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Virtual Collection: Rocks - Collections of interactive 3D models of representative samples from each of the major rock groups .
Virtual Collection: Rocks - Collections of interactive 3D models of representative samples from each of the major rock groups .
Learning Objectives
Learning Objectives
Each statement represents the primary learning objective for the corresponding major heading within the chapter.
Each statement represents the primary learning objective for the corresponding major heading within the chapter.
After you complete the chapter, you should be able to:
After you complete the chapter, you should be able to:
2.1 Sketch, label, and explain the rock cycle.
2.1 Sketch, label, and explain the rock cycle.
2.2 Describe the two criteria used to classify igneous rocks and explain how the rate of cooling influences the crystal size of minerals.
2.2 Describe the two criteria used to classify igneous rocks and explain how the rate of cooling influences the crystal size of minerals.
2.3 Define weathering and distinguish between the two main categories of weathering.
2.3 Define weathering and distinguish between the two main categories of weathering.
2.4 List and describe the different categories of sedimentary rocks and discuss the processes that change sediment into sedimentary rock.
2.4 List and describe the different categories of sedimentary rocks and discuss the processes that change sediment into sedimentary rock.
2.5 Define metamorphism, explain how metamorphic rocks form, and describe the agents of metamorphism.
2.5 Define metamorphism, explain how metamorphic rocks form, and describe the agents of metamorphism.
Concept Checks
Concept Checks
2.1
Sketch and label the rock cycle. Make sure your sketch includes alternative paths.
2.2
What is magma? How does magma differ from lava?
In what basic settings do intrusive and extrusive igneous rocks originate?
How does the rate of cooling influence crystal size? What other factors influence the texture of igneous rocks?
List and distinguish among the four basic compositional groups of igneous rocks.
How are granite and rhyolite different? In what way are they similar?
Explain how magmatic differentiation might lead to the formation of several different igneous rocks from a single magma?
2.3
When a rock is mechanically weathered, how does its surface area change? How does this influence chemical weathering?
Explain how water can cause mechanical weathering.
How does biological activity contribute to weathering?
How is carbonic acid formed in nature? What products result when carbonic acid reacts with potassium feldspar?
2.4
What minerals are most abundant in clastic sedimentary rocks? In which rocks do these sediments predominate?
Distinguish between conglomerate and breccia.
What are the two groups of chemical sedimentary rock? Give an example of a rock that belongs to each group.
Describe the two processes by which sediments are transformed into sedimentary rocks. Which is the more effective process in the lithification of sand- and gravel-sized sediments?
List three common cements. How might each be identified?
What is the single most characteristic feature of sedimentary rocks?
2.5
Metamorphism means to “change form.” Describe how a rock may change during metamorphism.
List the four agents of metamorphism and describe the role of each.
Distinguish between regional and contact metamorphism.
What feature easily distinguishes schist and gneiss from quartzite and marble?
In what ways do metamorphic rocks differ from the igneous and sedimentary rocks from which they formed?
Concepts in Review
Concepts in Review
2.1: Name the processes that are represented by each of the letters (A–E) in this rock cycle diagram.
2.3: Which category of weathering is represented by the broken glass in this image? What about the rusty cans?
2.4: This photo was taken in the Grand Canyon, Arizona. What name(s) do geologists use for the characteristic feature found in the sedimentary rocks shown in this image?
2.5: Examine the photograph. Determine whether this rock is foliated or nonfoliated, then determine whether it formed under confining pressure or differential stress. Which of the pairs of arrows shows the direction of maximum stress?
concept check 2 ch 2.jpgrock cycle ch 2.jpgconcept check 3 ch 2.jpgconcept check 1 ch 2.jpgGive It Some Thought
Give It Some Thought
Refer to Figure 2.1. How does the rock cycle diagram, in particular the labeled arrows, support the fact that sedimentary rocks are the most abundant rock type on Earth’s surface?
2. Apply your understanding of igneous rock textures to describe the cooling history of each of the igneous rocks pictured here.
3. Is it possible for two igneous rocks to have the same mineral composition but be different rocks? Support your answer with an example.
4. Would you expect all of the crystals in an intrusive igneous rock to be the same size? Explain why or why not.
5. One of the photos below shows an outcrop of metamorphic rock; the other two show igneous and sedimentary outcrops, respectively. Which do you think is the metamorphic rock? Explain why you ruled out the other rock bodies.
6. If you hiked to a mountain peak and found limestone at the top, what would that indicate about the likely geologic history of the rock there?
7. Give two reasons why sedimentary rocks are more likely to contain fossils than igneous rocks.
8. Use your understanding of magmatic differentiation to explain how magmas of different composition can be generated in a cooling magma chamber.
9. Dust collecting on furniture is an everyday example of a sedimentary process. Provide another example of a sedimentary process that might be observed in or around where you live.
10. Examine the accompanying photos, which show the geology of the Grand Canyon. Notice that most of the walls of the canyon consist of layers of sedimentary rocks, but if you were to hike down into what is known as the Inner Gorge, you would encounter the Vishnu Schist, which is a metamorphic rock.
give it some thought 1 ch 2.jpggive it some thought 2 ch 2.jpggive it some thought 3 ch 2.jpgKey Terms
Key Terms
rock cycle
igneous rock
magma
lava
extrusive (volcanic) rock
intrusive (plutonic) rock
granitic (felsic) composition
basaltic (mafic) composition
andesitic (intermediate) composition
ultramafic
peridotite
texture
fine-grained texture
coarse-grained texture
porphyritic texture
phenocryst
groundmass
vesicular texture
glassy texture
pyroclastic (fragmental) texture
granite
rhyolite
obsidian
pumice
andesite
diorite
basalt
gabbro
Bowen’s reaction
series crystal settling
magmatic differentiation
mechanical weathering
frost wedging
sheeting
exfoliation dome
chemical weathering
carbonic acid
sedimentary rock
Sediment
clastic sedimentary rock
Conglomerate
breccia
Sandstone
shale
siltstone
chemical sedimentary rock
biochemical sediment
limestone
coquina
travertine
evaporite deposit
coal
lithification
compaction
cementation
strata (beds)
fossil
metamorphic rock
Metamorphism
contact metamorphism
regional metamorphism
confining pressure
differential stress
Foliation
Nonfoliated
slate
phyllite
schist
gneiss
marble
quartzite
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