill Hall Trail descends to the floor of the Esplanade along one such cone formed of rubble stacked on an underlying slope of Hermit Shale.
After the slope moderates, the trail straightens out into a steep, but easy path through scattered pinon-juniper woodland favored by blackbrush, sagebrush, and yucca. The trail briefly negotiates a minor draw to meet the cairn-marked junction with the Thunder River Trail at 2.97 miles (Map 2D.1.2). Red-brown sandstone outcrops nearby offer a first glimpse of the Esplanade Sandstone; you have now reached a depth of erosion exposing the last of the Permian rock formations, and the first formation of the Supai Group. Take the left-hand branch of the Thunder River Trail generally south for several miles across the nearly level Esplanade Platform (Figure 2D.1.7). Typically waterless except after recent rains, and hot during midday, the trail crosses expansive, sandstone slickrock sections as it works around several small tributaries of Deer Creek; hikers need to be alert for cairns that mark the route ahead. It is good practice to try to locate the next cairn before the last one is lost from view. This portion of the Thunder River Trail is quite alluring; scenic vistas abound, with extensive outcrops of swirled slickrock exhibiting eolian-generated crossbedding, the outcrops often broken up by a checkerboard pattern of joints and weathered into weird red-brown sandstone hoodoos shaped not unlike gigantic snowmen or mushrooms. It is an otherworldly place best hiked in the morning or evening when shadows accentuate every feature. In some areas, enough sand has accumulated to support a smattering of scraggly pinon pine and juniper; in these areas be sure to remain on the trail to avoid disturbing the cryptobiotic soil (Figure 2D.1.8a). The soil forms through a symbiosis between algae and lichen, and in this arid environment, it develops over thousands of years. Figure 2D.8b offers a close-up view of the soil showing its typically knobby surface. Cryptobiotic soil is vital for reducing erosion during infrequent but intense rains and one misstep can crush what nature take many human lifetimes to generate; please be careful.
Figure 2D.1.7. The Esplanade Platform; a slickrock sandstone bench that is generally quite flat except where interrupted by water-carved gullies and canyons, it is normally quite hot and dry (although a lucky rainstorm can fill potholes on its surface as pictured here).
Figure 2D.1.8. Sandy patches on the Esplanade Platform are often covered in a blanket of fragile cryptobiotic soil; formed by a symbiosis of algae and lichen over hundreds to thousands of years, the crust is essential for preventing erosion during infrequent but intense rainstorms.
With a well-cairned tread on slickrock or firm sand, the trail is a relatively easy saunter and not difficult to follow as it passes a pretty variety of exposed rock, gnarled trees, and Upper Sonoran Zone shrubs including scrub live oak, blackbrush, Utah serviceberry, Fremont barberry, manzanita, mountain mahogany, yucca, and agave. Soon, the trail contours around the first tributary, and at about 3.35 miles (Map 2D.1.2), the first good outcrops of cross-bedded Esplanade Sandstone are exposed. Continuing onward, at 3.90 miles (Map 2D.1.2) the trail begins paralleling a narrow fin of rock capped by a band of sandstone about 10 feet thick exhibiting steeply dipping cross beds that rests on a thin layer of horizontally laminated brick-red mudstone. In about a tenth of a mile, your route passes through a gap in the narrow ridge, the end of which forms a mushroom-shaped hoodoo nicely displaying the combination of sandstone-mudstone strata (Figure 2D.1.9). The mudstone layers make up a minority of the Esplanade Sandstone and are interpreted as floodplain deposits, while the majority of the Esplanade is of course, formed of the cross-bedded sandstones interpreted as migrating sand dunes; the entire package likely representing an arid coastal plain crossed by meandering rivers.
Figure 2D.1.9. The interbedded layers of sandstone and mudstone exposed in this hoodoo formed at the end of a long, narrow fin of Esplanade Sandstone reveals the origins of this rock unit; an arid coastal plain crossed by meander rivers and periodically subjected to inundating sand dunes.
The trail now traverses the broad, gently undulating divide between the two main tributaries; several patches of slickrock here expose tightly checkerboarded jointing in the sandstone (Figure 2D.1.10). This “biscuit” jointing often forms when the rock expands as the pressure exerted by overlying material is released during erosional stripping of the landscape and is not uncommon in homogeneous sandstones. After rounding through the head of the second Deer Creek drainage, at 5.06 miles (Map 2D.1.2) the trail reaches a distinctive pair of twin, red-brown hoodoos (Figure 2D.1.11); note the interlayering of thin mudstones and thick sandstones. Shortly afterwards, your route bends to the right and begins a gradual westward-trending descent through layers of sandstone toward the Esplanade rim. Near 5.48 miles (Map 2D.1.2), the trail rounds a large outcrop of the red-brown sandstone and then drops down stratigraphically into gray sandstones, probably the uppermost part of the Pennsylvanian Wescogame Formation. You are approaching the rim of the Esplanade Platform, and this area’s many buff-colored hoodoos and scraggly trees provide some resting shade, a good place to stash some water for the return journey, or great little campsites, with incredible views near at hand into Surprise Valley. Ahead, at 5.80 miles (Map 2D.1.2), a good-sized campsite at trailside and right on the edge of the escarpment can accommodate a larger group. Besides, progressing any further brings you to a series of steep switchbacks through the remaining Supai Group and Redwall Limestone to the floor of Surprise Valley. The descent is long and rough and the southern exposure makes the entire area infamously hot. The park service strongly recommends that you avoid hiking in Surprise Valley after 10 a.m. during warm weather.
Figure 2D.1.10. Checkerboard or “biscuit” jointing in the Esplanade Sandstone typically forms by the release of pressure and rock expansion when overlying layers of rock are removed by erosion.
Figure 2D.1.11. Snowman-shaped twin hoodoos of Esplanade Sandstone mark a right-angle bend in the trail toward the west; note the differential weathering and erosion of resistant beds of sandstone and weaker mudstone, a commonly expressed feature of this rock unit.
The sunset and sunrise vistas are well worth an overnight stay along the rim either on the way in or out, and the geology on display is awesome to behold. Figure 2D.1.12 reveals it all. To the southwest, the soaring cliffs of Great Thumb Mesa offer a spectacular display of variegated colors and readily identified Paleozoic rock units where the Colorado makes a huge sweeping bend to the north and west after passing around Powell Plateau. More to the west, the Inner Gorge of the Colorado River slices a deep notch into the Esplanade as it disappears into the distance. From your rim perch, Surprise Valley, choked with the debris of massive landslides (and several smaller adjoining slides) unfolds immediately below. The depression before you may have originated as an enclosed, fault-controlled graben long ago, evidenced by lake deposits formed in the basin that are now dissected by Bonita Creek. The topographic alignment of the valley more or less parallel to the trend of the modern Colorado and/or in line with upper Tapeats Canyon is a geomorphic curiosity. Its east-west alignment suggests that it could be the former course of the Colorado River or Tapeats Creek, when either water course flowed at a stratigraphically higher level. Blockage and diversion of the river could have resulted from an early mega-landslide now buried beneath younger debris. In the distance, to the south, you can see a sliver of the Colorado River in the canyon’s depths. Between Great Thumb Mesa’s Redwall Limestone cliffs and the bowl-shaped depression of Surprise Valley lies a grayish hump capped by a thin veneer of red material. This is Cogswell Butte, its grayish slopes formed of Redwall Limestone washed clean of its red, Supai Group mud coating. The butte forms the outer edge of Surprise Valley and is itself fixed in place, its northeast slopes plastered in a blanket of landslide debris. The upper end of Bonita Creek just east of Cogswell Butte is similarly choked with landslide debris; the reddish boulders at the northeast base of the butte and choking the stream drainage are the same as the sandstone you’ve been treading on across the Esplanade Platform and originated on the escarpment around you.
Figure 2D.1.12. Surprise Valley and Great Thumb Mesa from the Esplanade rim on the Thunder River Trail; the inner gorge of the Colorado swings north, then west around the mesa cutting a deep, narrow trench in the resistant sandstone tableland of the Esplanade Platform.
