Earth Science Textbook Chapter 6 Volcanoes

. Chapter Standards Preview Plate tectonic accounts for of Earth surface and molar geologic . As a basis tor understanding this concept . Students know that earthquakes are sudden along breaks in the ( run called faults and that volcanoes and are lo where magma the surface . Students know major geologic events , sum as earthquakes , eruptions and , result from plate , Students know how to explain major features ( geology mountains . faults , and volcanoes ) In terms of plate . Topography is reshaped by the weathering of rock and soil and by me trans and deposition of sediment . As I East for this corrupt ti . Students know earthquakes , eruptions . landslides . and change human and progress it made by asking questions and careful investigations . As a basis for understanding this and addressing the content in the other three strands , students should develop their own questions and perform investigations . Students will Interpret events by sequence and time from natural phenomena ( the relative age of rocks and ) lava fountain erupts from Mount , a in Hawaii .

haw ! Halal smut Volcanoes Focus on the ' What causes volcanoes , and how do they change . Earth surface ?

If Check What You Know I You know that if you want to open a bottle of soda , you must do so carefully . Otherwise , the soda might spray out of the bottle ' as soon as you loosen the cap . What causes the ' soda to rush out with such force ?

How is this similar to what happens when a volcano erupts ?

Explain . 211 Science The images shown here represent some of the key terms in this chapter . You can use this vocabulary skill to help you understand the meaning of some key terms in this ( Use Clues to Determine Meaning textbooks often contain unfamiliar words . When you are reading , use clues to figure out what these words mean . First look for clues in the word itself . Then look at the surrounding words , sentences , and paragraphs . Look at the clues to the meaning of hot spot in the following text . Unfamiliar words Some volcanoes result from but in , Definition , mantle . hot is an arm material tin mantle rugs and that melts . A volcano forms itl . a hot spot Explanation Hat spot is the subject of the rough the crust and reaches the surface . A hot spot in ocean liner can gradually form a series . For , the an Islands one by one ( I a hot spot . Apply It ! Review the clues to the meaning of hot spot . Then complete the following . What clue tells you that hot spot might be followed by a definition ?

What example helps you understand hot spots ?

As you come across an unfamiliar word in this chapter . look ( or clues to its meaning . 211 Chapter Vocabulary Section volcano magma lava Ring of Fire island arc hot spot magma ( DIP ?

vent lava flow ( a pyroclastic flow dormant extinct geyser Section shield ( under ( one composite volcano caldera volcanic ne ( duke sill intrusion batholith basin Central Valley Build ( Use Chapter 213 to i . co Outlines You have learned to use headings and to identify main ideas and details to guide you as you read . An outline uses these skills to show the relationship between main ideas and supporting details . An outline usually is set up like the one below . Roman numerals show the main topics or headings . Capital letters show the . Numbers show supporting details and key terms . Volcanic landforms I Landforms From lava and Ash A . Shield Volcanoes . Lava gradually from a vent . A wide . gently sloping mountain forms Cinder Cone Volcanoes Mal I . May produce ash , cinders , bombs . Steep . mountain forms Composite Lava Plateaus Soils From Lava and Ash II Landforms From Magma or ideas or Apply It ! Answer each of the following questions . What are the most important ideas in this outline ?

What details support the subheading Shield Volcanoes ?

Copy the outline above into your notebook . Use the headings , and key terms to help you select information to complete the outline for Landforms From Magma in Section . Create an outline for Kinds of Volcanic Eruptions In Section .

Standards Investigation Volcanoes and People The eruptions oi a volcano can be dangerous . Yet volcanoes and people have been closely connected throughout history . People often live near volcanoes because of the benefits they , from rich soil to minerals to hot springs . In this investigation , you will research the people living in a volcanic region . Your Goal To make a documentary about life in a volcanic region Your documentary must describe the type of volcano you chose and give its history focus on one topic , such as how people have from living near the volcano or how people include the volcano in their art and stories use a variety of media follow the safety guidelines in Appendix A Plan It ! Brainstorm with a group of other students which geographic area you would like to learn about . Your teacher may suggest some volcanic regions for you to check out . Decide what research resources you will need . For media , you might consider video , computer art , a skit , or a mural . Be creative ! When your documentary is finished , present it to your class .

Section Volcanoes and Plate Tectonics a da , Standards ( for important features of surface and major geologic events . As a basis tor understanding this concept ( Students know events , such as , nit eruptions , and mountain build , result from plate motions Where are must at taunt ! How do hot spot volcanoes form ?

Key I volcano magma lava I Ring of Fire I island arc hot spat Where Are Volcanoes Found on Earth Surface ?

Look at the map of Earth Active in Figure . What symbols are used to represent volcanoes What other symbols are shown on the map ?

Do the locations of the volcanoes form a pattern ?

