Hawaii sits in the middle of the Pacific Ocean, far from any plate boundary. So why is it so volcanic? Underneath the seabed there’s a stationary “hotspot” - a permanent plume of hot rock rising from deep in Earth’s mantle. The Pacific Plate slides over it like a conveyor belt.
Each spot of seafloor that drifts over the plume gets melted from below. Lava builds up underwater, eventually pokes above the ocean, and forms a brand new island. Over millions of years the plate moves on, the volcano slides off the hotspot, and a fresh one starts growing.
That conveyor has built a 2,400-kilometre chain of islands and underwater volcanoes. The Big Island is the youngest and still erupting. A new island, Loihi, is already forming on the ocean floor - give it another 10,000 to 100,000 years and it’ll poke above the waves.
