In Borgarfjörður the area around Reykholt provides naturally about 400 liters per second of boiling hot water. The Reykjanes Ridge line to NE and the NW line of Hekla intersect there and create these extraordinary conditions.
The valleys are oriented E-W due to the outer pressure on the polygon. A cube of mainly ductile material breaks from one corner to the other). The combination of side pressure and heat source creates a geothermal area.