Earth’s rocky outer shell, its crust, is actually made of dozens of huge pieces of rock known as tectonic plates. These plates ride on currents of molten rock in the upper mantle, which lies just below the crust. Activity in the mantle and crustal plates results in earthquakes and volcanic eruptions. Most of these seismic events take place where two plates come together or tear apart.
The Hawaiian Islands, however, sit in the middle of the Pacific plate. They lie over a hot spot, where magma from the mantle pushes to the surface. The Hawai'i hot spot remains in one place while the Pacific plate moves steadily northwest. Hawai'i’s “Big Island” is still being formed by Mauna Loa and Kilauea, two volcanoes currently sitting over the hot spot. Loihi, an undersea volcano, also sits above the hot spot and will likely become the next Hawaiian island.
- The Loihi seamount is an active volcano on the seafloor about 35 kilometers (22 miles) southeast of the Big Island of Hawaii.
- Mauna Kea sits 4,205 meters (13,796 feet) above sea level, but its total height from the seafloor to its summit is 10,200 meters (33,500 feet).
- Hydrothermal vents on the seafloor were first discovered, sampled, and photographed in 1977. Scientists had long suspected that these undersea geysers existed but were shocked to find the thriving community of organisms living around them without access to sunlight.
intensely hot region deep within the Earth that rises to just underneath the surface. Some hot spots produce volcanoes.
molten, or partially melted, rock beneath the Earth's surface.
middle layer of the Earth, made of mostly solid rock.
thin layer of the Earth that sits beneath ocean basins.