The fjords you'll cruise out of Aurland aren't rivers, and they aren't ordinary bays. They're glacier-carved valleys drowned by the sea — some of them well over a kilometre deep, with sheer rock walls and waterfalls spilling off the top. Here's the four-step story of how ice, gravity, and rising seawater built the most photographed landscape in Norway.
A fjord is a valley that a glacier carved, then the sea moved into. Start with a river valley cut into the mountains of western Norway. During the ice ages, a thick tongue of ice filled that valley and, over hundreds of thousands of years, ground it far deeper and wider — turning a narrow V-shaped notch into a broad U-shaped trough.
Because the ice was so thick and heavy, it kept cutting even below the level of the sea — a trick called overdeepening. When the climate warmed and the glaciers retreated, that over-deep trough was left open to the coast, and the ocean simply flowed in and filled it.
Result: a long, narrow, startlingly deep arm of seawater walled in by cliffs — with the side valleys left "hanging" high above, so their rivers now fall straight into the fjord as waterfalls.
Rivers drew the first lines — V-shaped valleys along the weak seams in the bedrock, long before any ice.
Glaciers were the excavators — they followed those valleys and bulldozed them into deep U-shaped troughs.
Overdeepening = the ice cut below sea level, so the trough floor ended up underwater-deep.
The sea was the finishing touch — it flooded the empty trough when the ice was gone.
A fjord is just the ocean sitting in a glacier's old bulldozer track.
Nothing about a fjord happens fast. It's the sum of a pre-glacial river, roughly two million years of on-and-off ice, and one relatively sudden flood.
Long before the ice ages, rivers carved V-shaped valleys down through the highlands of western Norway, following lines of weaker rock. The Sognefjord valley already existed as a river valley — it just had gentler slopes and no seawater in it.
In the ice ages, glaciers up to ~3,000 m thick filled those valleys. Ice doesn't cut a sharp V — it plucks and grinds the whole cross-section into a broad, flat-bottomed U-shape, widening and deepening the valley enormously.
Where the ice was thickest and fastest, it gouged the floor below sea level — overdeepening. Near the coast the ice spread out, lost its grip, and cut less, leaving a shallow rock lip: the sill at the fjord mouth.
When the last ice sheet melted, roughly 11,000 years ago, the over-deep trough lay open to the Atlantic. The rising ocean poured in over the sill and filled it — and the fjord was born.
This is the strange part, and the whole signature of a glacial fjord: the water inside is far deeper than the water at the mouth. Sognefjord — your fjord's parent — is the extreme case.
Ice flowing downhill has enormous erosive power where it's thick and confined. In the middle of a long fjord it bites hardest, hollowing out a deep basin. Sognefjord's floor drops to about 1,308 m below sea level — and it stays more than 1,000 m deep for roughly 100 km of its length.
Near the open coast the glacier fanned out, thinned, and stopped cutting deep. So most fjords end in a rocky sill — Sognefjord's is only about 100 m below the surface. That underwater doorstep, with a deep basin behind it, is the fingerprint that says "a glacier made this," not a river.
Running water always flows downhill to the sea; it can't cut a hole below sea level and then leave it there. Only a thick glacier — pushed forward by the weight of ice behind it — can grind out a basin far below sea level and pile the debris up as a sill near the coast. That over-deep basin behind a shallow lip is why geologists can look at a flooded valley anywhere on Earth and say for certain whether ice or water made it.
The waterfalls aren't decoration — they're a direct side-effect of how the fjord was cut. Two things put them there: hanging valleys hand the water a cliff to fall off, and a very wet coast keeps the water coming.
The main trunk glacier — the thick one that gouged the fjord — cut far deeper than the smaller side glaciers feeding into it. When the ice melted, those tributary valleys were left stranded high up the fjord wall, "hanging" hundreds of metres above the new waterline. Their streams reach the lip and have nowhere to go but straight down. That's why fjord waterfalls are tall, thin, and start partway up a sheer cliff instead of at a riverbed. The Seven Sisters in Geirangerfjord (De syv søstrene) are the classic set — seven streams off one hanging shelf — with the Suitor (Friaren) facing them from across the water and the Bridal Veil nearby.
Norway's west coast is one of the rainiest places in Europe, and it's no accident. Moist Atlantic air is forced up over the coastal mountains, cools, and dumps heavy orographic rainfall on the way over. Add snowmelt and meltwater draining off the high plateau — the fjell — and there's a near-constant supply of water at the top of thousands of feet of near-vertical rock. Anything that reaches the rim becomes a waterfall.