Do the seem related to any other features on Think About It Hypotheses Develop a hypothesis to explain where Earth volcanoes are located In . Etna erupted in ' and . limited on the of Sicily in the ' i Sui . is ' the List years . it has erupted often . The . Greeks believed ( grid til the . the ) the , i . for i ' Greek gods . events on Earth . A volcano is weak spot in the crust where ni , conic to . Magma is it of , and ' twin . When I ' the ( it is called lava . has . it solid melt . Lint during . builds up ' Haunt have Flow on Mount Etna A lava from Mount in almost bun this building

Volcanoes and Plate Boundaries , There are about 600 active volcanoes on land . Many more lie ' plates . The belt of beneath the sea , where it is for scientists to observe and i ' map them . Figure shows the location of some of Earth ' major volcanoes . Notice how volcanoes occur in balm that , extend across continents and oceans . One major volcanic belt is the Fire . formed by the many volcanoes that rim the Ocean . belts form along the boundaries of Earth plates . At plate boundaries . huge pieces of the crust spread apart or collide . As a result . the crust often fractures . allowing magma to reach the surface . Most volcanoes form along spreading boundaries such as ridges and along boundaries where subduction takes place . For example . Mount Etna formed near the boundary of the Eurasian and African plates . Spreading Volcanoes form along the ocean ridges . which mark spreading boundaries . Recall that ridges are long , underwater mountain ranges that sometimes have a rift valley down their center . Along the rift valley . lava pours out of in the ocean . gradually building new mountains . Volcanoes also form along spreading boundaries on land For example , there are several large volcanoes along co the Great Rift Valley in East Africa . I 117

Flaunt Volumes at colliding Volcanoes often form where two plates collide or where an oceanic plate collides with a continental plate . In both situations , an oceanic plate sinks beneath a trench . Rod above the plate melts to form magma , which later erupts as lava . III Colliding Many volcanoes form near colliding boundaries where oceanic plates return to the mantle . noes may form where two oceanic plates collide or when an oceanic plate collides with a continental plate . Figure shows how colliding plates produce volcanoes . Many volcanoes occur near boundaries where two oceanic plates collide . Through subduction . the older . plate sinks beneath a trench into the mantle . Some of the rock above the plate melts and forms magma . Because the magma is less dense than the surrounding rock . it rises toward the surface . Eventually , the magma breaks through the ocean floor . creating volcanoes . The resulting volcanoes create a string of islands called an inland arc . The curve of an island arc echoes the curve of its trench . Major island arcs include , New . Indonesia . the Philippines , the . and the Caribbean islands . Volcanoes also occur where an oceanic plate is beneath a continental plate . Collisions of this type produced the volcanoes of the Andes in South America and the volcanoes of Northern California . Oregon . and Washington . How do the volcanoes lo the Andes Mountains form ?

an ridge Activity Hot Spot in a Box . Fill a plastic box at cold water . This represents the mantle . Mix red food ( with not water in a small , Hold your finger over the , the Pa plate movement carry mom , of home as you Island of away from the hot spot . Inferring which island on the map farmed ?

he home he center of the box . The mouth of the bottle must be under water . I . Float a flat piece of plastic Some volcanoes result from hot spots in Earth mantle . A ' Wat ?

hot spot is an area where material from deep within the mantle ! rises and then melts , Forming magma . A volcano forms Take ' the above a hot spot when erupts through the crust Ind bum and iii , the surface . Some hot spot volcanoes lie in the middle happen , of plates far from any plate boundaries , Other hot spots occur Making Move me on or near plate boundaries . 193 . gong , A hot spot in the occult can gradually form a series of Where does the magma volcanic mountains . For example . the Hawaiian islands 79 ' OW formed . one by one . over millions of years as the plate drifted over a hot spot . Hot spots can also form under the . Yellowstone National Park in Wyoming marks a hot spot under the North American plate . section Assessment . Vocabulary Skill Um Clues to Determine ' Reread the on island arcs . under the heading Ing In ( What are some examples of mu . arcs ?

em . you mum . Punk Reviewing Key Concepts that will visit volcanoes . Defining What is volcano ?

93 ' Reviewing Where arr most volcanoes located ?

Relating Cause and Effect causes volcanoes to form at a spreading plate boundary ?

Defining is a hut spot ?

Summarizing How does a hot spot volcano form ?

Predicting What features form at a hot spot ?

9119 Guided Inquiry Mapping Earthquakes and Volcanoes Problem Is there a pattern In the locations of earthquakes and volcanoes ?

Skills Focus Interpreting am Procedure . Use the information in the table to mark the location of each earthquake on a world map . Use a colored pencil to draw a letter inside a circle at each earthquake location . Use a pencil of a second color to mark the volcanoes on the world map . Indicate volcano with the letter inside a circle . Use a third pencil to lightly shade the areas in which earthquakes are found . Use a fourth colored pencil to lightly shade the areas in which volcanoes are found . 35 ' 15 ' 20 ' on 40 15 ' 30 ' 10 ' 41 ' 53 Analyze and Conclude . Interpreting Data How are earthquakes distributed on the map ?

