Leka Island

The Leka Ophiolite Complex is 497+/- 2 million years old. The age was determined by examining weak radioactive minerals in the silica-rich lavas.
Later, the complex was eroded down to sea level and sedimentary rocks were deposted on top. These were later folded and lithified to the conglerates, sandstones, marbvles and shales we see today. They are found in a belt from Gangstøen, through Leka Camping, past Havna and north on the eastern side of Skeisnesset.
In this area of Norway where continental bedrock dominates, The Leka Ophiolite Complex is an exotic remnant of oceanic material. In some places the old continental bedrock breakes the surface. On the mainland (Gutvik/Austra), granitic gneiss is the main rock type. These rocks are ca. 1800 million years old and formed when granites undergo high stresses or temperatures.
The sedimentary rocks deposited in continental basins or on the continental shelf were folded during the Caledonian orogeny as well. On Solsemøyene we find this type of sedimentary rock. The rocks that were shoved deepest became so warm that they melted partially. There were also intrusions from melt from the mantle. This magmatic material formed intrusive rocks like granites, syenites and gabbros. In Horta, we find all three of these rock types together with metamorphosed sedimentary rocks. There are also granites on Sklinna.
On the path up to the Solsem Cave, we find what might be the country’s youngest rock - a conglomerate that is approximately 10,000 years old. It is formed by cementing loose grains and gravels to make a conglomerate and was formed after the last Ice Age.