:16:06
Man has been uniquely favored
:16:08
by the forces which move
and alter the Earth's crust
:16:12
yet through all his history
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he has remained a hostage
to their powers of destruction.
:16:24
As new earth's crust is created
:16:26
in the spreading rifts
and ridges of the earth
:16:29
older crust is destroyed
:16:31
in a second great tectonic
process called "subduction."
:16:35
When an ocean floor plate
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collides with a continental plate
:16:39
the havier seafloor plate
is subducted.
:16:42
lt fractures
:16:43
and plunges beneath the thicker,
more buoyant continental plate
:16:46
creating an ocean tranch.
:16:50
Ponderously
:16:51
moving inches in years,
the great slab descends
:16:56
generating deep earthquakes
when it moves.
:16:59
The heat of friction
and of the Earth's interior
:17:02
slowly consumes the plate.
:17:04
lts lighter elements rise
as magma toward the surface
:17:08
fracturing paths
:17:09
through the continental plate
:17:11
emerging in the violence
of volcanic eruptions.