Earth Science SE
Chapter6RocksChapter Outline1 Rocks and the RockCycleThree Major Types of RockThe Rock CycleProperties of Rocks2 Igneous RockThe Formation of MagmaTextures of Igneous RocksComposition of IgneousRocksIntrusive Igneous RockExtrusive Igneous Rock3 Sedimentary RockFormation of SedimentaryRocksChemical Sedimentary RockOrganic Sedimentary RockClastic Sedimentary RockCharacteristics of ClasticSedimentsSedimentary Rock Features4 Metamorphic RockFormation of MetamorphicRocksClassification ofMetamorphic Rocks132Chapter 6Why It MattersThe hundreds of different types ofrocks on Earth can be classifiedinto three main types: igneous,sedimentary, and metamorphic.This formation in Arizona is madeof sedimentary rock. When youknow the type of rock, you knowsomething about how that rockformed.
Inquiry LabSedimentary SandwichUse slices of different types of bread to modellayers of different types of sediment deposits. Next,put your model in a plastic bag. Place a weight ontop of the bag to simulate the process ofcompacting sediment into rock. Then, use an emptyfilm canister to obtain a core sample of thesedimentary sandwich. Trade samples with anothergroup and observe the other group’s sample.Identify the different layers of rock and determine ifrock layers are the same thickness or if some arethicker than others.15 minQuestions to Get You Started1. Make a labeled diagram showing the rock layers inthe sample you observed.2. Which factors might affect the thickness of a rocklayer in a real rock formation?3. Your model has layers of different types of rocks.In a real formation, what might changes inrock type indicate about theformation’s geological history?133
These reading tools will help you learn the material in this chapter.FoldNotesGraphic OrganizerPyramid Pyramid FoldNotes help youcompare words or ideas in sets of three.Chain-of-Events Chart A chain-of-eventschart is similar to a flow chart. A chain-ofevents chart shows the order in which thesteps of a process occur.Your Turn Before you read this chapter,make a Pyramid FoldNote as described inAppendix A. Label the sides of the pyramidwith “Igneous rock,” “Sedimentary rock,”and “Metamorphic rock.” As you read thechapter, define each type of rock, and writecharacteristics of each type of rock on theappropriate side of the pyramid.kcroryantIgnedimeouYour Turn In Section 3, you will readabout the formation of sedimentary rocks.Make a chain-of-events chart like the onestarted below to describe compaction, oneof the processes that form sedimentaryrock. Use as many boxes as you need torecord all steps of the process.In a sedimentdeposit, there areopen spaces betweenthe pieces ofsediment.s rockSeNote TakingSummarizing Ideas Summarizing thecontent of each paragraph or set ofparagraphs under a heading is a simple wayto take notes. A few tips on summarizing arelisted below.1 Summary statements should be short,but fully express the idea.2 Use the green subheadings for guidancein forming summary statements.3 Many paragraphs start or end with asentence that summarizes the main ideaof the paragraph.Your Turn As you read each section, takenotes by summarizing the main ideas. Youmay add structure to your notes by alsowriting the section title and red headings inthe appropriate places.For more information on how to use these and other tools, see Appendix A.134Chapter 6Rocks
SECTION1Rocks and the Rock CycleKeyeyy Ideasdeass❯ Identify the three major types of rock, andexplain how each type forms.❯ Summarize the steps in the rock cycle.❯ Explain Bowen’s reaction series.❯ Summarize the factors that affect the stability ofKeyeyy Termse sWhyy Itt Mattersatte srock cycleSome rocks crumble andothers make for solidbuildings. The physicaland chemical propertiesof rock are determinedby the conditions underwhich the rock forms.Bowen’s reactionseriesrocks.The material that makes up the solid parts of Earth is known asrock. Rock can be a collection of one or more minerals, or rock canbe made of solid organic matter. In some cases, rock is made ofsolid matter that is not crystalline, such as glass. Geologists studythe forces and processes that form and change the rocks of Earth’scrust. Based on these studies, geologists have classified rocks intothree major types by the way the rocks form.Three Major Types of RockVolcanic