|Which are the types of plate boundaries where
volcanic eruptions can occur?
Volcanos are most commonly found at subduction
zone boundaries. This is where the thinner
oceanic plates get pulled under the thicker
continental plates. As the plates go deeper, they
melt and form pockets of magma which can cause
mountains to be built and as the hot magma rises,
it erupts out of volcanos. One area that this is
very evident is along the Andes Mountains in South
America. Also, the Sierra Nevada was formed this
way and the granite of the Sierra Nevada was
formed by the very slow cooling of silica rich
magma. Volcanos are also found along spreading
centers (under water and at the surface in
Iceland) where the thinner oceanic crust is being
pulled apart the the hot magma is bubbling up
(remember heat rises). A third place is where
these are weakness in the earth's crust, commonly
called hot spots. Hawaii and Yellowstone are
excellent examples of this. These weaknesses are
not associated with any plate boundary, but are
holes in the earth's crust that move as the plate
they are associated with moves. That is why there
is a chain of islands in Hawaii. Each island was
formed as the hot spot hole allowed magma to come
up and form new land above the crust.
Yellowstone's movement is noted by where the
active geysers are.
Volcanism occurs regularly at two of the three
types of plate Boundaries. The most volcanism
occurs at diverging plate boundary where plates
separate. Volcanoes also form at converging plate
boundaries where one plate dives beneath the other
at subduction zones.
Usually volcanoes are found near subduction
zones, where oceanic crust sinks beneath
continental crust. In fact, they're quite often
about 200 km inland (on the continental plate)
from where the subducting plate sinks below the
overriding plate. As the subducting plate sinks,
it melts. That rock melt, mixed with water that is
pulled down into the subduction zone with the
subducting plate, erupts as a volcano at the
surface.You have a nice animation to the volcano
in the next link: animation
Volcanoes occur along both divergent
sea-floor-spreading plate boundaries and
convergent subduction boundaries, but the
volcanoes are very different in character between
them (the divergent plate boundaries having
fissure flow eruptions and the convergent plate
boundaries making strata volcanoes). Transform
plate boundaries and continent-continent collision
plate boundaries do not normally form volcanoes.
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