Are they scattered evenly or concentrated in zones ?

Interpreting Data How are volcanoes distributed ?

Are they scattered evenly or concentrated in zones ?

Inferring From your data , what can you infer about the relationship between earthquakes and volcanoes ?

communicating Suppose the locations of additional earthquakes and volcanoes were added to the map . Would the overall pattern of earthquakes and volumes change ?

Explain in writing why you think the pattern would or would not change More to Explore Pick one earthquake and one volcanic eruption to investigate . You can use the list of earthquakes in Figure 19 on page 198 and the Science History timeline on volcanoes on pages ) Plot and label the events on the map you just made . Research how the events relate to plate motions and how powerful they were . Report your to your class . 2200

Section Volcanic Eruptions ( Standards Focus Students that quakes are sudden motion along breaks in the crust called faults and that volcanoes and fissures are locations where magma reaches the surface . Students know quakes , volcanic eruptions . slides , and ( hange human and wildlife habitats . What happens when a volcano erupts ?

What are the two types of volcanic eruptions ?

What are a stages of activity ?

Key Terms magma chamber ' vine ' vent lava flow crater flow dormant extinct geyser What Are Volcanic Rocks Like ?

Volcanoes produce lava . which hardens into rock . Two of these rocks are pumice and obsidian . Observe samples of pumice and obsidian with a hand lens . How would you describe the texture of the pumice ?

What could have caused this texture ?

Observe the surface of the obsidian . How does the surface of the obsidian differ from pumice ?

It Over Developing Hypotheses What could have produced the difference in texture between the two rocks ?

Explain your answer . Obsidian In Hawaii , there are many myths about Pele ( PAY lay ) the of volcanoes . According to legend , lives in the depths of erupting volcanoes . When Pele is angry , she causes volcanic eruption . One result of an eruption is ele hair . a , rock formed by lava . hair forms when lava sprays out of the ground like water from a . As it cools . the lava stretches and into thin strands . as shown in Figure . Where does this lava come from ?

Lava begins as magma , which usually in the . The materials of the are under great pressure . Liquid magma is less dense than the solid material it . Therefore . magma flows upward into any cracks in the ruck above . magma rises , it trapped beneath layers of rod ( But if an opening in weak rock allows the to reach the surface , volcano forms . From Hair hair is a type at formed from lava . Each strand is as fine as spun glass . chapters om

Gases in Magma the gas bubbles In a volcanic eruption . In a bottle . Will 10 of baking soda into 65 of water . Put about six in the waler , the water and raisins , add 65 of vinegar and my . the liquid slaps moving , observe the Making Models happens after you add the vinegar ?

What do ihe and bubbles How is this model lo the way magma behaves a volcano Magma Reaches Earth Surface is Volcano is ' Inside a Volcano All have packer 01 ' more which the 111 ( in 21 pocket 11 magma chamber . The 111111 pipe . 11 long in the that ) In ' You we in Figure . gas . the through 1111 up vent . is 1111 van ! the ( many also ' lava 11 arm by il ' crater 11 , ol 10114110 . A Volcanic Eruption What pushes in the ' similar In ' pup because il in liquid . when yuu . is . and i . rush In , gases in . Tin ) gusts 111 I . FIGURE Lava Burp During an eruption of Mount . the force of a gas bubble pushes up a sheet of lava ,

As magma I ( toward the surface . the of the rounding rock on the magma . The dissolved begin to expand . forming bubbles . As ' falls within the magma . Silt of gas bubbles greatly . gases exert an force . When I volcano erupts . the force of the expanding gases pushes from the magma through the pipe until it or explodes out of the vent . Once escapes from the volcano and lava . the remaining gases bubble nut . What to En magma is magma rises toward the sumac ?

at Go act For Eruption Visit Web ( ode A volcano Erupts A volcano forms where magma breaks through Earth crust and lava over the surface . What pan of a volcano connects the vent with the magma chamber ?

chapters on I Pahoehoe and Aa Both pahoehoe and aa can come the same volcano . Pahoehoe flows easily and hardens into a rippled surface . Aa hardens into rough chunks Magma Composition Magma varies In composition and is classified according to the amount of silica it contains . The graphs show the average composition of two types of magma . Use the graphs to answer the questions , Reading Graphs Study both graphs . What materials make up both types of magma ! Reading Graphs Which type of magma has more silica ?

About how much silica does this type of magma contain ?

Estimating A third type of magma has a silica content that is halfway between that ol the other two types . About how much silica does this magma contain ?

