About twenty thousand years ago, Earth was one-third covered by glaciers, the remains of which are now being tapped as a source for bottled water. Alaskan tidewater-calving glaciers are melted for bottling, and elsewhere the water is harvested just before it would run into the ocean.

The sources steep terrain is often inhospitable to humans or animals, and access is restricted by environmental regulations. Even so, some contamination concerns remain (see the discussion of icebergs below). Glacier water is old water, sometimes formed more than seventeen thousand years ago. Typically, it has an extremely low mineral content and is similar in taste and other qualities to rainwater. Ice Age is one of the glacier waters that appear in this book.