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Anatomy of a Slide


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1: Wind-loading

High winds scour snow from one side of a peak and deposit it on the opposite side. This can cause big, unstable slabs to form. Know the direction the wind has been blowing and stay off slopes with new deposits of wind-drifted snow.

2: Crown

The crown is the upper section of an avalanche. If there’s a large crown above a slide path, you might not even be able to safely search for a lost comrade.

3: Fracture Line

The fracture line, which can range in depth from several inches to 18 feet or more, is the line between weak and strong snow.

4: Cornice

The Utah Avalanche Center calls these formations – which can range from the size of a curb to the size of a house – “the bombs of the backcountry.” Savvy backcountry skiers sometimes release them to trigger slides. But beware: Cornices can collapse underneath you, or break above you, and cause the slope to avalanche.

5: Crown Face
The upper fracture of a slab. It can range in depth from inches to feet.

6: Slope Angle
Most slab avalanches occur on slopes between 30 and 45 degrees – which coincidentally are the same angles skiers favor for powder skiing. Buy an inclinometer and use it to learn the true angle of the lines you want to ski.,p>7: False Anchor
Rocks, lone trees, or small groupings of trees, where shallow snow creates weak spots in the snowpack. False anchors are most typically found in continental and intermountain regions of Canada and the U.S. Often, these shallow, weak areas are trigger points for larger avalanches.

8: Bed Surface
The main sliding surface upon which an avalanche moves. This can be the ground (in the case of a climax slide), or an old consolidated layer on top of which the weak layer grew or was deposited.

9: The Safest Way
The best way to get yourself killed is to charge up a loaded face en route to a summit. Travel smart. On your approach, use ridges and low-angle slopes. On ridges, stay far away from cornices, which can break beneath you. If you’re postholing up a loaded chute, you’re just asking for it.

10: True Anchors
Heavily treed slopes – where it’s almost too tight to ski – work well to anchor the snow. But beware: If the trees are too far apart and the slope is steep enough, it can become a trauma factory. Ditto if a slope above the forest breaks and washes through – knocking you around like a pinball.

11: Debris Pile
The snow that has slid. Chunks from a slab avalanche can range in size from a 10th of a millimeter to the size of an RV. This is where avalanche victims are most often found.

12: Terrain Trap
Just as you don’t want to stand in a ditch during a flash flood, you don’t want to ski a harmless-looking gully or hollow. You face dire consequences when a small slide fills it with debris.

13: Runout
Also known as the deposition zone, this is the bottom boundary of an avalanche path, often identified by debris from an earlier avalanche or by trees that have broken off during a slide. Avoid crossing runouts whenever possible. If you must traverse or ski them, travel one person at a time.

Other Factors: Track the Weather
Start gathering data about the backcountry before you head out. Has it snowed? Was it windy last night? Ask your friends about their observations. Call your local avalanche center or check its website daily. Knowledge in the backcountry is power.


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