Data Kinds of Volcanic Eruptions Some volcanic eruptions occur gradually . Others art dramatic explosions . Geologists classify volcanic eruptions as quiet or explosive . The of di how at cano erupts . an eruption is quiet or explosive depends on silica content and the magma is thin and runny or thick and sticky . Silica is a mati found in that is formed from the oxygen and silicon . Quiet Eruptions A volcano erupts quietly if its magma is low in silica , magma is thin and runny and flows . The gases in the magma bubble out gently . silica lava quietly from the vent and can for many kilometers . Quiet eruptions can produce two different types of lava that in . hoh is moving , lava that is thin and runny . The surface of a lava formed looks like solid mass of and coils . Lava that is cooler and slow is called ( AH ah ) An is thicker than pahoehoe , When an hardens . it forms a rough consisting of lava chunks . The Hawaiian Islands formed from quiet eruptions . On the Big Island of Hawaii . lava pours out of the crater on Mount . But law also flows out of long cracks . called , on sides . eruptions have built up Big Island over hundreds of of years . Moth Mathematical Reasoning . Predicting What type ol magma would be more thick and sticky ?

Explain . Magma Magma 2240 Eruption Eruptions A erupts explosively if its magma is high in silica . magma is thick and sticky . It builds up in the pipe , plugging it like cork in bottle . gases . including water vapor . can not escape the thick magma . The trapped gases build up pressure until they explode . The erupting gases and steam push the magma out of the volcano with incredible force . That what happened during the eruption of Mount . shown in Figure . An explosive eruption breaks lava into fragments that quickly cool and harden into pieces of sizes . The pieces an volcanic . ky particles as small as at speck of dust . particles are called . Larger pieces . called bombs . may range from the size of a ball to the size ofa car . A ( py KI AS tik is type of explosive eruption that hurls out a mixture of hot gases . ash . Cinders , and bombs . Pumice and obsidian . which you observed if you did the Standards activity . form from lava . Obsidian forms when lava cools very quickly . giving it a smooth . glossy surface like glass . Pumice forms when gas are trapped in lava , leaving spaces in the rock . What is a ?

Alter Eruption must An Explosive Eruption Mount in Washington State erupted at AM . on May 18 , 1980 . The explosion blew oh the top of the mountain . Relating Cause and Effect Why did Mount Helen erupt so explosively ?

Volcano Hazards Although eruptions and produce different . both types of eruption can most damage far from the rim . During a . lava flows from . soiling to , and then burying , in its path . A quiet eruption can cover large areas with thick of lava . During an explosive eruption . a volcano can belch our hot clouds of gases as well as ash . and bombs . nic ash can bury towns . If it . the heavy ash can cause roofs Io collapse . If a plane sucks ash into its engine , the engine may stall . Eruptions can cause landslides and of mud , snow , and rock . The and shows the effects of explosive . How does ash cause damage ?

Science and History The Power of Volcanoes Within the last 150 years . major eruptions have greatly affected the land and people around them . 1912 Mount Today , a river in Allah cuts through the thick layer of ash from the emotion of Mount . 1902 Mount Mount , a Caribbean volcano . spewed out a burning cloud of hot gas and flows . The cloud killed residents of Pierre . city on the volcano flank . only two people survived . 1883 The violent eruption of volcano in Indonesia threw 18 cubic kilometers of ash . The blast was heard away . 1850 1875 2260

Stages of Volcanic Activity The activity of at may last from less than a decade to more 10 million years . Geologists try to determine ano past and whether the volcano will erupt again . Life Cycle of a Volcano Geologists usethe terms active , dormant , or extinct lo describe a stage of activity . An active . or live , is one that is erupting shown signs it may erupt in the near future . A dormant . ur sleeping . volcano is like sleeping hear . Sci expect a volcano in in the future and active . extinct . or dead . volcano is unlikely to erupt again . In ( In California , lass Peak and Mount are ered active volcanoes . Lassen Peak last erupted in . and ' it Mount . li ist . erupted during the latte . near Lung ?

33 Valley on the side of the Sierras are but could , up , ne , one 54 become active again . the eruption in the timeline . Then write a letter what someone observing the eruption might have seen . 2002 Mount Etna Bulldozer ! constructed a wall against of lava creeping down the slopes of Mount Etna in Sicily . 1991 Mount in the Philippines spewed out huge quantities of ash that rose high into the atmosphere and buried nearby areas . 1980 Mount Helena when Mount Helen In Washington exploded , it blasted one kilometer of material skyward .

