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Earth 2: Rocks
Julie Sandeen
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Printed: June 19, 2015
AUTHORJulie Sandeen
CONTRIBUTORMary Lusk
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Contents www.ck12.org
Contents
1 MS Rocks 11.1 Types of Rocks on Earth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21.2 Igneous Rocks: Formation, Properties, & Uses . . . . . . . . . . . . . . . . . . . . . . . . . . . 101.3 Sedimentary Rocks: Formation, Properties, & Uses . . . . . . . . . . . . . . . . . . . . . . . . 171.4 Metamorphic Rocks: Formation, Properties, & Uses . . . . . . . . . . . . . . . . . . . . . . . . 241.5 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
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CHAPTER 1 MS RocksChapter Outline
1.1 TYPES OF ROCKS ON EARTH
1.2 IGNEOUS ROCKS: FORMATION, PROPERTIES, & USES
1.3 SEDIMENTARY ROCKS: FORMATION, PROPERTIES, & USES
1.4 METAMORPHIC ROCKS: FORMATION, PROPERTIES, & USES
1.5 REFERENCES
Have you ever heard the phrase “rock solid?” Something is rock solid if it does not and cannot change. It will notfail or go wrong. A rock-solid plan is a sure bet. A rock-solid idea is sure to be doable. Devil’s Tower in Wyominglooks rock solid. It looks like it would not change or move. Even in a million years it would look just like it doesnow.
In this chapter you will find out that rocks do change. Rocks can change from one type to another. Rocks can alter tohave different characteristics but still be the same type. Most changes in rocks take place over long periods of time.More rarely the changes take only a short time. This rock formation’s days are numbered. . . and a diamond is notforever.User:Example/Wikimedia Commons. commons.wikimedia.org/wiki/File:Devils_Tower_CROP. jpg. Public Domain.
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1.1 Types of Rocks on Earth
Points to Consider
1. What are rocks made from?
2. What processes are involved in making rocks?
Lesson Objectives
• Define rock and describe what rocks are made of.• Know the three main groups of rocks.• Explain how each of these three rock types are formed.• Describe the rock cycle.
Vocabulary
• deposit: Collection of sediment that has been dropped by wind, water, or another agent of erosion.• sediment: Small particle of soil or rock deposited by wind, water, or another agent of erosion.
Fill in the blank with the appropriate term.
1. Rocks are made of one or more types of __________.2. Geologists classify rocks into three main types based on how the rocks __________.3. Sandstone is an example of __________ rock.4. Crystals in igneous rock are __________ when melted rock cools more slowly.5. Mica schist is an example of __________ rock.6. Weathering and erosion are processes involved in the formation of __________ rock.7. Some __________ rocks form when solid minerals are left behind after a liquid evaporates.
Introduction
There are three major rock types. Rock of any of these three rock types can become rock of one of the other rocktypes. Rock can also change to a different rock of the same type. Rocks give good clues as to what was happeningin a region during the time that rock formed.
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The Rock Cycle
All rocks on Earth change, but these changes usually happen very slowly. Some changes happen below Earth’ssurface. Some changes happen above ground. These changes are all part of the rock cycle. The rock cycle describeseach of the main types of rocks, how they form and how they change. Figure 1.1 shows how the three main rocktypes are related to each other. The arrows within the circle show how one type of rock may change to rock ofanother type. For example, igneous rock may break down into small pieces of sediment and become sedimentaryrock. Igneous rock may be buried within the Earth and become metamorphic rock. Igneous rock may also changeback to molten material and re-cool into a new igneous rock.
FIGURE 1.1The rock cycle.
Rocks are made of minerals. The minerals may be so tiny that you can only see them with a microscope. Theminerals may be really large. A rock may be made of only one type of mineral. More often rocks are made of amixture of different minerals. Rocks are named for the combinations of minerals they are made of and the waysthose minerals came together. Remember that different minerals form under different environmental conditions. Sothe minerals in a rock contain clues about the conditions in which the rock formed ( Figure 1.2).
Three Main Categories of Rocks
Geologists group rocks based on how they were formed. The three main kinds of rocks are:
Igneous
1. Igneous rocks form when magma cools below Earth’s surface or lava cools at the surface ( Figure 1.3).
Pause to Consider
1. What is the difference between magma and lava?
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FIGURE 1.2Rocks contain many clues about the conditions in which they formed. Theminerals contained within the rocks also contain geological information.
