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Volcanoes and Plate Tectonics. What is a volcano?. Volcanoes are weak spots in the crust where magma rises to the surface. Location of Volcanoes. Volcanic belts form along the plate boundaries. Volcanoes occur in belts like the Ring of Fire. Location of Volcanoes.
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What is a volcano? • Volcanoes are weak spots in the crust where magma rises to the surface.
Location of Volcanoes • Volcanic belts form along the plate boundaries. • Volcanoes occur in belts like the Ring of Fire
Location of Volcanoes • Most volcanoes occur along diverging plate boundaries or in subduction zones.
Volcanoes at Diverging Plate Boundaries • Volcanoes form at the mid-ocean ridge underwater
Volcanoes at Converging Plate Boundaries • Volcanoes form in subduction zones • Two oceanic plates collide • An oceanic plate and continental plate collide
Volcanoes at Converging Boundaries • If subduction zone involves two pieces of oceanic crust, volcanoes are created • These volcanoes create a string of islands called an island arc
Volcanoes at Converging Boundaries • If subduction zone involves oceanic and continental crust, volcanoes are created on land.
Hot Spot Volcanoes • Hot spot is an area where magma melts through the crust like a blow torch • Hot spots are not often at plate boundaries
Hot Spot Volcanoes • Hot spots volcanoes can be created in the ocean floor • Hawaii
Hot Spot Volcanoes • Hot spots can form under continents • Yellowstone National Park
Types of Volcanoes • There are three major types of volcanoes • Shield • Cinder Cone • Composite
Shield Volcanoes • Lava slowly leaks onto crust and hardens • Wide, gently sloping mountains
Cinder Cone Volcanoes • Steep, cone-shaped hill or mountain • Lava is thick and produces ash and cinders • This material piles up and forms the mountain
Composite Volcanoes • Tall, cone-shaped mountain • Layers of lava alternate with layers of ash • Lava leaks out in between explosions
Lava Plateaus • Sometimes, lava does not form mountains • Lava flows out of crust and collects in one area, forming a high plateau
Calderas • Enormous eruptions can empty the magma chamber under the volcano • With nothing left for support, the mountain collapses
Caldera • The hole left over is a caldera