The journey of a plate sinking into a trench
is a long and complex affair, and the effects
of this journey are apparent on the face of the
earth. Firstly, as the cold, stiff plate begins
its arduous descent, a continuous series of earthquakes
is created. The plate then starts to heat up and
at a depth of about 75 miles, certain magmas are
melted and rise toward the surface. Eventually
these magmas make their way up into the leading
edge of the overriding plate, where they add material
to the crust and build volcanoes above it. If
the upper plate is oceanic, the volcanoes pile
up until they poke through the surface of the
ocean and form an elegant arc. [Scientists believe
that this arc formation has something to do with
the curvature of the earth].
Examples of island arcs created in this way are
the Aleutians, the Kuriles, Japan, the Ryukyus,
and the Philippines, found clustered around the
northern and western borders of the Pacific Plate
like a necklace. There are other island arcs to
the south (Indonesia and the Solomon’s),
and although scientists are still puzzled by the
exact origin of these southern island arcs, plate
subduction is the suspected architect.
