The Siljan Ring consists of an annular outcrop of Lower Paleozoic sedimentary rocks within Proterozoic granites of the Dala series.

[9] In Dalarna, the basement rocks consist of granites dated as 1.6 billion years old, putting them at the boundary between the Paleoproterozoic and the Mesoproterozoic.

These erosional hollows are now occupied by lakes Siljan, Orsa, Skattungen and Ore.[8] In accordance with theories about abiogenic petroleum (that hydrocarbons can be formed without involving material from dead plants and animals), astrophysicist Thomas Gold suggested that there might be major deposits of oil and natural gas in the area.

[citation needed] The scientific premise for prospecting of this sort is based on the work of physicist Vladimir Kutcherov, who is cooperating with Igrene, the company financing the drilling operations.

[13] In 2019, a study of gases and secondary minerals revealed that long-term microbial methanogenesis and methane oxidation have occurred deep within the fracture system of the crater (for at least 80 million years).