# Field Trip: Periglacial and Glacial Features of Preston Park Gielstra, D., Butler, D.R., Cerveny, N.V., & Gielstra, J. # **Welcome to Preston Park, Glacier National Park, U.S.A!** “*...you will find yourself in the midst of what you are sure to say is the best care-killing scenery on the continent – beautiful lakes derived straight from glaciers, lofty mountains steeped in lovely nemophila-blue skies and clad with forests and glaciers, mossy ferny waterfalls in their hollows, nameless and numberless, and meadowy gardens abounding in the best of everything.*” -John Muir Established in 1910 by President William Taft, Glacier National Park showcases the stunning beauty of the alpine environment, featuring rugged terrain sculpted by glaciers from the Pleistocene (approximately 2.6 million to 11,700 years ago) and the Little Ice Age (approximately 1300 to 1850 AD). The park has subalpine and alpine forests, glacial lakes and streams, wildflower meadows, a diverse assortment of wildlife and physical features, and a rich cultural heritage. This field trip takes you through the glacial and periglacial features of Preston Park, Glacier National Park, Montana, U.S.A. Early advocates of the park, captivated by the glacially carved landscapes dubbed it the “Crown of the Continent.” The park's scenery and expansive viewsheds present a variety of perceptible geomorphic features and processes that allow for the exploration of alpine glacial environments and the unique processes that create them. ## **Land Acknowledgment** Before beginning the field trip, the valuable cultural heritage of this region is shaped by the Native communities that still reside there. We acknowledge that the land on which our data were collected in Glacier National Park, Montana is the home of the Blackfeet and Kootenai people. We take this opportunity to thank the original caretakers of this land.

Photo of Wild Goose Island at dusk. The view is influenced by smoke from the Hay Creek Fire in July 2021 (Photo Dianna Gielstra) [Enter VR of the Preston Park, Siyeh Trail vantage point just below Siyeh Pass](https://geoepic.app/scenes/preston-park-glacier-national-park-montana). Preston Park is located at latitude 48.7014° N and longitude 113.6695° W. Preston Park is located in the Lewis Range and in the lower southeastern portion of Glacier National Park boundary on the Siyeh Trail just below the Siyeh Pass (Preston Park map). Viewing the Continental Divide as a natural break between western and eastern Glacier National Park, the Lewis Range is on the east side of the divide. Accessing the trail from the Going to the Sun Road at the Loop parking lot, hikers pass lower subalpine forests that break into subalpine meadows once the terrain contains alpine features and associated flora and fauna. Along the Preston Park Trail, with the ascent in elevation, lower elevation subalpine forests, subalpine meadows, and ribbon forests are featured, extending above the alpine treeline. The higher elevation areas above the treeline are where this field trip takes place, as the vegetative growth forms are sufficiently low to provide views down the valley that leave glacial geomorphology features in clear view. From this vantage point, it is possible to identify glacial and periglacial features of interest to characterize and assess this site.

Map of the Preston Park site location for glacial and periglacial site assessment. ## **Why do we care?** As global deglaciation accelerates, environmental issues associated with this process may present and impact human communities (IPCC, 2018). Site assessment is a way that scientists identify and observe these glacial and periglacial features over time to systematically observe, monitor, and measuring changes in these physical forms. Through field notes and field surveys,information can be collected for use in disciplines like remote sensing and Geographic Information Systems to visualize and analyze the processes that influence and shape these landscapes. Evidence of change ( examples of glacial advance and retreat, erosion, ice and rock falls, frost heaving, avalanches, and sediment deposition to name a few) is knowledge that may be used to predict future changes and risks associated with natural disasters (landslides or glacial lake outburst floods). **Let’s practice field site assessment skills!** Developing and refining field assessment skills honed in geoscience work can be used to inform and manage adaptation strategies for human communities. These skills are ubiquitous in guiding infrastructure development, resource allocation, and disaster preparedness to mitigate the risks associated with global deglaciation. **Imagine** you have traveled to Glacier National Park as part of your field training to work for the United States Geological Survey (USGS). This training to refine your ability to note specific glacial and periglacial features of interest associated with processes like frost heaving, solifluction, and cryoturbation. Please use the included field report sheet to assess the site, describe the glacial geomorphic patterns and processes, and score the features for their risks associated with natural hazards. Before entering the virtual landscape, it is helpful to have background knowledge of the site, it’s geology, and the glacial geomorphology.

