Earth & Space Science: Session 4
A Closer Look: Hot Spots
The majority of volcanoes occur near plate boundaries, but there are some exceptions to this. For example, the Hawaiian Islands, which are volcanic in origin, formed in the middle of the Pacific Plate more than 3,200 km from the nearest plate boundary. How can this be?
In 1963, J. Tuzo Wilson, the Canadian geophysicist for whom the Wilson Cycle of supercontinent assembly, breakup, and re-assembly was named (Session 2), noted that in several locations around the world, such as Hawaii, volcanism was occurring in the interior of tectonic plates. Scientists think that deep in the mantle, possibly even near the core-mantle boundary, large pockets of heat generate plumes of melt which rise through the Earth, regardless of plate boundaries, and generate ‘intraplate’ volcanism. While plates on the surface of the Earth move, “hotspots” are thought to be fairly stationary, generating melts until their source of heat dies away.
The hotspot beneath Hawaii has remained fairly fixed in the Earth’s interior. However, as the Pacific plate moves northwest above the plume, volcanic islands are formed in a chain in the middle of the plate.
Most hotspots occur in the interior of plates but some can be found near mid-ocean spreading ridges, such as beneath the Azores Islands of Portugal and Iceland. Many geological phenomena related to hotspots, far from plate boundaries, have been identified around the world. For example, the geysers of Yellowstone National Park exist because magma from the Yellowstone hotspot is close enough to the surface to generate the heat that drives geyser "eruptions."
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