Reconstructing the dynamics of the highly-similar May 2016 and June 2019 Iliamna Volcano, Alaska ice–rock avalanches from seismoacoustic data

Toney, Liam; Fee, David; Allstadt, Kate E.; Haney, M. M.; Matoza, Robin S.

doi:10.5194/esurf-2020-47

Cited by 4 publications

(9 citation statements)

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“…From our interpretation of the Corona satellite data there was either one more event between 1969 and 1974, or the event dated "1968" actually happened a few years later. The next large mass flow (listed as ice avalanche in Chen et al, 2020, and debris flow in Tong et al, 2018; we interpret at least a large debris content) happened in 2014. The source of the mass flow must have been in the upper part of the main Sedongpu Glacier or its headwall as both lateral moraines of the glacier were heavily eroded from the glacier side (Rapid-Eye satellite data of [2013][2014][2015].…”

Section: Events Before 2018mentioning

confidence: 61%

“…The Chinese seismic database registered two large "landslide" events on 22 October 2017: a M3.2 event at 06:20 (China standard time) about 16 km west of Sedongpu and a M4.0 event at 06:22 directly at Sedongpu. Chen et al (2020) and Tong et al (2018) confirm that at least the latter signal stems from the Gyala Peri ice-rock avalanche. Subsequent satellite images suggest that the avalanche must have changed the surface of Sedongpu Glacier drastically.…”

Section: Events Before 2018mentioning

confidence: 66%

“…Debris stripes oriented in the avalanche direction are visible in high-resolution satellite images (not shown). lage and large downstream areas and triggered hazard management and investigations of the causes (Tong et al, 2018;Liu et al, 2019;Chen et al, 2020). The largest of the mass flows stemmed from the detachment of a large, low-angle glacier in 2018.…”

Section: Amneymentioning

confidence: 99%

“…The eastern tributary glacier to Sedongpu Glacier also showed a surge-like lobe (Sentinel-2, Planet, GoogleEarth). Driven by the geomorphological changes in the basin, a series of debris flows, some involving ice and likely nourished from the large amounts of unconsolidated debris left behind by the ice-rock avalanche, occurred after 22 October 2017 and into 2018 (Tong et al, 2018;Chen et al, 2020). The two 18 November 2017 M5.2 and M6.9 Linzhi, Milin, and Nyingchi earthquakes, with epicentres only a few kilometres from Sedongpu, may have contributed to the triggering of the debris flows (Hu et al, 2019;Zhao et al, 2019).…”

Section: Events Before 2018mentioning

confidence: 99%

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Sudden large-volume detachments of low-angle mountain glaciers – more frequent than thought?

et al. 2021

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Abstract. The detachment of large parts of low-angle mountain glaciers resulting in massive ice–rock avalanches have so far been believed to be a unique type of event, made known to the global scientific community first for the 2002 Kolka Glacier detachment, Caucasus Mountains, and then for the 2016 collapses of two glaciers in the Aru range, Tibet. Since 2016, several so-far unrecognized low-angle glacier detachments have been recognized and described, and new ones have occurred. In the current contribution, we compile, compare, and discuss 20 actual or suspected large-volume detachments of low-angle mountain glaciers at 10 different sites in the Caucasus, the Pamirs, Tibet, Altai, the North American Cordillera, and the Southern Andes. Many of the detachments reached volumes in the order of 10–100 million m3. The similarities and differences between the presented cases indicate that glacier detachments often involve a coincidental combination of factors related to the lowering of basal friction, high or increasing driving stresses, concentration of shear stress, or low resistance to exceed stability thresholds. Particularly soft glacier beds seem to be a common condition among the observed events as they offer smooth contact areas between the glacier and the underlying substrate and are prone to till-strength weakening and eventually basal failure under high pore-water pressure. Partially or fully thawed glacier bed conditions and the presence of liquid water could thus play an important role in the detachments. Surface slopes of the detached glaciers range between around 10∘ and 20∘. This may be low enough to enable the development of thick and thus large-volume glaciers while also being steep enough to allow critical driving stresses to build up. We construct a simple slab model to estimate ranges of glacier slope and width above which a glacier may be able to detach when extensively losing basal resistance. From this model we estimate that all the detachments described in this study occurred due to a basal shear stress reduction of more than 50 %. Most of the ice–rock avalanches resulting from the detachments in this study have a particularly low angle of reach, down to around 5∘, likely due to their high ice content and connected liquefaction potential, the availability of soft basal slurries, and large amounts of basal water, as well as the smooth topographic setting typical for glacial valleys. Low-angle glacier detachments combine elements and likely also physical processes of glacier surges and ice break-offs from steep glaciers. The surge-like temporal evolution ahead of several detachments and their geographic proximity to other surge-type glaciers indicate the glacier detachments investigated can be interpreted as endmembers of the continuum of surge-like glacier instabilities. Though rare, glacier detachments appear to be more frequent than commonly thought and disclose, despite local differences in conditions and precursory evolutions, the fundamental and critical potential of low-angle soft glacier beds to fail catastrophically.

