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Volcanoes
Parts of a Volcano
• magma chamber: a large reserve of magma that collects deep underground
• central vent: long tunnel which lava is pushed through
• fissures: small tunnels which release lava from the side of the volcano
• crater: funnel-shaped pit with an opening at the top of the volcano
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Types of Volcanoes
• Shield Volcano
• Cinder Cone Volcano
• Composite Volcano
• Dormant volcano - “sleeping” and currently not erupting
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What makes a volcano explode?
Viscosity
• Viscosity - magma’s ability to flow
• More silica = thicker lava = more explosive
Gas
• More gas = more explosive
Shield Volcano
• Flows in broad, flat layers
• Gently sloping sides• Largest type• Built from basaltic lava
layers• Generally not violent
eruptions
• Looks like a shield
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KilaueaHawaii, USA
Cinder Cone Volcano
• Short, steep sides• Moderate to violent
eruptions• Forms in groups
near other larger volcanoes
• High gas content = shorter eruptions
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Sunset CraterArizona, USA
Composite Volcano
• Steep-sided mountains• Made up of alternating
layers of lava and tephra (cinders, rocks, ash)
• Can have quiet or violent eruptions– Quiet eruptions release
lava– Explosive eruptions
release tephra
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Mt. St. Helens Washington, USA
What can happen during a volcanic eruption?
• lava flows: lava comes out of the crater and flows down the side of the mountain
• lava tubes: lava flows through channels of hardened lava; most travel underground and then break through the surface
• landslide: massive amount of rock and soil that races down the side of mountain
• plume: giant cloud of ash that reaches 12-16 miles above sea-level
• ash: extremely small particles of dust released from the eruption
• debris: tephra and solidified magma bombs ejected from the vent
• lahar: after the eruption, rain or melting snow triggers dangerous landslides of ash and mud
• pyroclastic flow: a giant cloud of very hot gases and rock fragments that rush down the mountain
• dome: lava pushes up like an inflating balloon but does not break through the surface of the Earth