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science test on volcanoes

Most Volcanoes occur along.....

diverging plate boundaries such as the mid-ocean ridge or in a subduction zones around the edges of oceans.

If oceanic crust collides with continental crust....

volcanoes form. The crust melts underneath and forms magma which rises to the surface. When it hits the top a volcano forms.

Oceanic crust colliding with oceanic crust causes...

island arcs. This is where magma rises to the surface again-but then you get islands formed by volcanos.

characteristics of magma

hotter the magma more fluid it is, amount of silica also makes a difference more silica= thicker, high silica forms light colored lava called obsidian and lava, low silica forms basalt.

type of volcanic eruption

the silica content of magma determines whether the volcanic eruption is quite or explosive.

quite eruptions

magma flows easily, gasses bubble out gently, thin runny lava oozes quietly from a vent two types of lava.


fast hot moving lava, looks like solid mass if wrinkles or rope like coils.


cooler lava and slower moving it forms a rough surface of jagged lava chunks

explosive eruption

if magma is thick and sticky a volcano erupts _________ thick magma doesn't come out well, plugs up like a cork, nothing escapes, over time it explodes.


is a fountain of water and steam the erupts from the ground

Cinder cone volcano

a steep, cone shaped hill or mountain is called a __________ , If a volcanoes lava is thick and stiff it may produce ash, cinders, and bombs, these pile up around the vent

composite volcano

lava flows alternate with explosive eruptions of ash, cinder and bombs, lava-ash lava-ash lava-ash, tall cone shaped mountains in which layers of lava alternate with layers of ash are _________


enormous eruptions may empty the main vent and the magma chamber beneath. It becomes hollow, with nothing supporting it it collapses, the huge hole is called a __________


a mass of rock formed when a large body of magma cools inside the crust

dome mountain

forms when rising magma is blocked y horizontal layers of rock the magma forces the layers of rock to bend upward into a domed shape .

most volcanoes occur along

diverging plate boundaries, such as the mid-ocean ridge or in subduction zones around the edges of oceans.

during a volcanic eruption ........

the gases dissolved in magma rush out carrying the magma with them


is a material formed from oxygen and silicon

pyroclastic flow

occurs when an explosive eruption hurls out ash, cinders, and bombs.

geothermal energy

water heated by magma can provide a clean reliable energy source

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