activity produces igneous rock. The word igneous isderived from a Latin term that means “from fire.” Igneous rockforms when magma, or molten rock, cools and hardens. Magma iscalled lava when it is exposed at Earth’s surface.Over time, natural processes break down alltypes of rock into small fragments. Rocks, minFigure 1 These rocks are examples ofthe three major rock types.eral crystals, and organic matter that have beenbroken into fragments are known as sediment.Sediment is carried away and deposited by water,Sandstone (sedimentary)ice, and wind. When these sediment deposits arecompressed, cemented together, and harden,sedimentary rock forms.Gneiss (metamorphic)Certain forces and processes, including tremendous pressure, extreme heat, and chemical processes, also can change the form ofexisting rock. The rock that formswhen existing rock is altered ismetamorphic rock. The word metamorphic means “changed form.”Figure 1 shows an example of eachmajor type of rock.Granite (igneous)135
Sedimentary rockFigure 2 The rock cycle illustrates thenMssund,apreonndsitingreaepooliratuErosion, dcongce mtemndpen, aengitati oChangingtemperature anM elt ing a nd coolingMetamorphic rockKeyword: HQXRXSF2it i oanti ndeposChelanret iogmeantErosion, dcechanges that igneous, sedimentary, andmetamorphic rocks undergo.ureessnd prIgneous rockThe Rock Cyclerock cycle the series ofprocesses in which rock forms,changes from one type toanother, is destroyed, and formsagain by geological processeswww.scilinks.orgTopic: The Rock CycleCode: HQX1319136Chapter 6RocksAny of the three major types of rock can be changed into anotherof the three types. Geologic forces and processes cause rock tochange from one type to another. This series of changes is calledthe rock cycle, which is shown in Figure 2.One starting point for examining the steps of the rock cycle isigneous rock. When a body of igneous rock is exposed at Earth’ssurface, a number of processes break down the igneous rock intosediment. When sediment from igneous rocks is compacted andcemented, the sediment becomes sedimentary rock. Then, if sedimentary rocks are subjected to changes in temperature and pressure, the rocks may become metamorphic rocks. Under certaintemperature and pressure conditions, the metamorphic rock willmelt and form magma. Then, if the magma cools, new igneous rockwill form.Much of the rock in Earth’s continental crust has probablypassed through the rock cycle many times during Earth’s history.However, as Figure 2 shows, a particular body of rock does notalways pass through each stage of the rock cycle. For example,igneous rock may never be exposed at Earth’s surface where therock could change into sediment. Instead, the igneous rock maychange directly into metamorphic rock while still beneath Earth’ssurface. Sedimentary rock may be broken down at Earth’s surface,and the sediment may become another sedimentary rock.Metamorphic rock can be altered by heat and pressure to form adifferent type of metamorphic rock.
Properties of RocksAll rock has physical and chemical properties that are determined by how and where the rock formed. The physical characteristics of rock reflect the chemical composition of the rock as a wholeand of the individual minerals that make up the rock. The rate atwhich rock weathers and the way that rock breaks apart are determined by the chemical stability of the minerals in the rock.Bowen’s Reaction SeriesIn the early 1900s, a Canadian geologist named N. L. Bowenbegan studying how minerals crystallize from magma. He learnedthat as magma cools, certain minerals tend to crystallize first. Asthese minerals form, they remove specific elements from themagma, which changes the magma’s composition. The changingcomposition of the magma allows different minerals that containdifferent elements to form. Thus, different minerals form at different times during the solidification (cooling) of magma, and theygenerally form in the same order.In 1928, Bowen proposed a simplified pattern that explains theorder in which minerals form as magma solidifies. This simplifiedflow chart is known as Bowen’s reaction series and is shown inFigure 3. According to Bowen’s hypothesis, minerals form in oneof two ways. The first way is characterized by a gradual, continuous formation of minerals that have similar