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Main Idea: Types of Volcanoes

Main Idea: Types of Volcanoes. A. How does a Shield volcano form?. They form when layers of lava accumulate over time. The eruptions are slow and nonexplosive. Shield volcanoes are the largest in size. B. How does a Cinder-Cone volcano form?.

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Main Idea: Types of Volcanoes

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  1. Main Idea: Types of Volcanoes

  2. A. How does a Shield volcano form? • They form when layers of lava accumulate over time. • The eruptions are slow and nonexplosive. • Shield volcanoes are the largest in size.

  3. B. How does a Cinder-Cone volcano form? • They form when lava is ejected high into the air and piles up around the vent. • Small in size less than 500 m high. • More explosive than shield volcanoes, because magma contains more water and silica. • Magma is more viscous, which leads to more gas

  4. C. How do Composite-Cone volcanoes form? • These volcanoes form when layers of lava alternate with layers of volcanic fragments (ash, tephra). • Larger than cinder-cone • Are the most dangerous of all volcanoes

  5. D. Where on earth can volcanoes be found? • Volcanoes are found along plate boundaries. • 80 % on convergent boundaries • 15 % on divergent boundaries • 5 % occur away from plate boundaries

  6. E. Hot spots • Areas on Earth’s mantle where high temperature causes sections of earth to rise (Hawaii). • The heat melts the rock, which is forced to the surface as magma. • The magma melts the crust forming volcanoes.

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