**Haas, P. 1, Gielstra, D.1, & Cerveny, N.V. 2** 1 Prescott College 2 Mesa Community College ## **Welcome to Grand Canyon National Park!** Established as a national park in 1919, the park exhibits unparalleled beauty in landscape and a depth of cultural heritage. This field trip explores the geodiversity of five sites along the South Bass Canyon and Boucher Trails found in the subcanyons within the park. In this virtual field trip you will experience a variety of geology that help define the geodiversity of desert canyon environments and discover the unique processes and features that make each canyon special. **Figure 1. View from Rim Trail (South Rim) near Trailview Overlook, Grand Canyon, Arizona, USA (Luyken, 2012).**

## Land Acknowledgment Grand Canyon National Park encompasses the ancestral lands of at least 11 tribes, who have called this area home since time immemorial. These indigenous groups were displaced and excluded from the area to make way for the creation of the park. Our photos and data were taken on the lands of these tribes, which include the Havasupai Tribe, Hopi Tribe, Hualapai Tribe, Kaibab Band of Paiute Indians, Las Vegas Band of Paiute Indians, Moapa Band of Paiute Indians, Navajo Nation, Paiute Indian Tribe of Utah, San Juan Southern Paiute Tribe, The Pueblo of Zuni, and the Yavapai-Apache Nation. ## Introduction A brief introduction to the South Bass Trail introduces us to the geographic and geologic setting which makes up a portion of the 50 miles of developed trail. Many of the trails within the Grand Canyon, including Bass’, were originally Indigenous peoples’ routes which Bass tailored to his own needs for mining and tourism and is an example of settler colonialism. South Bass Canyon is within the ancestral lands of Havasupai, Hualapai, and Hopi peoples (Grand Canyon Trust, n.d., Robison, 2021). **Figure 2. South Bass Canyon Trail’s 12.6 km trail with a difference of 1,386 m in elevation from the trailhead near the rim to the river (Grand Canyon Conservancy, n.d.).**

**Figure 3. Traditional tribal locations within the Grand Canyon area pre-colonial settlement adapted from Robison (2021, p.108)**

The area is named after William Bass, who used indigenous routes used by the Cohonina, who are thought to be ancestors of the Yuman, Hualapai, and Havasupai peoples. These paths were used to develop mining and tourism, which are considered important to the area’s geoheritage purposes. Bass is one of the first pioneers who settled at the Grand Canyon, and these authors could not find an original indigenous name attached to this site in the literature explored, so further research is needed to re-indigenize this place (McGill et al., 2021). ## Geodiversity Geodiversity describes the various rocks, minerals, soil, and fossils that are found on the landscape as well as describes the processes that form those patterns. In order to explore the differences between subcanyons, we have employed the Brilha (2016) geodiversity index to measure the geodiversity of individual subcanyons along the South Bass Trail and Boucher Trail in Grand Canyon National Park, Arizona. Table 1. Criteria, indicators, and parameters for scientific value to perform a quantitative assessment to comprehend the differences between the sites (Brilha, 2016).

Table 2. Weights used for the different criteria in the scientific assessment of the site (Brilha, 2016).

The inventory is important to help site managers to assess and conserve site features. Specifically, we evaluate the scientific and education value of these subcanyons of the sites. A major adjustment to the Brilha geodiversity index for this study includes incorporation of geomorphological diversity. The resultant scores highlight the differences between these glaciers and why those variations occur within this geomorphic setting. We will first explore South Bass Canyon, which is located on the South Rim of the Grand Canyon, west of the park’s main visitor area. South Bass Canyon can be followed from rim to river in a 4396 ft (1340 m) descent via the 7.5 mile (12.1 km) South Bass Trail. The canyon is situated in a northeast (mouth) to southwest (head) direction. The 360 degree view of the area was taken from a northwest facing slope, east and slightly above the center of the drainage, where water flows across land using natural channels. This field trip follows the trail down from the South Bass Canyon down to the Lava Falls and Ross Wheeler Beach. The geodiversity ranking and discussion will be used to explore each of these sites where 360 degree photographs were collected to create the photo spheres used to create the virtual reality sites for the field trip. **Figure 4. Locations for each of the sites where resources were collected and a geodiversity assessment was performed.**

## **Highest Ranking Sites: Lava (Bass) Beach and Lava Falls** The highest ranking sites for geodiversity both found at the location and found within the scene of the 360 photo sphere are Lava Beach and Lava Falls sections, which are unique because the sites can be accessed by both hiking and boating (Photography by Phoenix Haas, 2022). [Enter VR Lava Beach](/scenes/lava-beach-grand-canyon-national-park-arizona) [Enter VR Lava Falls](/scenes/lava-falls-grand-canyon-national-park-arizona) **Figure 5. Lava field sites in close proximity to the Colorado River**

