Key takeaways
- Sastrugi are sharp, irregular snow ridges and grooves carved by strong, persistent wind.
- Wind erodes softer snow, leaving hard wavelike formations aligned with the wind direction.
- Common on exposed ridges, plateaus, and polar regions; from small ripples to foot-high ridges.
- They make ski, foot, and sled travel rough and tiring, and indicate prevailing wind patterns.
From Russian zastrugi, meaning grooves cut by wind.
What sastrugi are
Sastrugi are sharp, irregular ridges and grooves carved into a snow surface by strong, persistent wind, which erodes softer snow and leaves hard, wavelike formations aligned with the prevailing wind direction. They range from small ripples to large, hard ridges a foot or more high.
Where and how they form
Sastrugi form where there’s loose snow plus strong, sustained wind and limited melting — classically on exposed alpine ridges and plateaus, in the Arctic and Antarctic, and on big open snowfields. The wind scours softer snow away and sculpts the rest into hard ridges and furrows. Their orientation indicates the direction of the wind that formed them.
Crossing an exposed plateau in a whiteout, a ski tourer can barely see — but the hard sastrugi ridges all run the same way, and knowing the prevailing wind direction, they use the sastrugi alignment as a rough compass to hold their course.
How they affect travel
Sastrugi make travel rough and tiring: the hard, irregular ridges create an uneven, jarring surface that’s awkward to ski across, walk over, or pull a sled through. Large sastrugi are a real obstacle for polar travelers and skiers, and the hard surface makes ski edges and crampons behave differently than on soft snow — related to other wind effects like the wind slab and cornice.
The bottom line
Sastrugi are sharp, irregular snow ridges carved by strong, persistent wind, aligned with the wind direction and ranging from ripples to foot-high ridges. Common on exposed ridges, plateaus, and polar regions, they make ski, foot, and sled travel rough, jarring, and tiring. Their orientation also reveals the prevailing wind — a handy navigation clue on featureless snow.
Frequently asked questions
What is sastrugi?
Sastrugi are sharp, irregular ridges and grooves carved into the snow surface by strong, persistent wind. The wind erodes and redistributes the snow, eroding softer areas and leaving harder, wavelike ridges that are typically aligned with the prevailing wind direction. The word comes from Russian, and the singular is sometimes 'sastruga.'
Where and how does sastrugi form?
It forms where there's loose snow plus strong, sustained wind and limited melting — classically on exposed alpine ridges and plateaus, in the Arctic and Antarctic, and on big open snowfields. The wind scours softer snow away and packs and sculpts the remaining snow into hard ridges and furrows. The orientation of sastrugi indicates the direction of the wind that formed them, which can be a useful navigation clue.
How does sastrugi affect travel?
It makes travel rough and tiring. The hard, irregular ridges create an uneven, jarring surface that's awkward and exhausting to ski across, walk over, or pull a sled through — you're constantly going up and over hard bumps and furrows. Large sastrugi (ridges a foot or more high) can be a real obstacle for polar travelers and skiers. The hard surface also means crampons or ski edges behave differently than on soft snow.
Sources
- Snow surface & terrain — The Mountaineers
- Snow science — National Snow and Ice Data Center