Successive ice ages have left clear traces on Finland’s bedrock. During the most recent period of glaciation, the continental glacier was at its most extensive about 20,000 years ago. Its melting edge retreated through Finland 10,000 - 13,000 years ago. The glacier crushed and ground up the rock. In the broken areas of the bedrock, it also carved out valleys, which have since been filled by numerous lakes.
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Ounasvaara Hill about 8,400 years ago.
The altitude of the surface of the water
is 100m above sea level.
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Rovaniemi’s bedrock was created more than 2 billion years ago of existing layers of sand, clay and lime and volcanic lava and ash. Rovaniemi’s soil was created from moraine deposited by the most recent continental ice sheets, and by gravel and sand formations, which accumulated from the glacial melt waters. After the edge of the continental glacier retreated, the ancient Baltic lake, Ancylusjärvi, stretched out into a wide area of Southern and Central Lapland. After the ice age, the centre of the City of Rovaniemi was completely underwater. As a result of isostatic uplift, the surface of the water quickly began to fall, revealing hill slopes. The waves washed the slopes and, with the winter ice, carried and rounded the rocks and boulders, forming them into beach cobble deposits and embankments. At the time of the melting of the continental glacier, ridges were created by sand and gravel carried by the melt waters flowing from the glacier.
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These ridges are usually long and narrow, and nowadays are important sources of sand, gravel and groundwater. Groundwater
is mostly stored in layers of sand and gravel. The Rovaniemi region has many ridges, which provide good groundwater. At the edges of the melting continental ice sheet, kettle holes were also formed as a result of wear by the powerful flows of melt water.
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The slopes of Sukulanrakka have 14 kettle holes, three of which are amongst Finland’s largest. Auttiköngäs, near Rovaniemi, is a north-south orientated fracture in the bedrock, which is millions of years old. During the ice ages, the continental glaciers wore down and rounded off the forms of the fracture. At the end of the ice age, Auttiköngäs belonged to a glacial river system running from the Kemijoki River valley to Korouomaa and on to Kuusamo. In the area of Auttiköngäs, raised beaches created during the time of Ancylusjärvi Lake. Geological maps provide much information on the soil and environment. The information on the maps can, for example, be used when planning a construction site or going trekking. These maps show, not only channels and boulder deposits created by the glacier, but also swamps, ridges and raised beaches.
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Sukulanrakka has 14 kettle holes
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The area of Rovaniemi in the forefield of the glacier about 10,000 years ago. The area pressed down by the ice was covered by the Baltic Sea’s Ancylusjärvi Lake. Ounasvaara Hill is a little island behind the archipelago at the bottom right.
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