chemical compositions.The second way is characterized by sudden, or discontinuous,changes in mineral types. As magma cools, the discontinuousand continuous reaction series occur simultaneously, or at thesame time.Chain-of-Events ChartMake a chain-of-events chart toshow each step of the discontinuous reaction seriesof Bowen’s reactionseries. Remember touse as many boxesas you need to showall steps.Academic Vocabularyremove (ri MOOV) to take away oreliminateBowen’s reaction series thesimplified pattern that illustratesthe order in which mineralscrystallize from cooling magmaaccording to their chemicalcomposition and melting pointSummarize Bowen’s reaction series. (SeeAppendix G for answers to Reading Checks.)Simultaneous processesFelsicPyroxeneAmphiboleBiotite micaCalciumrichsOrder of crystallizationMagma typesIntermediatesn seriectiore a e r a l susinuo g mt in e -Mon f FoMaficOlivineI n c r e a s i ng soof plagio dium cc l aseofeld ntenspa tCon t i nurousreo f p l agi oc l act ioasenf e l s erdspa i erUltramafic(low in silica) DiscEarly; hightemperature(1,000 C)Figure 3 Different mineralscrystallize at different times duringthe solidification of magma. Thus,as minerals crystallize from magma,the composition of the magmachanges.SodiumrichUltrafelsic(high in silica)Potassium feldsparMuscovite micaQuartzLate; lowtemperature(600 C)Section 1Rocks and the Rock Cycle137
Chemical Stability of MineralsThe rate at which a mineral chemically breaks downis dependent on the chemical stability of the mineral.Chemical stability is a measure of the tendency of a chemical compound to maintain its original chemical composition rather than break down to form a differentchemical. In general, the minerals that are most stableare minerals that formed at the lowest temperatures,under conditions similar to those on Earth’s surface.Minerals that formed at the highest temperatures, underconditions very different than those on Earth’s surface,are least stable.Physical Stability of RocksFigure 4 Devils PostpileNational Monument inCalifornia is one of the world’sfinest examples of the igneousrock structures known ascolumnar joints.Rocks have natural zones of weakness that are determined by how and where the rocks form. For example,sedimentary rocks may form as a series of layers of sediment. These rocks tend to break between layers. Somemetamorphic rocks also tend to break in layers that formas the minerals in the rocks align during metamorphism.Massive igneous rock structures commonly haveevenly spaced zones of weakness, called joints, that formas the rock cools and contracts. Devils Postpile, shown in Figure 4,is igneous rock that has joints that cause the rock to break intocolumns.Zones of weakness may also form when the rock is underintense pressure inside Earth. When rock that formed underintense pressure is uplifted to Earth’s surface, decreased pressureallows the joints and fractures to open. Once these weaknessesare exposed to air and water, chemical and physical processesbegin to break down the rock.Section 1 ReviewKey IdeasCritical Thinking1. Identify the three major types of rock.7. Applying Ideas Does every rock go through the2. Explain how each major type of rock forms.3. Describe the steps in the rock cycle.4. Summarize Bowen’s reaction series.5. Explain how the chemical stability of a mineral isrelated to the temperature at which the mineralforms.6. Describe how the conditions under which rocksform affect the physical stability of rocks.complete rock cycle by changing from igneousrock to sedimentary rock, to metamorphic rock,and then back to igneous rock? Explain youranswer.8. Identifying Relationships How could a sedi-mentary rock provide evidence that the rock cycleexists?Concept Mapping9. Use the following terms to create a concept map:rock, igneous rock, sedimentary rock, metamorphicrock, and rock cycle.138Chapter 6Rocks
