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. 

  1. The Pacific plate is moving northwest. Relative to Loihi, where might you expect the next undersea volcano to begin forming?

     

    • Answer

      Another volcano would be expected to form southeast of the Loihi seamount.

  2. If Mauna Kea is the tallest mountain on Earth, why do most people give the title to Mount Everest?

     

    • Answer

      The majority of Mauna Kea is hidden beneath the ocean’s surface, whereas all of Mount Everest’s height is above sea level. Therefore, most people consider Mount Everest to be the planet’s tallest mountain.

  3. Yellowstone National Park is located near the middle of the North American plate. It is also the site of frequent earthquakes and geysers, streams of superheated water and steam that spurt into the air. How can you explain this activity?

     

    • Answer

      Yellowstone National Park is located over a hot spot.

  • 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.
Noun

intensely hot region deep within the Earth that rises to just underneath the surface. Some hot spots produce volcanoes.

Noun

molten, or partially melted, rock beneath the Earth's surface.

Noun

middle layer of the Earth, made of mostly solid rock.

oceanic crust
Noun

thin layer of the Earth that sits beneath ocean basins.

Funder

This material is based in part upon work supported by the National Science Foundation under Grant No. DRL-1114251. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author and do not necessarily reflect the views of the National Science Foundation.