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Volcanoes C20-25 Volcano A mountain formed when red-hot melted rock flows through a crack onto the earth’s surface Magma Melted rock inside Earth Lava Melted rock that reaches Earth’s surface Vent A rocky opening that magma flows through to reach the surface of Earth Magma Chamber An underground pool that holds hot magma A Crater large basin formed at the top of a volcano when the top collapses after an eruption Rain can collect in a crater and form a lake. (Crater Lake, in Oregon) Ways Volcanoes Form (#1) Plates in the ocean move away from each other. As they move apart, magma rises toward the surface. When it reaches the surface, it hardens to form new ocean floor. Ways Volcanoes Form (#2) When ocean and continent plates collide (hit), the ocean plate falls into the mantle and melts. Then it comes to the surface as lava, through a vent. This forms volcanic How Volcanoes Form #3 Plates move over a hot spot in the mantle and hot lava comes through the surface to form volcanic islands. Hawaiian Volcano Hardened Lava Shield Volcanoes Large, gently sloping mountains Form from runny lava Many are found in Hawaii, rising from the ocean floor Cinder Cone Volcanoes Have steep sides Made of hardened lava chunks Not very tall Composite Volcanoes Medium-sized volcanoes Made of lava and cinders Have steep peaks and sloping sides Mt. Fuji (Japan), St. Helens (USA) Mount Vesuvius in Italy Explode when they erupt Mt. St. Helens, Washington Volcanoes Help Earth Minerals deposited into the soil around the volcano help crops grow. Form new crust on continents Form new ocean floor Volcanoes Harm Earth Erupting gasses and hot lava destroy everything in their paths. Temperature at an eruption point can reach 1470 degrees! The powerful blasts may be felt 10-15 miles away! Review Volcanoes form when melted rock called lava flows onto Earth’s surface. Most volcanoes form along plate edges. They add crust and ocean floor. They add minerals to the soil. They can destroy anything in their path.
