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