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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?
Kilauea, Hawaii, a hot spot volcano.
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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