The landslide evidence you can see from here is only the latest in a series of mega-landslides dating back 2-3 million years. The mass wasting found in the Surprise Valley area is known to geologists as the Toreva block style, named by Parry Reiche in a 1937 publication for Toreva, a settlement at the edge of Second Mesa on the Hopi Reservation at the edge of the Colorado Plateau in northern Arizona. Sedimentary rock layers on the intact parts of the mesa are nearly flat-lying, but the mesa is surrounded by elongated blocks of the same layering that tilt backwards toward the intact mesa, but are otherwise intact, despite being displaced from the mesa itself. Toreva blocks are enormous, intact landslide masses that move on curved failure surfaces, causing the backward tilting of the layering to develop (Figure 2D.1.13). Their movement is facilitated by a sequence of sedimentary strata consisting of strong, coherent sandstones, limestones, and/or lava flows associated with steep escarpments, resting on a thick section of weak, sloping shale and other mudrocks (Figure 2D.1.13a). The weak rock, especially when steepened and undercut, creates the initial concave failure surface which propagates upward through the overlying layers and allows the slide block to move without disintegrating (Figure 2D.1.13b). The cohesion of the strong rock layers allow the block to maintain its integrity despite its size and considerable displacement, and also allows the block to exhibit the backward tilting of the strata toward the parent cliff line during and after movement (Figure 2D.1.13b and Figure 2D.1.13c). The rotated Toreva blocks create an outcrop repetition of the cliff-forming section and are especially visible when “aged” by subsequent weathering and erosion.
Figure 2D.1.13. Formation of Toreva style landslide blocks; the blocks are enormous, intact masses of layered sedimentary rock that move on curved failure surfaces, causing the backward tilting of the layering to develop and create an outcrop repetition of the cliff-forming section on the slope below.
In the Surprise Valley area, the coherent, cliff-forming sedimentary rocks include the sandstones of the Supai Group and the Redwall Limestone, while the slope-forming Bright Angel Shale (and the muddier, lower portion of the Muav Limestone) form the weak layers where the curved failure surface is initiated. The displaced debris can be recognized as tilted and broken masses of rock which are all portions of a gigantic landslide complex consisting of nearly one cubic mile of material. The complex represents at least a half dozen separate Toreva style mass wasting events that generally advanced downcanyon from the Tapeats Creek to the Deer Creek watershed over past 2-3 million years, alternatively filling, damming, and diverting portions of Tapeats Creek, the Colorado River, and Deer Creek over time and at successive levels as the river and its tributaries continued to cut downward. As you descend into Surprise Valley tomorrow, more will be revealed about these massive landslides, a definite highlight of this backpacking trip.
Rise early and get on the trail. You don’t want to miss sunrise, and it gets hot down there. Just ahead, the Thunder River Trail enters a small drainage dotted with scrub live oak and climbs down to a small, sandy wash that pours from the Esplanade rim and your last “big picture” view of Surprise Valley. Continue your descent, the well-constructed trail takes advantage of the gentler slopes formed by the huge landslide. The first few switchbacks traverse rough, broken outcrops of Lower Supai Group mudstones and sandstones of the Pennsylvanian Wescogame Formation, Manakacha Formation and Watahomigi Formation before reaching the top of the Redwall Limestone at about 6.38 miles (Map 2D.1.2). Figure 2D.1.14 shows the typical, orderly cliff-slope-cliff outcrop pattern of the Manakacha Formation sandstones, Watahomigi Formation mudstones, and Redwall Limestone exposed to the right (southwest) of the trail. Working your way downward through the Redwall, your first good view of the most recent landslide mass opens up at about 6.63 miles (Map 2D.1.2), near the 14th to 15th switchbacks (Figure 2D.1.15). The obvious triple knolls below and to your left (southeast) are formed of back-tilted Redwall Limestone. It is the resistant sandstones of the Esplanade and Manakacha, as well as the Redwall Limestone that form the backward leaning layers expressed in the Toreva blocks through which you descend. At 6.71 miles (Map 2D.1.2), the trail reaches the apex of a large talus cone comprised of rubble of all shapes and sizes. As you continue the trail’s steep descent, weaving between huge slabs of Supai Group sandstone, you pass the triple Redwall knolls just to the left (southeast); the back-tilted bedding in the Redwall Limestone becomes quite plainly visible (Figure 2D.1.16a). Massive, broken and obviously displaced, but backward-tilted layers of Supai Group sandstones and mudstones occupy your right-hand view (Figure 2D.1.16b), the grayish cliffs of Redwall Limestone they lean against standing in sharp contrast. Dropping from the top of the westernmost knoll, at about 6.96 miles (Map 2D.1.2), the trail descends a wide gully with tilted outcrops of Redwall Limestone immediately to your left. The Redwall layers are definitely dropped and back-tilted relative to the intact cliffs behind you, but to the right, seeming undisturbed (albeit rotated out of the slope) layers of Supai Group rocks found at an even lower position on the slope have been displaced much further, at least hundreds of feet downward and away from their source.
Figure 2D.1.14. The slope to the right of the trail near mile 6.38 shows the typical, orderly cliff-slope-cliff outcrop pattern of the Manakacha Formation sandstones, Watahomigi Formation mudstones, and Redwall Limestone.
Figure 2D.1.15. The obvious set of three knolls below and to your left (southeast) of your position at 6.63 miles on the Thunder River Trail are formed of back-tilted Redwall Limestone, forming the most recent of many Toreva style landslide blocks to choke bowl-shaped depression of Surprise Valley.
Figure 2D.1.16. Descending the Thunder River Trail; superb examples of Toreva style landslide blocks can be observed on the left where the triple knolls comprised of Redwall Limestone exhibit easily observed, back-tilted bedding (A), and on the right where massive, broken and displaced, backward-tilted layers of Supai Group sandstones and mudstones rest against the Redwall Limestone cliffs (B).
Eventually, you exit the chaotic and disheveled landslide masses onto a generally straight path descending along the finer material of the debris apron on the toe slope of the landslide complex, a large gully cut into the debris apron lies on the right. Almost immediately, you reach an unmarked fork in the trail at 7.10 miles (Map 2D.1.2). Here, the Thunder River trail continues downward to your left, while the Deer Creek Trail begins on the right, descending into and across the gully’s wash. You will return to this point in a few days-time, completing the loop from Tapeats Creek to Deer Creek and back, but for now continue on the gentle grade of the Thunder River Trail to the left. As you descend the sunbaked debris apron of the lower landslide, another gully comes in from the left; be sure to return your gaze upslope to the rotated, Toreva style landslide blocks resting against the base of the Redwall cliffs; the gray knolls comprised of Redwall Limestone to the right are easily discernable from the red-brown Supai Group blocks to the left. A variety of plants, tolerant of the summer heat, cover the slopes here, including blackbrush, yucca, Mormon tea, and several species of cacti and bunchgrasses. Views of the pine-clad tableland of Powell Plateau and western edge of the Kaibab Plateau seem rather inviting now, but continue down the debris apron, passing red-brown boulders of Supai Group lying stretched out along a curved path sweeping down from the right (Figure 2D.1.17). The boulders must have been rafted into place on a debris flow originated from the more disarticulated portions of the Toreva blocks and are plastered onto the lower northeast flank of Cogswell Butte and choke the head of the Bonita Creek drainage.
Figure 2D.1.17. Far-traveled red-brown Supai Group sandstone boulders strewn along the lower northeast flank of Cogswell Butte.
At 7.44 miles (Map 2D.1.2), the trail reaches a second junction; the trail to the right is use as a shortcut to connect more directly with the Deer Creek Trail; ignore it, unless by chance, you descended to the floor of Surprise Valley during the heat of the day and are seeking a place of refuge from the sun and a descent camping spot. Then instead, do take the connector trail to the right. Almost immediately, a spur trail on the left crosses the lower fan and a rubbly wash to the Supai Group boulders in the near distance. A huge boulder here offers some shelter and camping for a small group. Back on the main Thunder River Trail, continue to the left through the gully wash a short distance ahead. This is the lowest position you reach in Surprise Valley.
After passing another dry wash, this one being the head of Bonita Creek, your route climbs gradually for roughly another mile to a low pass looking into the upper canyon of Tapeats Creek. Before reaching the pass, at 8.16 miles (Map 2D.1.2), the trail traverses steeply tilted layers of red-brown Supai Group rocks forming the cap of an older mega-landslide. Not far ahead, you will see the underlying Redwall Limestone layers of this massive landslide exposed at trailside. This Toreva block, or complex set of blocks, was truly enormous and is believed to have plugged the ancestral drainage of Tapeats Creek, forcing the stream to bend to the south and carve the canyon seen today. Evidence of a debris-filled channel clings high on the west wall of Tapeats Canyon and east wall of Bonita Canyon, possibly the original path of Tapeats Creek; in fact, lower Bonita Canyon may well be the remnants of the older, pre-landslide route of Tapeats Creek.
