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Volcanoes By Kiley Layman 3/11/10. Shield Volcanoes. Shield volcanoes are broad, gently sloping mountains that occur when thin layers of lava pour out of a vent and harden on top of previous layers. This type of volcano is what created the Hawaiian Islands. . Composite Volcano. - PowerPoint PPT Presentation
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VolcanoesBy Kiley Layman3/11/10
Shield Volcanoes
Shield volcanoes are
broad, gently sloping
mountains that occur
when thin layers of lava
pour out of a vent and
harden on top of previous
layers. This type of
volcano is what created
the Hawaiian Islands.
Composite Volcano
Side vent
Main vent
Layers of Lava and Ash
Composite volcanoes are tall,
cone-shaped volcanic
mountains that are made when
lava, ash, cinders, and bombs
harden on the mountainside
and build over time. Some
examples of composite
volcanoes are Mount Fiji in
Japan and Mount St. Helens in
Washington state.
Cinder Cone Volcano
A cinder cone volcano
is a cone-shaped
volcanic hill or
mountain that can be
very steep. This type
of volcano produces
very thick, stiff lava
that turns into ash,
cinders, and bombs.
Caldera Groundwater
Magma
Chamber
Geyser
When an enormous eruption empties the magma chamber, the mountain becomes a hollow shell. The top of the mountain collapses inward. This creates a caldera. Sometimes, water may fill up the hole and create a lake.
Hot Springs and GeysersGeyser Hot
springgroundwater
Magma chamber
Two examples of
volcanic activity that
don’t involve lava are
geysers and hot
springs. Groundwater
heated by magma
which rises to the
surface and collects in
a pool causes a hot
spring. Geysers are
formed when rising
hot water and steam
become trapped
underground in a
narrow crack. The
pressure builds and
the water sprays
above the surface.
Did You Know?
• Some other parts of a volcano are the volcanic neck, dike, and sill. • A volcanic neck is formed when magma hardens in a volcano’s pipe. The softer rock crumbles and reveals the hardened magma. • A dike occurs when magma forces itself across rock layers and hardens. •A sill is formed when magma squeezes itself between layers of rock.
Dike Sill
Volcanic neck