FIGURE 1.3Lava is molten rock. This lava will hardeninto an igneous rock.
2. What are igneous rocks? How do igneous rocks form?
3. How do minerals combine to form an igneous rock?
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Sedimentary
2. Sedimentary rocks form when sediments are compacted and cemented together ( Figure 1.4). These sedimentsmay be gravel, sand, silt or clay. Sedimentary rocks often have pieces of other rocks in them. Some sedimentaryrocks form the solid minerals left behind after a liquid evaporates.
FIGURE 1.4This sandstone is an example of a sedi-mentary rock. It formed when many smallpieces of sand were cemented together toform a rock.
Pause to Consider
1. What are sedimentary rocks? How do sedimentary rocks form?
2. How do minerals combine to form a sedimentary rock?
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Metamorphic
3. Metamorphic rocks form when an existing rock is changed by heat or pressure. The minerals in the rock changebut do not melt ( Figure 1.5). The rock experiences these changes within the Earth.
FIGURE 1.5This mica schist is a metamorphic rock. Itwas changed from a sedimentary rock likeshale.
Pause to Consider
1. What are metamorphic rocks? How do metamorphic rocks form?
2. How do minerals combine to form a metamorphic rock?
Rocks can be changed from one type to another, and the rock cycle describes how this happens.
Processes of the Rock Cycle
Any type of rock can change and become a new type of rock. Magma can cool and crystallize. Existing rocks canbe weathered and eroded to form sediments. Rock can change by heat or pressure deep in Earth’s crust. There arethree main processes that can change rock:
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• Cooling and forming crystals. Deep within the Earth, temperatures can get hot enough to melt rock. Thismolten material is called magma. As it cools, crystals grow, forming an igneous rock. The crystals will growlarger if the magma cools slowly, as it does if it remains deep within the Earth. If the magma cools quickly,the crystals will be very small.
• Weathering and erosion. Water, wind, ice, and even plants and animals all act to wear down rocks. Over timethey can break larger rocks into smaller pieces called sediments. Moving water, wind, and glaciers then carrythese pieces from one place to another. The sediments are eventually dropped, or deposited, somewhere. Thesediments may then be compacted and cemented together. This forms a sedimentary rock. This whole processcan take hundreds or thousands of years.
• Metamorphism. This long word means “to change form.“ A rock undergoes metamorphism if it is exposed toextreme heat and pressure within the crust. With metamorphism, the rock does not melt all the way. The rockchanges due to heat and pressure. A metamorphic rock may have a new mineral composition and/or texture.
The rock cycle really has no beginning or end. It just continues. The processes involved in the rock cycle take placeover hundreds, thousands, or even millions of years. Even though for us rocks are solid and unchanging, they slowlychange all the time.
Pause to Consider
1. What clues do the minerals in an igneous rock give about how the rock formed? A metamorphic rock? Asedimentary rock?
2. Describe how an igneous rock can change to a metamorphic rock.
3. If Earth’s interior was cool, how would this change the types of rocks formed on Earth?
Lesson Summary
• There are three main types of rocks: igneous, sedimentary, and metamorphic.• Melting and later cooling, erosion and sedimentation, and metamorphism transform one type of rock into
another type of rock or change sediments into rock.• The rock cycle describes the transformations of one type of rock to another.
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Lesson Review Questions
True or False
Write true if the statement is true or false if the statement is false.
_____ 1. When a rock changes from one type to another, it usually happens very quickly.
_____ 2. One type of rock can change to any other type of rock.
_____ 3. All the processes of the rock cycle take place underground.
_____ 4. To see the minerals in rock, you always need to use a microscope.
_____ 5. Rocks are named for the minerals they contain and how the minerals came together.
_____ 6. A rock formed from pieces of gravel and sand would be classified as an igneous rock.
_____ 7. A rock resulting from the formation of mineral crystals would be classified as a sedimentary rock.
_____ 8. Sedimentary rocks include sandstone and shale.
_____ 9. Plants and animals can act to wear down rocks.
_____ 10. Metamorphism may change a rock’s mineral composition.
Multiple Choice
Circle the letter of the correct choice.