Location of Preston Park, Glacier National Park, U.S.A within its geomorphic setting. Image captured from Google Earth. The geology in the Preston Park area there are sedimentary **rocks** of the Belt Supergroup, which are ancient sedimentary layers that are 1.6 to 1.4 Ga with the Siyeh Formation deposited and lithified into limestone and dolomite 1.1 Ga ago. Sedimentary rocks are made up of bits and pieces of pre-existing rock that is weathered and eroded and then lithified into a unique layer. There is a notable magmatic diorite sill of igneous rock found that was formed in the Late Proterozoic by a deposited submarine lava flow. The sill is the dark layer of lava that intrudes between layers of limestone and is approximately 100 feet thick (30m). The presence of white metamorphic marble was caused by the heat of the magmatic intrusion recrystallizing the Siyeh limestone (National Park Service, n.d.). Please note the color designations of the layers as these are perceptible in the Google Earth image above (Figure from National Park Service).

A **glacier** is a moving body of ice that formed on land from snow accumulation that transforms into dense glacial ice over a number of years. The transformation of snow into ice in the relatively warmer environment of Montana involves ice minerals at a pressure melting point (Martini et al, 2001). Glaciers build in stages: fresh snow with more surface area and crystals, old snow that is more rounded and compacted, and firn. Firn, a German term, translates to “last year snow”. **Firn** crystals are more rounded, compacted, and denser. The glacier moves downslope because of its weight, which increases with annual layer accumulation of ice. Glaciers interact with the surrounding geology to create glacial geology and landforms.

