Have you ever encountered a small stack of rocks along a Colorado trail? What are they for, and who put them there? Is this simply a national pastime, or does it serve some legitimate purpose? Here's what Colorado residents say via social media.

Those little stacks of rocks are called cairns. According to Wikipedia:

A cairn is a human-made pile (or stack) of stones. The word cairn comes from the Scottish Gaelic: càrn[ˈkʰaːrˠn̪ˠ] (plural càirn[ˈkʰaːrˠɲ]).[1] Cairns have been and are used for a broad variety of purposes, from prehistoric times to the present.

You'll see these all the time on trails like Gunny Loop, Eagle's Wing, and even the path leading up Mt. Garfield. Do people simply have too much time on their hands?

Sometimes people stack rocks for the sake of stacking rocks. Cairns, however, do serve a purpose. You'll frequently see them in places where trails converge. Another benefit comes from cairns indicating places where a trail may be hard to follow.

Have you ever hiked a trail following a fairly heavy rainfall? Rain can mask parts of a trail, making it difficult to stay on track. For that matter, have you ever taken a trail while there's fresh snow on the ground and no footprints indicating where the trail goes? It's at times like these cairns come in very handy. They provide a visual cue as to where the trail goes.

There are people out there who knock these things down. That can be unfortunate. They do serve a purpose. Here's what some residents had to say about Western Colorado cairns.