It is Norway that is known for its magnificent fjords, which adorn numerous tourist brochures and advertisements. There are more than a thousand of them here, and some are large enough to receive a separate name.

Why so many?

Fjords are the product of repeated cycles of glacial growth and melting. Norway’s geographical location has placed it in the path of many glaciation cycles since the beginning of the Quaternary period approximately 2.6 million years ago. The last of these cycles lasted approximately 120,000 to 11,700 years ago, but this is only one of many ice ages experienced by this region and the Earth in general.

Some fjords are large enough to accommodate large ships / Photo: Unsplash

Although ice sheets appear static, they are actually quite dynamic. Ice either moves from high points to low points through its own internal deformation, or it can slide with the underlying sediments.

This movement drags the rocks, eroding the underlying sediments or bedrock. Over time, they form U-shaped valleys, one end of which comes into contact with the ocean. They are initially filled with ice, but when they melt the resulting space is filled with water from the ocean. This is what fjords look like.

Actually many cycles of glacial advance and retreat are required to form deep fjordsSimilar to what we saw in Norway.

Once U-shaped valleys are formed, they will become a trench for ice during future glaciations; They appear to “reproduce themselves once they exist,” said Anna Hughes, a palaeoglaciologist at the University of Manchester in the United Kingdom. Thus, a fjord that begins to form in one glacial cycle will grow in the next cycle as the ice continues to carve increasingly deeper grooves in the same places.

However, not every icy coast has the same number of fjords. Their formation largely depends on the geology, that is, the material of the rock surrounding the glacier.

Although softer rocks may seem easier to cut with ice, they must have “structural integrity” to form a high-relief fjord (mountain slopes on all sides). Scientists liken it to hard cheddar cheese and soft and brittle pieces of feta cheese: the former keeps its shape, while the latter crumbles. The hard igneous rocks off the coast of Norway are ideal for creating fjords with high, steep walls.

Elsewhere, such as the coast of British Columbia, fjords still exist, but the land around them is not as large because the geology that existed there before the Quaternary period is of a different character.

The west coast of Norway is a tectonic plate boundary where continental crust meets oceanic crust.

The most spectacular fjords are found where the ice sheet flows from the continent into the ocean. A thick continental crust next to a thin oceanic crust creates a situation where ice flows downward as if descending a staircase.
– says geologist Jason Briner from the University at Buffalo.

Neighboring Sweden also experienced extensive glaciation, but has only a few fjords. During most of the ice ages over the last million years, Sweden was in the middle of the ice sheet, not at its edge. In this part of the ice sheet, the ice was not restricted by topography such as mountains as in the other part. Instead of flowing into the ocean and forming fjords, the ice spread across the territory of modern Finland and Russia.