As you reach the pass, take a few moments to contemplate the course you have just traversed. The entirety of beautiful Surprise Valley is laid out to the west. Toreva blocks and loose landslide debris can be seen to sweep downslope from the cliffs backing the northern side of the valley. Note the east-west trend of Tapeats Creek Canyon and Surprise Valley; is their apparent alignment just coincidence, or could Surprise Valley be the former valley of Tapeats Creek itself prior to landslide blockage? Now begin the descent into Tapeats Creek. The view into upper Tapeats Canyon is spectacular (Figure 2D.1.18). Tapeats Creek has carved a deep, vertical notch through the lower Paleozoic sedimentary sequence and into an ancient eastward tilted graben containing the sedimentary rock units of the lower Mesoproterozoic Unkar Group, the lower part of the Grand Canyon Supergroup. Unkar Group rocks were originally deposited horizontally, as all good sedimentary rocks are, but were then subjected to upwarping and extension about 750 million years ago that broke the layers up into a series of east-dipping half-grabens. The rocks were plained-off by erosion, but where they had been tilted down into grabens, they were preserved. The Paleozoic sequence, beginning with the Cambrian Tapeats Sandstone, were deposited on top, sealing away the half grabens and their contents until exposed by erosion of the Colorado River.
Figure 2D.1.18. The vertical notch of upper Tapeats Canyon exposes lower Paleozoic Redwall Limestone, Muav Limestone, Bright Angel Shale and Tapeats Sandstone resting on an angular unconformity above eastward tilted layers of Shinomo Sandstone.
Figure 2D.1.18 shows the thick, red cliffs of the Redwall Limestone stacked on olive-yellow ledgy slopes of Muav Limestone, which are in turn overlying greenish-gray slopes of Bright Angel Shale. The Tapeats Sandstone forms the basal, dark brown cliffs far up the canyon. Nearer your position, where the stream makes a sharp bend southward, buff-colored, cliff-forming strata of the Unkar Group’s Shinomo Sandstone are tilted eastward and upcanyon and are overlain by Cambrian Tapeats Sandstone and Bright Angel Shale resting on a buried erosion surface and angular unconformity. Immediately below you, the verdant green pocket of dense vegetation marks the position of the springs which gush forth to instantly form Thunder River, which quickly joins Tapeats Creek in the shadowy depths of the canyon. The steep trail initially descends several switchbacks in a steep gully filled with landslide rubble comprised of red-brown Supai Group rocks, the aforementioned “cap” of an ancient mega-landslide. Nearly vertical layers of Supai Group rocks can be seen to the left of the gully. Shortly, the trail angles diagonally down to the south and after the 3rd, right-hand switchback at 8.40 miles (Map 2D.1.2) crosses onto highly tilted layers of gray Redwall Limestone, presumably the nearly vertically rotated basal portion of the same mega-landslide (Figure 2D.1.19).
Figure 2D.1.19. Nearly vertical, highly rotated Redwall Limestone layers exposed on the trail at mile 8.40, part of an enormous, mangled Toreva landslide block capped by red-brown Supai Group rocks which can be seen upslope in the background.
This steep section of trail affords wonderful views of Thunder River Spring, which emerges as a full-force river from caves positioned near the contact between the Muav Limestone and Bright Angel Shale surrounded by greenery. At 8.65 miles (Map 2D.1.2), the trail comes level with the cave springs (Figure 2D.1.20); the torrent of water in this otherwise hot, dry, dusty place is nothing less than miraculous! Where does this water come from? It is really all a matter a gravity, time, and the right combination of bedrock conditions. Rainfall and snowmelt seeps into porous rocks capping the nearby Kaibab Plateau and gradually works its way downward through joints and faults and along bedding planes widened by groundwater dissolution, to eventually collect as a subterranean river near the base of the Muav Limestone. Downward movement is impeded by the thick, impervious Bright Angel Shale, so the groundwater flows laterally along bedding to emerge here, in this seemingly unlikely place, where erosion of Tapeats Creek has exposed the contact between permeable and impermeable rock layers. In this location, groundwater flow may be affected by major geologic structures such as the nearby Crazy Jug Fault and Tapeats Fault (directing water along fault traces) which Tapeats Creek cuts across upcanyon, and it may be affected by the slightly westward-dipping strata on the west side of the Kaibab Plateau (an asymmetric upwarp in the earth’s crust causing strata to dip toward Thunder River Spring on this side of the plateau and directing groundwater down the dip-slope).
Figure 2D.1.20. Thunder River issues voluminously from caves near the contact between the permeable Muav Limestone and underlying, impermeable Bright Angel Shale.
Continue your downclimb, just ahead, at about 8.72 miles (Map 2D.1.2), a spur trail leaves the main trail on the left. This short trail takes you to the right bank of Thunder River just below the cave springs. Keeping to the right on the main trail, you soon cross onto greenish-gray outcrops of Bright Angel Shale directly overlain by a coarse, angular, indurated breccia, probably the base of the mega-landslide deposits you have followed downslope since the pass (Figure 2D.1.21). Here, the Bright Angel Shale consists of infrequent thinly bedded brown sandstones dispersed among a majority of greenish-gray mudstones, some bedding planes preserve nicely formed ripple marks and trace fossils of burrowing marine worms. To your left, Thunder River pours over a resistant sandstone layer in the Bright Angel Shale forming a gorgeous four-stranded waterfall. From here, you tread alongside the Thunder River and its lush riparian splendor all the way to its confluence with Tapeats Creek. The sounds of water crashing over rocks is a welcome distraction from the sunny exposure on barren Bright Angel Shale slopes that you traverse.
Figure 2D.1.21. Outcrops of the Bright Angel Shale exposed along the Thunder River Trail near mile 8.72; note the abrupt change to iron-stained breccia upward within the exposure, the basal portion of landslide deposits from Surprise Valley.
The trail angles downslope more slowly than the shaley ridgeline to your right, and soon approaches the ridge crest at about 8.98 miles (Map 2D.1.2). Notice that you have not yet encountered the Tapeats Sandstone along your route, although when you look up Tapeats Creek Canyon to the east, the break in slope and contact between the gray Bright Angel Shale and brown Tapeats Sandstone occurs at about your level. Where is the Tapeats Sandstone on your side of the canyon? Look across Tapeats Creek to the east side of the canyon near the Thunder River-Tapeats Creek confluence, eastward dipping layers of Shinomo Sandstone are well exposed (Figure 2D.1.22). You might notice that the Bright Angel Shale rests directly on the Shinomo, the Tapeats Sandstone is missing here. Looking across the valley of Thunder River shows a wedge of Bright Angel Shale thickening to the northeast and up Tapeats Canyon. The cause for this odd stratigraphy is that the Shinomo Sandstone formed a resistant island during the Cambrian marine transgression that deposited the Tapeats Sandstone; it was not until water had risen deeply enough to deposits the muds of the Bright Angel Shale that the sandstone island was inundated by the waves several million years later.
Figure 2D.1.22. The eastward tilted layers of Shinomo Sandstone exposed in Tapeats Creek Canyon lack a cap of Tapeats Sandstone, but are covered by the Bright Angel Shale, evidence indicating that the Shinomo formed an “island” in the advancing Cambrian sea.
Near the ridgeline, you suddenly descend a series of tight switchbacks down a shaley slope nearly to the water’s edge. A close examination of the whitish boulders and small outcrops scattered on the slopes around you reveals cross-bedded, nearly pure quartz sandstones; these are not the coarse, immature feldspathic sandstones of the Tapeats, but instead, they are boulders of Shinomo Sandstone. Again, think “island” in the Cambrian sea. Larger, more consistent outcrops of Shinomo Sandstone begin to appear closer to the valley floor, some exhibit herringbone crossbedding and bedding planes covered in symmetric ripple marks, indicative of the shoreline setting in which the sand is thought to have accumulated. The Shinomo Sandstone also contains abundant examples of convolute, “marblecake” bedding, a type of soft sediment deformation thought by geologists to have formed by ancient earthquakes activity that shook the region some 1100 million years ago. After reaching the confluence of Thunder River with Tapeats Creek, the trail bends to the right, downcanyon. In short order, you reach Upper Tapeats Campsite at 9.71 miles (Map 2D.1.2), confined to a narrow swath of relatively level ground between perennial Tapeats Creek and a wall of Shinomo Sandstone. The camping area sports a composting toilet and several shady campsites. If you started your day early, a midday arrival here should afford you with ample opportunities to explore your surroundings (perhaps a short hike up Tapeats Canyon to examine dipping Supergroup strata?). Wading in pretty Tapeats Creek may also be in order, although the stream is usually flowing very swiftly and is quite cold (Figure 2D.1.23), so take care. In any case, take some leisure time to unwind, do a bit of reading, play cards, listen to the splashing stream and the breezes passing through the cottonwood trees; tomorrow is another day.
