The bedrock of the Pasvik-Inari area is dominated by basement gneiss which is strongly metamorphosed, and mostly orientated and striped. The estimated age of the basement gneiss is over 2,5 billion years. The other prevailing rocks are the innutritious deep-seated rocks like granite. Belts of more nutritious greenstones also occur in the Pasvik Valley. A slate area exists in Vätsäri, and also volcanic rocks occur. The bedrock is usually covered by thick masses of moraine and glaciofluvial sediments, in addition to mires and lakes. The moraine material contains a lot of large rocks.

Rudiments of the glacial period

The thick ice cover of last glacial period Dryas started to melt over 10 000 years ago, and the recession speed of the margin of the continental ice sheet towards south-south-west was 100-150 meters in a year. A massive ice blockage on the upper course of the present Pasvik River blocked the melted water and created the vast Inari basin. When the blockage melted, the melting water burst northeastwards through the Pasvik valley towards the Barents Sea.

Melting water left numerous and varied traces in the landscape, such as the gorge Revsaksskardet in the northeast of Øvre Pasvik National Park. Downstream of the gorge Revsaksskardet large amounts of sand and gravel were settled in deltas and eskers. Eskers are narrow gravel ridges settled by glacial streams that poured along tunnels or crevices in the ice. The deposits of the glacier streams are also seen in the terrain as moraine ridges and hummocks. Boulder covered hummocky moraines are common in the Nellim area.

The constantly flowing ice created the visible drumlin and fluting fields of Inari-Utsjoki area. Drumlins are moraine ridges that are parallel with the direction of the ice movement, and the stripes are long ridges which are lower than drumlins. The drumlin field of Inari and Utsjoki is over 100 km long and its width is about 50 km, and it extends to the Norwegian side. Westwards of Svartåsen in Øvre Pasvik National Park there are several large drumlins. In the northern part of the Vätsäri the terrain is dominated by the drumlins.