The area is more hazardous to access with three reported deaths (NPS, n.d.). A 200 ft pouroff drainage can be seen in the background, and this feature is perhaps part of the Royal Arch area. The geology of the area contains layers, dikes, and sills. Sedimentary rock layers are also found at this location in the fluvial floodplain and contain river sand, and a scour zone. Within the inner canyon Zoroaster granite and Vishnu schist are dominant with mica schists. These rocks are approximately 2 billion years old, and are some of the oldest rocks at this site. The rocks where the author took the photograph shows volcanic sea-floor extrusions. Kaibab Limestone is found in the area visible in the back, upper canyon and some of the youngest rocks in the Grand Canyon. Below these layers the Toroweap Formation is visible as are: Coconino Sandstone, Hermit Shale, and Supai group, Tempe Butte, Muav, and Bright Angel Shale positioned above the inner gorge. **Figure 6. Geologic units, faults, and folds associated with each site.**

Characteristic erosional landforms include cliff and bench topography, ground water gully of overland flow and stream piracy, and headwall erosion. The rocks at the site create drainage-diversions and erosional gradients with the overflow moving large cobble and boulders that when distributed in the river create rapids in that part of the canyon and influence water movement via flow and eddies. The beach extends upstream along the shoreline of the Colorado River; however the route tapers to and pinches out until no beach is left and ends at the canyon interface. Using the Brilha Geodiversity Index (2016), the Ross Wheeler Beach area ranked first in the SV with a weighted value of 64/100, and first in EV with a score of 55/100. Lava Falls ranked second highest in SV with a weighted value of 58/100, and is ranked higher in part for its role as a USGS benchmark geology and presence and second highest in EV with a weighted score of 54/100. **Figure 7. Location of Lava Falls, Lava Beach, and Ross Wheeler Beach in proximity to the Colorado River.**

## **Third Highest Ranked Site: South Bass Canyon** ### **Geodiversity of South Bass Canyon** The elevation at this site is approximately 5400 ft / 1646 m in elevation. The area reflects differential weathering, and this process forms what is known as cliff and bench topography. The colors of these rock units are tied to the minerals and elements that form them. Higher elevation views of the canyon are made up of the Supai Group. The Supai Group are redwall limestone sedimentary rocks that are high in iron. The Supai layer consists of four formations, which are from the top the Esplande (youngest layer) Wescogame (older) Manachaka (even older), and the Watahomigi (oldest) (McKee, 1975) . The group was deposited from the Pennsylvanian to early Permian periods, as an ancient ocean receded and advanced several times, leaving behind sand, mud, and fossils, which compressed to create sandstone, mudstone, and limestone. The group was named after Supai, the capital of the Havasupai Reservation, which is located within the Grand Canyon. The word Havasupai, meaning “People (Pai) of the Blue Green Water (Havasu)”, but the name for the group was shortened by settlers to Supai, which in itself has no meaning in the Havasupai language. **Figure 8. South Bass Canyon topography and terrain.**

