Stacked Stone Above the Treeline

The cairn as maintained structure

Below the treeline, a blaze — two inches by six of paint on bark or rock — is cheap to place and cheap to refresh. Above it, there is no bark, ultraviolet degrades paint faster on bare stone, and a post driven into thin soil lasts perhaps a season before frost-heave pulls it loose. The cairn, a stacked-stone marker whose name comes from the Scottish Gaelic càrn, is the solution that has outlasted every alternative in exposed terrain.

The word implies informality — a pile left by a passing walker — but the cairns that hold a route together above the treeline are a different thing entirely. On the GR20 in Corsica, one of the most technically demanding long routes in Europe, the route crosses extended stretches of granite above 2,000 metres where no other marking survives. The cairns there are substantial, maintained by the Parc Naturel Régional de Corse, and deliberately built to be visible in mist as well as clear conditions — height and profile are as deliberate as any painted symbol.

The same logic governs maintained cairns on the Kungsleden in northern Sweden and on high sections of the Appalachian Trail above the treeline in New England's Presidential Range. These are not folk monuments but managed infrastructure: the relevant managing body determines standard height, typical spacing, and which stones are keyed rather than simply stacked, so the structure sheds wind-load rather than collapsing into it.

Chronology and context

1. Scottish Gaelic càrnthe linguistic root of "cairn"; common in Scottish and Irish highland place-names
2. GR20, Corsicacairns maintained by Parc Naturel Régional de Corse above 2,000 m
3. Kungsleden, Swedencairned high-route sections managed by the Swedish Tourist Association (STF)
4. Appalachian Trail Presidential Range, New Hampshireabove-treeline cairned sections managed under the AT Comprehensive Management Plan

On the GR20 in Corsica, one of the most technically demanding long routes in Europe, the route crosses extended stretches of granite above 2,000 metres where no other marking survives.

Key distinction

Keyed cairn

stones interlocked so the structure resists lateral wind-load; a managed, built marker

Stacked cairn

stones placed without interlocking; informal, less stable, often removed by trail managers in already-marked terrain

More in How a route tells you where it goes

• Two inches by six, painted on a treeThe Appalachian Trail's white blaze is a fixed size and spacing, and the double blaze that signals a turn is the whole navigation system in two marks.
• Numbering a route so it can be describedMileposts and section numbering let a route be discussed precisely, which is what makes maintenance, rescue and record-keeping possible at all.