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How do volcanoes form and what affect do they have on the Earth?

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Presentation on theme: "How do volcanoes form and what affect do they have on the Earth?"— Presentation transcript:

1 How do volcanoes form and what affect do they have on the Earth?

2  The Vent is an opening in Earth’s crust though which lava flows onto the surface  As lava flows out, it can solidify into a mountain known as a Volcano  A bowl-shaped depression around the vent is known as a Crater

3  A Caldera is a bowl-shaped depression that forms around the central vent at the summit of a volcano  Form when volcano collapses  Larger than a crater Crater Lake

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5  Shield Volcano  Broad, gently sloping sides  Layers of Basaltic lava accumulate over time  Basaltic lava, non-explosive eruption  Hawaiian Islands (Mauna Loa)

6  Cinder Cone Volcano  Tephra accumulates around vent  Eject small pieces of andesitic magma  Steep sides, generally small volcano  Paricutin, Mexico

7  Composite Volcano  Large sloping volcano  Alternate volcanic fragments and lava  Violent eruptions, rhyolitic lava  Mount St. Helen’s, Mount Rainier, Mount Vesuvius

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10  Tephra  Rock fragments thrown into the air during a volcanic eruption  Classified by size Dust, ash, lapilli, volcanic blocks (size of cars/houses!)  Pyroclastic Flow  Rapidly moving volcanic material  Typically down a slope  Speeds up to 200km/h  May contain hot, poisonous gases (<700°C)

11 Tephra Pyroclastic Flow


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