Abstract
Abstract. Glacier detachments are a rare, but hazardous, phenomenon of glacier instability, whereof only a handful have been documented to date. Common to all known cases is that many million cubic meters of ice detached from the bed of relatively low-angle valley glaciers and turned into long-runout mass flows. Recently, two such detachments were observed in the Petra Pervogo range in Tajikistan. Using a variety of satellite imagery, including Landsat 1–8, Sentinel-2, ASTER, TanDEM-X, WorldView, and Keyhole, we characterized these events and identified in total 17 mass flows involving glacier ice (detachments, ice, and rock-ice avalanches; rock avalanches falling on glaciers) that clustered in four different catchments between 1973 and 2019. The runout distances range from 2 to 19 km, and the largest detached glacier volume was 8.8×106 m3. A total of 11 out of 13 detachments, ice, or rock-ice avalanches occurred between July and September in years with mean annual air temperatures above the trend of the past 46 years. The relatively large number of locally clustered events indicates that the Petra Pervogo range has particularly favorable conditions for glacier instabilities. The images and geology of the region suggest that easily erodible lithologies are widespread. These soft lithologies may be also one reason for the high density of surging glaciers in the Petra Pervogo range and the wider Pamir region. We conclude that high temperatures, combined with soft, fine-grained sediments, may increase the likelihood of mass wasting events and appear to be critical factors facilitating the detachment of entire valley glaciers, whereas such events appear to be relatively robust against earthquakes for our study area. The observed recurrence of mass wasting events make the Petra Pervogo range a potential candidate to witness glacier detachments by field studies.
Highlights
Glacier detachments are extremely rare events, but the scientific understanding of these events is rapidly evolving
In this study we built an inventory of glacier detachments and ice and rock-ice avalanches which occurred in the western Petra Pervogo range in Tajikistan
The fact that multiple detachments occurred under very similar conditions allows for studying external driving factors which can trigger the detachment of a valley glacier
Summary
Glacier detachments are extremely rare events, but the scientific understanding of these events is rapidly evolving. They occur when large volumes of glacier ice detach from valley glaciers with relatively low surface slopes (10 to 20◦) and turn into highly mobile, ice-rich mass flows. The classes are distinguished by their starting mechanism and the involved material Both glacier detachments and ice avalanches mainly involve glacier ice, but ice avalanches are much more frequent and typically originate from steep (hanging) glaciers. Rock avalanches – with sometimes long runouts if they descend onto glaciers or snowcovered terrain – form a second class; the combination of the first two classes, or mass movements that involve both ice and rock (Evans and Delaney, 2015), is classified as icerock or rock-ice avalanches. The high mobility leads to much longer runout distances compared to pure rock avalanches
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
