Dverghamrar (Dwarf Rocks) just east of Foss á Siðu, are two large and striking columnar basalt rock formations, topped with cube-jointed basalt. The landscape is thought to have been moulded at the end of the Ice Age when sea level was higher. It is believed that waves coming into contact with the molten lava caused the peculiar look of the rocks. Columnar basalt is formed when a lava flow cools suddenly and contraction forces build up. Cracks then form horizontally and the extensive fracture network that develops results in the hexagonal formation of columns which are always upright, standing perpendicular to the cooling surface. Dverghamrar is a protected natural monument.