Explain why do Norwegian fjords have such steep walls?

Geological origin of the Norwegian fjords

Norwegian fjords owe their spectacular appearance to a rather tumultuous geological history. It all begins hundreds of millions of years ago, when tectonic plates collide, pushing and folding rock layers to form an imposing mountain range known as the Caledonian chain (Caledonian orogeny). Over time, these very ancient mountains undergo intense erosion, gradually wearing down until they become almost flat and low, forming a fairly stable rocky plateau (peneplain). But it doesn't stop there. When the ice age arrives about two million years ago, massive glaciers take advantage of these ancient faults and fractures to carve deeply into the rock. These deep hollows, accentuated by the enormous pressures and the abrasive action of moving glaciers, will become the steep and narrow valleys we know today as Norwegian fjords.

Impact of glacial action on the verticality of cliffs

During the last major glaciations, immense glaciers slowly advanced through the Norwegian valleys, strongly eroding the terrain with their enormous weight. This ice acted like a gigantic scraper, tearing entire chunks of rock as it moved. The power and pressure of these glaciers, along with the rocks they carried with them, deeply carved the bedrock, significantly widening and deepening the valleys. This fierce erosion then shaped nearly vertical walls on the sides of the future fjords: this typical steep profile comes directly from this slow but powerful digging action by the ice. As the glaciers melted, the sea flooded these valleys, giving rise to today's fjords, bordered by these characteristic sheer cliffs.

Tectonic influence on the rugged terrain of fjords

Norway experiences a particular tectonic activity because it is located near areas where tectonic plates move and collide. These movements cause faults and fractures in the Earth's crust, generating broken rock blocks marked by steep reliefs. The weakened rock becomes vulnerable to the passage of glaciers, which then carve and accentuate these characteristic vertical walls. Ancient tectonic activity, dating back millions of years, has left these cracked geological structures, subsequently facilitating the intense erosion from glaciers and water. Without this prior weakening, the Norwegian fjords would likely not present such dramatically steep walls.

Effects of marine erosion on the slope of the walls

The sea regularly gnaws away at the cliffs at the base of the fjords, creating deep notches called basal notches. These notches gradually weaken the rock. When the weight of the walls above becomes too heavy, entire sections collapse at once, further steepening their slope. The waves then quickly carry away the rock debris from these landslides, preventing it from accumulating at the base of the cliffs. As a result, the walls of the fjords remain straight, almost vertical, without any gentle slope formed by accumulation. It is this simple yet constant mechanism that maintains the striking verticality of the Norwegian fjords.

Comparison with other similar geographic areas

Norwegian fjords are quite similar to the fjords of Chile or New Zealand: deep valleys carved by ancient glaciers, now submerged by the sea. At first glance, they look very alike, but their differences are often due to local geological features. For example, in New Zealand, fjords are often shorter but just as steep, a result of a very humid climate that accelerates erosion. Those in Chile (like in Patagonia) extend over vast mountainous territories with less uniform but equally breathtaking cliffs, influenced by strong tectonic activity. In contrast, in Canada, some fjords are less steep and wider because the rocks are softer or the glaciers have passed through for a shorter time. In short, the precise combination of rock type, climate, and glacial history means that each region has fjords with its own visual uniqueness.