Why 30 degrees of slope angle is the critical threshold, and how proper spacing on ascent and descent actually protects your group.
How far apart does your group need to be on a slope so an avalanche doesn't take out everyone at once? Honest answer: it depends on steepness — and the number to remember is 30 degrees. From this slope angle onward, dry slab avalanches can release, and nearly 95 percent of all avalanche accidents happen on slopes steeper than 30 degrees. Anything below that doesn't mean "safe," but the vast majority of events concentrate exactly in this zone.
That one number is your most important tool in the terrain, because you can roughly estimate it with the naked eye: around 30 degrees is where you need kick turns to walk — if you're zigzagging, you're in the critical zone. For reference: slopes from 30 degrees are considered steep, from 35 degrees very steep, from 40 degrees extremely steep. Every few degrees of increase changes the risk noticeably — that's not an academic nuance, it's the difference between routine and risk.
The eye notoriously misjudges slope steepness — most people significantly underestimate steep slopes. Use a slope-angle tool or app at critical spots instead of guessing. Past 30 degrees, every further decision gets stricter.
From around 30 degrees of slope angle, keep at least 10 meters of spacing during the climb. That relieves load on the snowpack — every additional person standing on the same spot increases the point load on the slope.
For the descent: below 35 degrees, keep at least 30 meters of spacing; at 35 degrees and steeper, everyone skis one at a time. The reason is simple — the descent adds dynamic loading from speed and turning, a different kind of force input than calm walking.
At danger level 3 (considerable), traversed slopes should be no steeper than 35 degrees; at level 4 (high), terrain bowls over 30 degrees should generally be avoided. These thresholds aren't advanced-level suggestions — they're baseline rules for every tour.
Slopes above and beside you count too — an avalanche can release from a slope you never actually ski and still catch you. Look at the whole terrain before you commit, not just your planned line.
Slope angle and spacing don't replace the avalanche bulletin — they're its practical application in the terrain. The 30-degree threshold is deliberately chosen as an easy-to-remember rule of thumb — if you're zigzagging, you're in the zone where almost all avalanche accidents happen. At danger level 4: terrain bowls over 30 degrees are avoided as a rule, no exceptions for "experienced" group members.
Say the spacing rules out loud before you enter a critical slope — don't just think them. Saying "we're spreading out 10 meters now" out loud anchors the rule for the whole team and stops someone from bunching up again out of habit. Small, spoken rituals work more reliably in the mountains than silent intentions.
From around 30 degrees, dry slab avalanches can release, and almost 95 percent of all avalanche accidents happen on slopes steeper than 30 degrees. That's the threshold where you need to be especially alert.
From around 30 degrees of slope angle, at least 10 meters per person — that relieves load on the snowpack and limits the damage if something does happen.
Below 35 degrees, at least 30 meters of spacing; at 35 degrees and steeper, everyone skis one at a time. The descent adds extra dynamic loading from speed and turning, which is why spacing is larger here than on the ascent.
Small groups of up to about six people are considered safer — larger groups make communication and keeping spacing in critical terrain harder.
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