Main Article Content
A four-month surge of Mount Kilauea eruptions (May to August 2018) on the Big Island reminds us that the whole chain of Hawaiian islands has been built by volcanic activity. Kilauea is one of five volcanoes that built the Big Island; a future island (Lo’ihi) is growing on the seafloor 20 miles to the southeast. A plume of rising magma from deep inside the Earth’s mantle underlies a seafloor hotspot; lava is forced through vents in the Earth’s crust; as the Pacific seafloor moves northwest from its origin at the East Pacific Rise, this stationary hotspot creates a line of volcanic islands. To the northwest, submerged seamounts remain as remnants of former islands once formed over this hotspot. A northward chain known as the Emperor Seamounts reveals that this same hotspot has created more than 100 volcanoes over 70 million years. The Hawaiian and Emperor seamounts are not unique. The New England Seamounts off the coast of Massachusetts, and similar lines in the South Atlantic record the east-west spread of the Atlantic seafloor over mid-ocean hotspots. In the Indian Ocean, north-running seamount chains record the northward movement of the Indian plate following the breakup of Pangea. In the United States, a line of extinct craters west of Yellowstone across Idaho mark the westward movement of the North American plate over the hotspot now under Yellowstone.