Avalanche Terrain Factors
These are all factors that you should consider when you are choosing your route down a mountain.
Are there any Terrain Traps?
A terrain trap is typically a gully or ravine area where a snow slide can take snow from a large area and concentrate it into a small area when the avalanche stops. In a terrain trap; even a small slide can bury a victim very deep beneath the surface of the snow.
Is There a Hazardous Outrun?
You should consider the nature of the terrain below a route when making a decision regarding your ascent/descent. If you are skiing in a “No fall zone”, any sign of instability in the snowpack should put an end to your trip. If the slope runs out into a flat area with no rocks, trees or cliffs; then you might be able to afford to assume a little bit more risk with consideration to the stability of the snowpack.
Are There any Natural Snow Anchors?
Some of the best natural snow anchors are pine trees and shrubs. The key component of a well anchored slope is tough fauna like pine branches that are sticking through the weak layers of the snowpack. This can help to hold weak layers of snow together.
Be aware that trees with few branches and little winter fauna will not act as sufficient anchors. Pine trees also do not act as sufficient snow slab anchors 100% of the time. It is easy to have an avalanche in a heavily wooded area – the presence of pine trees is just another factor that you can consider in your final decision to ski a slope or not to ski a slope.
Are There Escape Routes Where You Plan to Ski?
A wide-open bowl is more dangerous than a route with lots of variations in terrain. A large bowl area will have very few places that will allow you to escape from a large avalanche. If there is an avalanche, the fracture can easily propagate across the entire bowl and create a very wide avalanche. If there is an avalanche on terrain that has varied characteristics, the snow fracture is less likely to propagate across the ski slope. You are also more likely to be close to a safe area on the slope where you can escape from the avalanche.
Variations in Wind Loading
Wind loading can create huge slabs of snow on top of unstable layers. Wind loading is one of the reasons that some slopes may be relatively safe while adjacent slopes are avalanche prone. Don’t forget that wind loading can change on different parts of a particular slope. You might dig a snow pit near the slope that looks fine, the top of the descent might seem fine, but in the middle there could be a wind loaded snow slab that is ready to fracture.