SECTION2Igneous RockKeyeyy Ideasdeas❯ Summarize three factors that affect whether rockmelts.❯ Describe how the cooling rate of magma andlava affects the texture of igneous rocks.❯ Classify igneous rocks according to their composition and texture.Keyeyy Termse sWhyy Itt Mattersatte signeous rockThe many differentcompositions and textures of igneous rocksmake sense once youunderstand the processesby which they form.Useful applications ofthese properties includenuclear-waste disposal.intrusive igneous rockextrusive igneous rockfelsicmafic❯ Describe intrusive and extrusive igneous rock.When magma cools and hardens, it forms igneous rock. Becauseminerals usually crystallize as igneous rock forms from magma, mostigneous rock can be identified as crystalline, or made of crystals.The Formation of MagmaMagma forms when rock melts. Rock melts when the temperature of the rock increases to above the melting point of minerals inthe rock. The chemical composition of minerals determines theirmelting temperatures. In general, rock melts at lower temperaturesunder lower pressures. If excess pressure is removed from rock thatis close to melting, the rock may melt. Hot rock may also melt whenfluids such as water are added. The addition of fluids generallydecreases the melting point of certain minerals in the rock, whichcan cause those minerals to melt.Partial Meltingigneous rock rock that formswhen magma cools andsolidifiesDifferent minerals have different melting points, and mineralsthat have lower melting points are the first minerals to melt. Whenthe first minerals melt, the magma that forms has a specific composition. As the temperature increases and as other minerals melt,the magma’s composition changes. The process by which differentminerals in rock melt at different temperatures is called partialmelting. Partial melting is shown in Figure 1.Figure 1 How Magma Forms by Partial MeltingThis solid rock contains the mineralsquartz (yellow), feldspar (gray),biotite (brown), and hornblende(green).The first minerals that melt arequartz and some types of feldspars.The orange background representsmagma.Minerals such as biotite andhornblende generally melt last,which changes the composition ofthe magma.Section 2Igneous Rock139
Figure 2 As the temperaturedecreases, the first minerals tocrystallize from magma are mineralsthat have the highest freezingpoints. As the magma changescomposition and cools, minerals thathave lower freezing points form.Fractional CrystallizationWhen magma cools, the cooling process is the reverse of theprocess of partial melting. Chemicals in magma combine to formminerals, and each mineral has a different freezing point. Mineralsthat have the highest freezing points crystallize first. As mineralscrystallize, they remove specific chemicals from the magma. As thecomposition of the magma changes, new minerals begin to form.The crystallization and removal of different minerals from thecooling magma, as occurs in Bowen’s reaction series, is calledfractional crystallization and is shown in Figure 2.Minerals that form during fractional crystallization tend tosettle to the bottom of the magma chamber or to stick to the ceilingand walls of the magma chamber. Crystals that form early in theprocess are commonly the largest because they have the longesttime to grow. In some crystals, the chemical composition of theinner part of the crystal differs from the composition of the outerparts of the crystal. This difference occurs because the magma’scomposition changed while the crystal was growing.Quick LabCrystal FormationProcedure1 Add the following until three glasses are 2/3 full:glass 1—water and ice cubes; glass 2—water atroom temperature; and glass 3—hot tap water.2 In a small sauce pan, mix 120 mL of Epsom saltsin 120 mL of water. Heat the mixture on a hotplate over low heat. Do not let the mixture boil.Stir the mixture with a spoon or stirring roduntil no more crystals dissolve.3 Using a funnel, carefully pour equal amounts ofthe Epsom salts mixture into three test tubes.Use tongs to steady the test tubes as you pour.Drop a few crystals of Epsom salt into each testtube, and gently shake each one. Place one testtube into each glass.140Chapter 6Rocks20 min4 Observe the solutions as they coolfor 15 minutes. Let the glasses sitovernight, and examine thesolutions again after 24 hours.Analysis1. In which test tube are the crystals thelargest?2. In which test tube are the crystals the smallest?3. How does the rate of cooling affect the size of thecrystals that form? Explain your answer.4. How are the differing rates of crystal formation youobserved related to igneous rock formation?5. How would you change the procedure to obtainlarger crystals of Epsom salts? Explain your answer.
