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Bellringer
Describe the relationship between the silica
content of magma and the resulting eruption of the
volcano.
Volcanic Landforms
Notes
Landforms from Lava
and Ash
• A shield volcano is a gently sloping
mountain. Thin layers of lava build up
slowly over a large area around a vent.
• Examples include Mauna Kea, Hawai’i;
some of the Galapagos Islands;
Iceland; and Olympus Mons on Mars.
Landforms from Lava
and Ash
• A cinder cone is a steep, cone-shaped
hill or small mountain. It forms when a
volcano erupts explosively. Ashes,
cinders, and bombs pile up around the
vent. The tephra (rock pieces) are held
together very loosely.
Landforms from Lava
and Ash
• A composite volcano is a tall, cone-
shaped mountain. It forms when a
volcano erupts quietly and then
explosively, over and over again.
Layers of lava are followed by layers of
ash, cinders, and bombs.
• These volcanoes are also known as
stratovolcanoes.
http://dli.taftcollege.edu/streams/Geography/Animation
s/VolcanoTypes.html
Landforms from Lava
and Ash
• Sometimes lava forms a plateau
instead of a mountain. A lava plateau is
a high, level area. If forms when thin
lava flows out of many long cracks.
Landforms from Lava
and Ash
• If a magma chamber empties, a
volcano can collapse. This leaves a
huge hole called a caldera. A caldera
may fill with water and form a lake.
• Caldera is derived from the Latin
calderia, which is usually translated as
cauldron, or cooking pot.
Landforms from
Magma
• Sometimes, magma never breaches the surface
of the crust, and instead, cools within it, forming
intrusions of igneous (solid volcanic) rock that
can eventually be exposed as weathering
erodes away the surrounding rock.
• A volcanic neck (or volcanic plug) forms when
magma hardens in the pipe of a volcano. Softer
rock around the pipe erodes away, leaving just
the neck standing. A volcanic neck looks like a
giant tooth stuck into the ground.
Landforms from
Magma
• A dike forms when magma hardens
across rock layers. A dike is a vertical,
or up-and-down, igneous intrusion.
When erosion exposes the dike, it
leaves behind a long, thin ridge of
igneous rock.
Dike
Volcanic neck and accompanying dike
•
•
Landforms from
Magma
A batholith forms when a large amount of
magma hardens inside the crust. A
batholith is a large rock mass. It may
become a part of a mountain range.
A dome mountain forms when a batholith
or smaller chunk of hardened magma is
pushed up to the surface. The hardened
magma forces the layers of rock above it
to bend upward into a dome shape.
Geothermal Activity
•
•
Magma below the surface can heat
underground water. The heating of
underground water by magma is called
geothermal activity. Geothermal activity
is common where there are volcanoes.
A hot spring forms when water heated by
magma rises to the surface and collects
in a natural pool.
Natural geothermal hot springs in Iceland.
Geothermal Activity
• A geyser forms when hot water and
steam are trapped underground in a
narrow crack. Pressure builds up until
the hot water and steam erupt from the
ground. This happens over and over
again. Old Faithful is a geyser in
Yellowstone National Park. It erupts
about once and hour.
Geothermal Activity
• Hot water from underground can be
piped into homes to heat them. This is
how many people in Iceland heat their
homes. NO FOSSIL FUELS! 100%
RENEWABLE.
• Steam from underground can be piped
into electric power plants. In the power
plants, the heat energy in the steam is
turned into electric energy.