Does presence of ice change avalanche hazard?

I was climbing at Lincoln falls the other day. I know the approach frequently slides (2022, 2017, 2023, and it looked like it has already slid this year, we saw crowns above the slide path and debris from probably a few weeks ago). But I haven't heard of the descent sliding. On the descent, I noticed it was just snow on top of ice. I know there are other factors for this particular example like differing aspect, different amounts of overhead hazards, and the descent is much narrower and concave. But in general, does the presence of ice change how facets or slabs form? Does it make the temperature fluctuations throughout the day stabilize or not? I'm not asking because I want to be able to lower my guard on icy descents, I just want to know the snow science.

The short answer is that it’s possible for weak layers capable of producing natural and human triggered avalanches to form at that interface.  The exact mechanism was explained to me once a few years ago, but I’m not too good at snow geekery and promptly forgot.  (Edit to add: I assume it has something to do with the ice acting as a vapor barrier which can lead to faceting of the snow crystals directly above the ice)

Not exactly sure what you're asking. Cold air temps can make snow more stable or less stable, it depends.  

Patrick I highly recommend at the least getting a copy of The Avalanche Handbook and spending time reading and rereading it. Better would be an avy science class where you can learn first hand from someone with experience in snow science. There is a lot of subtlety both in seasonal buildup and in-situ analysis which are easier to wrap your head around when you have someone to feed it to you. Having a foundational level of knowledge of these concepts will empower you to use an avy forecast to it's fullest.

Snow science is not something you should learn from MP.  The questions you have are simultaneously basic and complex.  To put it another way, it's crucial for safe backcountry winter travel to have a basic understanding of ALL of snow science.  As the season progresses the snow pack is influenced by the entirety of the seasonal events.  Chapter 2 in The Avy Handbook will help explain the physical phenomena in play when you're skinning out to Lincoln Falls.

Andy Shoemakerwrote:

Not exactly sure what you're asking. Cold air temps can make snow more stable or less stable, it depends.  

Patrick I highly recommend at the least getting a copy of The Avalanche Handbook and spending time reading and rereading it. Better would be an avy science class where you can learn first hand from someone with experience in snow science. There is a lot of subtlety both in seasonal buildup and in-situ analysis which are easier to wrap your head around when you have someone to feed it to you. Having a foundational level of knowledge of these concepts will empower you to use an avy forecast to it's fullest.

Snow science is not something you should learn from MP.  The questions you have are simultaneously basic and complex.  To put it another way, it's crucial for safe backcountry winter travel to have a basic understanding of ALL of snow science.  As the season progresses the snow pack is influenced by the entirety of the seasonal events.  Chapter 2 in The Avy Handbook will help explain the physical phenomena in play when you're skinning out to Lincoln Falls.

This answer is funny to me because you told me not to ask this kind of question on mountain project, while also directing me to great resources in your response... in a mountain project forum comment...

So I think mountain project was the right place for me to ask the question, thanks!

Patrick Normilewrote:

This answer is funny to me because you told me not to ask this kind of question on mountain project, while also directing me to great resources in your response... in a mountain project forum comment...

So I think mountain project was the right place for me to ask the question, thanks!

MP is a great place to learn about resources.  It's not an ideal primary source for life saving information, that's all I'm saying  

Searching "wet slab avalanche ice layer" will apply to your specific question.  Or pages 100-102 in The Avy Handbook. But knowing this one scenario in isolation is essentially useless.  Gotta understand the entire snowpack.

Patrick Normilewrote:

This answer is funny to me because you told me not to ask this kind of question on mountain project, while also directing me to great resources in your response... in a mountain project forum comment...

So I think mountain project was the right place for me to ask the question, thanks!

Not really. He told you that MP isn't the place to learn snow science. He's right about that. It's far more complicated and nuanced than is possible to explain on an internet forum (let alone the garbage heap this on can be). 

The resources he gave you are excellent, but they aren't going to teach you everything you need to know either. 

I took this picture in Officer's gulch a few weeks ago. Don't know a ton about snow science, but the snow was powdery all the way to the ground (not the type I'd think would slide) and there wasn't a lot of it, but it did slide off the ice. 

NateCwrote:

Not really. He told you that MP isn't the place to learn snow science. He's right about that. It's far more complicated and nuanced than is possible to explain on an internet forum (let alone the garbage heap this on can be). 

The resources he gave you are excellent, but they aren't going to teach you everything you need to know either. 