Figure 2D.1.23. Tapeats Creek; the view is upstream from Upper Tapeats Campsite.
Your hiking goal today is the Colorado River. I recommend remaining a second night at Upper Tapeats Campsite and spending the day on an exploratory hike of lower Tapeats Creek canyon to the river and back; there is plenty of great geology to see, and this alleviates the difficulties of getting in a good study of the canyon while hauling a backpack along or worrying about the time slipping by before reaching your next campsite. Tapeats Creek is never far from the trail, so bring a water filter and pack light, with your eyes alert to the splendors of this marvelous canyon. There are two parallel trails leading down the canyon to the Colorado, both have their challenges, but sticking to the west (right) side of the stream avoids several potentially traitorous crossings of swift-flowing, often thigh-deep Tapeats Creek.
The trail heads downstream from Upper Tapeats Campsite, sticking to the outer edge of the narrow floodplain and generally avoiding the thick riparian vegetation nearest Tapeats Creek. Shortly, at 10.07 miles (Map 2D.1.2), your route squeezes between the stream and a low cliff, the first outcrop of the brick-red Hakatai Shale. The contact with the overlying Shinomo Sandstone is not exposed, but occurs nearby. A trail to the left here descends to a ford across Tapeats Creek, the recommended route described by the park service. However, despite its description as “sketchy,” stay to the right bank; the west-side trail is quite easily followed and avoids fording and then re-fording Tapeats Creek a couple of miles downstream.
Continuing on the right-hand path, it quickly ascends a rising ledge of mudstone between eastward dipping beds of more resistant sandstone. Take care on the narrow trail, but the Hakatai outcrops and slabs of rubble exposed here provide excellent examples of mudcracks and ripple marks formed in a coastal tidal flat environment 1000 million years ago (Figure 2D.1.24). These features are well-preserved in the shalely layers of the Hakatai and other Supergroup formations because higher forms of marine life had not yet developed to churn the sediments and disrupt finer details like bedding plane structures through processes of bioturbation (disturbance by burrowing and churning of animals). After climbing to a high point in a gully, your “alternate” Thunder River Trail bends sharply left, then undulates along Hakatai slopes to a second gully. Here, it descends back to the valley floor and traverses a long sandy stretch filled with Engelmann hedgehog and Engelmann prickly pear cacti gardens (the spring blooms are gorgeous!).
Figure 2D.1.24. This thin sandstone slab of Hakatai Shale preserves beautiful mud cracks superimposed on symmetrical ripple marks indicative of the rock unit’s coastal tidal flat origins.
At 10.30 miles (Map 2D.1.2), the trail abruptly bends right away from the stream, and rapidly ascends a rubbly slope to several hundred feet above the valley floor. Tapeats Creek hugs the western slope of the valley just ahead, forcing a detour up and around unpassable Hakatai cliffs. After traversing a south-facing slope of ledgy mudstones and sandstones in the Hakatai Shale with great views downcanyon, the trail reaches the apex of a talus cone at 10.67 miles (Map 2D.1.2). Note that many of the boulders strewn over the cone’s surface are comprised of coarse breccia, oxidized an orangish-yellow. Hakatai slopes above you support cliffs formed of the same breccia; this rock has been interpreted by geologists as landslide debris filling a former channel of Tapeats Creek when it flowed at a higher stratigraphic position as much as 2-3 million years ago (it had yet to cut to its current depth). Descend the talus cone back to the valley floor and cross a second sandy stretch of cacti gardens. Be sure to look back up the canyon here, the cliff-forming orangish-yellow landslide deposits can be readily observed, contrasting sharply with ledgy, brick-red slopes of Hakatai Shale (Figure 2D.25). Notice that the surface the breccia rests on is distinctly curved in places, suggesting the bottom of a former stream channel.
Figure 2D.1.25. Ancient landslide debris filling a former channel of the ancestral Tapeats Creek before it had eroded downward to its current stratigraphic level; the curved base of the landslide deposits is strongly suggestive of the position of the old channel and/or valley floor.
The trail once again heads downcanyon, alternately traversing patches of sandy valley bottom, rubbly valley toe slopes, and lower slopes of exposed Hakatai Shale for roughly three-quarters of a mile before ascending to a bench several hundred feet above Tapeats Creek at 11.43 miles (Map 2D.1.2). The ascent is necessitated by another by-pass around Hakatai slopes that have been over-steepened by undercutting of the stream on the west side of the valley. The location offers superb views up and down Tapeats Creek canyon. Looking downstream to the southeast and high above the valley floor, a 300-foot high cliff of Tapeats Sandstone can be seen to rest directly on an undulating surface carved into the alternating beds of mudstone and sandstone of the Hakatai Shale (Figure 2D.1.26). The Hakatai layers exhibit a down-to-the-northeast dip related to their preservation in an ancient half-graben, and the erosion surface separating them from the horizontally deposited Tapeats Sandstone is an exposure of the Great Unconformity, forming an angular unconformity on the east wall of Tapeats canyon. The unconformity itself undulates, indicating that wave-induced erosion during the initial marine invasion preferentially remove weaker mudstones over more resistant sandstones. A careful examination of the rocky debris covering the bench you are walking on reveals that some of the stones are round, obviously polished smooth by the passage of sediment-laden water. The only water in sight is Tapeats Creek several hundred feet below you. These rounded stones likely once formed a terrace similar to the sandy bench on the modern valley floor of Tapeats Creek when the stream once flowed at this level.
Figure 2D.1.26. The Great Unconformity exposed high on the cliffs above Tapeats Creek; the undulating erosion surface shows the considerable relief of the sea floor formed by wave erosion of sandstone and mudstone layers in the Hakatai Shale.
After traversing the outer edge of the bench, the trail turns sharply left and makes a swift, steep descent back to Tapeats Creek. Near the base of the slope, the rock outcrops change from the typical brick-red Hakatai to a grayish-yellow. This is an indication that you have passed the Hakatai Shale – Bass Limestone contact. Approaching the valley floor, a spur trail on the left invites you on a brief detour upcanyon to eastward dipping ledges of Bass Limestone; here, and elsewhere, when these resistant layers cross beneath Tapeats Creek, they form a temporary nick point where stream gradient is increased and a pretty little waterfall forms (Figure 2D.1.27).
Figure 2D.1.27. Beds of Bass Limestone dip northeastward beneath Tapeats Creek, each resistant layer causing an increased gradient and an idyllic little waterfall.
Return to the main Thunder River Trail and continue downcanyon. Shortly, another trail joins from the left. This trail fords the stream and is the lower end of the east-side trail described previously. If the water in Tapeats Creek is low, this trail could be followed as an alternative back to Upper Tapeats Campsite. Do not follow the east-side route any further downcanyon; the trail climbs high above Tapeats Creek, but upon reaching the mouth of the canyon, there is no way down to river level. Now back to the main west-side trail. After crossing a short, sandy, creek-side section of trail, your route passes onto a protruding ledge of Bass Limestone squeezed between cliff and froughing stream. Just beyond, at about 11.75 miles (Map 2D.1.2), begin looking for evidence of stromatolites, fossilized mats of bacteria and algae that flourished in shallow coastal waters some 1200 million years ago. These are the only macro-scale fossils to be found in Supergroup rocks because multicellular life did not develop until about 650 million years ago. Thin, wavy laminations in outcrops next to the trail provide a cross-sectional view of these spectacular lifeforms (Figure 2D.1.28a), while nearby on the ascending tread of the trail, rounded, cabbage-head-like lumps, many displaying concentric banding where plained-off by stream erosion, complete their 3-D configuration (Figure 2D.1.28b).
