Hot Spots and Mantle Plumes
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Click here for activities and teaching suggestions about hot spots.
History of Concepts
In the 1960s, geologists were seeking ways to prove or disprove the new
idea of moving plates. Exploration of magnetic anomalies at mid-ocean
ridges provided strong support for
seafloor spreading
. Geologists
studied other ocean features to see how they related to
plate tectonics.
While visiting Hawaii, Tuzo Wilson, one of the founders of the theory of
plate tectonics, noticed some interesting features about ocean islands.
On a map of the Pacific basin, he found three linear chains of volcanoes
and submarine volcanoes (seamounts).
Although separated by thousands of miles, the three linear chains are
parallel to each other. Of the three, the Hawaii-Emperor seamount chain
was the most well known. Wilson reviewed the reports that had been
published on these island chains and recorded the age of each island. An
interesting pattern emerged. For each chain, the islands become
progressively younger to the southeast. The extreme southeast end of
each chain is marked by active volcanoes.
Wilson proposed that the Hawaiian islands formed successively over a
common source of magma called a hot spot. The Island of
Hawaii
is currently located above
the hot spot.
Image Source: Eruptions of Hawaiian Volcanoes: Past, Present, and Future: U.S. Geological Survey General Interest Publication.
Hot, solid rock rises to the hot spot from greater depths. Due to the
lower pressure at the shallower depth, the rock begins to melt, forming
magma. The magma rises through the Pacific Plate to supply the active
volcanoes. The older islands were once located above the stationary hot
spot but were carried away as the Pacific Plate drifted to the northwest
.
