FOCUS ON EARTH SCIENCE (9)

Shaping Earth’s Surface Captured in Time This plaster cast was made by archaeologists from remains left in Herculaneum by the A.D 79 Vesuvius eruption 450,000–9,200 Years Ago April 18, 1906 May 1915 Mount Shasta volcanic cones are active San Francisco earthquake, the largest in America’s history, measures 8.3 on the Richter scale Lassen Peak erupts over several days 27,000 Years Ago Lassen Peak forms from eruptions A.D 240 240 (bkgd)Roger Ressmeyer/CORBIS, Ted Streshinsky/CORBIS 1800 1900 August 79 October 1737 August 1883 Vesuvius erupts in Italy, burying the towns of Pompeii and Herculaneum Largest tsunami in recorded history measures 64 m (210 ft.) above sea level Krakatoa erupts in Indonesia, triggering a tsunami and sending ash 27 km in the air 1920 August 1914 World War I begins To learn more about archaeologists and their work, visit ca6.msscience.com Interactive Time Line To learn more about these events and others, visit ca6.msscience.com December 1941 May 1980 October 1989 Pearl Harbor, on the Hawaiian island of Honolulu, is attacked, bringing the U.S into World War II Mt St Helens erupts in the state of Washington, triggered by an underground earthquake measuring 5.1 on the Richter scale Loma Prieta earthquake hits San Francisco, measuring 7.1 on the Richter scale 1940 1960 1980 2000 2020 May 1960 July 1976 December 2004 World’s biggest earthquake in recorded history— measuring 9.5 on the Richter scale—hits Chile and triggers tsunamis that reach Hawaii The most devastating earthquake in modern times hits China Measuring 8.3 on the Richter scale, it claims 240,000 lives An earthquake measuring 8.9 on the Richter scale causes a tsunami that kills hundreds of thousands in Asia 241 241 (t)Roger Ressmeyer/CORBIS, (b)Peter Dejong/AP/Wide World Photos Earthquakes /iÊ Êì> Earthquakes cause seismic waves that can be devastating to humans and other organisms 1.d, 1.e, 7.e Earthquakes and }Plate > Boundaries *VÌÕÀi ì> LESSON >Êì> Most earthquakes ,i>`} occur at plate boundaries when rocks iV break and move along faults 1.g, 7.e Earthquakes } and > *VÌÕÀi ì> Seismic Waves LESSON ,i>`} Earthquakes >Êì> iV cause seismic waves that provide valuable data 1.g, 7.b, 7.g Measuring Earthquakes LESSON >Êì> Data from }are record> waves seismic *VÌÕÀi ì> ed and interpreted to determine ,i>`}the location iV and size of an earthquake LESSON 1.g, 2.d, 7.a, } 7.b, 7.d > *VÌÕÀi ì> Earthquake Hazards ,i>`} and Safety iV >Êì> Effects of an earthquake depend on its size and the types of structures and geology in a region 242 > ì> } *VÌÕÀi Now how did that happen? On January 17, 1995, at 5:46 A.M., the people of Kobe, Japan, awoke to a major earthquake that toppled buildings, highways, and homes The Kobe earthquake, also known as the Great Hanshin earthquake, killed 6,433 people and injured 43,792 -ViViÊÊ+PVSOBM Have you ever experienced an earthquake? If so, write a paragraph about the event If not, write how you imagine it would feel to experience an earthquake Start-Up Activities Rocks Stretch When stressed, rock can stretch until it fractures and breaks apart Can you model the strength of rocks? Earthquakes Make the following Foldable to organize the causes and effects of earthquakes STEP Fold a sheet of paper in half lengthwise Procedure Complete a lab safety form Lay a rubber band in front of you Mold modeling clay into a worm shape Mold the clay into a spiral shape around half of the rubber band Put your fingers in the loops of the rubber band and pull gently STEP Fold the top edge of the paper down from the top as shown Think About This • Describe what happened to the clay as you pulled and stopped pulling the rubber band • Relate your observations to how materials near plate boundaries deform in response to stress 1.d, 7.e STEP Unfold to form two columns Label as shown Ã >ÕÃi vviVÌÃ Visit ca6.msscience.com to: ▶ ▶ ▶ ▶ view explore Virtual Labs access content-related Web links take the Standards Check ELA6: R 2.4 Recognizing Cause and Effect As you read the chapter, explain the causes of earthquakes in the left column Describe several effects of earthquakes in the right column 243 Get Ready to Read Questioning Learn It! Asking questions helps you to understand what you read As you read, think about the questions you’d like answered Often you can find the answer in the next paragraph or lesson Learn to ask good questions by asking who, what, when, where, why, and how Practice It! Read the following passage from Lesson An earthquake