Chapter Menu Lesson 1: Volcanoes and Plate Boundaries Lesson 2: Volcanic Eruptions and Features Lesson 3: Hazards of Volcanic Eruptions Click on a hyperlink to view the corresponding lesson.

7.1 Volcanoes and Plate Boundaries vent fissure eruption hot spot

7.1 Volcanoes and Plate Boundaries What is a volcano? A volcano is a land or underwater feature that forms when magma reaches the surface of Earth. Volcanoes can cause the eruption of liquid, gas, and/or solid materials.

What is a volcano? (cont.)

7.1 Volcanoes and Plate Boundaries How do volcanoes form? When rocks become hot enough and conditions are right, they can melt. Magma is less dense than surrounding rock. Magma rises towards Earth’s surface because of the buoyant force pushing up.

Convergent Plate Boundaries 7.1 Volcanoes and Plate Boundaries Convergent Plate Boundaries Volcanoes tend to erupt more violently. Volcanic arcs—form when an oceanic plate subducts beneath a continental plate Island arcs—form when two oceanic plates move toward each other

Divergent Plate Boundaries 7.1 Volcanoes and Plate Boundaries Divergent Plate Boundaries Eruptions can occur in either the ocean, as a mid-ocean ridge, or on a continent, as a continental rift. Magma reaches Earth’s surface as fissure eruptions.

7.1 Volcanoes and Plate Boundaries Heat Escapes Magma erupts through a circular or oval opening of a volcano, called a vent. Fissure eruptions occur when magma escapes through narrow and elongated cracks in Earth’s crust.

Volcanoes Away from Plate Boundaries 7.1 Volcanoes and Plate Boundaries Volcanoes Away from Plate Boundaries Not all volcanoes occur along plate boundaries. Hot spots are localized areas of high heat in Earth’s interior. Hawaiian Islands

Where do volcanoes occur? 7.1 Volcanoes and Plate Boundaries Where do volcanoes occur?

What causes magma to rise toward Earth’s surface? A temperature 7.1 Volcanoes and Plate Boundaries A B C D What causes magma to rise toward Earth’s surface? A temperature B cooling water C erosion D buoyant force Lesson 1 Review

Fissure eruptions occur when? 7.1 Volcanoes and Plate Boundaries A B C D Fissure eruptions occur when? A magma escapes through cracks in Earth’s crust B magma escapes through the vent C magma does not reach Earth’s surface D magma flows slowly Lesson 1 Review

Volcanic arcs form _____. 7.1 Volcanoes and Plate Boundaries A B C D Volcanic arcs form _____. A when two oceanic plates are pushed together B when two continental plates are pushed together C when an oceanic plate sinks beneath a continental plate D when a continental plate sinks beneath an oceanic plate Lesson 1 Review

End of Lesson 1

7.2 Volcanic Eruptions and Features viscosity shield volcano cinder cone volcano tephra composite volcano

What controls volcanic eruptions? 7.2 Volcanic Eruptions and Features What controls volcanic eruptions? The composition of magma controls how lava flows and the way a volcano erupts. The percentage of silica and oxygen in magma is related to the energy of a volcanic eruption.

7.2 Volcanic Eruptions and Features Composition of Magma Viscosity is a physical property that describes the material’s resistance to flow. How does magma’s composition affect a volcano’s eruption?

Dissolved Gases and Temperature 7.2 Volcanic Eruptions and Features Dissolved Gases and Temperature The higher the temperature of magma, the more easily it flows. The more gas present in magma, the more explosive the eruption. Most dissolved gas in magma is water vapor.

