Sluff vs Slab: The Deadly Difference

All over the world, people are killed by avalanches either by skiing, driving in an avalanche-prone area, or ski mountaineering. Many places in Colorado and the States are at a high risk of avalanches in the winter. These areas in Colorado are any mountain with a grade higher than 30 percent. And areas where slides have happened in the past. There are many different types of avalanches but the killer avalanche is a slab avalanche. A “slab” is a cohesive plate of snow that slides as a unit on the snow underneath. If you are climbing up a mountain or skiing down one and you see a crack in the snow, that is the indicator that a slab avalanche is going to start. If you see a crack in the snow but the snow beneath the crack hasn't started to move yet. Don’t go near it, it’s waiting for something to trigger it. The bonds holding a slab in place typically fracture at 350 kilometers per hour (220 miles per hour) and it appears to shatter like a pane of glass. It’s typically about the size of half a football field, usually about 30-80 centimeters (1-3 feet) deep and it typically reaches speeds of 30 km/hr (20 mph) within the first 3 seconds and quickly accelerates to around 130 km/hr (80 mph) after the first, say, 6 seconds. Dry slab avalanches can lie patiently, teetering on the verge of catastrophe, sometimes for days to even months. The weak layers beneath slabs are also extremely sensitive to the rate at which they are stressed. Many alpine touring skiers have triggered a slab and got caught in it.

If you manage to survive, you are among the lucky few. The survival rate of a victim buried by an avalanche is roughly 91% if rescued in 18 minutes or less. When a rescue takes anywhere between 19 and 35 minutes after the avalanche. The survival rate drops down to 34%. Even if you do survive the initial flow of the avalanche, you are more likely to die from severe wounds, hypothermia, or suffocation. Loose Snow Avalanche. These avalanches are commonly called “sluff” avalanches. These happen when loose snow from a higher part of the mountain falls downhill or when a skier or snowboarder kicks up the powder causing it to fall down the mountain. These types of avalanches usually start from a point and fan outward as they descend, and because of this they are also called “point releases.” Very few people are killed by sluffs because they tend to be small and they tend to fracture beneath you as you cross a slope instead of above you as slab avalanches often do. Many people call them “harmless sluffs'' because they really don’t cause all that much damage to the body. However, if you do get caught in one, it can easily take you over a cliff, bury you in a crevasse, or put you in a terrain trap. Most of the people who get caught in these are climbers who are caught in naturally triggered sluffs. These are more prone to happen in wet or springtime conditions.

All and all, avalanches can vary from downright deadly to you may get some bruises but that's all. Slab and sluff avalanches are like the polar opposite of each other. One will most likely kill you and the other will probably give you some bruises.