Figure 2D.1.28. Stromatolites preserved in the Bass Limestone record evidence of life on earth 1.2 billion years ago; (A) shows a cross-sectional view of the wavy laminations formed by the stromatolitic mats of algae and bacteria, while (B) provides an aerial view showing the third dimension of the cabbage-head-like structures.
From here, nearly to the Colorado River, the trail climbs gradually up the dipslope of the Bass Limestone beds. The exposure on this section of trail offers some challenge to those fearful of heights, but it is in good condition and easily followed. The trail is made more exciting by the wild crashing of the turbulent stream, which is shielded from view by the growing height of the nearly vertical cliffs below you. Great views into the trail-side deepening gorge of the lower Tapeats Creek narrows reveal exposures of a dark, greenish-hued rock beneath the layers of Bass. This rock is diabase, a crystalline igneous rock formed by mafic magma intruded parallel to bedding near the base of the Bass Limestone. Magma intruded laterally between weak layers of rock forms a plutonic body of igneous rock known as a sill. Mafic intrusions here and elsewhere in the Grand Canyon are restricted to the Mesoproterozoic Unkar Group and are believed to coincide with the massive outpourings of lava that produced the final rock unit of this group, the Cardenas Basalt, about 1100 million years ago. Geologists speculate that the magma’s temperature during intrusion was close to 2200 F; this caused contact metamorphism of the surrounding Bass Limestone and formed a distinctive light-gray zone of recrystallized limestone that caps the diabase.
At 12.10 miles (Map 2D.1.3), you reach a high point above the mouth of Tapeats Creek canyon and a picture-perfect view of the stream’s confluence with the Colorado River (Figure 2D.1.29). If the Colorado is running silty after summer thunderstorms, the contrast between crystal-clear groundwater-fed stream and muddy surface-runoff-fed river is amazing. No wonder that pre-dam era river runners described the Colorado as “thick as soup.” The rough waters of Tapeats Creek rapids lay just downcanyon of the confluence; a rank of 7 out of 10 on the Grand Canyon rating scale makes them quite exciting to run. As with most rapids on the Colorado River, these have formed at the mouth of a tributary canyon that periodically dumps a fresh supply of bouldery debris into the river during flash floods. Below your position, you can see the elongated fan of debris stretching into and down the river. The coarse deposits create a temporary (but frequently renewed) barrier to flow, a steepening of gradient, and the turbulence which forms the rapids.
Figure 2D.1.29. The confluence of Tapeats Creek and the Colorado River at the mouth of Tapeats Creek canyon; note the contrast between clean spring water-fed Tapeats Creek and the muddy Colorado and the raging Tapeats Rapids just downriver.
Just ahead, the Thunder River Trail in Tapeats canyon claims its last obstacle, a plunging descent of a large gully sliced through the diabase cliff and its accompanying talus cone that reaches nearly to river level. However, before making the downclimb, you may want to make a short detour. Where the trail bends sharply left and downward; instead, take the spur trail straight ahead (Map 2D.1.3). This trail will not get you to the river, but it does afford outrageous views up and down the Colorado. Follow the path southward around the corner ahead on your right; from a long ledge in the Bass Limestone, you can continue on the trail for several hundred yards, but you don’t need to go that far for gorgeous up- and down-canyon scenery. Figure 2D.1.30 shows the view upriver along the inner gorge of the Colorado River. Note the black cliffs of the diabase sill and contrasting light gray metamorphosed Bass Limestone above; these layers form the base of the Mesoproterozoic Unkar Group and clearly dip to the east upriver associated with the tilted half-graben they are preserved in. The bench on the south side of the river above the Bass Limestone nearly coinciding with your position is a strath (erosional) terrace formed when the river flowed at that stratigraphic level within the canyon. Figure 2D.1.31 offers a view downriver; in the middle distance near river level, brown Tapeats Sandstone cliffs rest directly on Proterozoic Vishnu Schist and Zoroaster Granite. Oddly, a grayish-yellow mélange, mainly composed of Redwall Limestone debris, lies above the brown sandstones and fills a dish-shaped depression cut into the Tapeats. This is evidence of yet another huge landslide mass that fell from the north wall of the canyon long ago, choking and diverting the course of the ancestral Colorado River to the south. Lower Granite Gorge begins where the Colorado was forced to cut a new channel, forming a narrow slot gouged through crystalline basement rocks, the narrowest width of the inner gorge anywhere in the Grand Canyon.
Figure 2D.1.30. An upcanyon view along the inner gorge of the Colorado River shows eastward tilted layers of the Mesoproterozoic lower Unkar Group; the bench on the south side of the river almost even with your position is a strath terrace formed by river erosion when the ancestral Colorado once flowed at a higher stratigraphic level.
Figure 2D.1.31. A downcanyon view along the inner gorge of the Colorado River shows evidence of another ancient landslide; this one once plugged the channel of the ancestral river, diverting it sideways to the south where it subsequently carved the narrow trench through the Tapeats Sandstone and underlying crystalline basement.
Once you’ve had you fill, return to the main trail and descend to the confluence of river and stream at 12.35 miles (Map 2D.1.3). As you carefully negotiate the steep descent, be sure to examine outcrops of metamorphosed Bass Limestone and diabase sill as you go (Figure 2D.1.32). Figure 2D.1.32a shows that the original calcite mud in the limestone has been recrystallized to visible green, fibrous crystals of asbestos; while Figure 2D.1.32b shows an outcrop of coarsely crystalline diabase comprised on pyroxene, amphibole, and plagioclase feldspar. Lower Tapeats Campsite offers no shade; but does make a good lunch spot and a place to observe boats shooting Tapeats Rapids. The yawning mouth of Tapeats Creek canyon lies to your left, its dark walls of diabase looking rather ominous (Figure 2D.1.33). Above the diabase sill, the pale layers of metamorphosed Bass Limestone contrast sharply with the dark, greenish-black rocks of the igneous intrusion. If you are hiking back to Upper Tapeats Campsite, this is a good turn-around point; if you are continuing on to Deer Creek, don’t remain too long, the next stretch of trail traverses the inner gorge and gets quite hot by midday.
Figure 2D.1.32. Intrusion of the Bass Limestone by mafic magma resulted in contact metamorphism that recrystallized the original calcite into green, fibrous crystals of asbestos by with an intruding diabase sill; (B) shows an outcrop of coarsely crystalline diabase comprised of pyroxene, amphibole, and calcium-rich plagioclase feldspar.
Figure 2D.1.33. The mouth of Tapeats Creek canyon looms dark and mysterious from river level at Lower Tapeats Campsite; its greenish-black lower walls are formed of a diabase sill intruded near the base of the Bass Limestone.
Begin your trek to Deer Creek with a predawn wakeup. You will want to get an early start because the inner gorge stretch of the hike gets uncomfortably hot by late morning. The connecting trail between Lower Tapeats Campsite and Deer Creek is a well-established route, taking roughly 4-5 hours to complete, but does offer its challenges and should only be used by experienced Grand Canyon backcountry hikers. That being said, the excellent trail creates a rare opportunity for backpackers to make a loop hike in the Grand Canyon. If the water level in Tapeats Creek was low, and you decided to try the west-side trail on your hike back to Upper Tapeats Campsite yesterday, then you can decide which trail best suits you. Either way, strap on that backpack and return to Lower Tapeats Campsite at the confluence of Tapeats Creek with the Colorado River at 12.35 miles (Map 2D.1.3); today’s trail description will begin from there.
From Lower Tapeats Campsite, travel downriver along a sloping beach strewn with boulders above the river’s high-water mark. Initially, your sandy path weaves among clumps of tamarisk and seep-willow; the boulder-hopping gets old after a while, but the sights are wonderful. At 12.78 miles (Map 2D.1.3), you reach a significant obstacle barring your path forward where the diabase sill projects into the river. Look for cairns guiding you up and over the rough, ledgy outcrops with some exposure and eventually to a steep, 15-foot high protruding wall necessitating scrabbling involving hands and feet to get you back to the sand. Before descending from the diabase sill, be sure to set your gaze downcanyon to the imposing mouth of Lower Granite Gorge; Figure 2D.1.34 provides the view. Here, the landslide-filled trough of the ancestral Colorado River channel and the river’s newly carved Granite Narrows notch loom larger than life.
Figure 2D.1.34. From your perch on the diabase sill adjacent to Colorado River, looking downcanyon reveals a larger-than-life view of the landslide-filled trough of the ancestral Colorado River channel and the river’s newly-carved notch through crystalline basement at Granite Narrows.