Hot Springs and Geyser Hot spring and geyser are often found in areas of present or past volcanic activity . A hot spring when water deep underground is heated by a nearby body of magma or by hot rock . The hot water rises to the surface and in a natural pool . Sometimes . rising hot water and steam become trapped in a narrow crack . Pressure builds until the mixture suddenly sprays above the surface as a geyser . A geyser ( is a fountain of water and steam that erupts from the ground . Volcanoes Geologists use instruments to detect changes in and around a volcano . These changes may give ing a short time before a erupts . But geologists can not be certain about the type of eruption or how powerful it will be . Geologists use and other instruments to detect slight changes in elevation and tilt caused by magma moving underground . They monitor any gases escaping from the volcano . A increase in underground water may be a sign that magma is nearing the surface . Geologists also monitor the many small earthquakes that occur around a volcano before an eruption . The upward movement of magma triggers these quakes . A Geyser Erupts , a geyser in Yellowstone National Park , erupts about every 33 to 93 minutes . leading . Writing Assessment Section Target Reading Skill Create Outlines Complete your outline for the section Volcanic Eruptions . What are three important details that you included under the heading Life Cycle of a Volcano ?

a . Naming What are the three stages of volcanic activity ?

Predicting Which is more likely to be volcano that erupts frequently or a volcano that has been inactive for a hundred years ?

Why ?

Reviewing Key Concepts a . Listing What are the parts of a volcano ?

Describe the order of parts through which magma travels as it moves to the surface . Relating Cause and As a volcano erupts . what force pushes magma out of a volcano onto the surface ?

Identifying What are the ' main kinds of volcanic ?

lam . Explaining What properties of magma help to determine the type of eruption ?

What do lava made of pahoehoe and an indicate about the type oi volcanic eruption that occurred ?

Writing in Science You an a television news who will a geologist . The returned studying a nearby that may soon erupt . Write tho questions that you would nit . eruption is coming . the we of , and any you expect for each question .

Section Volcanic Landforms ( Students know how to How can , anl ( explain major features of California change Earth su ace . Use tape to secure the neck of ' balloon over one end of a straw . plate tectonics . new by . Place the balloon in the center of and time from natural a box me ud ' phenomena re , me . Partially inflate the balloon . ol rocks and intrusions ) Put damp sand on top of the balloon until it is covered . Slowly inflate the balloon more . Observe what happens What landforms do lava and ash he sun . the mi ( 16312 ?

ow . a ' Making Model This activity models one of the ways in which ! volcanic activity can cause a mountain to form . What do you think the sand represents ?

What does the balloon represent ?

Key Terms shield volcano ' Me . have created some of most spectacular forms . The perfect cone of Fuji iii . shown in , Wank Figure I is famous around the world . we much of Earths history , volcanic activity on and sill the has built up Earth arms . Volcanic activity also formed the rock of the ocean . volcanic ' landforms arise when lava flows build up mountains and on surface . Other volcanic landforms arc the insult of the buildup of magma beneath the surface . 11 Mount Full The volcanic cone of Mount Fuji in Japan has long been a favorite subject for artists . 0229

Flaunt 12 Volcanic Mountains Volcanic activity is responsible for up much of Earth surface . Lava from volcanoes ( and hardens into three types of mountains . It can also term lava plateaus . What type of volcano is formed from thin . lava ?

Landforms From Lava and Ash ( Volcanic eruptions create landforms made of lava , ash , and other . These include shield volcanoes , cinder cone volcanoes , volcanoes . and lava plateaus . Look at Figure 12 to tee these features . Another , called i caldera . mulls from ( mountain . Shield Volcanoes Al places on Earth , thin ' I ol ' i pour out of at will and harden on top of previous lil ) Such lava ( build it ' sloping mountain shield volcano . Islands and the Lalo in northern . Cinder Cone Volcanoes i ) is high in silica . it may ash . and . build up the vent in a , cum hill or small called cinder cone . For , in erupted in in a . The up cone about 400 meters high . Volcano Quiet eruptions alternate with explosive , oi lava and ash . Mount , Philippines

Composite Volcanoes . lava with explosive eruptions of ash , cinder , and bombs . The result is a volcano . Composite volcanoes arc tall . shaped mountains in which layers of lava with layers Volcanoes of ash . Examples include Fuji in and Mount Shasta and Lassen Peak in California . Lava Plateaus form high . level areas lava ' ILlS . First . lava out of several lung cracks , or fissures , in an aim . The thin . runny lava travel far before and solidifying . Again and again . of lava on top of earlier ( After millions of years . these layers of lava can form high plateau . include the ( Plateau in Washington , Oregon , and . and the Modoc Plateau in . Shield Volcano Quiet eruptions gradually build up I gently sloping mountain . Cone Volcano Ash . cinders . and bombs amp ! explosively to form can . em a hill . I Layers of lava Plateau A lava plateau made up of many layers of thin , runny lava that erupt from long cracks in the ground .

How I Caldera Forms Today . Crater Lake ( right ) fills an almost circular caldera . A caldera forms when a ano magma chamber empties and the roof oi the chamber collapses . top of a composite volcano explodes . Lava flows partially empty the magma . The roof of the magma chamber collapses . a caldera . later . a small cinder tone forms in the caldera . which partly fills with water . 1310 The huge hole left by the collapse of a nic mountain is called at caldera Ital uh ) The hole is with the pieces of the volcano that have fallen inward , as well as some lava and ash . How does a caldera form ?