is the rupture and sudden movement of rocks along a fault Remember, a fault is a fracture surface along which rocks can slip A fault ruptures, or breaks, when rocks are strained so much that they no longer can stretch or bend This movement causes the release of complex waves that can move objects, as shown in Figure —from page 246 Here are some questions you might ask about this paragraph: • What is an earthquake? • When does a fault rupture? • What causes the release of complex waves? Apply It! As you read the chapter, look for answers to lesson headings that are in the form of questions 244 Target Your Reading Use this to focus on the main ideas as you read the chapter uesCreate q f l e s r u nd Test yo ead to f i r n e h t d tions an wn o your o t s r e w s an s question Before you read the chapter, respond to the statements below on your worksheet or on a numbered sheet of paper • Write an A if you agree with the statement • Write a D if you disagree with the statement After you read the chapter, look back to this page to see if you’ve changed your mind about any of the statements • If any of your answers changed, explain why • Change any false statements into true statements • Use your revised statements as a study guide Before You Read A or D Statement After You Read A or D Earthquakes are waves of energy that travel across Earth’s surface Tsunamis are huge tidal waves Most earthquakes occur in the middle of lithospheric plates Seismic waves are produced at the focus of an earthquake magnitudeearthquake earthquakereleases releasesabout abouttwice twiceasas A 4.0 magnitude-4 much energy as a 3.0 magnitudeearthquake earthquake magnitude-3 Print a worksheet of this page at ca6.msscience.com Some parts of the United States are at higher risk for earthquakes than others Secondary waves are the fastest seismic waves The San Andreas Fault is a fault zone Fire and landslides are major earthquake hazards 245 LESSON Science Content Standards 1.d Students know that earthquakes are sudden motions along breaks in the crust called faults and that volcanoes and fissures are locations where magma reaches the surface 1.e Students know major geologic events, such as earthquakes, volcanic eruptions, and mountain building, result from plate motions 7.e Recognize whether evidence is consistent with a proposed explanation Reading Guide What You’ll Learn ▼ Explain what an earthquake is ▼ Describe how faults and earthquakes are related ▼ Understand that most earthquakes occur at plate boundaries Why It’s Important Understanding what causes earthquakes helps scientists identify where they are likely to occur in the future Vocabulary earthquake elastic strain focus Review Vocabulary fault: a fracture in rock along which rocks on one side have moved relative to rocks on the other side (p 211) 246 Chapter • Earthquakes U.S Geological Survey Earthquakes and Plate Boundaries >Êì> Most earthquakes occur at plate boundaries when rocks break and move along faults Real-World Reading Connection You’re expecting a call Finally, the cell phone vibrates in your pocket The shaking stops as you answer the phone When the ground beneath your feet vibrates during an earthquake, there is no way to stop } >the shaking ì> *VÌÕÀi What ,i>`}is an earthquake? iV An earthquake is the rupture and sudden movement of rocks along a fault Remember, a fault is a fracture surface along which rocks can slip A fault ruptures, or breaks, when rocks are strained so much that they no longer can stretch or bend This movement causes the release of complex waves that can shake objects, as shown in Figure Most earthquakes occur in Earth’s crust, although some happen at great depths where lithospheric plates subduct Large earthquakes have also occurred in regions far from plate boundaries Part of the energy released is spread as complex waves that travel through and around Earth Figure The shaking during an earthquake is disorienting and frightening Loose objects that are thrown or that fall down can be dangerous Elastic Strain Energy How can heat from within Earth lead to the shaking people feel during an earthquake? Recall from Chapter that heat in Earth’s mantle is a source of energy for plate movement Some of the heat energy from Earth’s interior is transformed into kinetic energy, or energy of motion, for Earth’s lithospheric plates Especially at boundaries between plates, stresses cause strain that occasionally breaks and moves rocks 9Z[dgbVi^dcd[gdX`h & Dg^\^cVaedhî^dc HigZVb ;Vjai ' 7jâYjed[ZcZg\n