Types of Magma and Lava Basaltic Magma and Lava 7.2 Volcanic Eruptions and Features Types of Magma and Lava Basaltic Magma and Lava Low percentage of silica Low viscosity Produces quiet, non-explosive eruptions

Types of Magma and Lava (cont.) 7.2 Volcanic Eruptions and Features Types of Magma and Lava (cont.) Granitic Magma and Lava High percentage of silica High viscosity Tends to trap gases and produce explosive eruptions

Types of Volcanoes Shield Volcanoes 7.2 Volcanic Eruptions and Features Types of Volcanoes Shield Volcanoes Huge, gently sloping volcanic landform Mainly composed of basaltic lava Hawaiian Islands are an example

Types of Volcanoes (cont.) 7.2 Volcanic Eruptions and Features Types of Volcanoes (cont.) Cinder Cone Volcanoes Cone shaped Mainly composed of solid fragments called tephra Typically produce explosive eruptions

Types of Volcanoes (cont.) 7.2 Volcanic Eruptions and Features Types of Volcanoes (cont.) Composite Volcanoes Forms tall, majestic mountains Mainly composed of alternating layers of lava and tephra Typically produce alternating quiet and explosive eruptions

Types of Volcanoes (cont.) 7.2 Volcanic Eruptions and Features Types of Volcanoes (cont.)

Volcanoes in California 7.2 Volcanic Eruptions and Features Volcanoes in California A variety of active volcanoes occur along the western coast of the United States. Form at convergent plate boundary as part of a volcanic arc

Intrusive Volcanic Features 7.2 Volcanic Eruptions and Features Intrusive Volcanic Features Types of intrusive features include: batholiths—largest intrusive features sills—magma that is parallel to rock layers and hardens dikes—magma that cuts across rock layers and hardens volcanic necks

Intrusive Volcanic Features 7.2 Volcanic Eruptions and Features Intrusive Volcanic Features

Other Volcanic Features 7.2 Volcanic Eruptions and Features Other Volcanic Features Volcanic neck—erosion wears away the volcano and leaves behind the hardened vent Lava domes—forms when a mass of highly viscous lava slowly erupts from the vent Lava tubes—a hollow tube that forms when lava flows through a channel, cools, and hardens on the surface Caldera—a large, circular depression that forms when the tops of a volcano collapses

Other Volcanic Features (cont.) 7.2 Volcanic Eruptions and Features Other Volcanic Features (cont.)

D low gas concentration 7.2 Volcanic Eruptions and Features A B C D Which characteristics of magma would likely result in an explosive eruption? A low viscosity B high viscosity C high temperature D low gas concentration Lesson 2 Review

Which type of volcano is mainly composed of tephra? A caldera 7.2 Volcanic Eruptions and Features A B C D Which type of volcano is mainly composed of tephra? A caldera B composite C cinder cone D shield Lesson 2 Review

Which is the largest intrusive volcanic feature? A dike B lava dome 7.2 Volcanic Eruptions and Features A B C D Which is the largest intrusive volcanic feature? A dike B lava dome C lava tube D batholith Lesson 2 Review

End of Lesson 2

7.3 Hazards of Volcanic Eruptions volcanic ash lahar pyroclastic flow

Volcanic Ash Volcanic ash is a very fine grained tephra. 7.3 Hazards of Volcanic Eruptions Volcanic Ash Volcanic ash is a very fine grained tephra. Composed of tiny, sharp mineral and glasslike particles Affects humans and wildlife habitats by burying plants and animals and their food sources and contaminating the water supply.

7.3 Hazards of Volcanic Eruptions Lahars A lahar is a rapidly flowing mixture of volcanic debris and water. Some large lahars begin as landslides. A fast-moving lahar provides little time for warning.

7.3 Hazards of Volcanic Eruptions Gas Emissions Gas released from volcanic eruptions can be a silent hazard to humans and wildlife. Sulfur dioxide and hydrogen sulfide gases, when mixed with water, can form sulfuric acid precipitation.