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Section: Events Before 2018mentioning

confidence: 61%

Section: Events Before 2018mentioning

confidence: 66%

Section: Amneymentioning

confidence: 99%

Section: Events Before 2018mentioning

confidence: 99%

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Sudden large-volume detachments of low-angle mountain glaciers – more frequent than thought?

et al. 2021

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“…-A number of ice-rock avalanches have occurred from different locations on Iliamna volcano, Alaska, the last of which is documented for June 2019 (Toney et al, 2020). Failure surfaces were typically on the order of 40°, and volumes reached 138 up to around 20 10 6 m 3 (Caplan-Auerbach and Huggel et al, 2007).…”

mentioning

confidence: 99%

Sudden large-volume detachments of low-angle mountain glaciers – more frequent than thought

Kaeaeb¹,

Jacquemart²,

Gilbert³

et al. 2020

Preprint

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Abstract. The detachment of large parts of low-angle mountain glaciers, resulting in massive ice-rock avalanches, have so far been believed to be a unique type of event, made known to the global scientific community first for the 2002 Kolka Glacier detachment, Caucasus Mountains, and then for the 2016 collapses of two glaciers in the Aru range, Tibet. Since 2016, several so-far unknown glacier detachments have been discovered and described, and new ones occurred. In the current contribution, we compile, compare and discuss 19 actual or possible large-volume detachments of low-angle mountain glaciers at nine different sites in the Caucasus, the Pamirs, Tibet, Alaska’s St. Elias mountains, and the Southern Andes. Many of the detachments reached volumes in the order of 10–100 million m3. Commonalities and differences between the cases investigated suggest that a set of different conditions drives a transient combination of factors related to low basal friction, high driving stress, concentration of shear stress, and low resistance to exceed stability thresholds. Particularly, soft bedrocks below the detached glaciers seem to be a common condition among the observed events, as they offer smooth contact areas between the glacier and its substratum while being prone to till-strength weakening and eventually basal failure under high pore-water pressure. Surface slopes of the detached glaciers range between around 10° and 20°, possibly on the one hand low enough to enable development of thick and thus large-volume glaciers, and on the other hand steep enough to allow critical basal stresses to build up. Most of the ice-rock avalanches resulting from the detachments in this study have a particularly low angle of reach, down to around 0.1 (apparent friction angle), likely due to their high ice content and connected liquefaction potential, the ready availability of soft basal slurries and large amounts of basal water, and the smooth topographic setting typical for glacial valleys. Low-angle glacier detachments combine elements, and likely also physical processes of glacier surges and ice break-offs from steep glaciers. The surge-like temporal evolution ahead of several detachments or their geographic proximity to other surge-type glaciers suggests the glacier detachments investigated can be interpreted as end-members of the continuum of surge-like glacier instabilities. Though rare, glacier detachments appear more frequent than previously thought and disclose, despite local differences in conditions and precursory evolutions, the fundamental and critical potential of low-angle soft glacier beds to fail catastrophically.

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Insights on Multistage Rock Avalanche Behavior From Runout Modeling Constrained by Seismic Inversions

et al. 2022

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Inversion of low‐frequency regional seismic records to solve for a time series of bulk forces exerted on the earth by a landslide (a force‐time function) is increasingly being used to infer volumes and dynamics of large, highly energetic landslides, such as rock avalanches and flowslides, and to provide calibration information on event dynamics and volumes for numerical landslide runout models. Much of the work to date using landslide runout modeling constrained by seismic data has focused on using single‐phase models with frictional or velocity‐weakening rheologies. Awareness of multistage landslide initiations is increasing, with discrete failures separated in time contributing to the final impact of an event. Our work utilizes a method for incorporating seismic data as a calibration constraint for landslide runout models, considering variable rheologies and different initiation conditions. This study presents a systematic examination of multiple rheologies and initiation conditions, and shows how these factors affect the force‐time function derived from the landslide runout model. Our work confirms that, while rheology and fragmenting or initially coherent initiations affect the force‐time function, multiple collapses separated by tens of seconds have the greatest impact on the shape and amplitude. We apply this method to the analysis of three real rock avalanches to better constrain plausible initiation conditions and rheology parameters using both seismic and field data. This study provides insights on how assumptions about the initiation dynamics of the source zone and the runout model definition can aid in the interpretation of seismic inversions for multistage rock avalanches.

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Reconstructing the dynamics of the highly-similar May 2016 and June 2019 Iliamna Volcano, Alaska ice–rock avalanches from seismoacoustic data

Cited by 4 publications

References 58 publications

Sudden large-volume detachments of low-angle mountain glaciers – more frequent than thought?

Sudden large-volume detachments of low-angle mountain glaciers – more frequent than thought?

Sudden large-volume detachments of low-angle mountain glaciers – more frequent than thought

Insights on Multistage Rock Avalanche Behavior From Runout Modeling Constrained by Seismic Inversions

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