Pasvik Reserve is situated in the extreme north of Baltic (Fennoskandia) crystalline sheet; the area is mainly formed by the Precambrian (the Archaean and the Proterozoic) and late Paleozoic rocks. The Archaean rocks predominate and make a foundation for the Palaeogene and Proterozoic rocks. The earth's crust is cut by deep fissures and the ancient rocks are well seen in the relief.
Area's geological structure is complicated. The metamorphic Archaean acid rocks such as granites, gneisses, granite and gneiss, migmatites and some others are in the south of the reserve. The rest of the area is formed by metamorphic magmatic rocks of basic and ultrabasic structure such as gabbros, amphibolites with a high content of calcium oxide and andesides. Different schists predominate in north of the reserve. They are mica-schists, garnet and mica-schists, amphiboles and biotite schists, chlorites and carbonaceous schists. In the centre of the reserve there is a rib, Kalkupya Mountain. It consists of intrusion rocks of Kaskama complex which was formed in two periods. The early period consists of piroxenites, gabbros, gabbros and anorthosites, amphibolites; the late period is composed of diorites, granodiorites, plagiogranites and gneisses.
Quaternary sedimentations of Scandinavian glacier which vary in thickness and structure cover the bedrocks. The glacier did a lot to form the present day relief: the bedrock was stripped, ploughed and polished. Its activity can be seen today: smoothed tops of residual mountains, plucking, glacier scars as well as stretched hills, lakes and lowering on the way of its movement. Except its ruinous activity there was an accumulation of moraine which is the main type of quaternary sediments there. It is presented by a mixture of rough boulders, sand and sandy loam with crushed stones. Moraine covers nearly all the plain. The bedrock is often outcropped on the steep slopes of the residual mountains, denuded ranges and massifs in the north of the reserve.
There was a gulf in the present day Paz River valley in the late glacial and postglacial periods. Plenty of marine transgressions left their marks there: river shores which are up to 65-70 meters above sea level are composed of marine sandy loam, loamy soil and clay. Marine valleys emerged in the lowland. Menikka Island which is in the north of the reserve is one of them. Later biogenic sediments or different types of peat appeared there; they can be up to three meters thick.
Different stability of bedrock against denudation, glacier's activity and modern quaternary sediments make area's general profile. Rreserve’s relief as well as relief of adjacent areas is denuded and tectonic; it is presented by numerous moraine hills and ridges with marshy lowering. On the average the plain is about 50 meters above sea level. Moraine hills and ridges are about 200 meters above sea level. They rise above the plain at a height of 10-50 meters. Several residual mountains or insular mountains (which were not inundated by the sea at transgression time) are in the northern and central parts of the protected area. The highest residual mountain is Kalkupya; it is 357 meters above sea level. There are two more mountains opposite the reserve's area: Kaskama (351 meters high) and Korablekk (386 meters high); they are based on the same bottom. Alteration of high-altitude zones is typical for all of them.