First it was landslides

now it's avalanches

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DOH!
That's a flying saucer that's impacted into the hillside & flow off again.
I know, I saw it once on the X Files.

Wow – can't quite read the signs, where was it?

Interesting that Andy, was half expecting something like that for the last week or so on some of the more open faces round here as there has been a few unconsolidated layers in the snowpack since pre-Christmas- wasn't particularly expecting a full-depth slide like that though.

I was planning a wee ski tour just along from there but was put off the steeper slopes by some of the weaknesses. Hopefully a slight thaw will help to stabilise things but not get rid of the cover completely. Nice pics.

a slight thaw wont be stabilising things nor was that slide caused by "unconsolidated layers" in the snow pack. If it was a weakness in the snowpack formed by poorly bonded layers then it wouldn't of slipped the whole way to the base. A slight thaw will cause moisture in the snow pack potentially lubricating the layers or the ground, making slides more likely. A slight thaw in the day will them freeze in the evenings, causing a melt/freeze layer this will be very dangerous if any fresh or wind blown snow is deposited on top, or if it occurs within the existing snow pack.

So if youre going ski touring id either go do a course, or go and hire a guide.

It looks like the slide took place on snow covered rock, the rock will have warmed slightly and caused the snow to slide off. Additionally given the shallow snow pack and cold temps its likely that the presence of depth hoar has contributed to the slide as well.

It is a slab avalanche and it is on a convexity (not sure of the gradient from the pic) so its definitely an area to watch out for in terms of risk.

Wow.

You don't have any volcanoes up there do you?

wow……. you know your stuff ganic 😐

Yes, looks to have started on a convexity (high stress) portion of the snow pack.

Wow – can't quite read the signs, where was it?

Melmerby…ish I'd guess

Hi Ganic,

My post above was mainly referring to the fact that it had fractured at full depth, rather than as a layer of unconsolidated snow on windslab or hoar (of which there have been a number building up over the last month- I've done several shovel-block tests that have failed at differing depths on some fairly gentle aspects since the 20th). What I meant was I would have expected to see some slides that weren't full depth due to this before now, not that there was no chance of a full depth slide.

I agree, a slight thaw will lead to some massive instabilities, especially given relatively unfrozen ground and the steep temperature gradient across the snowpack. Given this, I'd imagine there will be plenty of full depth slides as any depth hoar becomes saturated- especially on avalanche prone slopes like the one pictured (steeper, over a bulge, even ground, relatively grassy, unfrozen in places) .

However, higher up, a more constant temperature hovering at or below 0 rather than fluctuating from -18 or so to -8 (for example) would (I'd have thought) allow some of the existing layers to settle and improve the density of the base layers. Whilst there will be obvious loss and avalanche danger on some aspects, this process will probably make the snowpack on the tops less prone to a severe thaw (or so I'd think). Perhaps I shouldn't have used the term stability to describe this- sorry I'm no expert but am always trying to learn- but that's what I meant by improving stability. Clearly prone slopes will have a high likelihood of remaining dangerous, but the chances are conditions on the tops will improve for touring in the longer term.

Like I say, I'm no expert, but try to learn as much as I can, I realise I don't have all the correct English for some terms, but hopefully what I've typed above makes better sense. Please correct me where I'm wrong though, especially if there is better terminology to describe things with.

Looks like a slab avalanche

ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ

Think someones just rolled a massive snowball!

Pffff. We get worse than that on Cannock Chase, I'll tell you.

Is this really unusual?
Avalanches happen in the Lake district (an all other UK mountain areas) frequently every winter.

I caused a mini avalanche in the peaks on Saturday, I've always wanted to 'fall' through a cornice so I gave it a go. Great fun. Good 10ft drop and I broke off a good 5 or 6 foot of overhang.

its very difficult to tell from a photo, and even if you dig a pit or do a block test, its only ever going to tell you what its like on the particular bit of slope you examined.

There are so many variables that contribute to the risk of a slide occurring, and youve mentioned a few above. I was in Cumbria on Friday and some of the slopes i was riding had a fairly solid wind and/or freeze melt crust on them, so potentially there is a hazard there. In the above case id be tempted to say that the actual snow pack looks well bonded, the instability was actually in the base (either sun warming the rock, water running through the pack onto the rock, or depth hoar, or all of that).

It doesnt look like the trigger was a person, so it has to be something else, temperature change, wind, warming rock.

Either way, the one thing the slide certainly tells you is that slopes in that locality, on that aspect, and gradient, are potentially dangerous. The danger will only increase with a rise in temps, this will give rise to a risk of a wet snow slide which can happen on much gentler slopes.

PS its not all unusual, just commenting on a forum while at lunch. Makes a change from all the usual crap about "which bike for a fatty who rides 10 miles a month and doesn't want to spend less than £2,500"

So if youre going ski touring id either go do a course, or go and hire a guide.

Are there many Cumbrian ski guides? 🙂

All qualified mountain guides have to be able to guide skiing as well as climbing.

Wow lots of lovely snowpack talk there… but neither of you have mentioned that fact that it is right on a rollover on the windloaded side of the hill.

TBH that would be more of a signal to not go there, even before we start talking about weather and bonding layers etc

but neither of you have mentioned that fact that it is right on a rollover on the windloaded side of the hill.

langy
How did you know it was on the lee slope?. Just asking, not trying to catch you out or nothing.

EDIT: there does appear to be a bit of a cornice.

you should go and investigate it…im pretty sure that you will agree that its caused by slippage of snowage

Wow avalanche nerds. 😛

There's a good avalanche awareness test online, I think it's done by one of the instructing companies PYB or Glenmore Lodge or someone. Lots of different senarios, some of them are not immediately obvious.

You have to be grum 😉

interperting SAIS reports is the pinnacle of avalanche nerding.

Standing outside the bakery in Melmerby?
Just wait for the Helm Wind.

Wow lots of lovely snowpack talk there… but neither of you have mentioned that fact that it is right on a rollover on the windloaded side of the hill.

TBH that would be more of a signal to not go there, even before we start talking about weather and bonding layers etc

"before" is the key word here, because you can't just take one or the other into account (being that it's a combination of windloaded snow and weak layers that gives the real danger)

… but the point you make is correct: it's quicker to spot a windloaded side on a rollover than it is to examine the layers of the snowpack in detail taking into account recent temperatures etc.

/\__/\__/\_______________ doooooooooooooooooooooooooooooooo 😉

Eve – the time spent in the mountains. And as you say with your edit the fact that the early stages of windloading are visible in the form of a "cornice"; these sort of things are things that you notice readily when you have been looking for them for a long time. Also, I lived in Colorado for a number of years where the snowpack is very sensitive, so in many ways you pay more attention than in Europe where it is (very, very) generally more stable.

Ash – that is exactly it; I wasn't get stuck into what was being said, just that if we are looking at minimising risk when skiing/boarding/snowmobiling/whatever(which despite the editing style that makes it look as though it is to the contrary in most of the snow flicks these days), then you start with terrain. Even the most stable snowpack in the world can fail; if the terrain is selected wisely it is not as much of an issue.

Also, hopefully obviously, terrain choice alone won't save you just as weather reports, pit analysis, wearing transcievers or carrying the appropriate complimentary tools won't on their own save you. It is just one part of the whole system. And sometimes it still doesn't stop it from happening; not something anyone wants to experience at any level.