HIGH

Submerged Glacial Moraines & Icebergs

Navigating near tidewater glaciers, submerged moraines, and iceberg hazards in Prince William Sound.

Submerged Glacial Moraines

Many of the bays and fjords in Prince William Sound were carved by massive glaciers that have since retreated. As they retreated, they left behind terminal moraines—large deposits of rock and sediment.

These submerged moraines often stretch entirely across a fjord or bay entrance, creating a shallow underwater sill.

  • Hazard: At lower tides, these moraines can be dangerously shallow, causing vessels to run aground or strike submerged boulders.
  • Action: Always consult your chart and depth finder when in the vicinity of these features. Enter during high tide if clearance is questionable.

Critical Submerged Moraine Areas in PWS

Mariners need to pay special attention to charts and depth finders when navigating near these twelve documented glacial moraine locations:

  1. Barry Arm: Deep inside Port Wells; severe shoaling and moraine rocks exist at the narrows.
  2. Pakenham Point: Located at the entrance to Harrison Lagoon and Port Wells northern reach.
  3. Northwestern Entrance to Esther Passage: A shallow sill that limits draft for vessels transiting the passage.
  4. Southeastern Entrance to Esther Passage: Rocks and shallow moraine deposits guard this narrow entrance.
  5. Northwestern Sector of Esther Passage: Mid-passage shallow spots formed by ancient glacial retreats.
  6. Eaglek Bay Entrances: Multiple shallow reefs and sills where the glacier once grounded.
  7. North Side Entrance to Lake Bay: Extreme caution is required when approaching the Wally Noerenberg Hatchery.
  8. North Side Entrance to Hidden Bay: A very narrow, shallow entrance channel blocks large-draft vessels.
  9. North Side of Applegate Island: Shallow moraine flats in the western Sound.
  10. Crafton Island Area: Guarding the entrance to Port Nellie Juan, where moraine sills can cause turbulent water.
  11. Entrance to Bay of Isles: Located on Knight Island; complex moraine features present navigation hazards.
  12. Harrison Lagoon: The entrance bar goes nearly dry at low tide; access is highly tide-dependent.

Note: This list identifies known moraine hazards but must not be used as a primary source for navigation. Always refer to official NOAA charts.