Paraglacial Rockslope Stability, Grewingk, Alaska
Funding: German Research Foundation
Project duration: 2021-2024
Project Partners: University of Alaska, Ground Truth Trekking
Retreating glaciers precondition, prepare, and trigger rock slope instability. The site at Grewingk Glacier and Lake in Southcentral Alaska exhibits many hazard factors, including rapid glacier retreat, documented history of a deep-seated tsunamigenic failure, high and steep slopes, frequent minor failures, signs of active fracturing along the ridge, possible melting permafrost, and deep water. It is also a popular tourist destination, sometimes attracting hundreds of people on a busy summer day.
The aim of this project is to better understand interactions between the processes that can destabilize a rock mass. This means combining thorough characterization of the rock mass, careful interpretation of past documentary evidence and geological records, 3D numeric analysis of the failure type and processes involved, and ongoing monitoring of both deformation and of relevant environmental variables. Specifically, our objectives are to:
- Quantify the influence of glacier retreat on slope deformation and stability.
- Differentiate slope failure patterns over a range of spatial and temporal scales.
- Back-calculate the 1967 slope failure and combine the results with detailed site investigations to forward model potential future failure scenarios.
- Monitor slope deformation to assess future hazards.
- Study the relationship between failures at multiple scales, potentially ranging across seven orders of magnitude from ~10 m3 to 100 million m3.
- Document fractures and scarps that are re-activating after (centuries?) of inactivity.
The 1967 Landslide Scarp
This image shows the scarp of a ~3-million-cubic-meter slope failure in 1967 on Grewingk Ridge, which caused a tsunami that swept across the delta (next image) and into Kachemak Bay.