Our most impressive rock formations are not mountains with towering peaks. They are the smooth and polished rocky shores on which we relax on a warm summer’s day.
What is a smooth rocky shore?
Cliffs and sandy beaches are very common, but the polished rocky shores are unique to Norway – almost. They do exist in other places, but not many. Stretches of such rock formations can be found from the Swedish west coast and up to Stockholm’s archipelago, and also in Greenland, Scotland, Alaska and possibly New Zealand. The rest of the world, however, does not have anything resembling these beautiful shores we associate with Southern Norway and the Oslo Fjord. The reason is that not many areas fulfil the two conditions required for such polished, smooth rocks to be formed. High-grade metamorphic rock such as gneiss or granite is required, and this coarse-grained formation must have been scoured and rubbed smooth by a thick layer of ice. As old as time itself!
The Norwegian rocky shores originated long before the ice arrived - maybe as much as a billion years. Formation started 1.8 billion years ago and ended 1200 million years later. The time-span is almost incomprehensible! When the ice retreated for the last time, the rocky shores were given a last finish and took their current shape. This is only 10 000 years ago. Since then, the land has risen as much as 200 metres in some areas. Hence,
the rocky shorescurrently lining the water’s edge were far below sea level and a thousand metres or more under the ice when they were formed.
As the ice moved, masses of sand, gravel and stone were pushed in front and below. These deposits were pressed down and rubbed against the bedrock with immense force. This was how Norway’s rocky shores were formed. Soft elements were scoured away, and the hard rock was left polished, smooth and rounded. In several areas, characteristic scour lines are still evident, and some cracks in the actual bedrock can also be seen.