Once off the sill, immediately cross the dry wash of Bonita Creek and continue your boulder-hop westward along the river. Although it is difficult to tell with outcrops lacking on the rubbly slopes to your right, the intruding diabase sill comes to an abrupt end just downriver of Bonita Creek. Continuing onward, eventually the route emerges onto a pleasant stretch of sandy beach adjacent to 135-Mile Rapids at 13.62 miles (Map 2D.1.2); the rapids is a mere riffle compared to Tapeats Creek Rapids just upriver. Although this area is shadeless, if you were to time it right and arrive here late in the day, the inviting beach and its inaccessibility to river-runners makes this quite a cozy campsite. The Colorado is your only source of water, however, so plan accordingly.
From the beach area, nearer Granite Narrows, you can observe layers of ledgy eastward (upcanyon) tilted Bass Limestone resting directly on Vishnu Schist and Zoroaster Granite that truncate against flat-lying Tapeats Sandstone cliffs at the Great Unconformity. The Bass Limestone pinches out altogether not far downriver. Following the Tapeats Sandstone upriver, the curved contact between it and the landslide debris filling the former channel of the Colorado River is close at hand.
Hike to the western end of the beach, but before passing your first outcrops of crystalline basement emerging from the river’s north bank, look for multiple cairns that mark your way up and out of this seeming impasse. Trails converge on the lower slopes above the river at the base of the smaller, and upriver, of two gullies trundling down through layers of Bass Limestone perched above. A large cairn here acts as a gateway to your upcoming venture: a very steep, 600-foot ascent over three-quarters of a mile, mostly over light-colored, highly reflective landslide debris in a breezeless cul-de-sac that makes this section of trail bake you like an oven. A quick ascent leads to a short traverse along bedding in the Bass Limestone and through the larger, downriver of the two aforementioned gullies with nice views into the upper end of Granite Narrows (Figure 2D.1.35). Past the gully’s dry wash, the trail climbs in earnest up through landslide debris comprised of blocky limestone, the same debris pile that you could see choking the old channel of the Colorado River earlier in your hike. Eventually you reach a promontory about 2600 feet above the river at 14.30 miles (Map 2D.1.2) and turn right (west) parallel with the river as you continue downcanyon. Your hot climb was not without its merits however, as the views upcanyon from the exposed slopes are marvelous (Figure 2D.1.36).
Figure 2D.1.35. Granite Narrows, at the head of Lower Granite Gorge, the narrowest and youngest slice through crystalline basement rocks in the Grand Canyon; here, near the narrows, tilted layers of Bass Limestone rest on Vishnu Schist and Zoroaster Granite at the “greatest” unconformity and are themselves overlain by cliffs comprised of Tapeats Sandstone at the Great Unconformity (in the upper right of the photograph).
Figure 2D.1.36. As you make the arduous climb from river level topping out above the Tapeats Sandstone, marvelous views up the inner gorge of the Colorado River await to distract you.
Your promontory is the first of three before the trail swings northwest into tributary drainage below Cogswell Butte. All three prominences cross low ridges comprised of olive-gray muddy limestones stacked on a narrow bench formed above the Tapeats Sandstone. A prominent band of resistant limestone can be seen to undulate along the slope near the trail, higher on the ridges, but lower in the saddles. You are walking on lower layers of the Muav Limestone, deformed as they slid into this position to form the base of the large bulbous landslide mass that your route is currently circumnavigating, appearing to be draped onto the Tapeats Sandstone. This is the same landslide the plugged the Colorado River channel long ago. Not far past the third and largest of the ridge crests, your tread turns to slopes of remobilized landslide debris crumbling from the fractured cliffs above; this material is a mix of limestone rubble from the Muav Limestone and Redwall Limestone formations. After passing through a minor gully at 14.54 miles (Map 2D.1.2), nondescript other than it lies directly below a prominent overhanging cliff of deformed Redwall Limestone, the trail returns to undisturbed layers of brownish mudstone and thin sandstones, here comprising the Bright Angel Shale.
As you round through the head of the tributary below Cogswell Butte, several points of geological interest are worth noting, although not particularly discernable from your position. Above you, at the head of the leftmost branch of the tributary drainage, a wedge-shaped landslide mass fills a former narrow defile, presumably the original course of the tributary you are now crossing. Oddly, this wedge consists of nearly undisturbed red-brown Supai Group resting on smashed and highly deformed gray Redwall Limestone. Below you, on the right-hand (east) side of the tributary, the Tapeats Sandstone pinches out against crystalline basement in the walls of the inner gorge and doesn’t return until just upriver from the mouth of Deer Creek. You are now walking above a knob of resistant crystalline basement rock covered by Bright Angel Shale that once formed an “island” in the advancing Cambrian sea. The absence of Tapeats Sandstone indicates that the “island” was not inundated until deeper water conditions prevailed and deposition of the Bright Angel was underway. Finally, the Bass Limestone also pinches out just upriver, indicating that you have passed to the west of the half-graben containing Supergroup rocks that was so well exposed in Tapeats Creek canyon.
The trail now continues on a pleasantly rambling traverse that remains at nearly the same stratigraphic position within the lower portion of the Bright Angel Shale for about one and half miles, entering and exiting several minor tributaries along the way. The views are, as always, stupendous with the walls of Great Thumb Mesa looming a mere stone’s throw away across the river and open vistas both up and down the inner gorge of the Colorado River. Along this section of trail, outcropping layers exposed on the slopes indicate that the rock units are stacked in the order that they accumulated; Bright Angel, Muav and Redwall. The variegated slopes of Bright Angel Shale offer little shade as only scattered spiny masses of barrel cactus and clumps of desert shrubs such as brittlebush and Mormon tea find purchase. Near 15.43 miles (Map 2D.1.4), the trail swings through the head of a small tributary and temporarily leaves the alternating ledges and slopes of Tapeats Sandstone to cross yet another landslide mass. Here, layers of Muav Limestone lie backtilted into the slope forming a huge Toreva-style slide block. Look to the left and upslope as you cross the dry wash of the main gully, layers of Muav Limestone at the base of the slide mass are deformed into a series of small folds, rumpled like a carpet (Figure 2D.1.37); this probably occurred when overlying material was dragged downslope over these weaker muddy layers that form the lower portion of the formation.
Figure 2D.1.37. These deformed layers of Muav Limestone are found at the base of the cliff near mile 15.03 on the Thunder River-Deer Creek Loop trail; the folding was probably formed as the immense weight of an overlying Toreva-style landslide block was rotated outward and dragged down slope over weaker layers of muddy limestone.
From the wash, your route heads up and around the tilted block of Muav and along the right-hand side of a gully draining from the final ridge separating you from the valley of Deer Creek. Across the gully to your left (west) layers of brownish Bright Angel Shale are exposed, but the trail remains at the outer edge of the slide mass. As you crest the rise, note the thick band of resistant sandstone forming the western end of the ridgeline. Just ahead at 15.67 miles (Map 2D.1.4), your ridge crest position affords a gorgeous view into spacious upper Deer Canyon (Figure 2D.1.38); the vigorous growth of cottonwood trees and stream-bank hugging willows whispering that you are nearly there. Before descending, however, get a good look around. Compare the east and west sides of the valley. On the east, a normal stratigraphy prevails, with Bright Angel Shale forming the lower slopes, Muav Limestone above, and the towering cliffs of Redwall Limestone resting on top. To the west, at least nearer your position, lies a jumbled mass of broken boulders, debris forming one of the youngest of the gigantic landslides to tumble from the cliff buttress behind. This immense mound of rubble blocked the course of Deer Creek, forcing it to gouge a new channel through the Tapeats Sandstone (now the famous Tapeats Narrows of the Deer Creek drainage) and it extends several miles downriver.
Figure 2D.1.38. Your first view of upper Deer Creek canyon, its picturesque, accommodating valley and lush riparian zone beckoning you forward; this valley too has its share of landslide history, with much of its western flank comprised of a massive pile of rubble cleaved from the cliffs above that choked-off the original valley and forced the stream to carve a new course through the Tapeats Sandstone, forming the sinuous and beautiful Deer Creek Narrows and its accompanying waterfall.