11. Major types of rocks include
1. a. sedimentary rocks.b. metamorphic rocks.c. igneous rocks.d. all of the above
12. Which rocks may form on Earth’s surface?
1. a. sedimentary rocksb. metamorphic rocksc. igneous rocksd. two of the above
13. Weathering and erosion occur because of the actions of
1. a. ice.b. wind.c. water.d. all of the above
14. The process in which sedimentary rocks form begins with
1. a. erosion.b. deposition.c. weathering.d. compaction.
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15. The rock called limestone forms when shells of sea organisms settle to the bottom of the water and graduallybecome pressed and cemented together. Which type of rock is limestone?
1. a. igneousb. metamorphicc. sedimentaryd. none of the above
16. If limestone is buried under the ground and placed under pressure until it becomes extremely hot, it changes tomarble. The process in which marble forms from limestone is
1. a. melting.b. compression.c. sedimentation.d. metamorphism.
17. Which process is involved when a sedimentary rock changes to an igneous rock?
1. a. metamorphismb. meltingc. sedimentationd. weathering
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1.2 Igneous Rocks: Formation, Properties, &Uses
Points to Consider
1. Granite is one type of igneous rock. What are some uses for granite?
2. Could an igneous rock cool at two different rates? What would the crystals look like?
Lesson Objectives
• Describe how igneous rocks are formed.• Describe the properties of some common types of igneous rocks.• Relate some common uses of igneous rocks.
Vocabulary
• extrusive rock: Igneous rock that forms on Earth’s surface from rapidly cooling lava.• intrusive rock: Igneous rock that forms beneath Earth’s surface from slowly cooling magma.
Fill in the blank with the appropriate term.
1. Rocks are made of one or more types of __________.2. Geologists classify rocks into three main types based on how the rocks __________.3. Sandstone is an example of __________ rock.4. Crystals in igneous rock are __________ when melted rock cools more slowly.5. Mica schist is an example of __________ rock.6. Weathering and erosion are processes involved in the formation of __________ rock.7. Some __________ rocks form when solid minerals are left behind after a liquid evaporates.
Introduction
Most of the Earth is made of igneous rock. The entire mantle is igneous rock, as are some areas of the crust. Oneof the most common igneous rocks is granite ( Figure 1.6). Many mountain ranges are made of granite. People use
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granite for countertops, buildings, monuments and statues. Pumice is also an igneous rock. Perhaps you have used apumice stone to smooth your skin. Pumice stones are put into giant washing machines with new jeans and tumbledaround. The result is stone-washed jeans!
FIGURE 1.6This life-size elephant is carved fromgranite.
Forming Crystals
Igneous rocks form when magma cools and forms crystals. These rocks can form at Earth’s surface or deepunderground. Figure 1.7 shows a landscape in California’s Sierra Nevada that consists entirely of granite.
FIGURE 1.7The Sierra Nevada of California are com-posed mainly of granite. These rocksare beautifully exposed in the YosemiteValley.
Intrusive igneous rocks cool and form into crystals beneath the surface. Deep in the Earth, magma cools slowly.Slow cooling gives large crystals a chance to form. Intrusive igneous rocks have relatively large crystals that are
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easy to see. Granite is the most common intrusive igneous rock. Figure 1.8 shows four types of intrusive rocks.
FIGURE 1.8(A) This granite has more plagioclasefeldspar than many granites. (B) Dior-ite has more dark-colored minerals thangranite. (C) Gabbro. (D) Peridotite isan intrusive igneous rock with olivine andother mafic minerals.
Extrusive igneous rocks form above the surface. The lava cools quickly as it pours out onto the surface ( Figure1.9). Extrusive igneous rocks cool much more rapidly than intrusive rocks. They have smaller crystals, since therapid cooling time does not allow time for large crystals to form. Some extrusive igneous rocks cool so rapidly thatcrystals do not develop at all. These form a glass, such as obsidian. Others, such as pumice, contain holes wheregas bubbles were trapped in the lava. The holes make pumice so light that it actually floats in water. The mostcommon extrusive igneous rock is basalt. It is the rock that makes up the ocean floor. Figure 1.10 shows four typesof extrusive igneous rocks.
