Cairn at a glance
- Used
- Above treeline and on slabs
- Rule
- See the next before leaving the last
- Building your own
- Discouraged or prohibited
Where cairns are used and why
Above treeline there is nothing to nail a blaze to, and on bare rock there is no tread to follow. A line of cairns is the only practical marker, and on granite slabs or in a boulder field it may be the only thing distinguishing the route from a hundred equally plausible ways up.
Following one is a matter of not moving until you have found the next. From a cairn you should be able to see the following cairn, or at least the ground where it ought to be. When you cannot, the correct move is to go back to the last one you were sure of rather than pressing on and hoping.
Why building your own is a problem
A decorative stack next to the real route sends someone off a cliff eventually, and it does so with the authority of something that looks official. Rangers dismantle rogue cairns for exactly this reason, and several parks explicitly prohibit building them.
There is an ecological cost too. Turning over rocks to build a stack destroys the microhabitat underneath and, in alpine and desert areas, exposes soil that took centuries to stabilise.
When cairns run out
Fog, snow and dusk all erase a cairned route very effectively, and this is where a loaded track earns its keep. A route on a watch or phone tells you whether you are still on the line when you cannot see the next marker, which is the specific failure a cairned route produces.
What this means when you're choosing
- A loaded GPX track for any route above treeline, where markers can vanish in minutes
- A device with breadcrumb navigation, which works without a map behind it
- Whether the park asks visitors not to build cairns, which many now do
The common mistake
Trusting every stack you see
Decorative cairns, old abandoned routes and someone else's wrong turn all look identical to the official line. If a cairn takes you somewhere that stops making sense, go back to the last one you were certain about rather than committing to the next plausible stack.
Common questions
Should I build a cairn?
No. A stack that is not on the official route misleads the next person with the authority of something that looks official, and moving rocks destroys what lives under them. Several parks prohibit it outright.
What do I do if I lose the cairns?
Return to the last one you were certain of. Pressing on toward a plausible-looking stack is how people end up cliffed out. A loaded track on a watch or phone is what saves you when fog or snow erases the line.
Where this is defined
- Leave what you find, Leave No Trace Center for Outdoor Ethics
- Trails and route finding, National Park Service