The most basic cairns are often a single stack of rocks intended to mark a path, a territory, or a specific site. The intent is utility and meaning, rather than art. Those who place them are thinking of those who will come after. Those who find and follow them are trusting travelers who went before. Many experienced hikers fondly call them "trail ducks" when the top rock is larger and points the way at a turn. In Hawai'i such a cairn is referred to as an ahu.
Acadia National Park has an extensive system of cairns and rules about their construction.
Simple cairns and similar assemblages have recently been adopted by the Deep Ecology movement. Stacked or balanced, these offer places and moments for reflection at spiritual-environmental retreats such as Earth Sanctuary center on Whidbey Island, Washington. Visitors to the lush grounds will find the paths punctuated with what its founder describes as "balanced stones designed to stand for a long time without falling," as well as contemporary megaliths and stone circles. A recent guest installation, however, entitled "Sticks and Stones", emphasized the reciprocal trend of impermanence and complex flux.
A modern memorial cairn has been begun in County Donegal, North West Ireland. People visiting the site are encouraged to bring a small rock or stone to add as a personal statement. This Peace Cairn has since 1993 symbolized the "laying down of primitive weapons - turning them into building blocks of a better future." Amen.
High in the French Alps, Andy Goldsworthy has constructed a number of his unique installations, including cairns along the path to the Digne-les-Bains Geology Museum of Haute-Provence. Professor Jim Locke has not only documented these, but illustrated the mother rock from which they are made and the fossils found within strata around it. His College of Marin educational website reminds us that not only human rock artifacts have a history, but so, too, do the very stones used for their making.
A vertical assemblage of rocks within an enclosing circle is a common -- even ancient -- focus for ritual or ceremony. Unlike mere heaps resulting from the clearing of stony land, these constructions are obviously deliberate and usually have some character of esthetics.
example: National Park Service Whidbey Island archeological site.
