Chapter 6 Volcanoes 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. What causes volcanoes, and how do they change Earth’s surface?

Chapter 6 Volcanoes Unfamiliar words Hot spot is the subject of the sentence. Definition, follows boldface Explanation Example Use Clues to Determine Meaning Some volcanoes result from hot spots in Earthís mantle. A hot spot is an area where material from within the mantle rises and then melts. A volcano forms above a hot spot when the hot material erupts through the crust and reaches the surface. A hot spot in the ocean oor can gradually form a series of volcanic mountains. For example, the Hawaiian Islands formed one by one over millions of years as the Pacific plate drifted over a hot spot.

Chapter 6 Volcanoes Apply It! Review the clues to the meaning of hot spot. Then complete the following. 1. What clue tells you that hot spot might be followed by a definition? The term is in boldface and is the subject of the sentence. 2. What example helps you understand hot spots? The Hawaiian Islands formed one by one over millions of years as the Pacific plate drifted over a hot spot

Chapter 6 Volcanoes End of Chapter Preview

Chapter 6 Volcanoes Warm-Up How do volcanoes change the land?

Chapter 6 Volcanoes 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. What causes volcanoes, and how do they change Earth’s surface?

Chapter 6 Volcanoes Section 1: Volcanoes and Plate Tectonics Lesson Objectives You will be able to identify where Earth’s volcanic regions are located and explain why they are found in these areas. You will be able to explain how hot spot volcanoes form.

Chapter 6 Volcanoes Section 1: Volcanoes and Plate Tectonics California Standards 6.1 Plate tectonics accounts for important features of Earth’s surface and major geologic events. .e Students know major geologic events, such as earthquakes, volcanic eruptions, and mountain building, result from plate motions.

Chapter 6 Volcanoes Section 1:Volcanoes and Plate Tectonics Where are most of Earth’s volcanoes found? How do hot spot volcanoes form?

Chapter 6 Volcanoes Volcanoes

Chapter 6 Volcanoes A volcano is a weak spot in the crust where molten material, or magma, comes to the surface.

Chapter 6 Volcanoes Lava is molten material, or magma, that has reached the surface.

Chapter 6 Volcanoes Magma is molten material that has not reached the surface and is still underground.

Chapter 6 Volcanoes Ring of Fire is a major volcanic belt that rims or circles the Pacific Ocean.

Chapter 6 Volcanoes Island Arc is a string of islands formed by weak spots or hot spots in the crust where magma burns through.

Chapter 6 Volcanoes Volcanoes and Plate Boundaries Volcanic belts form along the boundaries of Earth’s plates.

Chapter 6 Volcanoes 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.

Chapter 6 Volcanoes Hot Spot Volcanoes A volcano forms above a hot spot when magma erupts through the crust and reaches the surface.

Chapter 6 Volcanoes More on Volcanoes Click the PHSchool.com button for an activityabout volcanoes.

Chapter 6 Volcanoes End of Section:Volcanoes and Plate Tectonics

Chapter 6 Volcanoes Warm-Up What causes volcanoes to form at a spreading boundary?

Chapter 6 Volcanoes Warm-Up Where are most of Earth’s volcanoes found? Explain.

Chapter 6 Volcanoes Warm-Up Describe the order of parts through which magma travels as it moves to the surface.

Chapter 6 Volcanoes Warm-Up Which is more likely to be dangerous: a volcano that erupts frequently or a volcano that has been inactive for a hundred years? Why?

Chapter 6 Volcanoes Section 2: Volcanic Eruptions Lesson Objectives You will be able to explain what happens when a volcano erupts. You will be able to describe the two types of volcanic eruptions. You will be able to identify a volcano’s stages of activity.

Chapter 6 Volcanoes Section 2: Volcanic Eruptions California Standards 6.1.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. 6.2.d Students know earthquakes, volcanic eruptions, landslides, and floods change human and wildlife habitats.

Chapter 6 Volcanoes Section 2:Volcanic Eruptions What happens when a volcano erupts? What are the two types of volcanic eruptions? What are a volcano’s stages of activity?

Chapter 6 Volcanoes Volcanic Eruptions

Chapter 6 Volcanoes 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.

Chapter 6 Volcanoes Magma Reaches Earth’s Surface Magma chamber is a pocket beneath a volcano where magma is collected or stored.

Chapter 6 Volcanoes Magma Reaches Earth’s Surface Pipe is a long tube inside a volcano that connects the magma chamber to the Earth’s surface.

Chapter 6 Volcanoes Magma Reaches Earth’s Surface Vent is an opening through which molten rock and gas leave the volcano.

Chapter 6 Volcanoes Magma Reaches Earth’s Surface Lava flow is the area covered by lava as it pours out of a vent.

Chapter 6 Volcanoes Magma Reaches Earth’s Surface Crater is a bowl-shaped area that may form at the top of a volcano.

Chapter 6 Volcanoes Magma Reaches Earth’s Surface Pahoehoe is a very thin, fast moving lava. Pahoehoe contains low amounts of silica, which gives it it’s thinness. When Pahoehoe hardens, it forms wrinkle and rope-like rock formations. Pahoehoe is hotter than Aa.

Chapter 6 Volcanoes Magma Reaches Earth’s Surface Aa is a very thick, slow moving lava. Aa contains high amounts of silica, which gives it it’s thickness. When aa hardens, it forms a rough surface consisting of jagged (sharp) lava chunks.

Chapter 6 Volcanoes Magma Reaches Earth’s Surface Pyroclastic flow is an explosive eruption that includes hot gases, cinders (volcanic ash), and bombs (volcanic rocks).

Chapter 6 Volcanoes Composite Volcano Eruption Activity Click the Active Art button to open a browser window and access Active Art about composite volcano eruption.

Chapter 6 Volcanoes 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. Use the graphs to answer the questions.

Chapter 6 Volcanoes Silica, other oxides, and other solids. Reading Graphs: Study both graphs. What materials make up both types of magma? Magma Composition

Chapter 6 Volcanoes 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? Magma Composition

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