What is kinetic energy? The plates’ kinetic energy is transferred to rocks near the faults This energy is eventually released as earthquakes, which occur mainly at or near the plate boundaries This is like the energy stored in a stretched rubber band The rocks change shape just as the rubber band did Energy stored as a change in shape is called elastic strain When the rocks cannot stretch to change shape anymore, the faults break and slip as earthquakes ;Vjai ( GjeijgZZVgi]fjV`Z ;Vjai ) :cZg\ngZaZVhZY Faults and Earthquakes Figure shows how faults and earthquakes are related The arrows shown in steps and show how rocks slide horizontally past each other The fault is marked before, during, and after the fault ruptures As rocks slowly move past each other, elastic strain energy builds up along the strike-slip fault Eventually, rocks rupture and slip along the fault, as shown in Figure The sudden slip sends complex waves radiating out in all directions into the surrounding rocks It is the energy in the waves that causes the shaking during an earthquake Elastic strain energy that was stored in the rocks is partly released by the breaking and moving, and partly released as seismic waves ;Vjai Figure Strained Rocks Elastic strain energy builds up in the rocks near the fault The strength of the rocks is reached, and the fault ruptures, causing an earthquake and releasing the energy Identify the type of fault Figure What clues are present in the drawings that show how elastic strain energy is released? Lesson • Earthquakes and Plate Boundaries 247 Figure Energy and Rupture When elastic strain energy overcomes the strength of the rocks, a rupture begins at the focus The rupture spreads away from the focus, along the fault, sometimes reaching the ground surface After the earthquake, most of the elastic strain energy is released & 6gjeijgZWZ\^chVii]Z[dXjh# ;dXjh ;Vjai ' 6gjeijgZhegZVYhVlVn[gdbi]Z[VjaiVcY bdgZZcZg\n^hgZaZVhZY# LVkZhigVkZadjilVgY[gdbi]Z[dXjh ;dXjh ;Vjai Focus Earthquakes start at the focus (plural, foci), which is the location on a fault where rupture and movement begin Figure shows the focus, from which a rupture spreads out with time along the fault As the rupture gets bigger, more and more energy is released into the surrounding rocks In general, the closer the focus is to Earth’s surface, the stronger the shaking will be Larger faults can have larger ruptures, which tend to produce larger earthquakes It takes many small earthquakes to release as much energy as a single, large earthquake Fault Zones A plate boundary is often shown as a single line on a map In reality, plate boundaries are much more complicated Instead of a single fault, boundaries are usually zones These fault zones are about 40–200 km wide The San Andreas Fault is an example of a fault zone In Figure 4, notice that the San Andreas is a group of faults As a group, these faults result from the plate motion between the Pacific Plate and the North American Plate Figure Identify three faults that are part of the San Andreas Fault zone ( Bdhid[i]ZZaVhi^XhigV^cZcZg\n^hgZaZVhZY! V[iZgi]ZZVgi]fjV`Z# Figure The San Andreas Fault is a zone that contains many faults 8Va^[dgc^V ; Vh gZ cY c6 HV 9^heaVXZbZciVadc\i]Z[Vjai HVc ;gVcX^hXd E68>;>8 D8:6C DlZchKVaaZn ;Vjai Vj Most earthquakes occur at plate boundaries when rocks break and move along faults • An earthquake is a sudden rupture and movement on a fault • Energy from motion of lithospheric plates builds up in rocks as elastic strain until it ruptures as an earthquake 1.d, 1.e, 7.e earthquake (p 246) • elastic strain (p 247) • focus (p 248) • } > An earthquake begins at the focus ì> } *VÌÕÀi • > Some earthquakes occur in the middle of plates • *VÌÕÀi ì> Lesson ,i>`} Earthquakes and Seismic Waves ,i>`} iV >Êì> Earthquakes cause seismic waves that provide 1.g, 7.e iV valuable data • Seismic waves travel outward in all directions from the focus Primary and secondary waves travel through Earth’s interior • Surface waves travel around the planet within a thin layer of the crust • epicenter (p 253) primary wave (p 254) • secondary wave (p 254) • seismic wave (p 252) • • Earth’s internal structure was discovered by analysis of seismic waves } > *VÌÕÀi ì> Lesson Measuring Earthquakes ,i>`} iV Data from seismic waves are recorded and >Êì> interpreted to determine the location and size of earthquakes • Instruments called seismographs produce records of seismic waves called seismograms • The difference in P- and S-wave arrival times allows