Bierstadt Lake Professional Review and Guide
"After a short climb, this walkway wanders through the woods to a uniquely formed lake. Bierstadt Lake sits atop Bierstadt Moraine. Actually, Bierstadt Moraine, a ridge more than 1 mile long between Hollowell Park and Glacier Basin, should be called Bierstadt Moraines, for two lateral moraines dumped along the sides of two glaciers of different ages are jammed parallel to each other.
The older moraine is the northerly one, formed by glaciers that flowed from the high peaks from about 127,000 years ago until approximately 87,000 years ago (expert opinions vary). During this time of colder average annual temperature, the first half of Bierstadt Moraine formation began when prevailing east-blowing winds dumped snow to a depth of at least 250 feet on the east side of the Continental Divide."