Publication History: Proceedings of the 1997 Conference on
Outdoor Recreation and Education (ICORE): Adventuras En Mexico, Universidad
Autonoma de Yucatan. Rob Jones and Brian Wilkinson (eds) The Association
of Outdoor Recreation and Education, Boulder, 1998.
Snow crystal identification is followed by a discussion of equi-temperature
and temperature gradient metamorphism. Once again, LaChapelle has some
excellent photographs which illustrate the changes happening to snow crystals
as each of the processes take place. To do it right, plan on at least two
hours to cover snow physics. In my courses that's all I do the first night.
The next night is allocated to the more interesting subject of the causes
and behavior of avalanches. If you have only one night, however, then you'll
want to minimize the amount of time spent on studying snow. Metamorphic
processes can be confusing and can side track some students, causing them
to miss some of the important safety material. If your time is limited
then identify some basic snow crystals and dispense with snow physics altogether.
About 25 years ago, his father had taken a photograph of a bridge built on Teton Pass just outside of Jackson Hole, Wyoming. When designing the new road, highway engineers were well acquainted with one especially nasty avalanche on the pass known as Glory Slide. To deal with Glory, the engineers decided to build a bridge which spanned the path of the avalanche. The idea was that when Glory Slide came down, it would go under the bridge, forgoing the need to close the road, a frequent and annoying happening on the Teton Pass. Alas, during the first winter, before the highway was opened, Glory Slide came down and took out the bridge. During the lecture, I first show my friend's photo of the bridge. Then I show a photo in the winter taken from the same place the year after the bridge. The two slides--the first showing a bridge and the next showing no bridge--are powerful visual tools to illustrate the tremendous force of avalanches.
As another example of how you can use slides and overheads to make your avalanche lecture more interesting, let's use the topic of settlement as an example. Settlement is important since it provides a visual clue to the backcountry traveller how quickly a new snow fall is stabilizing. When I talk about settlement, I first show an overhead of an illustration of a snow pack made up of stellar snow crystals, the arms of which are keeping adjacent snow crystals far apart. Side by side on the overhead is a second illustration showing a snow pack with equi-temperature snow grains. The rounded snow grains pack together easier and the illustration graphically shows that the snow pack has settled. This isn't anything out of the ordinary. The illustrations are commonly found in avalanche texts. Moreover, it easy enough for anyone to make up such overheads using colored fine point magic markers.
While the illustrations on the overhead are still visible, on a second
screen I project slides of a meter stick placed in the snow measuring total
snow depth. The first slide is a close up showing the total depth of the
snow pack after a new snow fall. The second shows the total depth (now
reduced) after a few days of moderate temperatures. The two forms of visual
aids, overhead and slides, compliment one another and help make your lecture
more understandable.
One story that I tell and illustrate with slides is about a journey that I took a number years ago down Marsh Creek which is one of the source streams of the Middle Fork of the Salmon River in Idaho. As we began skiing into the canyon we noticed very large sunballs on the hillsides. The sunballs were about four days old. Sun balls are one of the indicators of equi-temperature metamorphism which is a good sign, a sign that the snow pack is stabilizing. It's a good sign, however, as long as the sun balls are small. When the balls get larger, it indicates that free water is percolating deeper into the snow pack, lubricating old crust layers or worse yet, lubricating a depth hoar at the bottom of the pack.
It wasn't too long on our trip before we came across the deposition
zones of some incredibly large avalanches. The avalanches were about the
same age as the sun balls, about four days old, and they were impressive.
One after another, they had come hurtling into the canyon, descending 2,000
to 3,000 feet and ripping out mature ponderosa pine three feet in diameter.
About midway through our trip, we came upon one massive avalanche which
had dammed Marsh Creek. The four of us on the trip stood in awe, looking
at the huge pile of snow and the place where the water had finally breached
and cut an icy "V" through the face of the rubble.
1. New Snow (amount of new snow, crystal types making up the new snow fall, degree of new snow settlement)
2. Old Snow or Existing Snow Pack (surface of old snow, depth of the snow pack, layering and types of crystals within the snow pack)
3. Terrain (steepness of slope, slope aspect, anchoring features, i.e. tree and brush)
4. Wind (transporting effect of wind, effect of wind on crystals, windward & leeward slopes, deposition areas)
5. Temperature (storm trends, warm temperatures helps stabilize packs to a point but too warm creates very unstable packs)
The use of a combination of slides and overhead overlays as discussed earlier can make this part of the lecture particularly effective. Use drawings on the overhead to illustrate basic concepts and then slides from backcountry trips to illustrate specific instances. I'm a believer in picking out one fact whenever you give a lecture. I tell the class that if they remember anything in the lecture, remember this one fact. For avalanches it is this: avalanche danger is greatest during and shortly after intensive snow falls. Since it is so important, it is the first topic that I cover. It's easily illustrated. Just use a slide that you've taken during a blizzard.
