Earthquakes Types of Seismic Waves Seismic waves carry energy from an earthquake away from the focus, through Earth’s interior, and across the surface.

Earthquakes. *Focus: Point beneath the earth’s surface where the earth moves *Epicenter: The point on the surface directly above the focus. It is where the strength of the earthquake is strongest. -

Earthquakes Types of Seismic Waves P waves are seismic waves that compress and expand the ground like an accordion. S waves are seismic waves that vibrate from side to side as well as up and down.

Earthquakes Types of Seismic Waves Surface waves move more slowly than P waves and S waves, but they produce the most severe ground movements. -

Earthquakes Seismic Waves Activity fp&wcsuffix=1022&area=view&x=8&y=7ss - Earthquakes and Seismic Waves Phschool.com Webcode: cfp-1022

Earthquakes - Forces in Earth’s Crust Types of Stress The stress force called tension pulls on the crust, stretching rock so that it becomes thinner in the middle.

Earthquakes Types of Stress The stress force called compression squeezes rock until it folds or breaks. - Forces in Earth’s Crust

Earthquakes Types of Stress Stress that pushes a mass of rock in two opposite directions is called shearing. - Forces in Earth’s Crust

Earthquakes Kinds of Faults Tension in Earth’s crust pulls rock apart, causing normal faults. - Forces in Earth’s Crust

Earthquakes Kinds of Faults A reverse fault has the same structure as a normal fault, but the blocks move in the opposite direction. - Forces in Earth’s Crust

Earthquakes Kinds of Faults In a strike-slip fault, the rocks on either side of the fault slip past each other sideways, with little up and down motion. - Forces in Earth’s Crust

Earthquakes Changing Earth’s Surface Over millions of years, the forces of plate movement can change a flat plain into landforms such as anticlines and synclines, folded mountains, fault-block mountains, and plateaus. - Forces in Earth’s Crust

Earthquakes Changing Earth’s Surface Over millions of years, the forces of plate movement can change a flat plain into landforms such as anticlines and synclines, folded mountains, fault-block mountains, and plateaus. - Forces in Earth’s Crust

Earthquakes Building Vocabulary A definition states the meaning of a word or phrase. As you read, write a definition of each Key Term in your own words. Key Terms:Examples: - Forces in Earth’s Crust stressStress is a force that acts on rock to change its shape or volume. tensionThe stress force called tension pulls on the crust, stretching rock so that it becomes thinner in the middle. compressionThe stress force called compression squeezes rock until it folds or breaks. shearingStress that pushes a mass of rock in two opposite directions is called shearing. normal faultTension in Earth’s crust pulls rock apart, causing normal faults. reverse faultA reverse fault has the same structure as a normal fault, but the blocks move in the opposite direction. Key Terms:Examples: hanging wall footwall strike-slip fault anticline syncline plateau The block of rock that lies above a normal fault is called the hanging wall. The rock that lies below is called the footwall. In a strike-slip fault, the rocks on either side of the fault slip past each other sideways, with little up or down motion. A fold in rock that bends upward into an arch is an anticline. A fold in rock that bends downward to form a valley is a syncline. A plateau is a large area of flat land elevated high above sea level.

Earthquakes Measuring Earthquakes The Mercalli scale was developed to rate earthquakes according to the amount of damage at a given place. - Earthquakes and Seismic Waves

Earthquakes Richter Scale The Richter Scale for measures the 'size' or 'strength' of an earthquake. This scale is quantitative and based on the amount of energy released by an earthquake.quantitative The energy of a quake is a function of both the amplitude and the duration of a single wave. The seismogram below shows waves with a wide range of amplitude and duration. This would be magnitude 8 quake!

Earthquakes - Earthquakes and Seismic Waves

Earthquakes Seismic Wave Speeds Seismographs at five observation stations recorded the arrival times of the P and S waves produced by an earthquake. These data are shown in the graph. - Earthquakes and Seismic Waves

Earthquakes Seismic Wave Speeds X-axis––distance from the epicenter; y-axis––arrival time. Reading Graphs: What variable is shown on the x-axis of the graph? The y- axis? - Earthquakes and Seismic Waves

Earthquakes Seismic Wave Speeds 7 minutes Reading Graphs: How long did it take the S waves to travel 2,000 km? - Earthquakes and Seismic Waves

Earthquakes Seismic Wave Speeds 4 minutes Estimating: How long did it take the P waves to travel 2,000 km? - Earthquakes and Seismic Waves

Earthquakes Seismic Wave Speeds 2,000 = 3.5 minutes 4,000 = 4.5 minutes Calculating: What is the difference in the arrival times of the P waves and the S waves at 2,000 km? At 4,000 km? - Earthquakes and Seismic Waves

Earthquakes Locating the Epicenter Geologists use seismic waves to locate an earthquake’s epicenter. - Earthquakes and Seismic Waves

Earthquakes The Modern Seismograph Seismic waves cause the seismograph’s drum to vibrate. But the suspended weight with the pen attached moves very little. Therefore, the pen stays in place and records the drum’s vibrations. - Monitoring Earthquakes

