Geology topics

C. Huggel

Publications and source records attributed to C. Huggel.

4 recordsLinked to original sources

USGS2021

A massive rock and ice avalanche caused the 2021 disaster at Chamoli, Indian Himalaya

On 7 Feb 2021, a catastrophic mass flow descended the Ronti Gad, Rishiganga, and Dhauliganga valleys in Chamoli, Uttarakhand, India, causing widespread devastation and severely damaging two hydropower projects. Over 200 people were killed or are missing. Our analysis of satellite imagery, seismic records, numerical model results, and eyewitness videos reveals that ~27x10 6 m 3 of rock and glacier ice collapsed from the steep north face of Ronti Peak. The rock and ice avalanche rapidly transformed into an extraordinarily large and mobile debris flow that transported boulders >20 m in diameter, and scoured the valley walls up to 220 m above the valley floor. The intersection of the hazard cascade with downvalley infrastructure resulted in a disaster, which highlights key questions about adequate monitoring and sustainable development in the Himalaya as well as other remote, high-mountain environments.

Chamoli↗

USGS2017

Precursory seismicity associated with frequent, large ice avalanches on Iliamna Volcano, Alaska, USA

Since 1994, at least six major (volume>106 m 3 ) ice and rock avalanches have occurred on Iliamna volcano, Alaska, USA. Each of the avalanches was preceded by up to 2 hours of seismicity believed to represent the initial stages of failure. Each seismic sequence begins with a series of repeating earthquakes thought to represent slip on an ice-rock interface, or between layers of ice. This stage is followed by a prolonged period of continuous ground-shaking that reflects constant slip accommodated by deformation at the glacier base. Finally the glacier fails in a large avalanche. Some of the events appear to have entrained large amounts of rock, while others comprise mostly snow and ice. Several avalanches initiated from the same source region, suggesting that this part of the volcano is particularly susceptible to failure, possibly due to the presence of nearby fumaroles. Although thermal conditions at the time of failure are not well constrained, it is likely that geothermal energy causes melting at the glacier base, promoting slip and culminating in failure. The frequent nature and predictable failure sequence of Iliamna avalanches makes the volcano an excellent laboratory for the study of ice avalanches. The prolonged nature of the seismic signal suggests that warning may one day be given for similar events occurring in populated regions.

Alaska↗

USGS2011

Recent extreme avalanches: Triggered by climate change?

On 25 September 2008, seismo meters operated by the Alaska Volcano Observatory (AVO) registered strong ground shaking. On the basis of previous experience with such large seismic signals, AVO personnel were able to rapidly identify the seismic event as an avalanche. Two days later, an AVO overflight of Iliamna volcano, near Alaska's Cook Inlet, confirmed that a massive chunk of glacial ice and rock had broken free from its position on the upper flanks of the volcano, generating a massive avalanche that could have buried an entire town had it occurred in a more populated area. Rapidly moving rock, ice, or debris avalanches, such as the one that occurred on Iliamna, can be highly destructive and deadly. Similar events have caused the deaths of hundreds to thousands of people [ Keefer and Larsen, 2007]. In general, avalanches that move more than 1 million cubic meters of material are rare. However, a remarkable series of large avalanches recently occurred in Alaska and the Caucasus, providing a new opportunity to better understand this type of hazard. All events initiated in steep mountain slopes, involved rock and significant amounts of ice, and traveled for 10–35 kilometers.

Eos, Transactions, American Geophysical Union↗

USGS2007

Monitoring and modeling ice-rock avalanches from ice-capped volcanoes: A case study of frequent large avalanches on Iliamna Volcano, Alaska

Iliamna is an andesitic stratovolcano of the Aleutian arc with regular gas and steam emissions and mantled by several large glaciers. Iliamna Volcano exhibits an unusual combination of frequent and large ice-rock avalanches in the order of 1 ?? 106??m3 to 3 ?? 107??m3 with recent return periods of 2-4??years. We have reconstructed an avalanche event record for the past 45??years that indicates Iliamna avalanches occur at higher frequency at a given magnitude than other mass failures in volcanic and alpine environments. Iliamna Volcano is thus an ideal site to study such mass failures and its relation to volcanic activity. In this study, we present different methods that fit into a concept of (1) long-term monitoring, (2) early warning, and (3) event documentation and analysis of ice-rock avalanches on ice-capped active volcanoes. Long-term monitoring methods include seismic signal analysis, and space-and airborne observations. Landsat and ASTER satellite data was used to study the extent of hydrothermally altered rocks and surface thermal anomalies at the summit region of Iliamna. Subpixel heat source calculation for the summit regions where avalanches initiate yielded temperatures of 307 to 613??K assuming heat source areas of 1000 to 25??m2, respectively, indicating strong convective heat flux processes. Such heat flow causes ice melting conditions and is thus likely to reduce the strength at the base of the glacier. We furthermore demonstrate typical seismic records of Iliamna avalanches with rarely observed precursory signals up to two hours prior to failure, and show how such signals could be used for a multi-stage avalanche warning system in the future. For event analysis and documentation, space- and airborne observations and seismic records in combination with SRTM and ASTER derived terrain data allowed us to reconstruct avalanche dynamics and to identify remarkably similar failure and propagation mechanisms of Iliamna avalanches for the past 45??years. Simple avalanche flow modeling was able to reasonably replicate Iliamna avalanches and can thus be applied for hazard assessments. Hazards at Iliamna Volcano are low due to its remote location; however, we emphasize the transfer potential of the methods presented here to other ice-capped volcanoes with much higher hazards such as those in the Cascades or the Andes. ?? 2007 Elsevier B.V. All rights reserved.

Journal of Volcanology and Geothermal Research↗