Textures of Igneous RocksIgneous rocks may form beneath Earth’s surface or on Earth’ssurface. Magma that cools deep inside the crust forms intrusiveigneous rock. The magma that forms these rocks intrudes, orenters, into other rock masses beneath Earth’s surface. The magmathen slowly cools and hardens. Lava that cools at Earth’s surfaceforms extrusive igneous rock.Intrusive and extrusive igneous rocks differ from each othernot only in where they form but also in the size of their crystals orgrains. The texture of igneous rock is determined by the size of thecrystals in the rock. The size of the crystals is determined mainlyby the cooling rate of the magma. Examples of different textures ofigneous rocks are shown in Figure 3.intrusive igneous rock rockformed from the cooling andsolidification of magma beneathEarth’s surfaceextrusive igneous rock rockthat forms from the cooling andsolidification of lava at Earth’ssurfaceFigure 3 Igneous RockTexturesCoarse-Grained Igneous RockIntrusive igneous rocks commonly have large mineral crystals.The slow loss of heat allows the minerals in the cooling magma toform large, well-developed crystals. Igneous rocks that are composed of large mineral grains are described as having a coarsegrained texture. An example of a coarse-grained igneous rock isgranite. The upper part of the continental crust is made mostly ite)Fine-Grained Igneous RockMany extrusive igneous rocks are composed of small mineralgrains that cannot be seen by the unaided eye. Because these rocksform when magma cools rapidly, large crystals are unable to form.Igneous rocks that are composed of small crystals are described ashaving a fine-grained texture. Examples of common fine-grainedigneous rocks are basalt and rhyolite (RIE uh liet).Porphyritic(granite)Other Igneous Rock TexturesSome igneous rock forms when magma cools slowly at first butthen cools more rapidly as it nears Earth’s surface. This type ofcooling produces large crystals embedded within a mass of smallerones. Igneous rock that has a mixture of large and small crystalshas a porphyritic texture (pohr fuh RIT ik TEKS chuhr).When a highly viscous, or thick, magma cools quickly, few crystals are able to grow. Quickly cooling magma may form a rock thathas a glassy texture, such as obsidian. When magma contains a largeamount of dissolved gases and cools rapidly, the gases becometrapped as bubbles in the rock that forms. The rapid cooling processproduces a rock full of holes called vesicles, such as those in pumice.This type of rock is said to have a vesicular texture.Glassy(obsidian)Vesicular(pumice)What is the difference between fine-grainedand coarse-grained igneous rock?Section 2Igneous Rock141
Figure 4 Felsic rocks, such asthe outcropping and hand sampleshown above (left), have lightcoloring. Mafic rocks (right) areusually darker in color.Academic Vocabularyproportion (proh POHR shuhn) therelation of one part to another or to thewholeComposition of Igneous RocksThe mineral composition of an igneous rock is determined bythe chemical composition of the magma from which the rockformed. Each type of igneous rock has a specific mineral composition. Geologists divide igneous rock into three families—felsic,mafic (MAF ik), and intermediate. Each of the three families has adifferent mineral composition. Examples of rock from the felsicand mafic families are shown in Figure 4.Felsic Rockfelsic describes magma origneous rock that is rich infeldspars and silica and that isgenerally light in colormafic describes magma origneous rock that is rich inmagnesium and iron and that isgenerally dark in colorRock in the felsic family forms from magma that contains alarge proportion of silica. Felsic rock generally has the light coloring of its main mineral components, potassium feldspar and quartz.Felsic rock commonly also contains plagioclase feldspar, biotitemica, and muscovite mica. The felsic family includes many common rocks, such as granite, rhyolite, obsidian, and pumice.Mafic RockPyramidCreate a pyramid FoldNote torecord your notes on the threefamilies of igneous rock—felsic, mafic, and intermediate.For each term, write thedefinition andinclude anexample ofa rock fromthat family.142Chapter 6RocksRock in the mafic family forms from magma that containslower proportions of silica than felsic rock does and that is rich iniron and magnesium. The main mineral components of rock in thisfamily are plagioclase feldspar and pyroxene minerals. Mafic rockmay also include dark-colored ferromagnesian minerals, such ashornblende. These ferromagnesian components, as well as themineral olivine, give mafic rock a dark color. The mafic familyincludes the common rocks basalt and gabbro.Intermediate RocksRocks of the intermediate family are made up of the mineralsplagioclase feldspar, hornblende, pyroxene, and biotite mica. Rocksin the intermediate family contain lower proportions of silica thanrocks in the felsic family do but contain higher proportions of silicathan rocks in the mafic family contain. Rocks in the intermediatefamily include diorite and andesite.
