An Ice Age, or a glacial period, is a result of a colder climate when large areas of land are covered with ice. The climate turns slowly colder because of the changes in the Earth’s orbit around the sun, for example.
One Ice Age can include several glaciations. When we are talking about an Ice Age, we often refer to the latest Ice Age, called Weichsel here in the Northern Europe. Weichsel started about 115 000 years ago and ended in the World Heritage area about 10 500 years ago. The inland ice of Weichsel covered most of the Northern Europe.
Over the last 600 000 years, the Earth has had three Ice Ages. It is possible to see traces from these three Ice Ages, but the traces of the latest Ice Age are the clearest ones on the terrain, also in the High Coast and the Kvarken Archipelago. Researchers do not know when the next Ice Age begins, but usually the warmer periods between the Ice Ages last 10,000 to 30,000 years. Because of the climate change caused by humans, it might take even longer for the next Ice Age to begin.
Inland ice shaping the landscape
During the latest Ice Age, this World Heritage Site was under tremendous pressure. At times, the centre of the inland ice covered this area, which means that the ice mass could be up to three kilometres thick. The heavy inland ice pressed the Earth’s crust down about one kilometre. When the ice started to melt and relieve the pressure, the land began to rise. This phenomenon is called the postglacial land uplift. Read more about the land uplift here.
The inland ice pressed the Earth’s crust down, but it did not lie still. Nor was it a solid mass. The ice’s own weight created so much pressure that it made the ice soft and plastic. The plastic ice could flow slowly into valleys, for example. The ice also moved across the landscape in different directions in different times. It grew during colder periods and became smaller as it melted during warmer periods. You can only imagine how the massive inland ice rounded mountains, wore down entire hills and made valleys and ravines shallower and wider.
Rocks on the move
The inland ice carried with it a blend of boulders, stones, gravel, sand and finer materials, which form together a soil type called till. When the ice moved, the till ended up in various shaped and sized piles and layers, which are called moraine formations. Read more about moraine formations here. Also, large icebergs broke away from the inland ice and floated away. The icebergs left rocks and till wherever they finally melted. Till was also gathered in the cracks of the inland ice or flushed away with large rivers of meltwater under the ice.
traces on the terrain tell the story of the Ice Age
The traces of the latest Ice Age are still visible in the World Heritage Site, even though the Ice Age ended about 10 000 years ago. You could even call the joint World Heritage Site an outdoor Ice Age museum! What traces of the Ice Age you can find?