23 September 2022

The 17 September 2022 rock avalanche at Lamplugh Glacier in Alaska

Posted by Dave Petley

The 17 September 2022 rock avalanche at Lamplugh Glacier in Alaska

It has been a busy few days for rock avalanches in North America.  Hot on the heels of the massive landslide at Ecstall River in British Columbia in Canada comes news of another.  This event was detected by Matt Haney of the Alaska Volcano Observatory using seismometer data, and quickly narrowed down to a site on Lamplugh GlacierDan Shugar (@WaterSHEDLab) of the University of Calgary has tweeted the details – once again do read the full set of tweets to understand this one in detail:-

https://twitter.com/WaterSHEDLab/status/1572202447032188928

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Planet Labs captured a beautiful image of the site on 18 September 2022, the day after the failure:-

Satellite image of the 17 September 2022 rock avalanche at Lamplugh Glacier, collected on 18 September 2022.

Satellite image of the 17 September 2022 rock avalanche at Lamplugh Glacier, collected on 18 September 2022. Image copyright Planet Labs, used with permission.

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The rock avalanche has a runout distance of about 6 km by my initial calculation.  Unlike the landslide at Ecstall River it has not been channelised, and in this case it has run out across ice.  Thus, the deposit has a very different morphology.  The flow structures at the tow are beautiful, illustrating the spreading of the landslide in the late (low velocity) stage of movement:-

Satellite image of the toe of the 17 September 2022 rock avalanche at Lamplugh Glacier, collected on 18 September 2022.

Satellite image of the toe of the 17 September 2022 rock avalanche at Lamplugh Glacier, collected on 18 September 2022. Image copyright Planet Labs, used with permission.

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As Dan has pointed out in his tweets, this rock avalanche has in part travelled across the deposit of the even larger 23 June 2016 rock avalanche at the same site (although a different section of the slope collapsed to generate that one).  The relationship between the two landslides is captured on the Planet Labs imagery:-

Satellite image of the two rock avalanche deposits at Lamplugh Glacier, collected on 18 September 2022.

Satellite image of the two rock avalanche deposits at Lamplugh Glacier, collected on 18 September 2022. Image copyright Planet Labs, used with permission.

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Once again the team that identified this enormous landslide will, I’m sure, produce a detailed analysis of it in due course.  I shall look forward to seeing that publication.

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Acknowledgements

The project team outlined above have rapidly undertaken an analysis of this event and have posted the information online.  Thanks to them for doing so.  The images are from the wonderful people at Planet Labs.

Planet Team (2022). Planet Application Program Interface: In Space for Life on Earth. San Francisco, CA. https://www.planet.com/