Unit 4 Lesson 7 Mountain Building Copyright Houghton
Unit 4 Lesson 7 Mountain Building Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 4 Lesson 7 Mountain Building Indiana Standards • 7. 2. 4 Explain how convection currents in the mantle cause lithospheric plates to move causing fast changes like earthquakes and volcanic eruptions, and slow changes like creation of mountains and formation of new ocean floor. Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 4 Lesson 7 Mountain Building Stressed Out How can tectonic plate motion cause deformation? • The movement of tectonic plates causes stress on rock structures. • Stress is the amount of force per unit area that is placed on an object. Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 4 Lesson 7 Mountain Building How can tectonic plate motion cause deformation? • When a rock is placed under stress, it deforms, or changes shape, in a process called deformation. • Deformation cause rock to bend or break. Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 4 Lesson 7 Mountain Building What are two kinds of folds? • Folding occurs when rock layers bend under stress. • Rock layers start out as horizontal layers deposited over time. • A fold, or bend, in the rock layers means that deformation has happened. Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 4 Lesson 7 Mountain Building What are two kinds of folds? • Two common types of folds are synclines and anticlines. • In a syncline, the youngest layers of rock are at the core of the fold. • In an anticline, the oldest layers of rock are at the core of the fold. Copyright © Houghton Mifflin Harcourt Publishing Company
Anticline old Syncline es n st e g t u Yo
Unit 4 Lesson 7 Mountain Building What are two kinds of folds? • Identify the oldest and youngest layers in this diagram. Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 4 Lesson 7 Mountain Building Faulted What are three kinds of faults? • Sometimes rock is under so much stress that it breaks. • A crack called a fault forms when large blocks of rock break and move past each other. • The three main kinds of faults are strike-slip faults, normal faults, and reverse faults. Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 4 Lesson 7 Mountain Building What are three kinds of faults? • Faults are classified based on how the fault blocks move. • The fault plane is the location where two fault blocks meet. • The fault block that tilts over the fault plane is called the hanging wall. • The fault block below the hanging wall is called the footwall. Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 4 Lesson 7 Mountain Building What are three kinds of faults? • strike-slip fault, the fault blocks move past each other horizontally. • Strike-slip faults form when rock is under shear stress, or stress that results from the sliding of rock structures in parallel but opposite directions. Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 4 Lesson 7 Mountain Building What are three kinds of faults? • normal fault, the hanging wall moves down relative to the footwall. • Normal faults form when rock is under tension, which is stress that stretches or pulls rock apart. Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 4 Lesson 7 Mountain Building What are three kinds of faults? • reverse fault, the hanging wall moves up relative to the footwall. • Reverse faults form when rocks undergo compression, which is stress that squeezes or pushes rock together. Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 4 Lesson 7 Mountain Building What are three kinds of faults? • Which kind of fault is shown in each image? Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 4 Lesson 7 Mountain Building Moving on Up What are three kinds of mountains? • Mountains can form through folding, volcanism, and faulting. • The process by which land rises or mountains form is called uplift. • Because tectonic plates are always in motion, some mountains are constantly uplifting. Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 4 Lesson 7 Mountain Building What are three kinds of mountains? • Folded mountains form when rock layers are squeezed together and pushed upward. • Most folded mountains form at convergent boundaries. Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 4 Lesson 7 Mountain Building What are three kinds of mountains? • Volcanic mountains form when melted rock erupts onto Earth’s surface. • Most volcanic mountains form at convergent boundaries. Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 4 Lesson 7 Mountain Building What are three kinds of mountains? • Fault-block mountains form when tension makes the lithosphere break into many normal faults. • Pieces of the lithosphere sink, and the blocks left standing are the mountains. Copyright © Houghton Mifflin Harcourt Publishing Company
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