Key for Chapter 4, Section 2 Igneous Rocks Directed Reading A

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Skills Worksheet
Directed Reading A – Key
Section 2: Igneous Rock
B_____ 1. What kind of rock forms when hot, liquid rock, or magma, cools and
solidifies?
a. sedimentary
c. metamorphic
b. igneous
d. mineral
A_____ 2. Which kind of rock has a name that comes from a Latin word that
means “fire”?
a. igneous
c. metasedimentary
b. metamorphic
d. sedimentary
3. What two factors affect the type of igneous rock that is formed?
The two factors that affect the type of igneous rock that is formed are the
composition of the magma and the amount of time the magma takes to
cool.
ORIGINS OF IGNEOUS ROCK
4. Igneous rock begins as magma.
5. What are the three ways that magma can form?
The three ways that magma can form are when rock is heated, when
pressure is released, or when rock changes composition.
6. What three factors affect the formation of magma?
Three factors that affect the formation of magma are temperature,
pressure, and composition.
7. How does the composition of the magma affect the temperature at which it
solidifies?
_______________________________________________________________
_______________________________________________________________
COMPOSITION AND TEXTURE OF IGNEOUS ROCK
8. Light-colored igneous rocks are less dense than Skills dark-colored igneous
rocks are
Original content Copyright © by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor.
Holt Science and Technology
4
Rocks: Mineral Mixtures
Directed Reading A continued
9. Light-colored igneous rocks that are rich in aluminum, potassium, silicon, and
sodium are called felsic rocks.
10. Dark-colored igneous rocks that are rich in calcium, iron, and magnesium are
called mafic rocks.
11. The longer it takes for a rock to cool and solidify, the more time mineral
crystals have to grow, giving the rock a(n) coarse grain.
12. The more quickly an igneous rock cools and solidifies, the finer the grain.
IGNEOUS ROCK FORMATIONS
Match the correct description with the correct term. Write the letter in the space
provided.
a. pluton
A____13.a large, irregular-shaped intrusive body
b. dikes
C____14.the largest intrusive bodies
c. batholiths
D____15.sheetlike intrusions that lie parallel to previous
rock units
d. sills
B____16.sheetlike intrusions that cut across previous
rock units
17. Magma intrudes or pushes, into surrounding rock below the Earth’s surface to
create such formations as batholiths and sills.
18. Intrusive igneous rock usually has a(n) coarse grained texture.
19. Igneous rock that forms from lava, or magma that erupts onto the Earth’s
surface, is called extrusive igneous rock.
20. Lava can either erupt or flow from long cracks in the Earth’s crust called
fissures.
21. When lava flows from fissures on the ocean floor at places where tension is
causing the ocean floor to be pulled apart, new ocean floor is formed.
22. When a large amount of lava flows out of fissures onto land, the lava can
cover a large area and form a plain called a(n) lava plateau.
Original content Copyright © by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor.
Holt Science and Technology
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Rocks: Mineral Mixtures
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