Lake Thorutjorn has an area of 0,2 km². It is quite deep and situated 162 m above sea level.
Its discharge tributes to river Fossalar. The walking distance from the road mainly uphill to the lake is between 1 and 2 km. The lake abounds in small brown trout, because it has not been netted frequently enough. Its surroundings are boggy and well vegetated.
The distance from the capital is about 275 km and 17 km from Kirkjubaejarklaustur.