Similar yet so different
The High Coast and Kvarken archipelago are contrasting landscapes, where high meets low. But the processes involving land uplift, ice sheet and sea are the same in both areas. Due to the topographic differences, the traces differ, even though the processes are the same. The High Coast and Kvarken archipelago complement each other, some land uplift traces can be found in the High Coast, some in Kvarken Archipelago and some in both areas.
The highest point of the archipelago is just over 20 metres above sea level, and water depth is 25 metres at its most. In comparison, the waters of the High Coast can be 290 meters deep, and the highest points reach 350 meters. The High Coast is the only area around the Baltic Sea where high hills reach to the sea.
High meets low
Why is the High Coast high and the Kvarken archipelago low? The explanation to why the High Coast is high and the Kvarken archipelago is low is much older than the latest Ice age. Approximately 600 million years ago, the bedrock in the High Coast and Kvarken archipelago had been worn down to a flat surface, a peneplain. Tensions in the Earth’s crust caused faults or shifts, and some of the crust was pushed upwards, including the area we now call the High Coast, but not the Kvarken Archipelago.
The high laying landscape in the High Coast was more exposed to erosion. During millions of years, cracks in the bedrock eroded to valleys. The peaks of the hills in the High Coast of today are the remnants of the old peneplain. In the Kvarken Archipelago, the old peneplane still remains. That is why the Kvarken Archipelago is so flat. This happened because the high landscape was much more exposed to erosion than the lower areas in Kvarken Archipelago.
Next chapter: the changing nature
The land uplift and the geology create challenges but also unique opportunities for the nature in the World Heritage. How?