After Petersburg the glaciers begin. Suddenly the alpine scenery to the east becomes dramatic and the hanging glaciers fill the gaps between mountains to the lip. These are the great mountain carvers of Yosemite fame, and the earth movers that made the valleys of water we are traveling through, now flooded. A tidewater glacier spills into the ocean at some point, calving off icebergs. A hanging glacier sits crammed between mountains and fills the valley, only to melt back from the lower edge each summer, and to collect new snow and ice above in the winter. All over the world most glaciers are in rapid retreat due to global warming trends.