There's plenty of source material available which you can use to prepare your lecture, and it's beyond the scope of the this paper to go into any detail. What's important here, however, is how the material is covered. One of my goals in presenting the material is to try to keep the material tied as closely as possible to local areas. For instance, when discussing slope angles (which I cover under the "Terrain Factor") I use examples that my students will be familiar with. I have gone out to a number of nearby Alpine and backcountry areas and have used an inclinometer to measure slope angles. I then show the slides of each area, explaining what the slope angle is and the degree of risk associated with it.
Covering each of the five factors can easily take a couple of hours. If it is a one-evening course, you'll want to be sure that you leave room for a discussion of route finding, safety equipment and rescue:
I highly recommend that you hold field sessions in safe locations near a parking area. Unless you are teaching professional courses for ski patrollers or backcountry guides, it's not necessary to take a class up on a steep mountainside to dig snow pits and practice searching techniques. Remote locations take time to reach and invariably someone in the class doesn't have the equipment or skill to make it to and from such locations. If you're close to a parking lot and someone gets cold, he or she can easily return to a vehicle and warm up. That's not possible in the backcountry.
When avalanche courses are offered to the general public or, for that matter, to the general student body, you will end up with a great range of abilities and fitness levels. Several years ago, I had a woman in a class who had been ill the week before. The field session was held on a cold day, and still weak from her illness, she became hypothermic. By the time we realized something was wrong, she was already so faint and cold that she had to be carried to the nearby ski lodge. Fortunately, she recovered quickly at the lodge, and we were able to continue the class without much of a disruption. If, however, we had been in remote location, a simple avalanche class would have turned into a survival epic.
When it comes time to determine the location of the field session make sure you find a place with adequate parking, and, if possible, nearby slopes. If all you have to work with is flat, snow covered terrain, you can still hold a fairly effective and informative field session. You shouldn't forgo a field session simply because you don't have ideal terrain. Pay particular attention to the location of the snow pit. I often use a steep slope at the base of our local ski area which I know is perfectly safe.
If I'm not at the ski area, then I look for small gully running through a wheat field. Ideally, you want a short, safe slope or the side of the gully with at least a 30 degree angle for doing sheer and Rutschblock tests. Once again, if you can't find an ideal slope you can still demonstrate the basics of digging and analyzing a pit--even on level terrain. A good way of approaching the first field session is to set up three stations. The class divides into three groups, each group spending an hour at a station and then rotating to the next station until all three have been visited. The stations are:
The probing session, although tedious, is usually enlightening in that it shows how difficult it is to locate someone even in small avalanches. Too, it helps reinforce the importance of using transceivers when traveling in avalanche country. One hint with the probing session: be sure to strap a transceiver to each dummy you bury. A climbing friend of mine was helping me teach the probing session one year, and for the buried victim he used a racksack sack with his climbing rope inside.
The first group came up to his station and after some basic instruction, started going through a coarse probe and then a fine probe. In the end, they were unsuccessful in finding his pack. The next group came up and after an hour, they were unsuccessful. Finally, the third group arrived. After my friend explained that the previous two groups were unsuccessful in finding his pack, the students were determined to find it. But after another hour, they, too were unable to find it. By this time the slope had been so disturbed that my friend had no idea where he had buried his pack. We dug for several hours looking for it and eventually had to give up. It wasn't until months later in the spring that he returned and finally found it just starting to melt out of the snow.
The last of the three stations is a snow pit. At this station, students are talked through the steps of digging and analyzing a hasty pit. They look for layers in the snow pack, pick out crystals and try to identify them. Once they've had ample opportunity to look at crystals, sheer tests are done followed by a Rutschblock test. Any new crystals turned up by the tests are examined. When everything is finished, the students make a guess of how stable they think the pack is.
The equipment needed for a snow pit won't break the budget: hand lenses
for everyone, a couple of thermometers, snow cards, two or three compasses
with an inclinometer and some flash cards. The flash cards I use are home
made and are simply drawings of precipitated and metamorphosed crystals.
I found the flash cards very helpful, holding them up and talking about
identification characteristics while students are looking at crystals through
their lenses.
While one half of the class is working on the transceiver search, the
other half of the class is working on snow pits. Have them work in pairs
and give each pair a clip board with a snow profile chart. They, then,
dig their own pit, graphing out the pit profile, and indicating on the
chart where and what snow crystals are found. After doing some sheer tests
and a Rutschblock test, they give the pit an overall stability rating.
Lastly, something that I always try to incorporate in any class is information on where to find avalanche forecasts. For more advanced avalanche classes, you'll probably want to take it one step further. Print up a couple of avalanche forecasts off the Internet and hand out copies to everyone. Internet avalanche forecasts are terrific learning tools. The terminology used in the class, the metamorphic processes that you've discussed, the snow pits that students have dug in the field sessions, all come together in a practical way in an avalanche forecast. Read through the reports and ask questions about it to stimulate discussion among your class.
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