DULUTH, Minn. (AP) -- To some along the north shoreline of Lake Superior in Minnesota, building stacks of rocks, or cairns, is akin to making sandcastles and can even be meditative. To others, these manmade rock formations despoil nature's beauty and stand as monuments to the human ego.

Those who live along the north shore say cairns began appearing more often about five years ago, possibly because of the growth in popularity of Instagram and other social media sites.

Photographer Travis Novitsky, who grew up and still lives on the Grand Portage Reservation, where the shoreline extends north into Canada, said he wasn't bothered by cairns at first, but that he now sees them all along the lakefront.

Peter Juhl, who's been balancing rocks for decades, says it's a meditative process for him and he considers his stacks to be ephemeral works of art. He says he encourages others to try it but also to disassemble their stacks after taking a photo to be considerate to future visitors.