How are Ocean Islands formed?
Whilst most volcanic activity happens at plate margins, there are cases of volcanoes erupting in the middle of plates. When these erupt on oceanic lithosphere and breach sealevel they are usually known as "Ocean Islands". In the classic model, the magmatism is caused by a deep-seated mantle plume, that forms a chain of age-progressive islands as the plate moved over it. Alternate models suggest that fragments of continental crust may lie at the cores of some island groups. I have investigated these ideas at two sites, the Canaries in the Atlantic Ocean and the Seychelles in the Indian Ocean.