Download Part A The Rock Cycle

GEOLOGY 12
CHAPTER 3 WORKSHEET
IGNEOUS ROCKS AND PROCESSES
KEY
Part A The Rock Cycle
1.
A ROCK consists of many individual mineral grains firmly held together in a solid, cohesive mass.
2.
A rock with lots of void space within or between mineral grains would have good POROSITY.
3.
If the pores or cracks within a rock are interconnected, the rock has good PERMEABILITY.
4.
Force applied to an object is termed stress; deformation that results from stress is called STRAIN.
5.
If stress on a material exceeds its ELASTIC LIMIT the material will undergo some sort of permanent
deformation.
6.
Rocks which crystallize from hot silicate melts are called IGNEOUS rocks.
7.
The idea that rocks are continually subject to change over long periods of geologic time is the essence of
the ROCK CYCLE.
8.
Which situation below describes rocks that would have good porosity and good permeability?
a.
b.
c.
d.
9.
Which phrase below best defines the situation when rocks are being subjected to forces that are squeezing
them?
a.
b.
c.
d.
10.
rocks that consist of tightly packed interlocking crystals
rocks that have finer materials filling gaps between larger grains
rocks that consist of well-rounded grains of about the same size
rocks that consist of platy mineral grains, like clay minerals
rocks are undergoing compressive stress
rocks are subjected to plastic strain
rocks are undergoing tensile stress
rocks are showing elastic strain
In your own words, describe the processes involved and the rocks formed during the rock cycle.
(Use correct terminology but do not include shortcuts.) KNOW ALL OF THE TERMS USED BELOW
•
•
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MOLTEN MAGMA CRYSTALLIZES TO FORM IGNEOUS ROCK
ROCK IS UPLIFTED, WEATHERED AND ERODED TO FORM SEDIMENTS.
SEDIMENTS ARE DEPOSITED THEN BURIED. BURIAL COMPACTS THE SEDIMENTS.
DURING LITHIFICATION THE SEDIMENTS UNDERGO CEMENTATION AND DIAGENESIS
(PHYSICAL AND CHEMICAL CHANGES).
• FURTHER BURIAL RESULTS IN INCREASED TEMPERATURE AND PRESSURE.
• HEAT & PRESSURE CAUSES ADDITIONAL PHYSICAL AND CHEMICAL CHANGES SUCH AS
GROWTH OF CRYSTAL SIZE OR RECRYSTALLIZATION AND REALIGNMENT OF CRYSTALS
AND FORMATION OF BANDING OR FOLIATION TO FORM METAMORPHIC ROCK.
• INCREASED HEAT & PRESSURE CAUSES THE ROCK TO MELT TO FORM MOLTEN MAGMA.
Part B Igneous Rocks (Fill In The Blank)
1.
Rocks which crystallize from magmas are called IGNEOUS rocks. Those cooled slowly below the
surface of the crust have a COARSE-grained texture and are called PLUTONIC or INTRUSIVE.
2.
If the magma reaches the surface of the Earth it is called LAVA and the rocks, which cool relatively
quickly, have a FINE-grained texture and are called VOLCANIC or EXTRUSIVE.
3.
When lava cools so rapidly that no crystals form the rocks will have a GLASSY texture.
4.
The majority of magmas are formed in the UPPER MANTLE , at depths between 50-250 kilometers.
5.
If pressure is lessened on rocks at great temperatures, the rocks may begin to MELT.
6.
Dissolved water and various gases found in magmas are called VOLATILES.
7.
The effect of increased volatiles in a magma is to DECREASE OR LOWER the melting temperatures.
8.
The melting temperature of a mixture of minerals is always LOWER than the melting temperatures of
the individual minerals.
9.
PHASE diagrams plot temperature against composition for a given pressure.
10. Local sources of heat within the crust or mantle include concentrations of radioactive elements, and
FRICTION caused by plate motions.
11. According to Bowen's Reaction Series, the first minerals to crystallize from a silicate magma will be
relatively LOW OR POOR in silica.
12. The continuous reaction series applies to the PLAGIOCLASE (Ca/Na) FELDSPARS minerals.
13. The discontinuous reaction series applies to the FERROMAGNESIAN minerals.
14. A magma that is rich in magnesium and iron and relatively poor in silica is called MAFIC.
15. In the process of FRACTIONAL CRYSTALLIZATION, early-formed crystals may settle out of the
magma, thus changing the composition of the remaining melt.
16. The process by which a magma incorporates the rock around it is called ASSIMILATION.
17. In magma mixing, two or more magmas combine to produce a hybrid melt intermediate in mineral
COMPOSITION.
18. A VESICULAR basalt would contain bubbles or holes where gases were trapped as the magma cooled.
19. In a porphyritic rock, a finer groundmass or matrix surrounds the larger-sized PHENOCRYSTS.
20. A plutonic rock which consists almost completely of olivine and pyroxene would be described as
ULTRAMAFIC.
21. The most common volcanic rock, which makes up the seafloor, is BASALT.
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22. Geologists use THIN SECTIONS to examine the minerals in rocks with a special polarized-light
microscope.
23. Magmas with high VISCOSITY have great difficulty flowing through narrow cracks or other openings
in country rock.
24. If the contacts of a pluton are parallel to the structure of the country rock, the pluton is considered to be
CONCORDANT. An example of this type of pluton is a SILL.
25. A discordant, tabular plutonic body is known as a DIKE.
26. CHILLED margins can be recognized because they will be more fine-grained than the interior of the
intrusion.
27. In partial melting of rocks in the upper mantle, the first minerals to melt will be the constituents of
granite; that is, they will be richer in SILICA / QUARTZ.
28. ASSIMILATION of continental crust is an alternative source for the granitic magmas of batholiths.
29. Increasing the amount of pressure on minerals will generally
a. make them melt
b. lower their melting temperatures
c. raise their melting temperatures
d. have no effect on their melting temperatures
30. Granite, a coarse-grained igneous rock, forms when
a. mafic magmas cool slowly
b. felsic magmas cool slowly
c. mafic magmas cool quickly
d. felsic magmas cool quickly
31. Which pair of igneous rock names represents the most mafic members of the igneous rock family?
a. andesite and diorite
b. rhyolite and granite
c. gabbro and basalt
d. granite and gabbro
32. Which pair of igneous rock names represents the most felsic members of the igneous rock family?
a. andesite and diorite
b. rhyolite and granite
c. gabbro and basalt
d. granite and gabbro
33. Which pair of igneous rock names represents the intermediate members of the igneous rock family?
a. andesite and diorite
b. rhyolite and granite
c. gabbro and basalt
d. granite and gabbro
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LEVEL A
ANSWERS
1. b
2. b
3. b
4. a
5. a
6. b
7. a
8. a
9. b
10. d
11. b
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LEVEL B
ANSWERS
1. c
2. b
3. a
4. c
5. a
6. c
7. higher, lower
8. coarse, large
9. b
10. b
11. a
12. b
13. a
14. a
15. b
16. a
17. a
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LEVEL C
ANSWERS
1. a
2. a
3. c
4.
a) pyroxene
b) amphibole
c) biotite mica
d) Na-rich feldspar
e) quartz
f) discontinuous
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