 The island is a rare volcano type called a tuya, or moberg, which was formed by a three-stage eruption sequence below an ice cap.The first stage was a subglacial hyaloclastic eruption under a thick ice cap, which shattered the lava into glass, ash and sand, which has since weathered to yellow palagonite layers.The second phase was a lava eruption into a meltwater glacial lake contained in the ice cap, which resulted in volcanic breccia and basalt pillow lava (boulders of this can be seen along the shore).