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

Types of Volcanoes Shield Volcano Cinder Cone Volcano Composite Volcano Dormant volcano - “sleeping” and currently not erupting

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 Kilauea Hawaii, USA

Cinder Cone Volcano Short, steep sides Moderate to violent eruptions Forms in groups near other larger volcanoes High gas content = shorter eruptions Sunset Crater Arizona, 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 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 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