Nature · Earth Science
Valleys carved by ice, drowned by the sea
Fjords are long, deep, steep-walled inlets of the sea, carved by glaciers and then flooded as the ice melted and sea levels rose. Together with U-shaped valleys, hanging valleys and cirques, they are the signature landscapes left behind wherever great rivers of ice once ground their way to the coast.
During ice ages, thick valley glaciers gouged existing river valleys into deep U-shaped troughs, scouring below sea level near the coast. When the glaciers retreated, the sea flooded these over-deepened troughs, leaving sheer rock walls plunging straight into deep, sheltered water.
A U-shaped trough gouged below sea level, flooded by the ocean, with hanging valleys and waterfalls spilling from the walls.
Broad troughs planed flat by ice
A glacier grinds a former V-shaped river valley into a broad U, bulldozing spurs into blunt cliffs. When the ice is gone, these classic troughs remain — the parent form of every fjord.
Sea-drowned glacial troughs
A fjord is a glacial trough invaded by the sea. A rocky sill often guards the mouth where the glacier lost power, while the inner basin can be astonishingly deep and mirror-calm.
Side valleys left high above
Tributary glaciers cut less deeply than the main glacier, so when the ice melts their valleys are left "hanging" high on the trough wall — and their streams leap off as towering waterfalls.
Armchair hollows where glaciers were born
High on the mountainside, snow packs into a hollow and grinds out a steep-walled amphitheatre called a cirque. After the ice melts, meltwater often pools behind the rock lip as a jewel-like tarn.