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The Rock Cycle
Igneous
Sedimentary
Metamorphic
http://www.minsocam.org/MSA/K12/rkcycle/rkcycleindex.html
http://www.minsocam.org/MSA/K12/rkcycle/sedimentary.html
Sedimentary rocks
• Any rock (igneous, sedimentary, or metamorphic)
exposed at the Earth's surface can become a
sedimentary rock. The forces of wind, rain, snow, and ice
combine to break down or dissolve (weather), and carry
away (transport) rocks exposed at the surface. These
particles eventually come to rest (deposited) and
become hard rock. Sedimentary rocks tell us what the
Earth's surface was like in the geologic past. They can
contain fossils that tell us about the animals and plants
or show the climate in an area. Sedimentary rocks are
also important because they may contain water for
drinking or oil and gas to run our cars and heat our
homes.
http://www.minsocam.org/MSA/K12/rkcycle/igneousrks.html
Igneous rock
• There are places on Earth that are so hot that
rocks melt to form magma. Because magma is
liquid and usually less dense than surrounding
solid rock, it moves upward to cooler regions of
the Earth. As the magma loses heat, it cools and
crystallizes into an igneous rock. Magma can
cool on the Earth's surface, where it has erupted
from a volcano (extrusive rock) or under the
Earth's surface, where it has intruded older
rocks (intrusive rock).
Volcanic (extrusive) rocks
• Extrusive igneous rocks form when magma reaches the
Earth's surface a volcano and cools quickly. Most
extrusive (volcanic) rocks have small crystals. Examples
include basalt, rhyolite, and andesite.
•
• Basalt
•
• Rhyolite
•
• Andesite
Plutonic rocks
• Intrusive, or plutonic, igneous rocks form when magma
cools slowly below the Earth's surface. Most intrusive
rocks have large, well-formed crystals. Examples include
granite, gabbro, and diorite.
•
• Granite
•
• Gabbro
•
• Diorite
Metamorphic rock
http://www.minsocam.org/MSA/K12/rkcycle/metamorphic.html
• Any rock (igneous, sedimentary, or
metamorphic) can become a metamorphic
rock. If rocks are buried deep in the Earth at high
temperatures and pressures, they form new
minerals and textures all without melting. If
melting occurs, magma is formed, starting the
rock cycle all over again.
• The term "metamorphic" means "to change
form." Changes in the temperature and pressure
conditions cause the minerals in the rock to
become unstable so they either reorient
themselves into layers (foliation) or recrystallize
into larger crystals, all without undergoing
melting.
• Foliated metamorphic
rocks are formed within
the Earth's interior under
extremely high pressures
that are unequal,
occurring when the
pressure is greater in one
direction than in the
others (directed
pressure). This gives the
rock a striped look.
• Nonfoliated metamorphic
rocks are formed around
igneous intrusions where the
temperatures are high but the
pressures are relatively low
and equal in all directions
(confining pressure). The
original minerals within the
rock recrystallize into larger
sizes and the atoms become
more tightly packed together,
increasing the density of the
rock.