FIGURE 1.9(A) Lava cools to form extrusive igneous rock. The rocks here are basalts. (B) The strange rock formations ofChiricahua National Monument in Arizona are formed of the extrusive igneous rock rhyolite.
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FIGURE 1.10(A) This rhyolite is light colored. Fewminerals are visible to the naked eye. (B)Andesite is darker than rhyolite. (C) Sincebasalt crystals are too small to see, therock looks dark all over. (D) Komatiite isa very rare ultramafic rock. This rock isderived from the mantle.
Pause to Consider
1. What is the difference between an intrusive and an extrusive igneous rock?
2. Why do extrusive igneous rocks usually have smaller crystals than intrusive igneous rocks?
3. Why is the ocean floor more likely to have extrusive rocks than intrusive rocks?
Composition
Igneous rocks are grouped by the size of their crystals and the minerals they contain. The minerals in igneous rocksare grouped into families. Some contain mostly lighter colored minerals, some have a combination of light and darkminerals, and some have mostly darker minerals. The combination of minerals is determined by the composition of
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the magma. Magmas that produce lighter colored minerals are higher in silica. These create rocks such as graniteand rhyolite. Darker colored minerals are found in rocks such as gabbro and basalt.
There are actually more than 700 different types of igneous rocks. Diorite is extremely hard and is commonly usedfor art. It was used extensively by ancient civilizations for vases and other decorative art work ( Figure 1.11).
FIGURE 1.11This sarcophagus is housed at the Vat-ican Museum. The rock is the igneousextrusive rock porphyry. Porphyry haslarge crystals because the magma beganto cool slowly, then erupted.
Pause to Consider
1. List three common uses of igneous rocks.
2. How are igneous rocks classified?
3. Occasionally, igneous rocks will contain both large crystals and tiny mineral crystals. Propose a way that boththese sizes of crystals might have formed in the rock.
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Lesson Summary
• Igneous rocks form either when they cool very slowly deep within the Earth or when magma cools rapidly atthe Earth’s surface.
• Composition of the magma will determine the minerals that will crystallize forming different types of igneousrocks.
Lesson Review Questions
True or False
Write true if the statement is true or false if the statement is false.
_____ 1. The layer of Earth called the mantle is made entirely of igneous rock.
_____ 2. Rock on the ocean floor is intrusive igneous rock.
_____ 3. The Sierra Nevada Mountains in California are composed mainly of granite.
_____ 4. When melted rock cools more slowly, it forms larger crystals.
_____ 5. Melted rock cools more quickly underground than on Earth’s surface.
_____ 6. Obsidian forms when magma cools and forms crystals.
_____ 7. Pumice contains holes because gas bubbles were trapped in lava as it cooled.
_____ 8. Basalt crystals are too small to see with the unaided eye.
_____ 9. The combination of minerals in igneous rocks is determined by the composition of the magma or lava.
_____ 10. Both porphyry and diorite are extrusive igneous rocks.
Multiple Choice
Circle the letter of the correct choice.
11. Igneous rocks are classified by
1. a. the size of their crystals.b. the type of sediments they contain.c. their mineral composition.d. two of the above
12. How many different kinds of igneous rocks are there?
1. a. only 7b. about 70c. more than 700d. between 70 and 100
13. Granite is used to make
1. a. countertops.b. buildings.c. statues.d. all of the above
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14. How is pumice used?
1. a. to smooth rough skinb. to stonewash jeansc. to make vasesd. two of the above
15. The rock that makes up the ocean floor is
1. a. granite.b. basalt.c. diorite.d. peridotite.
16. One property of pumice is
1. a. a smooth glassy texture.b. very large crystals.c. the ability to float on water.d. none of the above
17. Many mountain ranges are made of
1. a. granite.b. gabbro.c. andesite.d. komatite.
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1.3 Sedimentary Rocks: Formation, Proper-ties, & Uses
Points to Consider
1. If you were interested in learning about Earth’s history, which type of rocks would give you the most infor-mation?
2. Could a younger layer of sedimentary rock ever be found under an older layer? How do you think this couldhappen?
3. Could a sedimentary rock form only by compaction from intense pressure?
Lesson Objectives
• Describe how sedimentary rocks are formed.• Describe the properties of some common sedimentary rocks.• Relate some common uses of sedimentary rocks.
