Logging Tasks
1. In your own words, define an escarpment.
2. What is likely to be causing the erosion at the Robert Service Way escarpment?
3. Can you spot any geohazard mitigation measures currently in place? What are they?
4. Please take a photo of yourself with the Robert Service Way escarpment in the background. You do not need to show your face. Alternatively, a photo of a personal item, such as your GPS or a piece of paper with your geocaching name and the date, with the Robert Service Way escarpment in the background is also acceptable.
Please send me this information through a Geocaching message and NOT in your log. Any logs containing the answers to my questions will be deleted.
Introduction
This EarthCache is intended to teach finders about geohazard mitigation methods. This EarthCache specifically focuses on the Robert Service Way escarpment, which is located within the city of Whitehorse along Robert Service Way.
Ground zero for this EarthCache is located at the Millennium Trail Nest along Robert Service Way. The Millennium Trail Nest is part of a public trail network accessed by a public road. It can be accessed from the south (from the Alaska Highway) or from the north (from downtown Whitehorse). There is parking for both smaller vehicles (such as cars) and larger vehicles (such as RVs), although parking may be more difficult to find during the tourist season (generally May to September).
Note that this EarthCache is only accessible when Robert Service Way is open. Over the past few years, Robert Service Way has been closed for weeks at a time during the spring while the escarpment is assessed, geohazard mitigation measures are put in place, and any necessary repairs are completed. There have often been landslides in the area.
The Robert Service Way Escarpment
Do you see that steep slope to the northwest? That’s the Robert Service Way escarpment. An escarpment is “a geographical feature that is characterized by a long cliff or a steep slope. These slopes are formed either by fault action or by erosion” [1]. In this case, the slope was formed by erosion. The steep slope results in an elevation difference between two relatively level areas: the Erik Nielsen Whitehorse International Airport above and Robert Service Way below.
Robert Service Way escarpment, taken October 24, 2025 [2]
What causes the erosion?
Although there are several potential causes for the erosion of the Robert Service Way escarpment, the City of Whitehorse believes that failures of the escarpment are typically driven by groundwater seepage. The groundwater flows quickly through the sand layer at the top of the escarpment but slowly through the silt layer below, so the groundwater will choose the path of least resistance and will reside in the space behind the escarpment face. seepage flows are highest during freshet, which is the period where seasonal snow and ice melt and influence river and groundwater systems. In Whitehorse, freshet generally takes place between the end of April and the end of June each year.
Generally, the process of slope failures of the escarpment looks like this:
- The escarpment face freezes during winter and traps seepage within the escarpment soils.
- Groundwater can build up behind the escarpment face throughout the winter, which saturates the soils.
- Water in the soil plus freezing can lead to ice lenses and frost fracturing of the soils.
- Definitions:
- Ice lenses: massive ice, millimetres to centimetres thick, forms as fine-grained soil freezes with excess pore water (water trapped in the space between soil grains). Due to many years of growth, ice lenses can grow to be metres thick in permafrost areas.
- Frost fracturing: the result of frost penetration into fine-grained soils that causes expansion and ice lenses. When the ground thaws, these fractures remain and can increase in size the following winter. Frost fracturing contributes to shallow mass movements (landslides) on the escarpment.
- As the soils thaw in the spring, they are saturated and lose their strength depending on the degree of saturation. Strength is reduced by ice lenses and frost fracturing as well.
- On steep slopes, these factors can allow the escarpment soils to fail with failure planes (sliding surface for a landslide) up to 5 m below ground surface. Sometimes failures occur because the near surface soils are thawed, and the subsurface soils are frozen [3].
Geohazard Mitigation Methods
Fortunately, the City of Whitehorse plays close attention to developments at the Robert Service Way escarpment. It retains several geotechnical and hydrogeological firms to assess the escarpment and to provide recommendations on geohazard mitigation.
Slope monitoring methods include:
- Visual inspections
- Targeted survey monitoring of critical slope areas
- Drone surveys
- A radar-based slope scanner
These monitoring methods provide information to support the implementation of geohazard mitigation methods.
Geohazard mitigation methods include:
- Public education
- Avoidance
- Monitoring
- Berms, walls, barriers, etc.
- Slope netting
- Soil anchors and shotcrete
- Slope angle relaxation [3]
Depending on the condition of the escarpment, different mitigation methods may be used. For example, if the possibility of landslides occurring is high, then Robert Service Way is partially or completely closed to vehicle and pedestrian traffic.
Lessons From This EarthCache
You should have learned:
- What an escarpment is
- What causes the erosion at the Robert Service Way escarpment
- Geohazard mitigation methods in place at the Robert Service Way escarpment
Logging Tasks (Again)
1. In your own words, define an escarpment.
2. What is likely to be causing the erosion at the Robert Service Way escarpment?
3. Can you spot any geohazard mitigation measures currently in place? What are they?
4. Please take a photo of yourself with the Robert Service Way escarpment in the background. You do not need to show your face. Alternatively, a photo of a personal item, such as your GPS or a piece of paper with your geocaching name and the date, with the Robert Service Way escarpment in the background is also acceptable.
Please send me this information through a Geocaching message and NOT in your log. Any logs containing the answers to my questions will be deleted.
A special thanks to AllThingsEarthCache and his series of YouTube videos that made it really easy to understand what a good Earthcache looks like.
References
[1] Bada, F. (2018). What Is An Escarpment? WorldAtlas. Accessed October 23, 2025 from https://www.worldatlas.com/articles/what-is-an-escarpment.html
[2] Taylor, M. (2025). Robert Service Way escarpment, taken October 24, 2025 [Photograph]. Millennium Trail Nest, Whitehorse, Yukon, Canada.
[3] City of Whitehorse (2023). Escarpment 2023 – FAQs and Glossary. Accessed October 23, 2025 from https://www.engagewhitehorse.ca/escarpment-2023/widgets/148348/faqs