Steep Ocean Inlets Are Called Fjords

A fjord (or fiord) is a long, narrow, deep inlet of the sea bounded by steep cliffs — carved by glaciers, then flooded by rising seas.

Formation

1. Glacier flows down pre-existing valley (V-shaped).
2. Ice erodes valley to U-shape: steep walls, flat bottom, overdeepened basin.
3. Glacier retreats; sea level rises (post-glacial) → floods valley.
4. Result: Fjord — often deeper inland than at mouth (threshold/sill).

Classic Examples

• Norway: Sognefjord (204 km, 1,308 m deep), Geirangerfjord, Nærøyfjord (UNESCO).
• New Zealand: Milford Sound (Piopiotahi), Doubtful Sound (Fiordland).
• Chile: Patagonian fjords (Chilean Fjords).
• Alaska: Glacier Bay, Tracy Arm, Kenai Fjords.
• Greenland: Scoresby Sund (largest system), Ilulissat Icefjord.
• Canada: British Columbia coast (e.g., Jervis Inlet).

Key Features

• Sill: Shallow bedrock ridge at mouth (terminal moraine) — restricts circulation, creates anoxic deep basins.
• Hanging Valleys: Tributary glaciers enter high → waterfalls (e.g., Stirling Falls, Milford).
• Stratification: Fresh surface layer (runoff) over saline deep water.

Not Fjords

• Rias (drowned river valleys — e.g., Chesapeake Bay, Galician rías) — no glacial overdeepening.
• Sounds (broad, often glacial but not overdeepened — e.g., Puget Sound).

Fjords are glaciers' signature on the coastline — deep, dramatic, and biologically unique.