And now for a quick descent to the valley floor on sun-drenched slopes of shale; then a ford of the perennial, but much less rambunctious, Deer Creek at 16.02 miles (Map 2D.1.4). Once across the stream, a turn to your left invites you into Dear Creek Narrows, but let’s save that for later. First, it is a short walk upstream along the left-hand bank of the creek to Deer Creek Campsite at 16.16 miles (Map 2D.1.4) and your resting place for the next two nights. Take a load off, maybe take a quick dip in the pleasant waters of Deer Creek, then find some shade under one Deer Creek’s sprawling cottonwoods and settle in for a nap before exploring your surroundings.
I am a firm believer that every great Grand Canyon backpacking trip deserves a layover day to relax and regroup before the rigor of the hike back to the rim. That goal is over ten miles distant and is best hiked over two days, so give yourself a break. The valley of Deer Creek, the lush vegetation of its riparian zone, its unique spring-feed source, the calm, crystal-clear waters of its ever-flowing stream, and its wonderous narrows accented by an equally wonderous waterfall, all make this an ideal spot for such a day of relaxation and sightseeing.
Let’s keep those leg muscles stretched with some exploratory hiking. First, I would suggest a trip through Deer Creek Narrows to the stream’s confluence with the Colorado River and a view of Deer Creek Falls. It is not much more than a mile round-trip to the river and back. Return to the ford and trail junction at mile 15.62 from yesterday (Map 2D.1.4). Continue downstream and into the confines of the shapely narrows where Deer Creek was forced to cut a new channel through the Tapeats Sandstone when a huge landslide blocked the original valley and its stream course long ago (Figure 2D.1.39). The narrowness of the channel has been determined by the resistance of the sandstone and the stream’s youth (Figure 2D.1.39a); its sinuosity is probably a result of the stream seeking a path of least resistance along joints in the sandstone as it cut downward (Figure 2D.1.39b). The trail to the river clings to a ledge high above the twisted gorge where weaker mudstones have weathered away, and in some areas, layers of sandstone overhang the trail. Be sure to examine bedding surfaces along this stretch of trail for an abundance of sedimentary structures. Figure 2D.1.40 shows two types of sole markings (structures preserved on the lower surface of a bed). In Figure 2D.1.40a, beautiful worm burrows sculpted from a layer that has fallen away were backfilled with sand from the next layer above; while in Figure 2D.1.40b, load casts formed when heavy sand pressed down on soft mud creating the bulbous, pillow-like features.
Figure 2D.1.39. The Deer Creek Narrows formed when a huge landslide blocked the valley of Deer Creek long ago, forcing the stream to cut a new path through Tapeats Sandstone (A); the narrowness of the stream channel and its sinuosity were controlled by the resistant, yet well-jointed sandstone and the youthfulness of its passage down through the rock (B).
Figure 2D.1.40. The trail through Deer Creek Narrows offers abundant opportunities to see sedimentary structures preserved in the Tapeats Sandstone; (A) shows worm borrows sculpted from a layer that has fallen away were backfilled with sand from the next layer above, while (B) displays load casts formed when heavy sand pressed down on soft mud (now fallen away) creating bulbous, pillow-like features on the underside of the sandstone layer.
Not far beyond the overhang, the trail emerges from the gorge, opening onto great views up and down river along the inner gorge of the Colorado River. The river’s confluence with Deer Creek lies directly below, its beaches often bedecked with a few rafts (Figure 2D.1.41); this is a popular stop for river runners. Look upriver, note the narrowness of the inner gorge, the narrowest section in all of the Grand Canyon, its shaped linked to its recent formation when the original river channel was blocked by one of the early Surprise Valley landslides, forcing the Colorado to carve a new channel further to the south. Look to the opposite side of the river and follow the prominent Tapeats Sandstone cliff upriver. The thick layer of horizontally bedded sandstones quickly pinches out against a protruding hump of Vishnu Schist and Zoroaster Granite; this is the downriver end of the “island in a Cambrian sea” discussed on yesterday’s hike over from Tapeats Creek. One can easily observe that while the Tapeats abruptly ends, the mudstone slopes of the Bright Angel Shale sail across the top of the protruding crystalline basement rocks, indicating that a significant rise is sea level was required to finally inundate and bury the “island.” Almost directly across the river from the confluence with Deer Creek, a vertical wall of crystalline basement rock appears to be injected up into the Tapeats Sandstone; rather, this knob of resistant rock probably formed a “seastack” adjacent to the larger “island” as the Cambrian ocean rose over both.
Figure 2D.1.41. A fantastic, geology-filled, upcanyon vista greets you as you emerge from the Deer Creek Narrows directly above the stream’s confluence with the Colorado River.
The trail now bends to the right and quickly descends to river level across layers of Tapeats Sandstone; look for a profusion of ripple marks, flute casts, and other sedimentary structures on slabs of rock found at trailside. To the right-hand side of the trail, a chaotic jumble of yellowish-gray limestone rubble provides ample evidence of the huge landslide that recently choked the lower end of the Deer Creek drainage. Be sure to follow the tight switchbacks through brown Tapeats outcrops, don’t veer to the right onto any of several trails heading across the rubble-strewn slopes. Green patches of vegetation on the rubbly slopes indicate seeping springs, suggesting that some groundwater still flows along the former, now buried, valley’s hydraulic gradient. At the base of these switchbacks, the trail temporarily crosses onto landslide debris, then creeps through a narrow slot along a weathered out joint in a 10-foot-thick band of sandstone. Follow the trail along a sandstone ledge past several groundwater seeps and descend more switchbacks; you soon find yourself on outcrops of late Proterozoic Zoroaster granite, indicating that you are now below the Great Unconformity (Figure 2D.1.42). The rush of nearby Deer Creek Falls will likely capture your attention, but when you return this way, take the time to examine these granitic outcrops; this is the only chance you’ll get to observe crystalline basement rock up close on this trip into the Grand Canyon. Much of the Zoroaster forms pegmatite dikes that intrude along foliation in slightly older metamorphic rocks such as the Vishnu Schist. No Vishnu is exposed here, but the Zoroaster Granite displays fine examples of coarsely crystalline, pink orthoclase feldspar, clear quartz, black hornblende, and silvery muscovite mica.
Figure 2D.1.42. An outcrop of Zoroaster Granite near Deer Creek Falls, the coarsely crystalline texture of this beautiful pegmatitic granite comprised of pink orthoclase feldspar, clear quartz, black hornblende, and silvery muscovite mica.
Any one of a maze of trails leads you to the beach at the confluence, but once there, a quick jog to your left brings you to the base of Deer Creek Falls (Figure 2D.1.43). The falls pour from a notch cut into a resistant bed of the Tapeats Sandstone and plunge a spectacular 120 feet into a large, deep, blue-green pool; despite the chill, the falls and pool are a popular swimming hole for hikers and rafters alike. Nearly all tributary streams have cut channels to the level of the Colorado River, keeping pace with the downcutting of the Colorado River, their local base level. However, because of the recent shift in the position of lower Deer Creek due to blockage of the old valley by an immense landslide, the youthful channel of Deer Creek has not yet cut to base level, thus forming the beautiful Deer Creek Waterfall at its confluence with the Colorado. While you gaze at the falls and listen to its roaring splash, take time to contemplate the Great Unconformity which is so nicely exposed in the rock wall behind and to the sides of the cascading water (Figure 2D.1.43). About 30 feet below the lip of the falls, horizontally deposited beds of Tapeats Sandstone give way to tannish crystalline granite. The granite is readily identified by its lack of bedding. Here, the Great Unconformity consists of 545 million-year-old sandstones resting on 1.75 billion-year-old granite, an erosion surface known as a nonconformity (undeformed sedimentary rock overlying crystalline basement) representing a gap in time of roughly 1200 million years.
Figure 2D.1.43. Lustrous Deer Creek Falls pours from a notch carved in Tapeats Sandstone high above its nearby confluence with the Colorado River, evidence of the youthfulness of lower Deer Creek valley; behind the falls, the Great Unconformity lies exposed, displaying some of the Grand Canyon region’s ancient history.
