Soils and bedrock

The bedrock

	© Jukka Husa, SYKE

The bedrock in Finland is among the oldest in the world. It was largely formed under highly varying geological conditions between 1,500 and 3,000 million years ago. Finland lies in a geological region dominated by the ancient Precambrian Shield, which has been exposed following the erosion of more recent formations. Most of this bedrock consists of acidic intrusive igneous and metamorphic rocks, notably granites. The bedrock is largely intact, though there are fracture zones and old fault lines in places.

Soils

	© Pekka Sipilä, GTK

Soils are made up of combinations of mineral material originating from the weathering and erosion of the bedrock, and organic material formed from the remains of plants and animals. The most widespread soil type in Finland is glacial till, or moraine, eroded and deposited during the last ice age by the massive continental ice sheet that completely covered this region of Europe for many thousands of years. Moraine covers almost half of the country.

Sandy and gravely features deposited by glacial rivers and along post-glacial shorelines are also found in many parts of Finland. Sand and gravel formations host  the most important aquifers in Finland. Soils consisting of silts and clays are found in areas that were submerged under lakes or the sea at the end of the ice age. In many boggy and marshy areas, soils feature layers of organic peat and sludge.

An important characteristic of soils in Finland is that they are typically frozen for 4–8 months a year. Without liquid water, chemical and biological reactions in the soil only occur very slowly, if at all.

Contamination

Soils may be contaminated locally by materials that directly enter the soil, or over wide areas via atmospheric deposition. Contamination of the soil at local point sources may occur wherever substances with potentially harmful environmental impacts are stored, processed or deliberately applied to the soil itself. Soil properties and hydrogeological conditions are important to know in order to assess the vulnerability of sites to kontamination.

Compared to soils elsewhere in Europe, soils in Finland are highly sensitive to acidification, and local conditions otherwise hinder the breakdown of harmful chemicals in the soil.

Construction, mining, quarrying, sand and gravel extraction, farming, forestry and reindeer husbandry can all affect groundwater reserves, as well as the physical, chemical and microbiological properties of soils.