Footprints in snow are supposed to sink. The ones in these photographs stand up instead, like rows of little white pedestals marching across a ridge. They are called raised footprints, and they appear wherever wind gets to work on fresh snow. The examples here come from the summit of Blencathra in the English Lake District, Snowdonia in north Wales, the Scottish hills, Alaska and the ice near McMurdo Station in Antarctica.
How raised footprints form
The trick happens in two stages. First, each step presses the soft snow beneath the boot or paw into a denser, harder block. The bonds between the grains strengthen as the compacted snow sinters, and that patch becomes much tougher than the loose powder around it.
Second, the wind arrives. It strips the soft, uncompacted snow from the surface and carries it away, but it cannot easily lift the hardened prints. The surface drops around them, and the footprints are left standing proud. Nobody lifted the snow. Everything else was blown away.
Once formed, the prints can last for weeks or even months before erosion wears them down. That is why a trail can remain visible long after the walker has gone home.
Raised footprints near McMurdo Station, Antarctica
Antarctica has the cold, dry snow and strong winds that make raised prints especially sharp. Alan R. Light photographed a series of them near McMurdo Station, the American research base at the southern tip of Ross Island on the Hut Point Peninsula. McMurdo opened on 16 February 1956 during Operation Deep Freeze. It is run by the US Antarctic Program of the National Science Foundation and is the largest community on the continent, with about 1,000 people in summer and fewer than 200 through the polar night.
Light's sequence shows the whole range: prints that still hold a clear boot outline, others worn into rounded stumps, and some that the wind has carved into strange sculpted shapes.
Paws work the same way as boots. Sledge dogs in Antarctica left trails of raised prints too.
Raised footprints in Britain and Alaska
You do not have to go to the poles to see them. Britain's hills catch strong winds off the Atlantic, and after a fresh snowfall the effect is common on exposed tops. Blencathra, also called Saddleback, rises to 868 m (2,848 ft) above the village of Threlkeld in Cumbria. Its summit ridge is a classic place to find them. Other examples here come from Snowdonia, from near Stirling in Scotland and from Foulshiels Hill. The last photograph comes from Bear Mountain in Alaska.
What raised footprints tell you about the snow
Mountaineers read raised prints as a sign of wind transport. The Scottish Avalanche Information Service notes that they form when soft snow is eroded away by the wind. On the slope where you see them, that usually points to improving stability, because the loose snow has gone. That snow has to land somewhere, though. Wind carries it onto lee slopes, into gullies and bowls and behind ridgelines, where it builds wind slab, a cohesive layer that can release as an avalanche.
Look out for wind slab on the sheltered side: smooth, chalky, dull-looking snow, a hollow sound underfoot, and cracks shooting away from your feet. If you see raised footprints on the windward side, read the avalanche forecast before you cross the lee slopes beyond the ridge.
More snow surfaces and snow art
For footsteps used on purpose, see Sonja Hinrichsen’s deliberate snow drawings, made by walking patterns into fresh snow on snowshoes. For a frozen surface that surprises the ear, listen to Cory Williams’ frozen-lake recording.
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