Earthquakes Instruments That Monitor Faults In trying to predict earthquakes, geologists have developed instruments to measure changes in elevation, tilting of the land surface, and ground movements along faults. - Monitoring Earthquakes

Earthquakes Using Seismographic Data The map shows the probability of a strong earthquake along the San Andreas fault. A high percent probability means that a quake is more likely to occur. - Monitoring Earthquakes

Earthquakes Earthquake Risk Geologists can determine earthquake risk by locating where faults are active and where past earthquakes have occurred. - Earthquake Safety

Earthquakes How Earthquakes Cause Damage A tsunami spreads out from an earthquake's epicenter and speeds across the ocean. - Earthquake Safety

Earthquakes Designing Safer Buildings To reduce earthquake damage, new buildings must be made stronger and more flexible. - Earthquake Safety

Earthquakes Asking Questions Before you read, preview the red headings and ask a what, how, or where question for each heading. As you read, write answers to your questions. Where is the quake risk highest?Earthquake risk is the highest along faults and where past earthquakes have occurred. How do earthquakes cause damage?Earthquake damage occurs as a result of shaking, liquefaction, aftershocks, and tsunamis. How can you stay safe during an earthquake? The best way to stay safe during an earthquake is to drop, cover, and hold. What makes buildings safe from earthquakes? Buildings can be made safer by being built stronger and with greater flexibility. - Earthquake Safety QuestionAnswer

Earthquakes - Volcanoes and Plate Tectonics Volcanoes and Plate Boundaries Volcanic belts form along the boundaries of Earth’s plates.

Earthquakes Volcanoes and Plate Boundaries Volcanoes often form where two oceanic plates collide or where an oceanic plate collides with a continental plate. In both situations, an oceanic plate sinks through a trench. Rock above the plate melts to form magma, which then erupts to the surface as lava. - Volcanoes and Plate Tectonics

Earthquakes Hot Spot Volcanoes A volcano forms above a hot spot when magma erupts through the crust and reaches the surface. - Volcanoes and Plate Tectonics

Earthquakes Properties of Magma Magma’s viscosity depends on its physical and chemical properties.  Magma is made of elements and of compounds, among them silica.  Viscosity depends on silica content and temperature. - Volcanoes and Plate Tectonics

Earthquakes Magma Composition Magma varies in composition and is classified according to the amount of silica it contains. The graphs show the average composition of the two types of magma. - Properties of Magma

Earthquakes Magma Composition Silica, other oxides, and other solids. Reading Graphs: Study both graphs. What materials make up both types of magma? - Properties of Magma

Earthquakes Magma Composition Rhyolite-forming magma; about 70 percent. Reading Graphs: Which type of magma has more silica? About how much silica does this type of magma contain? - Properties of Magma

Earthquakes Magma Composition About 60 percent Estimating: A third type of magma has a silica content that is halfway between that of the other two types. About how much silica does this type of magma contain? - Properties of Magma

Earthquakes Magma Composition Rhyolite-forming magma would have higher viscosity because it is higher in silica. Predicting: What type of magma would have a higher viscosity? Explain. - Properties of Magma

Earthquakes Magma Reaches Earth’s Surface When a volcano erupts, the force of the expanding gases pushes magma from the magma chamber through the pipe until it flows or explodes out of the vent. - Volcanic Eruptions

Earthquakes Composite Volcano Eruption Activity Click the Active Art button to open a browser window and access Active Art about composite volcano eruption. - Volcanic Eruptions

Earthquakes Kinds of Volcanic Eruptions Within the last 150 years, major volcanic eruptions have greatly affected the land and people around them. - Volcanic Eruptions

Earthquakes Landforms From Lava and Ash Volcanic eruptions create landforms made of lava, ash, and other materials. These landforms include composite volcanoes, shield volcanoes, cinder cone volcanoes, and lava plateaus. - Volcanic Landforms

Earthquakes Landforms From Lava and Ash A caldera forms when an volcano’s magma chamber empties and the roof of the chamber collapses. The result is a large, bowl- shaped caldera. - Volcanic Landforms

Earthquakes Landforms From Magma Features formed by magma include volcanic necks, dikes, and sills, as well as batholiths and dome mountains. - Volcanic Landforms

Earthquakes Batholiths A batholith is a mass of rock formed when a large body of magma cools inside the crust. Several large batholiths form the core of mountain ranges in western North America. Half Dome in Yosemite National Park, California, is part of the Sierra Nevada batholith. - Volcanic Landforms

Earthquakes Outlining As you read, make an outline about volcanic landforms that you can use for review. Use the red headings for the main topics and the blue headings for the subtopics. Volcanic Landforms I.Landforms From Lava and Ash A.Shield Volcanoes B.Cinder Cone Volcanoes C.Composite Volcanoes D.Lava Plateaus E.Calderas F.Soils From Lava and Ash II.Landforms From Magma A.Volcanic Necks, Dikes and Sills B.Dikes and Sills C.Batholiths D.Dome Mountains III.Geothermal Activity A.Hot Springs B.Geysers C.Geothermic Energy - Volcanic Landforms