Flow is seasonal. It surges as the winter snowpack melts, roughly May–July, then many of the famous falls dwindle by late summer — which is why guides say the Seven Sisters and the Suitor are best seen in early season. Cross the fjords in late spring and the walls run with water; come in September and some of those falls have all but switched off.
Geirangerfjord, UNESCO. Seven streams off a hanging shelf, about 410 m tall with a 250 m free fall in the tallest — Norway's most photographed falls.
At the head of Måbødalen above Hardangerfjord — a 145 m free fall (182 m total) off the edge of the Hardangervidda plateau, arguably Norway's most famous single waterfall.
The 93 m fall the Flåm Railway stops at, reachable only by train — you step onto a platform in the spray while it thunders past.
Near Norheimsund, a ~50 m fall with a path that runs behind the water curtain — you watch the valley through the falling water.
Your fjord legs — Aurland, Voss, Bergen — all sit on branches of one enormous glacial system, the Sognefjord.
The RIB safari out of Aurland runs down the Aurlandsfjord and into the Nærøyfjord — a narrow arm of the Sognefjord that UNESCO calls one of the most scenically outstanding fjord landscapes anywhere. Points are real locations; the deep-water label marks the central Sognefjord basin, not an exact single sounding.
Once you know the recipe, the whole landscape becomes readable from the deck of the boat.
The near-vertical rock faces rising a thousand metres or more straight out of the water are the polished sides of the glacial trough. In the Nærøyfjord the walls climb to about 1,760 m while the fjord narrows to as little as 250 m wide — an aisle of rock.
Smaller side glaciers couldn't cut as deep as the main trunk of ice, so when the ice left, their valleys were stranded high up the wall — "hanging" hundreds of metres above the fjord floor. You'll see them as green notches and shelves partway up the cliffs.
Rivers in those hanging valleys now have nowhere to go but straight down the wall, which is why fjords are lined with tall, thin waterfalls — the Seven Sisters on Geirangerfjord are the famous set; the Gudvangen end of the Nærøyfjord has its own, including the towering Kjelfossen.
Your boat's route is a set of nested glacial troughs. The Nærøyfjord is a branch of the Aurlandsfjord, which is itself a branch of the giant Sognefjord. Each smaller arm was carved by a smaller tributary of the same ice sheet — the same process at three scales.
In 2005, UNESCO added the "West Norwegian Fjords — Geirangerfjord and Nærøyfjord" to the World Heritage List, calling them archetypal fjord landscapes: a textbook, still-visible record of ice-age glaciation and the land's rebound afterward, in walls of clean crystalline rock. Nærøyfjord is your half of that listing.
Your fjord base, on the Aurlandsfjord. The RIB safari drops you into the UNESCO Nærøyfjord — this is the page's whole story at eye level: trough walls, hanging valleys, waterfalls, and water over a kilometre deep beneath the hull. The Stegastein viewpoint looks straight down the trough.
The valley town between fjord and coast sits in glacially scoured terrain too — its lake and broad flat valley floor are classic ice-carved shapes. The gondola up to ~820 m gets you above the trough to see the U-profile from the rim.
Your gateway on the coast, near where the fjords meet the open sea — the shallow, island-strewn "sill" end of the system, the opposite of the deep inner basins. Mt Fløyen's funicular gives the overview of ice-worked coast.
Norway made the word famous — "fjord" is a Norwegian loanword — but not the landform. The same recipe runs anywhere ice once carved deep valleys into a coast and the sea later flooded them. These are the global cousins of the fjords under your boat.
Fiordland, on the southwest corner of the South Island — Milford Sound / Piopiotahi and the larger Doubtful Sound among fourteen fjords, walled by rock faces over 1,200 m and hung with rainforest.
The southern Patagonian coast shatters into one of the most extensive fjord systems on Earth — a maze of glacier-fed channels and islands running down toward Cape Horn.
Scoresby Sound on the east coast is the largest and longest fjord system on the planet — a branching network reaching 340–350 km inland, dwarfing anything in Norway.
The British Columbia coast, Kenai Fjords in Alaska, Baffin Island, and Newfoundland's Gros Morne — where Western Brook Pond is a fjord the rebounding land has since lifted clear of the sea.
The Westfjords — the clawed peninsula in the northwest, all steep-sided glacial inlets. (You were just there.)
Scotland's sea lochs (Loch Fyne and the west-coast inlets) are technically fjords; so are parts of Svalbard, the Faroes, and even stretches of Antarctica.
Rivers drew the valleys, two million years of glaciers dug them out below sea level, and the melting ice let the ocean in. A fjord is a drowned glacier track — and Sognefjord, the one under your boat, is the deepest and longest track of them all.