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