UKH

Remarkable Avalanche Debris Unearthed in NW Highlands

© Iain Cameron

A highly unusual discovery has been made on Sgurr na Lapaich in the northwest Highlands, where signs suggest that a huge summertime avalanche of snow, mud and rock took place. This mixture has covered a pre-existing snow patch, an effect which bears a striking resemblance to a debris-strewn dirty glacier.

'Dirty glacier' on Sgurr na Lapaich  © Iain Cameron
'Dirty glacier' on Sgurr na Lapaich
© Iain Cameron

'I’ve never seen anything like it in the hills' says snow expert Iain Cameron, who photographed the site at the weekend.

'Nor for that matter has [mountain environment specialist] Dr Adam Watson, whom I showed the photographs to. It was quite extraordinary to come across it. I’d been given the heads-up on it last month by Donald Morris, but was keen to see it for myself.'

'It is a very reasonable assumption that sometime earlier in the year, later than June 14th (I have pictures of a very snowy SnL on that date), a huge full-depth avalanche came down from the corrie headwall, near the summit of Sgurr na Lapaich. This avalanche stripped many hundreds of tonnes of soil and rock with it, and transported it down the corrie where it covered the snow that was already lying there' Iain tells us.

Photo of the site clearly showing the source of the avalanche on the headwall  © Iain Cameron
Photo of the site clearly showing the source of the avalanche on the headwall
© Iain Cameron

'Such was the quantity of material transported that the mixture of soil and snow formed a very deep layer of protection to the in situ snow. In places the mud and soil was over a metre deep.'

'It very much looks to me that there are two distinct layers of snow here. The bottom layer is the in situ snow that has been there since winter. You can see that it's nice and layered and displays all the characteristics of snow that has lain for a period of time. The top layer, by contrast, is highly irregular, chaotic and potted. It looks to me as though this is the remnants of the avalanche snow that was transported from above, and is interspersed with the accompanying earth and rock.'

Different layers evident in the snow  © Iain Cameron
Different layers evident in the snow
© Iain Cameron

'What is certain, though, is that the debris is protecting the snow from melting ...to a significant extent. It provides both insulation from sunlight and a barrier for rainfall. Add to that the fact there would have been a very significant depth there of snow (still up to 4 metres deep by my reckoning) then you're looking at this snow have a very good chance of persisting until the new snows of winter.'

Each August Iain Cameron conducts an annual survey of summertime snow patch survival in the Scottish hills; this year's tally amounts to hundreds of patches, the highest number surveyed since 1994.
 

 


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29 Sep, 2015
That reminds me of this mucky corrie on the east side of Tom a' Choinnich just the other side of the loch, less than 8km away as the crow flies, taken last July https://www.facebook.com/photo.php?fbid=10152506944030498&l=0750e6dfe4 Also, if it's of interest to the author, this photo https://www.facebook.com/photo.php?fbid=10152506933845498&l=dc45cd7ff4 shows the snow patch (top left) where the rockfall is shown in the second photo on the article, taken last year also in July on the same trip. I've zoomed in and compared features and it's definitely the same corrie.
30 Sep, 2015
Fascinating stuff, great photos. And thanks to Fidget too.
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