Geology Chapter 3 Notes – Rocks
Objectives:
Define the term rock
Identify three major types of rocks and explain how they form
Describe the rock cycle
List the forces that power Earth’s rock cycle
Compare and contrast intrusive and extrusive igneous rocks
Demonstrate how the rate of cooling affects an igneous rock’s structure
Classify igneous rocks according to texture and composition
Describe the major processes involved in the formation of sedimentary rocks
Distinguish between clastic and chemical sedimentary rocks
Identify the features that are unique to some sedimentary rocks
Predict where most metamorphism takes place
Distinguish contact and regional metamorphism
Identify the three agents of metamorphism and explain what changes they cause
Recognize foliated metamorphic and describe how they form
Classify metamorphic rocks
I. Rocks
1. Rocks are any solid mass of mineral or mineral-like matter occurring naturally
as part of our ___________________
II. Types of Rocks
1. Igneous rock is formed by the __________of molten magma.
2. Sedimentary rock is formed from the weathered products of preexisting rocks
that have been transported, deposited, compacted, and ________________
3. Metamorphic rock is formed by the alteration of pre-existing rock deep within
Earth (but still in the solid state) by________, pressure, and/or chemically active
fluids.
III. The Rock Cycle
Shows the interrelationships among the three rock types (igneous, sedimentary,
and metamorphic)
A. ___________is molten material that forms deep beneath the Earth’s surface.
B. Lava is magma that reaches the surface.
C. ____________is a process in which rocks are broken down by water, air, and
living things.
D. Sediment is weathered pieces of Earth elements.
E. Energy That Drives the Rock Cycle
1. Processes driven by _______from the Earth’s interior are responsible for
forming both igneous rock and metamorphic rock.
2. Weathering and the movement of weathered materials are external processes
powered by energy from the ______________
External processes produce sedimentary rocks.
IV. Formation of Igneous Rocks
A. Intrusive igneous rocks are formed when magma hardens ___________Earth’s
surface.
B. Extrusive igneous rocks are formed when lava hardens
D. Classification of Igneous Rocks
1. Igneous rocks can be classified based on their composition and___________.
-Coarse-grained texture is caused by slow cooling resulting in larger
crystals.
- Fine-grained texture is caused by rapid cooling resulting in___________,
interconnected mineral grains.
- Glassy texture is caused by very rapid cooling.
- Porphyritic texture is caused by different rates of cooling resulting in
varied sized __________________
2. Composition
-Granitic composition rocks are made mostly
of light-colored quartz and _______________
- Basaltic composition rocks are made mostly of dark-colored silicate
minerals and plagioclase feldspar.
- Andesitic composition rocks are between ___________light-color
minerals and basaltic composition dark-colored minerals.
- Ultramafic composition rocks are made mostly from iron and
magnesium-rich minerals.
v. Formation of Sedimentary Rocks
A. _________________involves the weathering and the removal of rock.
B. Deposition occurs when an agent of erosion—water, wind, ice, or gravity—loses
energy and drops sediments.
C. Formation of Sedimentary Rocks
1. ____________is a process that squeezes, or compacts, sediments.
2. Cementation takes place when dissolved minerals are deposited in the tiny
spaces among the sediments.
D. Classification of Sedimentary Rocks
Two Main Groups
1. _____________sedimentary rocks are composed
of weathered bits of rocks and minerals
- Classified by particle size
- Common rocks include
Shale (most abundant)
_________________
Conglomerate
2. Chemical sedimentary rocks form when dissolved substances precipitate, or
separate, from water.
• Common rocks include
________________—most abundant chemical rock
microcrystalline quartz known as chert, flint, jasper, or agate
evaporites such as rock salt or gypsum
coal
3. Features of Some Sedimentary Rocks
Features of sedimentary rocks are clues to how and where the rocks are formed
VI. Formation of Metamorphic Rocks
1. Metamorphism means “to change form.”
2. Most metamorphic changes occur at elevated _____________and pressures.
3. Conditions for formation are found a few kilometers below the Earth’s surface
and extend into the upper mantle.
A. Contact metamorphism occurs when magma moves into rock
1. Occurs near a body of ______________________
2. Changes are driven by a rise in temperature.
B. Regional metamorphism results in large-scale deformation and high-grade
metamorphism
1. Directed pressures and high temperatures occur during mountain building
2. Produces the ______________volume of metamorphic rock
C. Agents of Metamorphism
Heat
• Provides the energy needed to drive________________ reactions
Pressure
• Causes a more compact rock with greater density
D. Hydrothermal Solutions
1. Promote recrystallization by dissolving original minerals and then depositing
new ones
E. Two main categories
Foliated Metamorphic Rock
- Has a banded or ______________appearance
Nonfoliated Metamorphic Rock
• Does not have a banded texture
Definitions:
1. rock: a consolidated mixture of minerals
2. igneous rocks: a rock formed from the crystallization of magma
3. sedimentary rocks: rock formed from the weathered products of preexisting rocks
that have been transported, deposited, compacted, and cemented
4. metamorphic rock: rock formed by the alteration of preexisting rock deep within
the earth by heat, pressure or chemically active fluids
5. rock cycle: a model that illustrates the origin of the three basic rock types and the
interrelatedness of Earth materials and processes
6. magma: a body of molten rock found at depth, including any dissolved gases and
crystals
7. lava: magma that reaches earth’s surface
8. weathering: the disintegration and decomposition of rock near Earth’s surface
9. sediments: loose particles created by weathering and erosion of rock, by chemical
precipitation from solution in water or from the secretions of organisms
10. intrusive igneous rocks: igneous rock that formed below earth’s surface
11. extrusive igneous rocks: igneous rock that formed at or above Earth’s surface
12. porphyritic texture: an igneous texture consisting of large crystals embedded in a
matrix of much smaller crystals
13. granitic composition: igneous rock composed of light colored silicates such as
quartz and feldspar
14. basaltic composition: igneous rocks composed dark silicate rocks and plagioclase
feldspar
15. andesitic composition: rocks made half with dark silicates and light silicates
16. felsic: light colored silicate rocks
17. ultramafic: igneous rock composed primarily of iron and magnesium-rich mineral
(dark-silicates)
18. erosion: transportation of material by wind, water, gravity and ice
19. deposition: when an agent of erosion loses its energy and deposits what it is
carrying
20. compaction: process by which sediments are squeezed together by the weight of
overlying materials
21. cementation: solidification of sediments by the deposition of dissolved minerals in
the tiny spaces between sedimentary particles
22. clastic sedimentary rock: a sedimentary rock made of broken fragments of
preexisting rock
23. chemical sedimentary rock: sedimentary rock consisting of material that was
precipitated from water
24. metamorphism: the changes in mineral composition and texture of a rock
subjected to high temperature and pressure within the earth
25. contact metamorphism: changes in rock caused by heat from a nearby mamga
body
26. regional metamorphism: metamorphism associated with large scale mountain
building
27. hydrothermal solution: the hot, watery solution that escapes from a mass of
magma during the later stages of crystallization
28. foliated metamorphic rock: a metamorphic rock with a texture that gives rock a
layered appearance
29. nonfoliated metamorphic rock: metamorphic rock that does not exhibit a banded
or layered appearance