scientists to determine the distance of a seismograph from the epicenter 1.g, 7.b, 7.g seismogram (p 261) • seismograph (p 261) • • > Different scales } are used to measure earthquake magnitude and intensity *VÌÕÀi Lesson Earthquake Hazards and Safety ì> ,i>`} iV >Êì> Effects of an earthquake depend on its size and the types of structures and geology in a region • Scientists use knowledge of faults and ground conditions to determine earthquake hazard • Land use helps reduce earthquake damage and loss of life Some types of construction are more earthquake-resistant than others } > • Earthquake-resistant structures save lives and property *VÌÕÀi ì> • You can protect yourself from future earthquakes by being prepared 1.g, 2.d, 7.a, 7.b, 7.d liquefaction (p 271) • tsunami (p 272) • • Download quizzes, key terms, and flash cards from ca6.msscience.com ,i>`} iV 284 Chapter • Standards Study Guide Interactive Tutor ca6.msscience.com Standards Review CHAPTER Linking Vocabulary and Main Ideas Use the vocabulary terms from page 284 to complete this concept map Earthquakes are measured with instruments called release can cause seismic sea waves called elastic strain sediment to behave as a liquid which record data as seismograms as as rocks break and move starting at the seismic waves three types are secondary waves arrival time differences allow determination of the Visit ca6.msscience.com for: ▶ ▶ ▶ Vocabulary PuzzleMaker Vocabulary eFlashcards Multilingual Glossary Using Vocabulary Fill in the blanks with the correct vocabulary words Then read the paragraph to a partner When an earthquake occurs, is released in the form of rocks breaking and To determine the 10 , the point moving and also in the form of on Earth’s surface directly above the focus, scientists analyze the arrival times 11 waves and 12 waves on data records known of 13 14 are also recorded, which are the seismic waves that as generally cause the most damage and loss of life resulting from an earthquake Chapter • Standards Review 285 Standards Review CHAPTER Understanding Main Ideas Use the figure below to answer questions and Choose the word or phrase that best answers the question H"lVkZhVgg^kZhZXdcY# Which builds up in rocks before an earthquake? A heat energy 1.d B elastic strain C chemical strain D kinetic energy Where the largest earthquakes occur? A convergent plate boundaries B elastic boundaries C transform plate boundaries D divergent plate boundaries E"lVkZhVgg^kZ[^ghi# 9ZXZbWZg'+!'%%)·>cY^VcDXZVc 1.e Where does the energy that causes earthquakes come from? A Earth’s interior 1.d B Earth’s surface C the Sun D tsunamis The map below includes data from an earthquake 8dVa^c\V Ze^XZciZg Hjg[VXZlVkZhVgg^kZaVhi# What is the printed record of ground shaking during an earthquake? A epicenter 1.g B seismogram C seismograph D seismologist Which seismic waves travel the fastest? A primary waves B secondary waves C surface waves D tsunami waves Which is a scale used to measure the energy released by an earthquake? A elastic scale B magnitude scale C modified Mercalli scale D shaking scale 1.g 1.g EVhdGdWaZh HVcAj^hDW^hed Which measure of an earthquake does this map show? A fault slip 1.g B intensity C moment magnitude D Richter magnitude 286 Chapter • Standards Review What is the name of the location where a fault rupture starts? A epicenter 1.d B focus C fracture center D hanging wall To locate an epicenter, data are needed from at least how many seismographs? A 1.g B C D 100 Standards Review ca6.msscience.com Standards Review Applying Science 10 Relate the transfer of kinetic energy from a lithospheric plate to rocks near a fault to what happens when you break a stick 1.d 11 Suggest a way to prepare an earthquake supply kit 2.d 12 Predict whether earthquakes would be larger or smaller if rocks that rupture along faults were stronger 1.g 13 Organize these locations with respect to earthquake safety: an open field, under a desk, outside next to your home, inside a tall building Defend your organization 2.d 14 Suggest a reason that surface waves more damage than primary waves Hint: Examine the illustration for questions and 1.g 15 Identify the type of seismic wave illustrated below 1.g EVgi^XaZb dkZbZci LVkZY^gZ Xi^dc 3CIENCE 16 Write an outline that includes strategies for city planning in an area at high risk for earthquakes Include design ideas for structures as well as land use strategies Use the outline to present your ELA6: W 2.5 ideas orally to the class Cumulative Review 17 Suggest a reason