28 June 2011
Updated: Video of the week: debris avalanche / lahar on Mount Rainier
Posted by Dave Petley
Youtube has a remarkable new video of a debris avalanche / lahar that occurred on Mount Rainier in Washington State, USA on 25th June:
Unfortunately there is little information about the event. Anyone have any details?
Updated:
There are further details about this landslide on the Mount Rainier Climbing blog.
The wonderful Eruptions blog also provides further details (as well as linking to this post).
Dave Petley is the Vice-Chancellor of the University of Hull in the United Kingdom. His blog provides commentary and analysis of landslide events occurring worldwide, including the landslides themselves, latest research, and conferences and meetings.
This looks like it might be a Rainier lahar almost … which are pretty common in the summer months, I think. There was a big one a few years back if I remember correctly and is a common event even without eruptions at Rainier.
For the sake of being able to find related stories later when the Twitter-feeds have moved to other topics: link to Erik’s post on non-eruptive volcanic hazards as related to this event.
Looks like Nisqually slide–for more info, interesting seismic data, see: http://mountrainierclimbing.blogspot.com/
There is now an article in the Seattle Times about the slides:
http://seattletimes.nwsource.com/html/localnews/2015453613_rainier29m.html
for the sake of technicalities… lahars occur during a volcanic eruption. That is they include fresh volcano induced material (ie lava and ash); not material laying on the volcano consumed by the debris flow. So specifically this video depicts a hyperconcentrated debris flow.
Cool video none-the-less.
[No, this is not really correct. There is a basket of definitions of the term lahar on the USGS website. For example:
Describing what is seen here as a lahar is entirely reasonable. Dave]
Thanks for the book quote… This landslide event did not extend beyond the park boundries nor did it involve any “Volcanic” activity (rather gravity and erosion) so as USGS/NPS indicates this is a debris flow. Yes you could just call it a lahar since it involved the collapse of volcanic rocks with water ice snow and mud but that is not correct and sensationalizes the event (somewhat creating “FEAR”)
Ironically the Seattle Times did not sensationalize…. “Huge rock avalanches rumble down Mount Rainier
-Some of the biggest rock avalanches in years have been roaring off Mount Rainier the past several days, kicking up billowing clouds of dust and propelling rivers of muddy debris nearly two miles down the volcano’s flanks.”
Finally as CVOs Vallance says, “Mount Rainier has unleashed massive mudslides, or lahars, in the past. But the current avalanches are tiny by comparison. Nor is there any hint of volcanic activity, which would be required to trigger a lahar from Rainier’s south side.”
As before, I am only nit-picking a geologic term and the technicality of using such a word. I think its important to be specific and true to the geologic phenonmenom.
[I am sorry, but I disagree. This blog is written for an international audience, and lahar is the internationally agreed term for these landslides. Locally, one can choose to use the term in a different way, but that is an exception not a rule. To use the internationally-agreed terminology to describe these landslides is not to sensationalise them, and nor is to create fear. I have been both specific and true to the geologic phenomenon, and absolutely stand by my use of the term – Dave].
BW Stanton, You are correct that technically, the term lahar can be used for a debris flow event that incorporates volcanic material. However, the USGS and NPS have adopted, in the case of Mount Rainier, using the term “Lahar” is to indicate any mudflow/debris flow event that is large enough to extend beyond the park boundaries and the term “debris flow” to indicate a similar event that is smaller (does not extend beyond park boundaries).
The mountain is old and after the ice melts and water gs deep underground the rocks loosen up and BINGO….
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