The Volcano White Island is part of the Taupo Volcanic Zone which formed from the subduction of the Pacific tectonic plate beneath the Indo-Australian plate upon which New Zealand is built. White Island is an andescite volcano. The island is like a giant sponge. It receives rainwater which circulates inside the cone and is heated from a hot magma source a few kilometres below the surface.
White Island is unique in a number of ways.
The vent is below sea level but shielded from the sea by high crater walls. Although it is surrounded by seawater, the vent is chemically sealed from it. This sealed zone traps an acid hot water system, which is derived from rain water. The island is also very accesible which makes it internationally important for scientists and volcanologists to study. The volcanic structure the island stands on is thought to be two million years old, with the volcano itself between 100,000 and 200,000 years old.