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From magma to rock:
When magma pours out of the Earth from
volcanoes and dikes, it hardens rapidly as
extrusive (volcanic)
igneous
rock. (This is the
beginning of the stone process.)
Over time, wind and rain can reduce all rock to
sediment, including deeply buried intrusive rock,
which is first exposed by erosion. Chemical
bonding and pressure from above compact the
sediment, transforming it into
sedimentary
rock.
(These are products of erosion and weathering).
The changes do not stop there. Extremely high
heat and pressure can gradually alter all rocks
into another type of rock, the
metamorphic
rock.
The full circle is completed when rocks of all
kinds are buried deep enough for the heat of the
Earth’s core to melt them into magma once
again.