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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. 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. 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 ________. pahoehoe Cool, slow-moving lava is called _____. aa What is a pyroclastic flow? A pyroclastic flow is an explosive eruption of ash, cinders, bombs, and gases. Vocabulary Shield Volcano: A wide, gently sloping mountain made of layers of lava and formed by quiet eruptions. Cinder Cone Volcanoes: A steep, cone-shaped hill or mountain made of volcanic ash, cinders, and bombs piled up around a volcano’s opening. Vocabulary Composite Volcano: A tall, cone-shaped mountain in which layers of lava alternate with layers of ash and other volcanic material. Caldera: The large hole at the top of a volcano formed when the roof of a volcano’s magma chamber collapses. Shield Volcano Belknap-Oregon Cinder Cone Volcano Composite Volcano St. Augustine, Alaska