The Hawaiian Islands were formed as the Pacific Plate moved in a Northwesterly direction over a hot spot. The hot spot never moves. Magma spurts out of the hot spot. Every million years or so, the hot spot under Hawai'i gets active and makes another island and then cools. This island moves as the Pacific Plate moves. Then when the hot spot gets active again, it forms another island. About 3 million years ago, O'ahu was over the hot spot. Today, Mauna Loa and Kilauea volcanoes on the island of Hawai'i are over the hot spot.