Unit 8 Lesson 3 How Do Movements of the Crust Change Earth? Copyright © Houghton Mifflin Harcourt Publishing Company

Inside the Earth Earth is a sphere made up of very different layers. Unit 8 Lesson 3 How Do Movements of the Crust Change Earth? Inside the Earth Earth is a sphere made up of very different layers. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 8 Lesson 3 How Do Movements of the Crust Change Earth? Inside the Earth Earth’s crust is a rocky outer layer made of many minerals. The crust is thinnest under oceans and thickest under mountains. It makes up only about one percent of Earth’s mass. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 8 Lesson 3 How Do Movements of the Crust Change Earth? Inside the Earth Right below Earth’s crust is the mantle, which is the thickest layer, making up about two-thirds of Earth’s mass. The mantle contains some liquid rock but is mostly solid. High heat and pressure in the mantle cause it to flow like warm plastic. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 8 Lesson 3 How Do Movements of the Crust Change Earth? Inside the Earth At the center of Earth is a core made of molten metal. The inner core is solid iron and nickel. The outer core is molten, liquid metal. The metal core makes up about one-third of Earth’s mass and is extremely hot. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 8 Lesson 3 How Do Movements of the Crust Change Earth? Plate Tectonics Many pieces of Earth’s crust, called plates, fit together like a jigsaw puzzle. The plates rest on Earth’s mantle and are always moving. The theory that Earth’s crust is divided into moving plates is called plate tectonics. Plates are made from continental crust, oceanic crust, or a combination of both. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 8 Lesson 3 How Do Movements of the Crust Change Earth? Plate Tectonics Certain land features form where plates collide. Other features form where plates separate. Mountain ranges, island chains, and enormous valleys are possible signs of a plate boundary. For example, the Great Rift Valley formed where the Arabian plate is splitting the African plate into two new, separate plates. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 8 Lesson 3 How Do Movements of the Crust Change Earth? Plate Boundaries Different types of plate motion produce boundaries that shape different landforms. Continental plates moving toward each other push up mountains. Oceanic plates moving toward each other can cause deep-ocean trenches and volcanic islands to form. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 8 Lesson 3 How Do Movements of the Crust Change Earth? Plate Boundaries Oceanic plates colliding with continental plates causes mountains and volcanoes to form along the boundary between the plates. When two plates pull apart, new crust forms a rift, or separation, on both sides of the boundary, becoming two separate landmasses. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 8 Lesson 3 How Do Movements of the Crust Change Earth? Earthquakes A fault is a break in Earth’s crust where rock on one side can move in relation to rock on the other side. As plates move, pressure increases along a fault, causing the rock on one side to snap free and slide past the rock on the other side. This release of energy and shaking of the ground is called an earthquake. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 8 Lesson 3 How Do Movements of the Crust Change Earth? Earthquakes The point inside Earth where an earthquake begins is called the focus. The point on Earth’s surface directly above the focus is called the epicenter, where earthquake motion is most severe. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 8 Lesson 3 How Do Movements of the Crust Change Earth? Earthquakes Scientists use seismographs to detect tremors and predict if an earthquake is likely to occur. Copyright © Houghton Mifflin Harcourt Publishing Company

Measuring Earthquakes Unit 8 Lesson 3 How Do Movements of the Crust Change Earth? Measuring Earthquakes An earthquake’s magnitude is the amount of energy it releases. The Richter scale measures the magnitude of earthquakes on a scale from 1 to 10. The Richter scale uses the size of waves on a seismograph to determine an earthquake’s strength. Copyright © Houghton Mifflin Harcourt Publishing Company

Measuring Earthquakes Unit 8 Lesson 3 How Do Movements of the Crust Change Earth? Measuring Earthquakes An earthquake measuring 6.0 or higher on the Richter scale can cause heavy damage in populated areas. Scientists have also developed the moment magnitude scale to more accurately measure the magnitudes of larger earthquakes. This scale, which also assigns numbers between 1 and 10, uses a mathematical formula to calculate the total energy an earthquake releases. Copyright © Houghton Mifflin Harcourt Publishing Company

Volcanoes The liquid rock below Earth’s crust is called magma. Unit 8 Lesson 3 How Do Movements of the Crust Change Earth? Volcanoes The liquid rock below Earth’s crust is called magma. A volcano is an opening in the crust that allows magma to reach Earth’s surface. Lava is the molten rock that erupts from the volcano along with ash and hot gases. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 8 Lesson 3 How Do Movements of the Crust Change Earth? Volcanoes Shield volcanoes are formed from non-explosive lava where broad sheets of lava steadily build up. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 8 Lesson 3 How Do Movements of the Crust Change Earth? Volcanoes Cinder cone volcanoes are formed from explosive eruptions where lava explodes into the air and quickly hardens. Copyright © Houghton Mifflin Harcourt Publishing Company

Unit 8 Lesson 3 How Do Movements of the Crust Change Earth? Volcanoes Composite volcanoes are formed from alternating types of eruptions which produce explosive eruptions where liquid lava flows. Copyright © Houghton Mifflin Harcourt Publishing Company