Download Chapter 4 Section 2 Igneous Rock

Chapter 4: Rocks – Mineral Mixtures
Section 2: Igneous Rock
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Chapter 4
Section 2 Igneous Rock
Origins of Igneous Rock
• Igneous rock forms when hot, liquid rock, or
magma, cools and solidifies. There are three ways
magma can form:
• When rock is heated
• When pressure is released
• When rock changes composition
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**Page 98**
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Chapter 4
Section 2 Igneous Rock
Composition and Texture of Igneous Rock
• Light-colored igneous rocks are called felsic rocks.
• Felsic rocks are rich in elements such as aluminum,
potassium, silicon, and sodium.
• Dark-colored igneous rocks are called mafic rocks.
• Mafic rocks are rich in calcium, iron, and magnesium.
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Chapter 4
Section 2 Igneous Rock
Igneous Rock Formations
• When magma intrudes, or pushes, into surrounding
rock below the Earth’s surface and cools, the rock
that forms is called intrusive igneous rock.
• Intrusive igneous rock usually has a coarse-grained
texture because it is well insulated by surrounding
rocks and cools very slowly.
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Chapter 4
Section 2 Igneous Rock
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Chapter 4
Section 2 Igneous Rock
Igneous Rock Formations, continued
• Igneous rock that forms from magma that erupts, or
extrudes, on the Earth’s surface is called extrusive
igneous rock.
• Extrusive igneous rock, commonly found around
volcanoes, cools quickly on the surface and
contains very small crystals or no crystals.
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Chapter 4: Rocks – Mineral Mixtures
Section 3: Sedimentary Rock
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Chapter 4
Section 3 Sedimentary Rock
Origins of Sedimentary Rock
• Wind, water, ice, sunlight, and gravity all cause rock
to physically weather into fragments.
• Through erosion, these rock and mineral fragments,
called sediment, are moved from one place to
another.
• The sediment is deposited in layers, and eventually
newer layers cover the older layers.
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or EROSION
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Chapter 4
Section 3 Sedimentary Rock
Origins of Sedimentary Rock, continued
• The most noticeable feature of sedimentary rock is
its layers, or strata.
• A single, horizontal layer of rock is sometimes
visible for many miles.
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Chapter 4
Section 3 Sedimentary Rock
Composition of Sedimentary Rock
• Sedimentary rock is classified by the way it forms.
• Clastic sedimentary rock is made of fragments of
rocks cemented together by a mineral such as calcite
or quartz.
• Clastic sedimentary rocks can have coarsegrained, medium-grained, or fine-grained
textures.
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**Page 103**
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Chapter 4
Section 3 Sedimentary Rock
Composition of Sedimentary Rock, continued
• Chemical sedimentary rock forms from solutions of
dissolved mineral and water.
• As rainwater slowly makes its way to the ocean, it
dissolves some of the rock material it passes through.
• Some of this dissolved material eventually
crystallized and forms the mineral that make up
chemical sedimentary rock.
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Chapter 4
Section 3 Sedimentary Rock
Composition of Sedimentary Rock, continued
• Organic sedimentary rock is made up of the
skeletons and shells of sea animals. These remains
collect on the ocean floor and eventually become
cemented together.
• Coal is a type of organic sedimentary rock that is
formed when decomposed plant material is buried
beneath sediment and is changed by increasing
heat and pressure.
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Chapter 4
Section 3 Sedimentary Rock
Sedimentary Rock Structures
• Many features indicate the way sedimentary rock is
formed. The most important feature is stratification.
• Stratification is the process in which sedimentary
rocks are arranged in layers.
• Strata differ from one another depending on the
kind, size, and color of their sediment.
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Chapter 4
Section 3 Sedimentary Rock
Sedimentary Rock Structures, continued
• Sedimentary rocks sometimes record the motion
of wind and water waves on lakes, oceans, rivers,
and sand dunes in features called ripple marks.
• Structures called mud cracks form when finegrained sediments at the bottom of a shallow body
of water are exposed to the air and dry out.
• Even raindrop impressions can be preserved in
fine-grained sediments, as small pits with raised
rims.
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