Gea Norvegica Unesco Global Geopark, Siljan

About

The landscape in Siljan has a fascinating geological history. Millions of years ago, molten rock solidified into bedrock. Since then, about 40 ice ages have eroded and shaped the mountains. This created a beautiful hilly landscape with ancient glacial river deltas, a dry former fjord bottom, lakes, and a winding river.

Today, Siljan is dominated by forests and rounded hills surrounding the central Siljandalføret valley. This valley was carved out by glaciers, and the glacial deposits left behind fertile soil well suited for agriculture.

Traces of the Ice Age in Siljanmarka

When hiking in Siljanmarka, you can see many visible traces from the Ice Age, including:

• Glacial striations carved into bedrock
• Large and small glacial erratics
• Crescentic gouges (sickle-shaped cracks)
• Potholes formed by glacial meltwater

These features offer a unique glimpse into the natural forces that shaped the region.

Oslo Rift and Ancient Volcanic Activity

Around 300 million years ago, this area was marked by intense volcanic activity. Large fractures opened in the Earth’s crust, and molten magma rose from deep below. This geological period lasted for about 50 million years and resulted in the formation of the region known today as the Oslo Rift.

Syenite and Larvikite – The Dominant Rocks of Siljan

The bedrock in Siljan mainly consists of two types of igneous rocks: syenite and larvikite. These rocks have different mineral compositions and weathering properties, which shape both the landscape and the vegetation.

Larvikite – Fertile and Lush

Larvikite weathers relatively easily and releases nutrients into the soil, supporting rich plant growth. Auenkollen is a good example — a low, rounded hill with dense, green vegetation.

Syenite – Hard and Nutrient-Poor

Syenite weathers very slowly and contributes little to soil fertility. This results in sparse vegetation and bare rock surfaces. Skriua in Siljan is a typical example, with steep cliffs and scattered pine, juniper, and heather.

Summary

The landscape in Siljan is a living testament to the forces of both ice and fire. Dramatic rock formations, unique bedrock types, and lush forests make it a perfect destination for nature and geology enthusiasts.