We often see depth hoar form in the early snow season; ever heard of that? If you are a winter backcountry hiker, climber, snowshoe enthusiast, snowmobiler, or XC-Skier, it would be good to understand what it is.
Basically speaking, to create an avalanche, the type that most often kills people, which is called a slab avalanche, you need four things.
One: A slope steep enough for gravity to pull it down the mountain – 38° is prime
Two: A load of snow that can be deposited by a storm, or wind carried from one slope to another slope.
Three: A somewhat smooth running surface
Four: A lubricating layer
Some may also say you need a trigger, which is also correct. A trigger can come in a couple of forms Human, a load that builds until it releases naturally, or a change in environmental conditions.
Depth-hoar, hoar frost, or temperature gradient (TG) snow often acts as lubricating layer. It forms within the snowpack when there is a temperature differentiation. It is often is found at the ground level, because the ground stays right around 32° F or 0° C. The day time temperatures, and nighttime temperatures can fall to well below that. This creates a temperature gradient (TG) or a difference in temperature between one part of the snowpack and another.
When this happens it causes the moisture to move from that part of the pack to another or to the air; leaving behind delicate, but pretty sparkly crystals (TG snow). You may have seen hoar frost, or surface hoar, on the surface of the snow – it sparkles in the sunlight, or night time when you shine a light on it. It creates a very good lubricating layer. Add that to a smooth grassy slope, or an icy crust, with a load on top of it, and whisss. .. it slides.
If you go out into the backcountry training in this sort of thing goes a long ways towards your safety.
Here are a few of my published articles on avalanches. Reading them will help. Most of the things I mention are principle based, meaning that they apply today, tomorrow and yesterday. Some of the things are technique based, meaning they may change with time.
change, and there are changes in techniques, but most of the information is “principle based,” so it does not change.
“Ways, Means, Methods, and Techniques Change, But Principles Never Do.”
I hope this information assists you in staying in the acceptable risk category during your adventures – have a great one! — Douglas S. Hansen
I would enjoy having you in a class. Please feel free to contact me if you have any questions, or if you are interested in training.
*Phone numbers for the various avalanche forecast centers may have changed.
Pieps, is one of the first makers of beacons. They have high quality transceivers. They are High Tech Beacons. This is one of their super light weight, small and good range beacons.
One last thought about training. Some say you can find everything you need on the internet, and more. That is sort-of true. The problem is finding it, and knowing the right questions to ask, to fill in the gaps that a good instructor does, the ones that experience provides.
Personally, I have taken, and look forward to attending more training. Some has been redundant, which is good too, but I find each instructor seems to have their own ways of communicating things, and I “always,” learn things I can use. Good training takes it to a level videos, books, magazines, etc. just can’t. “Always keep learning . . .”
Here’s a chart I use to communicate risk taking skills and safety. I teach it in a 90 minute class I call “Situational Awareness Training.” I developed this system over the past thirty years. It has kept me and my teams alive and without serious injury, it seems to work, but the principles and concepts to really understand it and make it work requires some formal instruction.