Ah yes, nothing like the mountain project comments to remind that this sport isn't about personal growth, progression, community, or fun, but about knowing everything and being better than everyone before ever stepping into the outdoors.

P Degnerwrote:

I took this picture in Officer's gulch a few weeks ago. Don't know a ton about snow science, but the snow was powdery all the way to the ground (not the type I'd think would slide) and there wasn't a lot of it, but it did slide off the ice. 

Nice I know officers gulch slides all the time. Thanks for sharing the photo

Patrick Normilewrote:

Ah yes, nothing like the mountain project comments to remind that this sport isn't about personal growth, progression, community, or fun, but about knowing everything and being better than everyone before ever stepping into the outdoors.

Understanding now, why you're on the internet asking randos about this.  Instead of in person, asking a mentor or friend.   An avy class should suit you well- they may even have the silver platter you're used to.  

Alternatively, adopt a beginner's mindset, start taking real initiative to educate yourself (contrast with having MP google for you), and express gratitude when other's help you.  You might find soon you have friends and mentors who are experts on this complex topic and are happy to pass along their knowledge.  Or don't and blame the world for your difficulties. That's hip and trendy.

Patrick Normilewrote:

Ah yes, nothing like the mountain project comments to remind that this sport isn't about personal growth, progression, community, or fun, but about knowing everything and being better than everyone before ever stepping into the outdoors.

Ahh, I'm really sorry little guy! You seem really insecure about yourself. That's sad. 

It's ok, let me help you. Here, I'll show you how to respond when 2 people offer you clarifying advice to a question you asked... "Thanks for the info." See? That's not so hard.

You're really not even good a being a jerk, just stop trying so hard.

You guys make me laugh. But once I read through the layers of condescension, your replies have been helpful, so I'll express my gratitude. For what it's worth, I have taken classes, hired guides, and spent many years in the backcountry on my own with partners more and less experienced than myself, but I forgot asking a question on the internet about something I haven't learned yet implies I have infant level brain power. I do plan on taking aiare 2 next, just wanted a little extra help learning my blind spots before I can take the class. Thank you for making me feel a part of the community I've already been a part of for a decade and a half <3

With avalanche education, I like to be in the part of the Dunning-Kruger curve where I know enough to be very afraid.
The snow science you seek might be as variable and fickle as snow-covered ice. 

This thread is getting weird but I’m interested in the original topic. At first thought, it seems like ice would be a perfect frictionless slide for a slab on top to easily slide. But as I think more about it, I can imagine a situation where the temps are right to let the layer of snow melt slightly into the ice and bond to it.

Obviously none of us should be taking any of this speculation into real life scenarios without knowing, but I never learned this in my avy course and haven’t really thought about it until now. 

Check this paper out.  Especially pages 105 and 106. Ice layers can add stability or lower it. Below describes one mechanism through which ice layers lower snowpack/slope stability. Earlier on page 104 it describes how ice layers can actually add stability.

Water will accumulate above high density ("ice") layers and interfaces with even a slight discontinuity in texture. Such layers are rarely completely impermeable or of low permeability for very long. However, significant grain growth can occur in just a few hours under the funicular regime (Raymond and Tusima 1979). When such metamorphism occurs at a distinct layer over much of an area, serious instability exists. The accumulated water can also act to lubricate the zone of shear, so that in the event of slab failure, the potential for downslope motion is greatly enhanced (Seligman 1936). If water is flowing downslope over the layer of restricted permeability, additional force may be imposed upon the overlying slab (Moskalev 1966). The instability may be relieved by any of the following: avalanches, freezing of the ponded water (Seligman 1936) and/or the slab itself, deterioration of the ice layer (Langham 1974) and subsequent drainage, or sufficient melting of the overlying slab to reduce the stress at the shear plane.

Thanks for the asking the question, Patrick. I was just there and had the same thought. Due to a number of factors beyond the ice alone, we decided to go one at a time in the more exposed areas of the walk off.

Wesley Dickersonwrote:

Thanks for the asking the question, Patrick. I was just there and had the same thought. Due to a number of factors beyond the ice alone, we decided to go one at a time in the more exposed areas of the walk off.

Same here! Near the top, I could plunge my tool through the snow with even pressure all the way to the ice, but down lower the snow on top of the ice felt like it had a harder layer on top of a less stiff layer. It got me thinking, and we made sure to do the sections one at a time.