The different types of island are tidal islands, continental islands, barrier islands, oceanic islands and coral islands. Continental islands are formed at the edges of continental shelves. When continents break apart, pieces of land are left behind, forming islands.
Continental islands are usually broken off from continents during tectonic plate movement. For instance, New Zealand is an island that has broken off from Australia. At one time all land was believed to be together in one mass.
Tidal and barrier islands are both types of continental islands. Tidal islands are only islands during high tide because they are still connected to the main landmass such the island of Mon Saint-Michel and France. Barrier islands are parallel to coasts, formed by the accumulation of sand and sediment caused by water currents. The Outer Banks on the eastern coast of the United States is a type of barrier island.
Oceanic islands are caused by volcanic activity such as in Japan or Hawaii. These islands usually contain volcanoes because they are located on hot spots. Coral islands are formed by the external skeletons of corals. When enough of these skeletons accumulate, coral reefs form, which can then form into an island. The Bahamas are coral islands.