Iceland is an island off of the coast of Western Europe in the Atlantic ocean. It is located just south of the Arctic circle. Approximately 11% of the island is glaciated. The geology of Iceland is unusual and complicated. Current theories suggest that the island, which is most definitely volcanic in origin, is actually situated on a mantle plume and a mid ocean ridge. This combination provides an interesting mineral makeup of the country rock. Petrologists have compared the mineral composition of the rocks on Iceland to MORBs, or Mid Ocean Ridge Basalts. MORBs are ultramafic in composition, and therefore are not generally seen above the sea floor. Certain historical events involving the sickness and death of many of the Icelandic inhabitants have been attributed to toxic gases and ash poisoning the animals and humans, specifically from noxious volcanic aerosols and fluorine.