Vocabulary
• cementation: Sticking together of sediments by mineral crystals from fluids.• compaction: Squeezing together of sediments by the weight of overlying sediments.• fossil: Preserved remains or traces of a once-living organism.
Fill in the blank with the appropriate term.
1. Most sedimentary rocks form from __________.2. Each layer of sedimentary rock is __________ than the layer below it.3. A beach or desert collects large deposits of sediments known as __________.4. Minerals that cement together sediments in clastic rock come from __________.
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5. __________ sedimentary rocks are classified by the size of the sediments they contain.6. Gypsum is an example of a(n) __________ sedimentary rock.7. Coal is an example of a(n) __________ sedimentary rock.
Introduction
FIGURE 1.12Layers of sand turned to rock are seenin the Navajo sandstone. The geologicfeature is a slot canyon called AntelopeCanyon.
Did you know that the White House, the official home and workplace of the President of the United States ofAmerica, is made out of the same material as the rock faces in Figure 1.12? This material is a sedimentary rockcalled sandstone. Sandstone is very porous. Water can easily move through it. So the sandstone of the White Housecould have been water damaged. But during construction workers covered the sandstone in a mixture of salt, rice,and glue. This mixture protects the sandstone and is what gives the White House its distinct white color.
Sediments
Most sedimentary rocks form from sediments. Sediments are small pieces of other rocks, like pebbles, sand, silt,and clay. Sedimentary rocks may include fossils. Fossils are materials left behind by once-living organisms. Fossilscan be pieces of the organism, like bones. They can also be traces of the organism, like footprints.
Most often, sediments settle out of water ( Figure 1.13). For example, rivers carry lots of sediment. Where the waterslows, it dumps these sediments along its banks, into lakes and the ocean. When sediments settle out of water, theyform horizontal layers. A layer of sediment is deposited. Then the next layer is deposited on top of that layer. Soeach layer in a sedimentary rock is younger than the layer under it. It is older than the layer over it.
FIGURE 1.13Cobbles, pebbles, and sands are the sediments that are seen on thisbeach.
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Sediments are deposited in many different types of environments. Beaches and deserts collect large deposits of sand.Sediments also continuously wind up at the bottom of the ocean and in lakes, ponds, rivers, marshes, and swamps.Avalanches produce large piles of sediment. The environment where the sediments are deposited determines thetype of sedimentary rock that can form.
Sedimentary Rock Formation
Sedimentary rocks form in two ways. Particles may be cemented together. Chemicals may precipitate.
Pause to Reflect
1. What are three things that sedimentary rocks may be made of?
2. If you see a sedimentary rock outcrop and red layers of sand are on top of pale yellow layers of sand, what do youknow for sure about the ages of the two layers?
Clastic Rocks
Over time, deposited sediments may harden into rock. First, the sediments are compacted. That is, they are squeezedtogether by the weight of sediments on top of them. Next, the sediments are cemented together. Minerals fill in thespaces between the loose sediment particles. These cementing minerals come from the water that moves throughthe sediments. These types of sedimentary rocks are called “clastic rocks.“ Clastic rocks are rock fragments that arecompacted and cemented together.
Clastic sedimentary rocks are grouped by the size of the sediment they contain. Conglomerate and breccia are madeof individual stones that have been cemented together. In conglomerate, the stones are rounded. In breccia, thestones are angular. Sandstone is made of sand-sized particles. Siltstone is made of smaller particles. Silt is smallerthan sand but larger than clay. Shale has the smallest grain size. Shale is made mostly of clay-sized particles andhardened mud.
Chemical Sedimentary Rocks
Chemical sedimentary rocks form when crystals precipitate out from a liquid. The mineral halite, also called rocksalt, forms this way. You can make halite! Leave a shallow dish of salt water out in the Sun. As the water evaporates,salt crystals form in the dish. There are other chemical sedimentary rocks, like gypsum.
Table 1.1 shows some common types of sedimentary rocks and the types of sediments that make them up.
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TABLE 1.1: Common Sedimentary Rocks
Picture Rock Name Type of Sedimentary RockConglomerate Clastic
Breccia Clastic
Sandstone Clastic
Siltstone Clastic
Limestone Bioclastic
Coal Organic
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TABLE 1.1: (continued)
Picture Rock Name Type of Sedimentary RockRock Salt Chemical precipitate
Pause to Reflect
1.Describe the two processes necessary for sediments to harden into rock.
