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Chapter 4: Rocks – Mineral Mixtures
Section 1: The Rock Cycle
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Chapter 4
Section 1 The Rock Cycle
The Rock Cycle
• A rock is a naturally occurring solid mixture of one
or more minerals or organic matter.
• New rock forms from old rock material constantly.
• The series of processes in which a rock forms,
changes from one type to another, is destroyed,
and forms again by geological processes is called
the rock cycle.
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Chapter 4
Section 1 The Rock Cycle
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**Show Brain Pop Video:
Rock Cycle**
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Chapter 4
Section 1 The Rock Cycle
The Value of Rock
• Rock has been an important natural resource for as
long as humans have existed.
• Ancient and modern civilizations have used granite,
limestone, marble sandstone, slate and other rocks as
construction materials.
• Rock is also an important ingredient in concrete and
plaster, both of which are commonly used in
construction.
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Chapter 4
Section 1 The Rock Cycle
Processes That Shape the Earth
• Certain geological processes make and destroy
rock.
• These processes shape the features of our planet.
• These processes also influence the type of rock
that is found in certain areas.
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Chapter 4
Section 1 The Rock Cycle
Processes That Shape the Earth, continued
•The process in which water, wind, ice, and heat
break down rock is called weathering.
• Weathering is important because it breaks down
rock into fragments of which sedimentary rock
is made.
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Chapter 4
Section 1 The Rock Cycle
Processes That Shape the Earth, continued
• The process by which wind, water, ice, or gravity
transports soil and sediment from one location to
another is called erosion.
• The process in which sediment moved by erosion
is dropped and comes to rest is called deposition.
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Chapter 4
Section 1 The Rock Cycle
Processes That Shape the Earth, continued
• Sedimentary rock can also form when buried
sediment is squeezed by the weight of overlaying
layers of sediment.
• If the temperature and pressure are high enough,
the rock can change into metamorphic rock.
• If the rock gets hot enough to melt, this creates the
magma that eventually cools to form igneous rock.
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Chapter 4
Section 1 The Rock Cycle
Processes That Shape the Earth, continued
• How the Cycle Continues Buried rock is exposed
at the Earth’s surface by a combination of uplift and
erosion.
• Uplift is the movement within the Earth that causes
rocks inside the Earth to be moved to the surface.
• When uplifted rock reaches the Earth’s surface,
weathering, erosion, and deposition begin.
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Chapter 4
Section 1 The Rock Cycle
Illustrating the Rock Cycle
• The rock cycle is the continual process by which
new rock forms from old rock material.
Round and Round It Goes
• Rocks may follow various pathways in the rock
cycle.
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Chapter 4
Section 1 The Rock Cycle
Rock Classification
Rock can be three main classes based on how the
rock is formed:
• Igneous rock
• Sedimentary rock
• Metamorphic rock
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Chapter 4
Section 1 The Rock Cycle
Rock Classification, continued
• Each class of rock can be divided further, based
on differences in the ways rocks form.
• Igneous rock can be divided again based on
whether the magma from which it forms cools on
the Earth’s surface or below ground.
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Chapter 4
Section 1 The Rock Cycle
Rock Classification, continued
• Sedimentary and metamorphic rocks are also
divided into smaller groups.
• Scientists study rocks in detail using two important
criteria: composition and texture.
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Chapter 4
Section 1 The Rock Cycle
Rock Classification, continued
• Composition is the chemical makeup of a rock.
Composition can describe either the minerals or
other materials in the rock.
• Texture is the quality of a rock that is based on the
sizes, shapes, and positions of the rock’s grains.
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