Tens of millions of years ago, a tectonic plate deep below the Pacific Ocean moved over a hot spot. It resulted in the formation of volcanoes that spewed hot lava. As the seafloor volcanoes erupted, cold ocean waters solidified the lava. The process repeated over and over until mountains of cooled lava eventually rose above the water. An archipelago of 137 islands, reefs, atolls, and seamounts stretched more than 1,500 miles across the middle of the North Pacific Ocean. Today, we know it as the Hawaiian Islands.