2. What type of sedimentary rock is coal?
3. Why do you think sandstone allows water to move through it easily?
Lesson Summary
• Most sedimentary rocks form from sediments. These sediments are deposited, forming layers.• The youngest layers are found on top, with older layers below.• Sediments must be compacted and cemented to make sedimentary rock.• Chemical sedimentary rocks are made of precipitated minerals.
Lesson Review Questions
True or False
Write true if the statement is true or false if the statement is false.
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_____ 1. Sandstone is very porous so water can move easily through it.
_____ 2. Sedimentary rocks may contain fossils.
_____ 3. Avalanches produce horizontal layers of sediments.
_____ 4. Particles of silt are smaller than particles of clay.
_____ 5. Fossils are always the remains of bones or teeth.
_____ 6. Sediments are pieces of rock.
_____ 7. Sediments on a beach may include cobbles and pebbles.
_____ 8. All sedimentary rocks form from sediments.
_____ 9. Shale may contain hardened mud.
_____ 10. Limestone is a chemical sedimentary rock.
Multiple Choice
Circle the letter of the correct choice.
11. Types of sediments that may make up sedimentary rocks include
1. a. pebbles.b. silt.c. clay.d. all of the above
12. A river deposits sediments when the water
a. slows down.b. enters a lake.c. reaches the ocean.d. all of the above
13. Which of the following sedimentary rocks contains the smallest sediments?
1. a. conglomerateb. sandstonec. siltstoned. shale
14. Which of the following rocks is not a clastic sedimentary rock?
1. a. limestoneb. brecciac. halited. two of the above
15. The White House in Washington, D.C., is made of
1. a. clastic rock.b. sedimentary rock.
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c. sandstone.d. all of the above
16. When sediments settle out of water, they form
1. a. chemical rocks.b. horizontal layers.c. precipitates.d. none of the above
17. Which sedimentary rock is formed of rounded stones that have been cemented together?
1. a. brecciab. sandstonec. conglomerated. limestone
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1.4 Metamorphic Rocks: Formation, Proper-ties, & Uses
Points to Consider
• Do you think new minerals could form when an existing rock is metamorphosed?
Lesson Objectives
• Describe how metamorphic rocks are formed.• Describe the properties of some common metamorphic rocks.• Relate some common uses of metamorphic rocks.
Vocabulary
• contact metamorphism: Changes in rock due to heating by contact with hot magma.• foliation: Formation of layers in rock due to extreme pressure.• regional metamorphism: Changes in rock over a large area due to pressure from other rock.• stable: State of minerals in rock after metamorphism.
Fill in the blank with the appropriate term.
1. Metamorphism changes rocks by extreme heat and/or __________.2. Hornfels is a rock that is formed by __________ metamorphism.3. Regional metamorphic rocks often display layering called __________.4. The minerals in hornfels separate from one another by __________.5. After metamorphism occurs, the minerals in a rock are more __________.6. Schist is a rock that is formed by __________ metamorphism.7. The rocky peak named the Matterhorn consists of the metamorphic rock called __________.
Introduction
Metamorphism changes rocks by heat and pressure. These agents create an entirely new type of rock. Metamorphismchanges rocks physically and/or chemically.
Metamorphism
Metamorphic rocks start off as some kind of rock. The starting rock can be igneous, sedimentary or even anothermetamorphic rock. Heat and/or pressure then change the rock’s physical or chemical makeup.
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During metamorphism a rock may change chemically. Ions move and new minerals form. The new minerals aremore stable in the new environment. Extreme pressure may lead to physical changes like foliation. Foliation formsas the rocks are squeezed. If pressure is exerted from one direction, the rock forms layers. This is foliation. Ifpressure is exerted from all directions, the rock usually does not show foliation.
There are two main types of metamorphism:
1. Contact metamorphism results when magma contacts a rock, changing it by extreme heat ( Figure 1.14).
FIGURE 1.14(A) Hornfels is a rock that is created bycontact metamorphism. (B) Hornfels isso hard that it can create peaks like theMatterhorn.