Diagram of glacially formed features that are common in Glacier National Park by T.R. Alpha (Carrara, 1993) **Glacier Features of Preston Park:** Glacial features are directly formed by the glaciers and their influence on the landscape as they grow, move, and melt. Overall, these can be considered large, slow-moving masses of ice. **Cirque glaciers** are bowl-shaped depressions found high in the mountains where glaciers form. These glaciers are typically perched on the lip of these depressions. For instance, Piegan Glacier in Glacier National Park is an example of a cirque glacier that is found in Preston Park. These glaciers form when snow accumulates in a depression, which is often described as a “bowl,” and ice compacts in the basin for many years. These types of glaciers are significant because they can lead to rockfalls and icefalls as they have a smaller forefront, which are potential hazards in the area. A complement to Piegan Glacier is Sexton Glacier. While the field team does not have VR views of Piegan, you can explore the front views and back views of Sexton Glacier to explore cirque glacier environments. [Enter VR for the Sexton Glacier Front View](https://geoepic.app/scenes/sexton-glacier-front) [Enter VR for the Sexton Glacier Back View](https://geoepic.app/scenes/sexton-glacier-back) Mount Reynolds is a classic **horn**, which is a pointed, pyramid-like, mountain peak surrounded by walls of glacial cirques. This sharpened peak is formed by the erosion of glaciers from multiple sides that work away at the rock creating that distinctive pyramid shape. Horns are important indicators of past glacial activity and are visually striking, notable features in the landscape. An **arete** is a narrow ridge formed between two glaciers. These ridges are sharp and steep, created as glaciers erode the sides of a mountain. Aretes are prominent features in alpine environments and can indicate the direction of past glacial movement. They are also potential sites for rockfall hazards due to their steepness. The **U-shaped valleys** are valleys that are initially carved by rivers and streams with fluvial process, but then are scoured by glaciers changing the characteristic valley V-shape. It erodes the valley floor and sides creating a U-shape indicative of glacial process of a moving ice mass (Martini et al., 2001). The valley floors transform into broad, flat valley floors and steep walls, and are easy to see on a landscape for visual evidence of past glacial activity. **Periglacial Features:** **Periglacial features** are differentiated from glacial features in that these features are associated with cold, non-glacial environments. Freeze and thaw action is the process that is dominant in these environments. These features occur in areas adjacent to glaciers and in regions with **permafrost**, which is permanently frozen ground. **Frost-Shattering** occurs when water intrudes into cracks found in rocks. As the water freezes, it expands, causing the rocks to break apart. This is an important process contributes to the formation of **talus slopes**, which are piles of broken rock at the base of cliffs. Talus material accumulates creating rock debris found at the base of valley walls, cliffs or steep slopes through frost-shattering. **Avalanche boulder tongues** are similarto talus slopes but result from rockfalls and avalanches. These features are characteristic of areas in which there is active mass wasting, and this activity may result in significant hazard potential because of the potential for large amounts of rock debris to move downslope. **Frost heaving** is a process in which soil or rock is uplifted because of freeze and thaw action associated with water’s presence at the surface and subsurface of soils. This process can disrupt soils, leading to instability that may affect plant life. In these periglacial areas, this type of frost heaving can yield uneven ground surfaces and contribute to the movement of soil and rocks. **Cryoturbation** is a term that refers to the mixing of soils because of freeze-thaw cycles. This process creates sorted and unsorted **patterned ground**, defined as changes in frozen terrain that yield a change in orientation of particles that can create cracks, circles, and nets. Cryoturbation processes influence periglacial environments, affecting soil structure and plant distribution. **Solifluction** is the downslope flow of water-saturated soil, and the movement tends to be slow. Solifluction occurs when the ground is frozen but only the surface layer thaws, becoming saturated with water and slowly flowing down gradient. Solifluction can patterns in the form of lobes and terraces on slopes. Such indicators of movement may show the potential of destabilized terrain. [Enter the VR of Preston Park, Glacier National Park](https://geoepic.app/scenes/preston-park-glacier-national-park-montana) **Now perform the site assessment:** Understanding these features helps in assessing natural hazards such as rockfalls, icefalls, avalanches, and glacier retreat. Changes in snow cover and ice dynamics can impact the stability of these features, posing risks to the environment and human activities. Climate change can exacerbate these hazards by altering temperature and precipitation patterns, leading to increased frequency and intensity of hazardous events. Please work together to compare and contrast site features for their natural hazard potential. You will need a tablet or pen and paper. Study the Site Assessment Report Template Student Guide [Table 1](https://strapi.geoepic.app/uploads/Preston_Park_Table1_244a58090d.pdf). Discuss with one another in the group the environmental observations and field conditions that you have, and fill out Site Assessment Report Template [Table 2](https://strapi.geoepic.app/uploads/Preston_Park_Table2_ef30698878.pdf). Teachers, there is a Site Assessment Report Template Teachers Guide to assist your students [Table 3](https://strapi.geoepic.app/uploads/Preston_Park_Table3_62fbf5d29b.pdf). Once you fill out the report, please use Table 4 to determine hazard potential. Please have your team draft an Executive Summary (500-700 words) that compiles the information from the field notes and Table 4 to describe the site and articulate its hazard potential. Table 4. Natural Hazard Potential Metrics Table

Low

Minimal risk with rare occurrences of minor events

-Frost Heaving

-Cryoturbation

-Uneven ground surfaces

-Mixed soils with minimal impact on stability

Medium

Moderate risk with occasional events that can cause localized damage

-Rockfalls

-Icefalls

-Solifluction

-Talus slopes with potential for small rock movements

-Falling ice from cirque glaciers

-Slow, downslope soil movement affecting small areas

High

Significant risk with frequent or severe events that can cause widespread damage

-Avalanches

-Rock avalanches

-Glacier retreat impacts

-Avalanche boulder tongues with rapid debris flow

-Large-scale rock movements from steep slopes

-Increased rockfall and icefall due to melting glaciers

Submit the report and executive summary for review. **References:** Carrara, P. E. (1993). *Glaciers and glaciation in Glacier National Park, Montana* (No. 93-510). US Geological Survey. Butler, D.R. (1986). Snow-avalanche hazards in Glacier National Park, Montana: meteorologic and climatologic aspects. Physical Geography, 7(1): 72-87. Google Earth. (n.d.). Preston Park 3-D view. Martini, P.I., Brookfield, M.E., & Sadura, S. (2001). Principles of Glacial Geomorphology and Geology. Prentice Hall. National Park Service. (n.d.).Climate change-Glacier National Park.https://www.nps.gov/glac/learn/nature/climate-change.htm