South and North Bass Canyons are found on opposite sides of the river. South and North Bass Canyon are situated in close proximity with South Bass Canyon along a normal, high angle fault near the Muav Fault system. A high angle fault means that the dip is greater than 45 degrees, with the Muav formation being a thick, “cliff-forming” unit of the Tonto Group (Snelling, 2022). Using the Brilha Geodiversity Index (2016), the five sites were ranked based on scientific value (SV) and educational value (EV). Bass Canyon ranked third in SV with a weighted value of 49/100, and fourth in EV with a score of 51/100. [Enter VR South Bass Canyon](/scenes/south-bass-canyon) ### **Botany of South Bass Canyon** Vascular plants found at this site include Nolina bigelovii (beargrass), and this species is found in and around the lower Permian Esplande sandstone but the Grand Canyon is the northern margin for this species’ range (Tillotson & McKee, 1936). *Quercus wilcoxii* (Wilcox oak, canyon oak) is found in this part of the canyon in drainages or drainage swales as these are moist microhabitat, thought these areas are exposed and more dry (Tillotson & McKee, 1936).The shade provided by these larger species reduce the harmful effects of a high light environment and help young plants establish and grow, and these types of plants are known as “nurse plants''. *Q. wilcoxii* individuals on the higher plateau show flagging, or wind-pruning, signs that the trees have been shaped by high winds moving through the environment in a dominant direction. The stress changes the physical structure and shows how the physical environment influences the biota on the landscape. *Philadelphus argenteus* (mock orange) is an upper elevation shrub that prefers dry, rocky places at the south rim,and other species include Amelanohler goldmani W. (serviceberry) and *Frasera utahensis* (deers ears) found around the predominant geology of the Tonto Group, Upper Bass Canyon. Fun Fact!: The coating of some of these rocks in this area is often assumed to be chemical precipitate, but the coating is really oxalate calcium patina created by lichen that encrusts the rock. Lichen presence creates an oxalate coating and the patina of bioprotection for the rock! ### **Traditional Indigenous Uses of Plants** There are 3 species of Ephedra commonly found in the Canyon. *Ephedra viridis* (green ephedra), also known as Mormon Tea, has been used by Indigenous tribes as well as settlers as an energizing tea. Indigenous peoples use the plant for flour, as a dye, an antiseptic, and for many other medicinal purposes. ## **Fourth Highest Ranked Site: Boucher Creek** **Fun Fact:** Boucher is pronounced “Boo-shay”! The Boucher Creek section has steep trails and is remote with about 2 days of hiking to access at about 2400 feet/732 m in elevation (NPS, n.d.). The site is unique in that there is a permanent water source and supports more diverse vegetation. Rocks falls are present as are smaller cobbles and pebbles that are moved along gravity-fed drainages. **Figure 9. Boucher Creek location topography and terrain in proximity to the Colorado River.**

These drainages create issues associated with water erosion and /water flow, which is visible in the 360 degree photo sphere as chewed through old deposits to the right of the scene if looking up into the canyon. Vegetation sizes and positions sort based on available site resources and positions to one another, but with lower platforms being more disturbed and containing smaller life forms of vegetation. At the higher plateaus flagging patterns in trees found at the site indicate high wind movement that the canyon funnels in a dominant direction (Photograph taken by Phoenix Haas, 2022). **Figure 10. Boucher location with shadows falling across the canyon.**

Using the Brilha Geodiversity Index (2016), the Boucher Creek area ranked fourth in the SV with a weighted value of 47.5/100, and first in EV with a score of 52.5/100 respectively. [Enter VR Boucher Site](/scenes/boucher-site-grand-canyon-national-park) ## **Lowest Ranking Site: Ross Wheeler Beach** Near the site of South Bass Canyon, Ross Wheeler Beach is found at a higher elevation than the water line because the boat was placed in that position and chained to the location (Photograph taken by Phoenix Haas, 2022). For education value, consideration of cultural components include the presence of the boat found on Ross Wheeler Beach. Abandoned by Russell and Tadge in 1915, the Ross Wheeler was constructed by Bert Loper. Mr. Loper earned the reputation as the “grand old man of Colorado River runners” (NPS, n.d.). **Figure 11. The Ross Wheeler Beach at the bottom of South Bass Canyon in proximity to the boat.** ![](https://strapi.geoepic.app/uploads/small_ross_wheeler_area_5d6fa316f6.jpg) Using the Brilha Geodiversity Index (2016), the Ross Wheeler Beach area ranked the lowest with a SV with a weighted value of 45.5/100, and is ranked slightly higher higher in part in EV with a weighted score of 50.5/100 because of the cultural and human history found at the site. [Enter VR Ross Wheeler Beach](/scenes/bass-beach) ## **GLOSSARY** **Cliff and Bench Topography** A geomorphic expression of rock layers in which some layers are more resistant to the forces of weathering (ex.sandstone and limestone layers) as compared to some that are less resistant (ex.shale). The difference creates a stair step effect in the rock’s morphology. **Differential Weathering Rocks** that are hard are more resistant to the weathering process that those rocks that are less resistant. **Drainage** Water movement across land using natural channels. **Geology** The study of the earth through rocks, including geologic features, geologic time for history, formations, and processes. **Geodiversity** The various rocks, minerals, soil, and fossils that are found on the landscape as well as describes the processes that form those patterns. **High Angle Fault** A fault that has a dip that is greater than 45 degrees. **Oxalate Coating** A type organic ester found in plants that can bind to minerals. When bound to calcium the coating becomes as hard a hard rind for rocks. ## **REFERENCES** Brilha, J. (2016). Inventory and Quantitative Assessment of Geosites and Geodiversity Sites: A Review. Geoheritage, 8:119–134. DOI 10.1007/s12371-014-0139-3 Gerke, S.B. (n.d.). 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