Once you have gazed, listened, and perhaps taken a cool plunge in the pool below the falls, make your way back to Deer Creek Campsite at 16.16 miles (Map 2D.1.4). After a lunch and a nap, you may wish to take a short hike upcanyon to visit the source of perennial Deer Creek at Deer Creek Spring; it is not much more than a mile round-trip. I suggest this as an early afternoon hike because I know that the spring is in deep shadow in the morning (the only time I have seen it). You will hike past the spring tomorrow, but it will be early, so an afternoon hike now may be worthwhile. From Deer Creek Campsite, walk up the valley on sandy terraces to a ford across the stream at 16.47 miles (Map 2D.1.4). Crossing to the east side, note how small the stream has become. Several small spring higher in the canyon feed this flow, but the main Deer Creek Spring which makes up the majority of the perennial flow of the creek flows from the canyon’s side wall below Surprise Valley which now lies almost due east of the ford. Climb rubbly slopes just north and to the left of the spring and stream, its flow supporting a ribbon of lush willows and other riparian vegetation; much of the rocky debris comes from recent rock falls cleaved from the soaring cliffs of Redwall Limestone just to the northeast. Once the trail reaches the first of several quick switchbacks near the base of Muav Limestone cliffs at 16.79 miles (Map 2D.1.4), the spring becomes visible on your right (southeast). The spring pours from a vertical joint in the Muav Limestone a few feet above its contact with the underlying Bright Angel Shale, a common location for springs in the Grand Canyon. Groundwater percolating downward through the sedimentary rocks above is focused along joints such as this one and forced to flow laterally until it finds an exit because the shales below are nearly impermeable. If you desire, a spur trail just after the second right-hand switchback (forth in all) can be taken over to the spring for a closer view; otherwise return to Deer Creek Campsite at your leisure.
While resting in a shady spot during the heat of the afternoon, don’t neglect that opportunity for a swim in Deer Creek; its gentle flow and multitude of small waterfalls and deep pools offer a delightful playground for the young and young at heart (Figure 2D.1.44). Make it an early evening, tomorrow you’ll want to get an sunrise start to beat the heat in Surprise Valley. I recommend packing out extra water for an overnight stay in a shady location on the Esplanade Platform (if you packed in and cached water all the better); it is a long, hot, ten-mile hike out of the canyon otherwise.
Figure 2D.1.44. The gorgeous water falls and pools of Deer Creek offer a paradise of swimming opportunities to entertain the weary hiker.
Day Six and Seven
I have combined day six and seven because much of the trek back to the North Rim is over trails you have already traveled on. Rise early, hit the trail, and return to Deer Creek Spring at 16.79 miles (Map 2D.1.4). From the spur trail to the spring, continue climbing on the main trail toward the left (north) over rubble-strewn slopes toward a gap in the Muav Limestone cliffs. This section of trail is quite rough, but backward views into Deer Creek provide a delight of variegated color and contrasting landscapes. A major right-hand switchback among large boulders from a recent rockfall allows you to cut back to the southeast above the Muav cliffs. Here, you cross onto a slope of gray to purplish gray dolostones; this is something new and a rare Grand Canyon sight! The rocks you tread as you angle up this slope comprise the Devonian Temple Butte Formation (Figure 2D.1.45). Since the Muav Limestone is Middle Cambrian in age, you have also passed a contact, a major erosion surface in this case, separating two undeformed layers of sedimentary rock; geologists call this type of unconformable contact a disconformity. The Temple Butte Formation forms a continuous layer here in the western Grand Canyon where a shallow ocean continuously covered the passive continental margin in the area west and south of the Grand Canyon, but further to the east, where most Grand Canyon trails are found, the formation occurs in discontinuous patches, filling coastal estuaries and tidal channel systems dissected into the Muav Limestone that where only temporarily flooded during marine transgression and subsequently eroded during regression. Eventually, a major marine transgression in the Mississippian deposited the Redwall Limestone, preserving what was left of the Temple Butte, a wedge-like body of rock thinning to isolated fingers toward the east.
Figure 2D.1.45. Sloping layers of the Temple Butte Formation sandwiched between cliffs of Muav Limestone below and Redwall Limestone above, as viewed near mile 16.85 on the Deer Creek Trail.
At 16.96 miles (Map 2D.1.4), you reach a spur trail on the right that takes you to an overlook of Deer Creek Spring and a last look at Deer Creek valley beyond. Across the broad expanse of the valet, huge mounds of landslide-generated rubble seem to fade into the distance giving you some perspective on the size of the Deer Creek slide mass. Afterward, the trail curves quickly to the east (left) and ascends the north slope of a long, narrow drainage coming down from Surprise Valley. Shortly, the Temple Butte Formation is replaced by a recently deposited talus cone, and then you cross the dry wash three times in rapid succession. Once on the right-hand (south) slope of the wash, you begin traversing through ancient landslide debris comprised mostly of the twisted and broken wreckage of the Redwall Limestone. Good exposures of the chaotic mix of landslide debris are preserved below the intact cliffs of Redwall Limestone to the north (left). The trail now climbs steadily along the drainage toward a low pass into Surprise Valley. It is a relatively easy route to follow and generally well-marked by cairns, although be weary of the occasional stretch that drops into the dry gravelly bed of the wash, the exits from these brief sections can be difficult pick out. This portion of the Deer Creek Trail is uniquely beautiful and affords a gentle pace as you gaze upon bounding cliffs of Redwall Limestone to the north and Cogswell Butte’s battlements to the south, and the lower and nearer slopes and valley floor dotted with tumbled boulders, shrubs of blackbrush and Mormon tea, hedgehog and barrel cacti, and yucca.
Near the pass into Surprise Valley, which you reach at 17.91 miles (Map 2D.1.2), the trail angles around a large slab of sandstone from the Supai Group, and then passes a low ridge on the right (south) formed of northeastward-dipping layers of red-brown Supai Group rocks. These layers seem to be draped onto gray Redwall Limestone exposed in the lower flanks of Cogswell Butte lying to the right (south) and have been displaced more than 700 vertical feet from the original location on the rim of the Esplanade Platform, now visible to the northeast. Figure 2D.1.46 offers a backward glance at these Supai rocks plastered onto the lower slopes of Cogswell Butte. From here to the trail’s unsigned junction with a spur trail heading toward Tapeats Creek at 18.13 miles (Map 2D.1.2), the trail crosses beds of Supai Group gradually tilted more to the north and you begin to realize that you are standing more or less on the top of an incredibly massive Toreva-style landslide block as much as 800 feet thick that rotated outward and down slope to fill the floor of Surprise Valley. The triple-tiered humps of Redwall Limestone that you can see closer to the valley’s northern headwall, must be a younger and smaller mass-wasting event (although still quite impressive). Turn left and upslope at the trail junction; the trail gently undulates over slope wash, then crosses a large dry wash, the head of Bonita Creek. Shortly, after climbing from the wash on a west-facing slope, the Deer Creek Trail ends as it reaches the junction with the Thunder River Trail heading toward Tapeats Creek at 18.60 miles (mile 7.10 coming in on day two) (Map 2D.1.2). Congratulations, you have closed the Thunder River-Deer Creek Loop, now only the stem of the lollipop remains.
Figure 2D.1.46. Supai Group rocks, displace from the rim of the Eslanade Platform by more than 700 vertical feet, lie draped onto the Redwall Limestone forming the lower slopes of Cogswell Butte on the outer (southern) edge of Surprise Valley).
Turn left and upslope, then continue your climb through the jumbled fragments of landslide debris you passed on the way in to Surprise Valley back on day two of your adventure. Once you reach the Esplanade Platform, I would look for a shady spot to rest during the heat of the afternoon hours; you can continue hiking the Esplanade in the early evening to make a few more miles. When the shadows lengthen, and you feel so inclined, a slickrock platform makes a perfect place to roll out your sleeping pad and bag. If you’re lucky, you’ll have planned your trek during a full moon, watching it soar up and over Bridger’s Knoll is a sight to sooth the sole of any Grand Canyon hiker (Figure 2D.1.47). Tomorrow, rise early once again, and complete your trip with just a few miles (and a few rock units) back to the trailhead and your waiting vehicle.
Figure 2D.1.47. A marvelous moonrise over Bridgers Knoll may well capture the essence of the Esplanade.
Optional Hiking Trail Maps
Map 2D.1.1. Shaded-relief map of the southeast quarter of the Tapeats Amphitheater, AZ 7.5 minute quadrangle.
Map 2D.1.2. Shaded-relief map of the southwest quarter of the Tapeats Amphitheater, AZ 7.5 minute quadrangle.
Map 2D.1.3. Shaded-relief map of the northeast quarter of the Powell Plateau, AZ 7.5 minute quadrangle.
Map 2D.1.4. Shaded-relief map of the southeast quarter of the Fishtail Mesa, AZ 7.5 minute quadrangle.