Call them keepsakes from the last ice age. The thousands of kettle lakes that dot North America (including Henry David Thoreau's renowned Walden Pond, pictured here) were left by retreating glaciers some 12,000 years ago. They endure as some of the most beautiful remnants of a chillier era when vast ice sheets covered all of Canada and most of the northern United States.
These prehistoric pools were formed when massive ice chunks broke off from glaciers as they receded. Outwash from the melting glaciers, carrying stones and soil, flowed behind and surrounded or buried these sitting blocks of ice. When the blocks finally melted, bowl-shaped holes, called kettles, were left in the debris plain and filled with water mostly from precipitation and surface or underground streams and springs. Watch this video for more on how kettle holes form.
Most kettle lakes range from a quarter mile to two miles in diameter and are less than 30 feet deep, though a few are bigger and deeper. What they all share is a unique story and personality, based on the landscapes, wildlife and people around them. Continue on to tour some of North America's most unforgettable kettle lakes.