Alsek Lake has formed after the combined Alsek Glacier and a branch of the Grand Plateau Glacier retreated. The Alsek River used to pass in front of the glacier, and was pushed up against the hillside. The deep lake now collects a lot of the sediment that used to continue down the river into Dry Bay. Austin Post has pointed out the  possibility that if the branch of the Grand Plateau retreats completely, and the bed beneath it is deep enough, Alsek Lake and Grand Plateau Lake may join, and the Alsek River may change course to drain via the Grand Plateau outlet. GPS surveys done in 2005 confirm that Grand Plateau Lake is lower in elevation than Alsek Lake.
  • Alsek Glacier and Alsek Lake
  • Looking across Alsek Lake at Grand Plateau Glacier
  • Looking across Alsek Lake at Grand Plateau Glacier
  • Looking across Alsek Lake at Grand Plateau Glacier, Alsek River delta forming in the lake.
  • Alsek Glacier and Alsek Lake
  • Alsek Glacier and Alsek Lake
  • Delta forming in Alsek Lake
  • Alsek Glacier and Alsek Lake
  • Looking across Alsek Lake at Grand Plateau Glacier
  • Delta forming in Alsek Lake
  • Gateway Knob, and the old river channel from when the Alsek Glacier had the river up against the hillside.
  • Gateway Knob, and the old river channel from when the Alsek Glacier had the river up against the hillside.
  • Looking across Alsek Lake at Grand Plateau Glacier
    • Delta forming in Alsek Lake
    • Lake shorelines near Haines Jct. from 1850 (approx) when the Lowell Glacier last damned the Alsek.