Submerged Glacial Moraines
Many of the bays and fjords in Prince William Sound were formed by glaciers that have since receded. As these glaciers retreated, they deposited ridges of rock, gravel, and sediment known as terminal moraines.
These moraines often extend across the entrance of a bay or fjord, forming a shallow underwater bar or sill:
- Hazard: These underwater ridges can be shallow, creating a risk of grounding or striking rocks, especially at low tide.
- Action: Check your nautical charts and monitor your depth sounder when navigating close to these formations. Enter during high tide if your draft is close to the reported depths.
Key Glacial Moraine Areas in PWS
Mariners should monitor their depth and consult charts when transiting near these twelve known moraine hazards:
- Barry Arm: Located deep in Port Wells; expects significant shoaling and rocks at the narrows.
- Pakenham Point: Guarding the passage near Harrison Lagoon and the northern reaches of Port Wells.
- Esther Passage (Northwest Entrance): A shallow bar that restricts access for deep-draft vessels.
- Esther Passage (Southeast Entrance): Features narrow channels, shallow shoals, and rocks.
- Esther Passage (Northwest Sector): Shallow mid-channel areas created by glacier deposits.
- Eaglek Bay Entrances: Multiple shallow bars where ancient glaciers terminated.
- Lake Bay (North Entrance): Approach the Wally Noerenberg Hatchery with caution.
- Hidden Bay (North Entrance): A narrow entrance channel that blocks larger vessels.
- Applegate Island (North Side): Features extensive shallow flats in the western Sound.
- Crafton Island Area: Located at the entrance to Port Nellie Juan; currents can create rough, standing waves over the shallow bar.
- Bay of Isles Entrance: Located on Knight Island; features complex, shallow moraine structures.
- Harrison Lagoon: The entrance bar dries out almost completely at low tide; access is highly dependent on high water.
Disclaimer: This list highlights key moraine hazards but is not a replacement for active navigation. Always verify depths using official NOAA charts.