View East from Haleakala Visitor Center

There are two theories that help explain the formation of Hawaiian volcanoes. First is the plate tectonic theory whereby the earth's crust is broken into plates that move as the earth's mantle circulates in currents below the plates. The plates move relative to one another at average speeds of a few inches a year Hawaii is located on the Pacific Plate, which is moving towards the northwest at a rate of four inches per year. Second is the hot spot theory. A stationary upwelling current rises through the mantle and allows magma to push its way through the crust and reach the surface of the earth. A broad, dome shaped shield volcano is formed from layer after layer of lava reaching the earth's surface, building beneath sea level, and eventually reaching the ocean surface and becoming an island. As the Pacific Plate moves towards the northwest, the volcano is carried away from the hot spot and eventually stops erupting. A new volcano begins forming over the stationary hot spot. This is why Hawaiian volcanoes form a chain of islands in the middle of the Pacific Ocean.