there is no continental drift on the Moon 1.a 18 Compare and contrast continental and oceanic lithosphere 1.b CHAPTER 19 Locate the Cascade and Transverse mountain ranges on a map of California 1.f Applying Math Use this table to answer questions 20–24 Seismic Wave Number Difference in Arrival Time from P-Wave to S-Wave (s) 4.9 8.7 12.3 17.8 18.0 19.0 24.4 42.7 51.9 10 52.9 20 Determine the distance from the origin of the third seismic wave to your current location MA6: NS 2.0 21 If both the second and third seismic waves occur at the same depth and direction from your location, how far apart are their origins? MA6: NS 2.0 22 Determine the distance from the origin of the forth seismic waves to your current location MA6: NS 2.0 23 If both the third and fourth seismic waves occur at the same depth and direction from your location, how far apart are their origins? MA6: NS 2.0 24 Determine the distance from the origin of the fifth seismic wave to your current location MA6: NS 2.0 Chapter • Standards Review 287 Standards Assessment CHAPTER Use the figure below to answer questions and 9^gZXi^dcd[ bdi^dc The figure below shows one type of instrument that records seismic waves GdiVi^c\ Ygjb LZ^\]i EZc GZkZghZ[Vjaihjg[VXZ A convergent plate boundary What is this instrument called? B divergent plate boundary A creepmeter C transform plate boundary B seismograph D strike-slip KZgi^XVa :Vgi]bdkZbZci A reverse fault typically occurs at what type of boundary? 1.d C spectrograph D tiltmeter Reverse faults at convergent plate boundaries typically produce what kind of earthquakes? A shallow, small in size 7ZYgdX` B shallow, large in size 1.g Waves of energy that travel through Earth’s interior and along Earth’s surface are called? A sound waves C deep, devastating D deep, no damage B energy waves 1.e C light waves Which best describes the epicenter of an earthquake? A the point on Earth’s surface located directly above the earthquake focus B the point inside Earth where movement first occurs during an earthquake C the surface of a break in a rock along which there is movement D the snapping back of a rock that has been 1.g strained by force 288 Chapter • Standards Assessment D seismic waves 1.g Which is the region where no seismic waves reach Earth’s surface? A pressure zone B seismic zone C shadow zone D waveless zone 1.g Standards Assessment ca6.msscience.com Standards Assessment Imagine a tsunami occurs near the Aleutian Islands The wave reaches the Hawaiian Islands, a distance of 3,800 km, h later At what speed is the wave traveling? C Tsunamis can occur B 670 km/h D Water becomes polluted C 700 km/h A Aftershocks can occur B Fires can occur A 570 km/h D 760 km/h 10 Why should you stay away from beaches after an earthquake has occurred? 2.d 2.d 11 The map below shows three circles drawn around three different seismograph stations What does earthquake intensity measure? A damage done B earthquake’s focus C energy released D seismic risk HiVi^dc( HiVi^dc& HVXgVbZcid HVc;gVcX^hXd 1.g The photo below shows the effects of liquefaction on structures during an earthquake HiVi^dc' Adh6c\ZaZh HVc9^Z\d Which labeled point on the map represents the earthquake’s epicenter? A Los Angeles B Sacramento C San Francisco D San Diego What is liquefaction? A ice melting during an earthquake to cause flooding 1.g 12 What is elastic strain? A the point on Earth’s surface located directly above the earthquake focus B rivers diverted by flooding caused by earthquakes B the point inside Earth where movement first occurs during an earthquake C seismic waves shaking sediment, causing it to become more liquid-like C the surface of a break in a rock along which there is movement D the stopping of S-waves by Earth’s liquid 2.d outer core D the snapping back of a rock that has been 1.d strained by force Chapter • Standards Assessment 289 ... during an 1.d earthquake Elastic Strain Energy Science nline For more practice, visit Standards Check at ca6.msscience.com Lesson • Earthquakes and Plate Boundaries 251 LESSON Science Content Standards... direction of wave travel B rolling motion or side-toside C perpendicular to direction of wave travel D diagonally Fastest Applying Science Illustrate the vibration direction and the direction of... your location, how far apart are their origins? Science nline For more math practice, visit Math Practice at ca6.msscience.com Lesson • Earthquakes and Seismic Waves 259 LESSON Science Content Standards

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