2. Regional metamorphism occurs over a wide area. Great masses of rock are exposed to pressure from rock andsediment layers on top of it. The rock may also be compressed by other geological processes.
FIGURE 1.15(A) Regional metamorphic rocks oftendisplay layering called foliation. (B) Re-gional metamorphism with high pressuresand low temperatures can result in blueschist.
Metamorphism does not cause a rock to melt completely. It only causes the minerals to change by heat or pressure.
Hornfels is a rock with alternating bands of dark and light crystals. Hornfels is a good example of how mineralsrearrange themselves during metamorphism ( Figure 1.14). The minerals in hornfels separate by density. The resultis that the rock becomes banded. Gneiss forms by regional metamorphism from extremely high temperature andpressure.
Uses of Metamorphic Rocks
Quartzite and marble are the most commonly used metamorphic rocks. They are frequently chosen for buildingmaterials and artwork. Marble is used for statues and decorative items like vases ( Figure 1.15). Quartzite is veryhard and is often crushed and used in building railroad tracks. Schist and slate are sometimes used as building andlandscape materials.
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1.4. Metamorphic Rocks: Formation, Properties, & Uses www.ck12.org
FIGURE 1.16(A) Marble is a beautiful rock that is com-monly used for buildings. (B) Many of thegreat statues of the Renaissance werecarved from marble. Michelangelo cre-ated this Moses between 1513 and 1515.
Pause to Reflect
1. Why do the minerals in a rock sometimes rearrange themselves when exposed to heat or pressure?
2. List and describe the two main types of metamorphism.
3. How does layering form in metamorphic rocks?
4.What clues in metamorphic rocks tell you how they were formed?
5. Suppose a phyllite sample was exposed to even more heat and pressure. What metamorphic rock would form?
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www.ck12.org Chapter 1. MS Rocks
Lesson Summary
• Metamorphic rocks form when heat and pressure transform an existing rock into a new rock.• Contact metamorphism occurs when hot magma transforms rock that it contacts.• Regional metamorphism transforms large areas of existing rocks under the tremendous heat and pressure
created by tectonic forces.
Lesson Review Questions
True or False
Write true if the statement is true or false if the statement is false.
_____ 1. When a rock undergoes metamorphism, it becomes an entirely new type of rock.
_____ 2. During metamorphism, ions may move and new minerals may form.
_____ 3. There are two types of metamorphism.
_____ 4. Contact metamorphism causes rock to melt and form magma.
_____ 5. The most commonly used metamorphic rocks are slate and gneiss.
_____ 6. Quartzite is a relatively soft metamorphic rock.
_____ 7. Gneiss forms by contact metamorphism.
_____ 8. Schist is sometimes used as a landscaping material.
_____ 9. In the 1500s, Michelangelo carved statues from marble.
_____ 10. Metamorphic rocks cannot undergo further metamorphism and change to different types of rocks.
Multiple Choice
Circle the letter of the correct choice.
1. During metamorphism, rocks may change
1. a. chemically.b. physically.c. permanently.d. two of the above
2. Metamorphism begins with
1. a. magma.b. sediments.c. lava.d. rock.
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1.4. Metamorphic Rocks: Formation, Properties, & Uses www.ck12.org
3. What type of change in rock is foliation?
1. a. physical changeb. chemical changec. mineral changed. two of the above
4. A metamorphic rock may undergo foliation when pressure is
1. a. exerted from just one direction.b. exerted from all directions.c. relatively weak.d. absent.
5. Slate is a metamorphic rock that is used for
1. a. building.b. landscaping.c. statues.d. two of the above
6. Which of the following types of rocks can undergo metamorphism?
1. a. sedimentary rockb. igneous rockc. metamorphic rockd. all of the above
7. All of the following are metamorphic rocks except
1. a. schist.b. quartzite.c. gneiss.d. granite.