Intrusive Igneous RockIgneous rock masses that form underground are calledintrusions. Intrusions form when magma intrudes, or enters, intoother rock masses and then cools deep inside Earth’s crust. A variety of intrusions are shown in Figure 5.Batholiths and StocksThe largest of all intrusions are called batholiths. Batholiths areintrusive formations that spread over at least 100 km2 when theyare exposed on Earth’s surface. The word batholith means “deeprock.” Batholiths were once thought to extend to great depthsbeneath Earth’s surface. However, studies have determined thatmany batholiths extend only several thousand meters below thesurface. Batholiths form the cores of many mountain ranges, suchas the Sierra Nevadas in California. The largest batholith in NorthAmerica forms the core of the Coast Range in British Columbia.Another type of intrusion is called a stock. Stocks are similar tobatholiths but cover less than 100 km2 at the surface.www.scilinks.orgTopic: Igneous RockCode: HQX0783LaccolithsWhen magma flows between rock layers and spreads upward,it sometimes pushes the overlying rock layers into a dome. Thebase of the intrusion is parallel to the rock layer beneath it. Thistype of intrusion is called a laccolith. The word laccolith means “lakeof rock.” Laccoliths commonly occur in groups and can sometimesbe identified by the small dome-shaped mountains they form onEarth’s surface. Many laccoliths are located beneath the Black Hillsof South Dakota.Volcanic neckWhat is thedifference between stocks andbatholiths?DikeSills and DikesWhen magma flows between thelayers of rock and hardens, a sillforms. A sill lies parallel to the layersof rock that surround it, even if thelayers are tilted. Sills vary in thickness from a few centimeters to hundreds of meters.Magma sometimes forces itselfthrough rock layers by followingexisting vertical fractures or by creating new ones. When the magmasolidifies, a dike forms. Dikes cutacross rock layers rather than lyingparallel to the rock layers. Dikes arecommon in areas of volcanic activity.DikeLaccolithSillStockBatholithFigure 5 Igneous intrusionscreate a number of uniquelandforms. What is the difference between a dike and a sill?Section 2Igneous Rock143
Figure 6 Shiprock, in NewMexico, is an example of avolcanic neck that was exposedby erosion.Extrusive Igneous RockA volcano is a vent through which magma, gases, or volcanicash is expelled. When a volcanic eruption stops, the magma in thevent may cool to form rock. Eventually, the soft parts of the volcano are eroded by wind and water, and only the hardest rock inthe vent remains. The solidified central vent is called a volcanicneck. Narrow dikes that sometimes radiate from the neck may alsobe exposed. A dramatic example of a volcanic neck called Shiprockis shown in Figure 6.Igneous rock masses that form on Earth’s surface are calledextrusions. Many extrusions are simply flat masses of rock calledlava flows. A series of lava flows that cover a vast area with thickrock is known as a lava plateau. Volcanic rock called tuff formswhen a volcano releases ash and other solid particles during aneruption. Tuff deposits can be several hundred meters thick andcan cover areas of several hundred kilometers.Section 2 ReviewKey IdeasCritical Thinking1. Summarize three factors that affect the melting7. Applying Ideas If you wanted to create a rockof rock.2. Contrast partial melting and fractionalcrystallization.3. Describe how the cooling rate of magma affectsthe texture of igneous rock.4. Name the three families of igneous rocks, andidentify their specific mineral compositions.5. Describe five intrusive igneous rock structures.6. Identify four extrusive igneous rock structures.144Chapter 6Rocksthat has large crystals in a laboratory, whatconditions would you have to control? Explainyour answer.8. Applying Ideas An unidentified, light-coloredigneous rock is made up of potassium feldsparand quartz. To what family of igneous rocks doesthe rock belong? Explain your answer.Concept Mapping9. Use the following terms to create a concept map:igneous rock, magma, coarse grained, fine grained,felsic, mafic, and intermediate.
