|Why are there fjords in Norway?|
|Question Date: 2020-05-29|
Thanks for an interesting question. As you probably know, beginning about two million years ago, the northern hemisphere grew a very large ice cap, which reached as far south as Chicago, New York City, all of Scandinavia, etc. Ice caps flow downhill, and from the "push" generated by their own mass. (Imagine building a really tall birthday cake. Even if you could keep it from tipping over, the taller it got, the more the lowest layers get compressed, and squished out to the side. At some point you reach equilibrium--for every new inch you add to the top of the cake, an equal amount gets squished out the bottom.)
As perhaps you know from visiting Yosemite, glaciers (fingers of ice caps, basically) carve the landscape, forming deep U-shaped valleys. In colder parts of the world, glaciers reach the ocean, carving valleys all the way to the coast.
Another thing to keep in mind--ice caps are formed from water that ultimately came from the ocean, in the form of precipitation. When ice caps are large, sea level drops. For example, 20,000 years ago, the height of the last ice age, sea level was about 120 meters lower than it is today--meaning the coastline was much more "oceanward" at the time (depending on the slope of the ocean bottom).
So...to tie this all together. 20,000 years ago, glaciers flowed over what's now Norway. Sea level was lower, so glaciers flowed far beyond the modern coastline, carving deep, U-shaped valleys all the way to the ancient coast As climate then warmed, glaciers retreated, emptying out these big, beautiful, glacially-carved valleys. Unfortunately, all this melting ice caused sea level to rise, so coastlines migrated landward, flooding the lower reaches of these newly formed valleys. There you have it--fjords are flood glacial valleys!
The stories landscapes can tell are fascinating. Keep pondering!
Fjords form when glaciers erode the crust they sit upon and flow from high elevations to lower ones with the oceans being the ultimate base level.
Fjords were (/are) formed by glaciers scraping away material to deepen a pre-existing valley . The relatively soft top material (and some of the underlying bedrock) are pushed away, creating a deep U-shaped valley. An advancing glacier (basically a large mass of mostly ice being dragged downhill by gravity) digs a valley to a depth below sea level. When that glacier retreats, the empty valley is left behind. If the bottom is then filled with sea water, it is called a fjord.
Thus, forming a fjord requires a glacier that is able to move downhill, and a "hill" to move down. This means that the best combination to make fjords are mountainous regions far away from the equator and on the western side of a large landmass. Mountains provide the slope for the glaciers to move down; far to the north or south to freeze the water and form the glacier; and on the western side is because prevailing winds at the high latitudes are directed west to east and will therefore carry water up to the top of the mountains where it will rain/snow, thereby creating/growing/replenishing the glacier.
Norway has many fjords because it happens to fit these criteria. It was also helped by being covered by a large ice sheet during the last ice age. Although typically associated with Norway, other locations do have fjords, mostly in regions fitting the above conditions. Some examples are the west coasts of Scotland, Alaska, British Columbia, and Chile, as well as a few on eastern coasts, such as in Maine, Greenland, and Argentina.
Around 490 to 390 million years ago, pieces of several continents collided in what is known as the Caledonian orogeny. This lifted up what is now Norway and also contributed to the development of folds and faults in the rocks there. These features created zones of structural weakness and in some places exposed weaker rocks as well. These areas probably began eroding as valleys that would later guide glaciers. During the past 2.5 million years or so, glaciers covered much of Norway. Over long periods of time, ice can flow like silly putty. Streams of ice converged in these valleys, scouring them out deeper. When the glaciers eventually melted and sea levels rose, the resulting steep-walled, U-shaped valleys were flooded, forming the fjords we see today.
Fjords are U-shaped valleys carved by glaciers and then flooded by the ocean. This happens wherever glaciers reach the coast, and then melt, leaving behind the U-shaped valleys, and then sea level rises, causing the ocean to flood those valleys. Melting ice causes sea level rise, so these go together.
Fjords are not only found in Norway, but anywhere that there are mountains at high enough latitude to get glaciers to sea level during ice ages. This includes Alaska, Greenland, Iceland, Sweden, Finland, Kamchatka, southern Chile, and Antarctica, in addition to Norway, and other places.
Read on this link, which has the better parts of the answer!
"As the ice retreats, it reveals large sea-arms digging deep into the land, filled with less-salted water stemming from the melting freshwater glaciers. That's what a fjord is, and that's why Norway has so many."
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