Fjord

Fjord is a Norwegian word for a narrow body of water, which in English is borrowed to refer specifically to those with cliffs or other steep sides as a result of glacier activity. The Norwegian loan word reflects the prevalence of such inlets along the Scandinavian coast, but fjords are found in other parts of the far north as well, such as Greenland, Iceland, and the Pacific Northwest, as well as at the opposite polar extreme in Antarctica, New Zealand, and the southernmost regions of South America. In all these regions, glaciers cut furrows into the crust and bedrock, which in most cases result in the fjords’ being deeper than the wider seas to which they connect. Fjords are not just striking in appearance: their unique formations can lead to unusual ecosystems as well.

Background

Glacial erosion has shaped geological features throughout the world. Glaciers form wherever ice and snow have accumulated over time at a rate greater than the processes (evaporation, melting, erosion) that remove them, and they shift due to deformations in their ice as well as sliding along the terrain once they become heavy enough that the pressure of their weight is sufficient to create a small amount of melt. Various ice ages contributed to the formation of glaciers, which currently cover about 10% of the world’s land, almost entirely at the poles. They contribute to the erosion of land and terrain features through processes of plucking (when pieces of rock and earth are picked up by the glacier as it moves along the surface) and subsequent abrasion (when the movement of that accumulated debris against the surface not only breaks the accumulated debris into smaller fragments but also scrapes, abrades, and polishes the surface as it passes, like sandpaper). This is why some cliff features have such sharp edges and smooth faces. Because glacial erosion in mountainous areas or coasts contributes to steeper valleys and cliffs, which in turn contributes to the likelihood of catastrophic erosion in the form of avalanches, the end results can be quite striking.

Mountain valleys are normally V-shaped, because in most cases the erosion that forms them is caused by water. Glaciers, whether carving new valleys or passing through V-shaped valleys, create U-shaped valleys instead; the valley is wider and deeper, the edges higher and more severe. It is these valleys that, when the glacier passes through a body of water, become fjords. Another process involved in glaciation in general and the formation of fjords specifically is postglacial rebound. The weight of glaciers during an ice age is considerable; it not only erodes the terrain but also bears down on it, pushing land masses down. As those glaciers eventually melt and the mass is redistributed as a body of water, the land rises—just as a bottle held under water will bob back to the surface when you let go of it. This rebound has different effects depending on the bedrock and other geological conditions; in some of the glaciated regions where fjords are found, you can also find layered beaches, for instance, which look almost like steps, as a result of the rebound occurring very slowly and in waves.

Overview

Fjords are similar but not identical to rias, coastal inlets formed when a river valley becomes submerged and open to the sea, often resulting in a tree-like outline similar to that of some fjord systems. Rias are not formed by glaciation and so are easily differentiated by both surface features and underground features: Rias lack the steep cliffs of fjords and often retain islands as a result of incomplete submergence; fjords usually have a sill, a sheet of rock that intrudes across other sedimentary layers as a result of glaciation, that can increase currents in the inlet and result in rapids. Many fjord systems are also marked by skerries, rocky islands too small to be inhabited, often appearing in hundreds or thousands along a coast where fjords are found.

The word fjord comes from Norwegian, and though it has a broader meaning in that language, Norway is famous for the fjords along its western coast, in the counties of Rogaland, Horaland, Sogn and Fjordane, and More and Romsdal. Archaeological evidence tells us that this is also the region where humans first settled Norway at the end of the last ice age some ten thousand years ago. It was around this same time that most of the Scandinavian fjords were formed, as the land rose due to postglacial rebound and the valleys filled with water from the now-melting glaciers. In some parts of Scandinavia, harbors have had to be relocated repeatedly because of the still-rising land and the resulting changes to the coast. The city of Pori on the west coast of Finland is a notable example, but throughout the region there are old inland places with coastal names meaning "sound," "point," even "island," places that were once on the coast or surrounded by water before the land rose up further.

Norway's fjords include the Sognefjord, the deepest fjord in the world and the second longest, at 4300 feet below sea level at its maximum depth and 127 miles long. The Sognefjord has long been a tourist attraction, with one of its branches named a UNESCO World Heritage Site. The power lines that cross its span are the second-longest spanning power lines in the world.

The longest fjord in the world is not in Norway but in nearby Greenland’s Scorsby Sund, an inlet system the east coast (across the sea from Norway). The complex system of fjords strongly resembles a cluster of trees, especially in satellite imagery, and the longest individual fjord in the system measures 217 miles, more than half again as long as the Sognefjord.

While fjords are seacoast features, according to the international scientific usage of the word, there are a small number of "freshwater fjords" which, while not technically fjords, were formed by glaciers in exactly the same way. The most noteworthy examples are Huron Bay and Baie Fine in the Great Lakes of North America.

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