Pyroclastic Flows A fast-moving body of hot gases and solids 7.3 Hazards of Volcanic Eruptions Pyroclastic Flows A fast-moving body of hot gases and solids Can burn and destroy all forms of life in its path Typically produced during explosive eruptions Tend to follow valleys

Lava Flows Occur from either an explosive or quiet volcanic eruption 7.3 Hazards of Volcanic Eruptions Lava Flows Occur from either an explosive or quiet volcanic eruption Destroy human and wildlife habitats by starting fires and releasing smoke Move slowly enough that humans can be warned of possible dangers

Predicting Volcanic Eruptions 7.3 Hazards of Volcanic Eruptions Predicting Volcanic Eruptions Volcanoes usually show signs of activity before an eruption. These signs include: small earthquakes gas emissions changes in ground movement and temperature around the volcano

Which location would be vulnerable to pyroclastic flows? 7.3 Hazards of Volcanic Eruptions A B C D Which location would be vulnerable to pyroclastic flows? A on a hill several miles away. B in a river valley downstream from a volcano. C in a commercial jet flying near a volcano. D none of the above Lesson 3 Review

What is a fast-moving body of hot gases and solids? A dike B ash cloud 7.3 Hazards of Volcanic Eruptions A B C D What is a fast-moving body of hot gases and solids? A dike B ash cloud C lahar D pyroclastic flow Lesson 3 Review

What is not a sign of a possible volcanic eruption? 7.3 Hazards of Volcanic Eruptions A B C D What is not a sign of a possible volcanic eruption? A frequency of small earthquakes increases B decline in gas emissions C increase in ground temperature D slight bulge in the ground surface Lesson 3 Review

End of Lesson 3

Chapter Resources Menu Chapter Assessment California Standards Practice Concepts in Motion Image Bank Science Online Interactive Table Virtual Lab Click on a hyperlink to view the corresponding feature.

What causes magma to rise to the Earth’s Surface? B C D What causes magma to rise to the Earth’s Surface? A Magma is more dense than surrounding rock and is pushed up by conductive forces. B Magma is less dense than surrounding rock and is pushed up by conductive forces. C Magma is more dense than surrounding rock and is pushed up by buoyant forces. D Magma is less dense than surrounding rock and is pushed up by buoyant forces. Chapter Assessment 1

Which properties occur in lava with a high percentage of silica? B C D Which properties occur in lava with a high percentage of silica? A thinner, slow moving, high viscosity B thicker, slow moving, high viscosity C thicker, fast moving, high viscosity D thicker, slow moving, low viscosity Chapter Assessment 2

A sulfur dioxide and hydrogen sulfide B ozone and sulfur dioxide C D What two gases, when emitted from a volcano and mixed with water, can form sulfuric acid rain? A sulfur dioxide and hydrogen sulfide B ozone and sulfur dioxide C nitrogen and hydrogen sulfide D argon and hydrogen sulfide Chapter Assessment 3

The Hawaiian Islands are an example of what type of volcano? A shield B C D The Hawaiian Islands are an example of what type of volcano? A shield B cone C pyroclastic D composite Chapter Assessment 4

What is a characteristic of magma with low viscosity? B C D What is a characteristic of magma with low viscosity? A erupts explosively B thick and lumpy C flows slowly D thin and runny Chapter Assessment 5

SCI 1.d A B C D What forms at a divergent plate boundary when an oceanic plate sinks beneath a continental plate? A island arc B volcanic arc C fissure eruption D tephra CA Standards Practice 1

The Hawaiian Islands have formed above a ____. A hot spot B island arc SCI 1.e A B C D The Hawaiian Islands have formed above a ____. A hot spot B island arc C volcanic arc D fissure eruption CA Standards Practice 2

B Lava flows in a hollow channel. SCI 1.f A B C D How does a caldera form? A The top of a volcano collapses and becomes wedged into the empty magma chamber. B Lava flows in a hollow channel. C A mass of thick, highly viscous lava slowly erupts from the vent. D Magma cools slowly and solidifies before reaching the surface. CA Standards Practice 3

What is a pyroclastic flow? SCI 2.d A B C D What is a pyroclastic flow? A slow moving body of lava that starts fires B a cloud of very fine-grained tephra C a fast moving body of hot gases and solids D a fast flow of lava that erupts from cracks in the seafloor CA Standards Practice 4

What forms a composite volcano? A tephra SCI 1.e A B C D What forms a composite volcano? A tephra B alternating layers of tephra and lava C volcanic ash D none of the above CA Standards Practice 5

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