Bubble Rock: Acadia's Famous Glacial Erratic

Bubble Rock is a 14-foot-tall boulder perched on the very edge of South Bubble's summit — positioned so precisely that it looks like it's about to roll off the cliff. It isn't. It has been balanced there for approximately 18,000 years, deposited by a retreating glacier at the end of the last ice age.

This is what geologists call a glacial erratic: a boulder transported far from its origin by a glacier and deposited when the ice melted. Bubble Rock likely originated somewhere to the northwest — the glacier carried it southward, over the mountains and down toward the sea, before the ice retreated and left it balanced on the edge of what we now call South Bubble Mountain.

The hike itself is short — 1.6 miles round trip — but the climb is steeper than its length suggests, gaining 400 feet in under a mile. The summit view overlooks Jordan Pond and the full extent of The Bubbles, with Pemetic Mountain rising beyond. This is one of Acadia's classic panoramas.

Combine this with the Jordan Pond Path for a longer morning: walk down the south side of the Bubble to the pond's edge and continue around the loop, adding 1.5 miles of flat, beautiful walking.