SECTION3Sedimentary RockKeyeyy Ideasdeas❯ Explain the processes of compaction andcementation.❯ Describe how chemical and organic sedimentary rocks form.❯ Describe how clastic sedimentary rock forms.❯ Identify seven sedimentary rock features.Keyeyy Termse sWhyy Itt Mattersatte scompactionSedimentary rock is acommon building material. Understanding itsproperties is crucial topublic safety. The ways inwhich it is formed affectsthe rock’s properties.cementationchemical sedimentaryrockorganic sedimentary rockclastic sedimentary rockLoose fragments of rock, minerals, and organic material thatresult from natural processes, including the physical breakdown ofrocks, are called sediment. Most sedimentary rock is made up ofcombinations of different types of sediment. The characteristics ofsedimentary rock are determined by the source of the sediment,the way the sediment was moved, and the conditions under whichthe sediment was deposited.Formation of Sedimentary RocksAfter sediments form, they are generally transported by wind,water, or ice to a new location. The source of the sediment determines the sediment’s composition. As the sediment moves, itscharacteristics change as it is physically broken down or chemically altered. Eventually, the loose sediment is deposited.Two main processes convert loose sediment to sedimentaryrock—compaction and cementation. Compaction, as shown inFigure 1, is the process in which sediment is squeezed and inwhich the size of the pore space between sediment grains is reducedby the weight and pressure of overlying layers. Cementation is theprocess in which sediments are glued together by minerals that aredeposited by water.Geologists classify sedimentary rocks by the processes by whichthe rocks form and by the composition of the rocks. There are threemain classes of sedimentary rocks—chemical, organic, and clastic.compaction the process inwhich the volume and porosityof a sediment is decreased bythe weight of overlyingsediments as a result of burialbeneath other sedimentscementation the process inwhich minerals precipitate intopore spaces between sedimentgrains and bind sedimentstogether to form rockFigure 1 Processes That Form Sedimentary RockOverlying layersWhen mud is deposited,When sand is deposited,squeeze sediment.there may be a lot of spacethere are many spacesbetween grains. Duringbetween the grains.compaction, the grains areDuring cementation,squeezed together, and thewater deposits minerals50-60% waterrock that forms takes upsuch as calcite or quartzless space.in the spaces around thesand grains, which gluesthe grains together.10-20% waterPore spacesbetweensedimentgrains areempty.Water movesthroughpore spaces.Minerals depositedby water cementthe grains together.145
Chemical Sedimentary Rockchemical sedimentaryrock sedimentary rock thatforms when minerals precipitatefrom a solution or settle from asuspensionorganic sedimentaryrock sedimentary rock thatforms from the remains ofplants or animalsChain-of-Events ChartMake a chain-of-events chartto show the steps in theformation of organic sedimentary rocks. Write thefirst step of theprocess in a box.Add boxes withadditional steps, andconnect the boxeswith arrows.Minerals made up of ions such as calcium, potassium, andchloride can dissolve in water. Chemical sedimentary rock formswhen the ions from dissolved minerals precipitate out
the rock cycle, which is shown in Figure 2. One starting point for examining the steps of the rock cycle is igneous rock. When a body of igneous rock is exposed at Earth’s surface, a number of processes break down the igneous rock into sediment. When sediment from igneous rocks is compacted and cemented, the sediment becomes sedimentary rock.
0.8 M Earth 1 M Earth 0.1 M Earth Planet Radius (R Earth): 0.95 R Earth 1 R Earth 0.5 R Earth Distance from Sun (DEarth): 0.7 D Earth 1 D Earth 1.5 D Earth Average Surface Temperature: 456 oC 10 oC -95 oC Atmosphere: T
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Interactive Textbook Answer Key 33 Earth Science Earth Science Answer Key Chapter 1 The World of Earth Science SECTION 1 BRANCHES OF EARTH SCIENCE 1. earthquakes 2. oceans 3. the study of Earth’s atmosphere, weather, and climate 4. Meteorologists can predict severe weather in time for people to get out of the way. 5. Unlike other branches of .
Introduction to Science Section 2 The Branches of Science, continued The branches of science work together. -biological science: the science of living things botany, ecology -physical science: the science of matter and energy chemistry: the science of matter and its changes physics: the science of forces and energy -earth science: the science of the Earth, the
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