The Hawaiian Islands were formed by volcanic activity as the Pacific tectonic plate moved over a stationary hot spot in the Earth's mantle. This hot spot produces magma that erupts through the ocean floor, gradually building up underwater volcanoes that eventually rise above sea level to form islands. As the plate continues to move northwest over the hot spot, new volcanoes form and older islands move away, eroding and eventually sinking below sea level, creating a chain of islands and seamounts extending across the Pacific Ocean.

The process explains why the islands are arranged in a linear chain with the youngest island, the Big Island of Hawaii, still volcanically active, and older islands progressively farther northwest. This volcanic hotspot activity has created all the major Hawaiian islands and continues underwater with future islands forming along the Hawaiian–Emperor seamount chain.