What are the forces that cause Mt. Kilauea to erupt constantly over long
periods of time, and why don't other volcanoes do this?
Bob Morton's 4th grade class
Dear 4th grade class and Mr. Morton:
The answers to both of your questions are related to the
hot spot
beneath
the Hawaiian Islands. The hot spot provides a steady supply of magma for
the eruptions. The forces behind the hot spot are poorly known.
Convection in the mantle and the distribution of heat in the core and
mantle are probably important factors but geologists haven't worked it
out yet. There are other hot spot volcanoes. Yellowstone and Iceland
are two you might be familiar with. Yellowstone differs in that the
magma must rise through a continent. As it does it becomes more silica
rich and eruptions are infrequent, large, and very violent. In Iceland
the composition of the magma does not change but volcanism is more
complicated because Iceland is also on the mid-Atlantic ridge, a
spreading plate boundary. Eruptions are similar to Hawaii in style buy
less frequent. Stratovolcanoes are associated with subduction zones
where oceanic plates are pushed beneath lighter plates, usually plates
with continental crust. Volcanism in this setting is influenced by how
much fluid leaves the subducted slab, composition of the mantle, amount
of melting, travel time to the surface, stress (extension or compression)
in the lithosphere. All these conditions must be favorable to have an
eruption so it doesn't happen very often (an eruption every 1000 or
10,000 years).
Steve Mattox, University of North Dakota
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