Enormous eruptions may empty the main vent and the magma chamber beneath a volcano . The mountain becomes a hollow shell . With nothing to support it . the top of the mountain collapses inward . fanning a caldera . In Figure you can see steps in the formation of Crater Lake . a caldera in Oregon . Crater Lake fanned about years ago when a huge explosive eruption partly emptied the magma chamber of a volcano called Mount When the volcano exploded . the top of the mountain was blasted into the atmosphere . The caldera that formed then with water from rain and snow . In California . the Long Valley caldera after huge eruption about years ago . Geologists have detected the release of carbon dioxide gas and earthquakes centered near the caldera . These events are signs that eruptions might someday occur in the same area . Soils From Lava and Ash Why would anyone live near an active volcano ?

People often settle Close to noes to take advantage oi the fertile volcanic soil . The lava . ash . and that erupt from a volcano are initially barren . Over time . however . the hard surface of the lava breaks down to form soil . When volcanic ash breaks down . it releases potassium . phosphorus , and other substances that plants need . As soil develops . plants are able to grow . Some volcanic soils are among the richest soils in the world . Rich soil is fertile , or able to support plant growth . Now an rolls important ?

Landforms From Magma Sometimes magma forces its way through cracks in the upper ' but fails to reach the surface . There magma tools and into rock . lime . forces that wear away as water . ice . or strip away the layers above the hardened and it . Features fanned by magma include volcanic necks . dikes . sills . and . Volcanic A volcanic neck like 31 giant tooth stuck in the ground . A volcanic neck forms when magma in pipe . The ruck the pipe wears away , the hard rock volcanic neck . Ship Rock in New Mo . shown in Figure is a volcanic neck mites and Magma can force its way across or between rock layers . Magma that forces itself across rock layers intu a dike . a dike be slanting through bedrock along at highway cul . When magma , horizontal layers of rock . it forms a sill . Dikes and sills are of igneous intrusions . An intrusion forms when magma to form igneous rock . An is always younger than the ruck around il . For Links my Visit Web ( ode Necks , and Magma that harden beneath the surface may . dikes . and sills . A dike extends outward from Ship Rock . a volcanic in New Mexico . Applying Concepts In the photograph af the sill below . which is alder the sill DI the layers above and below it ?

15 Several large form the ( ore of mountain ranges in western North America . including the Sierra Nevada , shown here . iths Large rock masses called form the core of mountain . A BATH uh ) is a of rock when a of cools crust . The map in Figure shows huw big are . The sierra Nevada extends for roughly 600 meters the eastern side of ( ihe photograph shows how a looks when the uf rock above it iy ' Reading . Writi Assessment Section Vocabulary Skill use Clues to Determine Meaning the ( Find clues fur a , an . and an of a caldera . Predicting millions of ) forms ( ruin hardened magma in the pipe of an extinct volcano ?

a . Listing ' arc in areas ' INT three main mes . Relating and Effect What causes a i of ?

I erupt ' A ( lug In of . type ut . and the materials that make up the volcano . I ' min and eruption involved aswellas What arc two ways In ' i can form as A mull of magma me me was WI Low , he hardening beneath surface ?

Figure 13 hem ) Section California Geology . Students know how to explain major features of California geology ( including mountains . faults . and volcanoes ) in terms of plate tectonics How does plate tectonics help to explain features of California geology ! Key Terms basin Central Valley Frank 16 ( Crater formed in the Mojave Desert about years ago . How Do Plate Motions Affect California ?

Look at the map of plate boundaries in Figure on page 236 . Study the map and the map key . What are the names of the plates that make up California and the nearby pan of the Pacific Ocean ?

Write the names of the plates in your notebook . Determine what types of plate boundaries are found in or near California . Write the types of boundaries in your notebook Think It Over Relating Cause and Effect Recall that there are volcanoes in northern California . which feature on the map causes the volcanoes there ?

Explain . If you in an airplane across the Mojave Desert . you might spot Crater . This extinct cinder cone would be easy to nearly half kilometer across . Why is there a volcano here ?

Plate caused the crust to stretch and crack . allowing magma to reach the surface . Many volcanic landforms dot the California landscape . But volcanoes are only one type of geologic feature that makes up a landscape . Plate Tectonics and California You have probably seen many maps of California . Plate tectonics helps to explain the geologic features on those maps . movements of the and North American plates produced California major geological features . These features include faults . volcanoes , mountain ranges . and basins . These features look shape over millions of years .