For Table 1.1,
• User:Jstuby/Wikipedia. http://commons.wikimedia.org/wiki/File:Lehigh_conglom.jpg . Public Domain.• Mark A. Wilson (Department of Geology, The College of Wooster). http://commons.wikimedia.org/wiki/Fi
le:UpperTriassicYorkCountyPA.jpg . Public Domain.• Courtesy of Ken Hammond, US Department of Agriculture. http://commons.wikimedia.org/wiki/File:USDA_-
Mineral_Sandstone_93c3955.jpg . Public Domain.• Courtesy of United States Geological Survey/Mineral Information Institute. http://commons.wikimedia.org
/wiki/File:ShaleUSGOV.jpg . Public Domain.• P K (Flickr:uair1). http://www.flickr.com/photos/56759497@N00/3870660087/ . CC BY 2.0.• Flickr:oatsy40. http://www.flickr.com/photos/68089229@N06/9333525319/ . CC BY 2.0.• User:ALM scientist/Wikipedia. http://en.wikipedia.org/wiki/File:Kehora_Salt_Cave.jpg . Public Domain.
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1.5 References
1. User:Woudloper/Woodwalker; modified by CK-12 Foundation. The Rock Cycle . Public Domain2. Leon Brooks. http://commons.wikimedia.org/wiki/File:Balancing_rock_at_castle_rock_porongurup.jpg . Pub-
lic Domain3. Courtesy of the U.S. Geological Survey. http://commons.wikimedia.org/wiki/File:Aa_large.jpg . Public
Domain4. Kevin Walsh (Flickr:kevinzim). http://www.flickr.com/photos/86624586@N00/17086401/ . CC BY 2.05. Charles de Mille-Isles. http://www.flickr.com/photos/46639194@N05/6433049943 . CC BY 2.06. Mark A. Wilson. http://commons.wikimedia.org/wiki/File:GraniteElephant.jpg . Public Domain7. Jon Sullivan. http://commons.wikimedia.org/wiki/File:Yosemite_Valley_with_Half_Dome_in_the_distance.jp
g . Public Domain8. (A) Image copyright MARGRIT HIRSCH, 2013; (B) Image copyright Tyler Boyes, 2013; (C) Mark A. Wilson
(Department of Geology, The College of Wooster); (D) Image copyright Marcin Sylwia Ciesielski, 2013. (A,B, D) http://www.shutterstock.com; (C) http://commons.wikimedia.org/wiki/File:GabbroRockCreek1.jpghttp://www.flickr.com/photos/jsjgeology/8455579081/ . (A, B, D) Used under licenses from Shutterstock.com;(C) Public domain
9. (A) Courtesy of the US Geological Survey; (B) Flickr:SonoranDesertNPS. (A) http://commons.wikimedia.org/wiki/File:Pahoeoe_fountain_edit2.jpg; (B) http://www.flickr.com/photos/65466304@N04/6127118377/. (A) Public Domain; (B) CC BY 2.0
10. (A, B) James St. John (Flickr:jsj1771); (C) Courtesy of the US Geological Survey; (D) User:GeoRanger/Wikipedia.(A) http://www.flickr.com/photos/jsjgeology/8456708386/; (B) http://www.flickr.com/photos/jsjgeology/8455600595/; (C) http://commons.wikimedia.org/wiki/File:BasaltUSGOV.jpg; (D) http://commons.wikimedia.org/wiki/File:KomatiiteCanada_682By512.jpg . (A, B) Used under license from Shutterstock.com; (C, D)Public Domain
11. David McSpadden. http://www.flickr.com/photos/familyclan/8847886370/ . CC BY 2.012. Steve Dunleavy. http://www.flickr.com/photos/stevedunleavy/5126762996/ . CC BY 2.013. Steven Depolo. http://www.flickr.com/photos/stevendepolo/3902888070/ . CC BY 2.014. (A) User:Fed/Ru.Wikipedia; (B) Flickr:CoreForce. (A) http://commons.wikimedia.org/wiki/File:Hornfels.
jpg; (B) http://commons.wikimedia.org/wiki/File:East_Face.jpg . (A) Public Domain; (B) CC BY 2.015. (A) Image copyright katatonia82, 2013; (B) Renee French. (A) http://www.shutterstock.com; (B) CK-12 F
oundation . (A) Used under license from Shutterstock.com; (B) CC BY-NC 3.016. (A) Courtesy of the US Geological Survey and the Mineral Information Institute; (B) User:Prasenberg/Wikipedia.
(A) http://commons.wikimedia.org/wiki/File:MarbleUSGOV.jpg; (B) http://commons.wikimedia.org/wiki/File:Moses_San_Pietro_in_Vincoli.jpg . (A) Public Domain; (B) CC BY 2.0
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