Iliamna Volcano landslide: a new image from the Alaska Volcano Observatory

The Alaska Volcano Observatory has released a new, high quality, three dimensional rendering of the Iliamna Volcano landslide on 20th June 2019.  The image uses PlanetSope near-infrared data draped onto Google Earth topography to give a clear impression of the size and scale of the failure:-

PlanetScope near-infrared scene from June 22nd, 2019 (approx. 2 days after June 21 Red Glacier avalanche) converted to grayscale and draped over Google Earth topography. Direction of view is approximately WSW. Image created by the Alaska Volcano Observatory.

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Interestingly, twelve years ago an analysis of seismic data associated with six large ice and rock avalanches on Iliamna volcano was published (Caplan-Auerbach and Huggel 2007). They note that at least eight events with a volume in the order of a million cubic metres occurred on Iliamna volcano between 1984 and 2005.  They explain this high frequency of large mass movements as follows:

There are several factors likely to be contributing to the frequency and volume of these events. A primary factor is the large volume of ice available for failure (Trabant, 1999). Furthermore, although the volcano has no confirmed historic eruptions, it has active fumaroles and experienced a dike intrusion in 1996 (Roman and others, 2004). Volcanic unrest could promote ice avalanches by increasing heat flux within the edifice, melting the base of the glacier cover and promoting slip at the glacier base. Furthermore, Iliamna’s exposed rock is heavily altered by hydrothermal activity, and is prone to failure (Waythomas and others, 2000). Avalanches may initiate in rock or they may entrain friable rock as they travel. This not only enhances avalanche volume but increases the density of the avalanche material, imposing a larger force upon the ground and thus increasing the amplitude of seismic signals associated with the avalanche.

Also of note is the timing of these major landslides.  Caplan-Auerbach and Huggel (2007) noted that:

The majority of Iliamna Volcano events occur in the spring or summer, suggesting that they are triggered by increases in meltwater along the glacial base, possibly promoted by crevasse opening at the headwall.

This is consistent with observations elsewhere in Alaska.  Rock and ice avalanches, such as the Iliamna Volcano landslide, can be a major hazard to mountain communities, as the tragic Giyari landslide showed in 2012.  Understanding these events better is clearly important.

Reference

Caplan-Auerbach, J., and Huggel, C. 2007. Precursory seismicity associated with frequent, large ice avalanches on Iliamna volcano, Alaska, USA. Journal of Glaciology, 53, issue.180, pp.53-128. DOI : 10.3189/172756507781833866