El El Plate Boundaries , mung aura winning an tsunami Hell ! 17 Plate Tectonics and California The movements of three plates have shaped the geologic features of California over million at years . What will happen to the Baja peninsula as spreading occur in the nearby Gulf of California ?

Section Vocabulary of a basin . Reviewing Key Concepts a . Listing What four features does plate tectonics explain ?

Explaining How does the San Andreas fault to explain why there are so many other faults in ?

Predicting Los Angeles lies on the plate . lies on the North plate . How will the distance the two change over millions of years ?

553 Skill Use Clues to Determine Meaning Reread the paragraphs under the heading Basins . Find clues for a , an explanation . and an example Faults are often found along or near the of plates . As you can see in Figure 17 , the and North ican slide past each other along the San Andreas fault . push and pull on ' crust with force . The crust breaks , forming many other faults , shown in Figure 18 . Volcanoes in Ocean north of California . the luan de plate is being beneath the North American plate . Mount Shasta and lawn Peak in arc that resulted from this process . Mountain Ranges Plate motion provides the force that pushes up ( mountains . The Sierra Nevada began to form several million years ago in plate movements . pushed up a batholith . Plate motions folded the crust to push up the northern Coast Ranges . The Transverse Ranges formed as plate motions rotated a block of crust and squeezed it upward . Basins Plate movements sometimes cause the crust to warp . or , downward . The result is a basin . A basin is a broad , valley . For . the Central Valley of Cal is a huge basin with the Sierras and Coast Ranges on either side . As these mountains rose . the crust forming the Central was bent downward . Slowly . a thick layer of sediment built up on the valley . Millions of years ago , some of California basins slowly sank below sea level . plate motions pushed the crust above sea level again . Assessment Modeling California Use plastic putty to make a model of California , showing the major geologic features . Use one color of putty for the part of the state that is on the Pacific plate and another color for the part that is on the North American plate . Explain your model to family members ,

Em ) Mi . nia ' Many geologic processes 73 ?

to form ' California landscape of I ' volcanoes . mountain . ranges , and basins . Thu San through me San Francisco . motion pushed up the Transverse in . PACIFIC OCEAN I Lin . Los Angela basin tanned where the oust was hem downward .

Guided sud Gelatin Volcanoes ' Problem How does magma move inside a volcano ! Skills Focus developing hypotheses . making models . observing Procedure ram , Before magma erupts as lava , how does it travel up from mold in bowl underground magma chambers ?

Record your hypothesis . Remove the gelatin trim the refrigerator . Loosen the gelatin from its container by placing the container ol gelatin in a larger bowl of hot water . Place the pizza pan over the gelatin so the mold is near the center ol the pizza pan . While holding the pizza pan against the top of the mold . carefully turn the mold and the pizza pan upside down . Carefully lift the bowl off the gelatin mold to create a gelatin ' volcano . Place the pizza pan with the gelatin mold on top of the oatmeal boxes as shown below . aluminum pizza pan with holes punched at intervals small cardboard Dames . Mix the red food coloring and water in the plastic cup . Then till the syringe with magma ( the red water ) Remove air bubbles from the syringe by holding it upright and squirting out a small amount of water . Insert the tip of the syringe through a hole in the pizza pan near BY ' the center of the gelatin . Inject the magma into the ' gelatin very slowly . Observe what happens to the magma . Repeat steps and as many times as possible Observe the ' movement of the magma each time . Note any in the direction the magma takes when the syringe is inserted into food ( owing . different parts ol the gelatin volcano . your observations . plastic cup , and water plastic syringe . 10 . and plastic knife unlined paper

Data Ta ble Position and Shape of Magma Bodies Initial Location of Mag ma . Look down on your gelatin volcano from above . Make a sketch of the positions and shapes of the magma bodies . Label your drawing Top View , 10 . Carefully use a knife to cut your volcano in half . Separate the pieces and examine the cut surfaces for traces of the magma bodies . 11 . Sketch the positions and shapes of the magma bodies on one of the cut faces . Label your drawing Cross Section . Analyze and Conclude . Observing Describe how the magma moved through your model . Did the magma move straight up through the center of your model volcano or did it branch off in places Explain why you think the magma moved in this way . Developing Hypotheses What knowledge or experience did you use to develop your hypothesis How did the actual movement compare with your hypothesis ?

Inferring How would you explain any differences in the direction the magma flowed when the syringe was inserted in different parts of the gelatin volcano ?

Making Models How does what you observed in your model compare to the way magma moves through real volcanoes How could you change your model to be more like a real volcano ?

Communicating Prepare your model as a display to teach other students about volcanoes . Make a list of the volcanic features in your model . For each feature . write a description of how the would form in a real volcano . Other observations i More to Explore Plan to repeat the investigation using a mold made at two layers of gelatin . Before injecting the magma , develop a hypothesis about the effect of layering on the movement of magma . Record your observations to determine if your hypothesis was correct . What volcanic feature is produced by this version of the model ?

