Presentation on theme: "Chapter 18 Volcanoes Section Two Volcanic Activity."— Presentation transcript:
Chapter 18 Volcanoes Section Two Volcanic Activity
Vocabulary Magma Chamber: The pocket beneath a volcano where magma collects. Pipe: A long tube through which magma moves from the magma chamber to Earth’s surface. Vent: The opening through which molten rock and gas leave a volcano.
Vocabulary Lava Flow: The area covered by lava as it pours out of a volcano’s vent. Crater: A bowl-shaped area that forms around a volcano’s central opening. Silica: A material that is formed from the elements oxygen and silicon; silica is found in magma.
How Magma Reaches Earth’s Surface True or False: Magma forms in the lithosphere. False What happens during a volcanic eruption? During a volcanic eruption gasses that have been dissolved in the magma rush out, carrying the magma with them.
Inside a Volcano Circle the letter of each feature that all volcanoes share. A. pocket of magma beneath the surface. B. crack to the surface. C. side vents. D. crater.
Inside a Volcano What is a lava flow? A lava flow is the area covered by lava as it pours out of a vent. Where does a crater form? A crater forms at the top of a volcano around the central vent. True or False: The pipe of a volcano is a horizontal crack in the crust. False
Characteristics of Magma What factors determine the force of a volcanic eruption. Factors that determine the force of a volcanic eruption include the amount of gas dissolved in the magma, how thick or thin the magma is, its temperature, and its silica content.
Types of Volcanic Eruptions Hot, fast-moving lava is called ________. Cool, slow-moving lava is called _____. What is a pyroclastic flow? A pyroclastic flow is an explosive eruption of ash, cinders, bombs, and gases. pahoehoe aa