Can you think of other volcanic features that you could model using gelatin layers ?

Obtain your teacher permission before carrying out your . Ari eruption at Mount , Ill ( 139 Chapter Study Guide eruptions result from plate motions and produce landforms such as volcanic mountains and lava plateaus . Volcanoes and Plate Tectonics Key ( hells the at Earth plates . A volcano forum a hot spot when magma through the mist and reaches the Key Terms volcano Ring of Fire island an lava hot spot Volcanic Eruptions ( Key Concepts , arm When a volcano erupts . the of the pushes magma lrom the through the pipe until it flows explodes nut vent . classify ( eruptions as quiet in ' Geologists often use the terms , ur in stage of activity . Key Terms pipe vent dormant lava extinct miter gel , Volcanic Landforms Key Concepts . eruptions landforms made lava , ash , and . These include shield volcanoes . cinder cone , and lava . formed by include necks , dikes . sills . and . Key Terms neck tinder cone dike ( xi caldera California Geology Key The movements and North . plates ( major features . These futures include . mountain ranges . and basins . Key Terms Central Valley 2400

Review and Assessment Target Reading Skill Create Outlines In your , add and definitions to your outline for Kinds of . in Section . Volcanic Eruptions I . Kinds of Volcanic Eruptions A . Quiet Eruptions Explosive Eruptions Reviewing Key Terms Choose the letter of the best answer . when ( plates sin ) island arc . hot spot . Ring of . i ! lava when it . magma . pipe . I . that term , coils when it called nu , silica . flow . volcanic up ash , cinders . and bombs is called shield . caldera . HINT . The ) mi ' may av I island arc , caldera . Wri ing in Science For Visit ?

Web . HINT hut might again in ' is . active . that hard in volt pipe MINT a neck . I ) sill . volcanic crater . hot spot . the following sentences so that your answers dearly explain the key terms . Far min plate , a may ' a hot spot , which . An ( an nun pyroclastic . which is 10 . When magma that is high in silica , il HINT can cinder ( one , which is . 11 . A thin ' i can in form a dike , which . 12 . Between ( Ranges and the Sierra Nevada lies Central , which is a volcanic arca . water and can ii geyser , which is . Write a comparison of the three different kinds of volcanoes Discuss the ways in which all three are similar and the ways In they are different . Use the correct terms to describe each type of volcano . Saul Volcanoes , rse Chapter

Review and Assessment Checking Concepts 14 . What is the Ring ?

15 . process causes volcanoes to form along the ?

16 What an twu ways em form neu ?

17 . What effect does have ( Ill the ( of ?

18 . Hun does shield form ?

the stages in ' cycle of volcano . 20 , Why can earthquake be sign an is about In ?

21 . What type in is the Central Valley of ( Huw did it ?

Thinking Critically 22 , Predicting is volcanic eruption likely on Fa oi the Stairs ?

your answer . 13 . Comparing and Contrasting the way in which an island are with the in which hot spot . 24 Making Generalizations How might it volcanic thi arr volcano . including its plant and animal life ?

15 . Relating Cause and Effect at the of at lava plateau below . Why deem ! the type that plateau produce volcanic instead ?

lava plateau 241 Applying Skills the diagram to answer Questions . 26 . Classifying What is this volcano ul ?

tin ( made ui ?

27 . Developing What feature labeled A iii the diagram ?

What is the feature labeled ?

How do ' 28 . Predicting What is the feature labeled ( ill the ?

I plugged with , what could the volcano ?

What is the feature labeled in the ?

What inlet this if the ?

Standards Investigation Performance Assessment Itl a volcanic region to how well your ! the yuu cull . As yuu the other , did sec urn how people regions live with ?

Standards Practice Choose the letter oi the best answer . A composite volcano is most likely to forth A above at hot spot . I where an oceanic plate collides with at continental plate . along the ridge . along I rift valley . Mount Shasta is a composite volcano in northern California . Mount Shasta formed as a result of a A hot spot . I sliding plate boundary . spreading plate boundary . colliding plate boundary . Which answer is a that explains why people might live in the region around a volcano ?

A A volcano removes trees . I Volcanic eruptions are interesting to watch . Volcanic soil is good for growing crops . Volcanoes release various gases . Study the diagram below . Which answer best describes the age of the sedimentary rock layers relative to the intrusion ?

A much younger I older the same age slightly younger My Sedimentary rock layers . Magma that hardens between layers of melt forms a A volcanic neck . I dike . batholith . sill . The diagram below shows the of what volcanic feature ?

A caldera I island arc volcano hot spot ridge . A geologist was observing the area around a dormant volcano . She decided that this volcano must have had an explosive eruption . Describe the evidence geologists would use to make this decision . In your answer . discuss the properties of the magma and the types of rock that would result from an explosive eruption . om