Download Section 9.1 How and where volcanoes form

Section 9.1
How and where volcanoes form
Please write any information that
you feel is important.
volcano
Any area where molten rock, ash, and
gasses can erupt
volcanic ash
Volcanic Lapilli
Volcanic bombs
• Iceland imovie
How magma forms
3 ways to form magma
• Decrease the pressure
• Increase the temperature
• Increase the amount of water in the
asthenosphere
Volcanic activity at different
boundaries
Observe an animation of volcanism at a
subduction zone.
Observe an animation of volcanism along a
rift zone.
Observe an animation of volcanic islands
forming over a hot spot.
Something to ponder.
How are the 3 different boundaries
connected to volcanoes?
What is one of the biggest reasons that we
are able to observe volcanic activity?
Why was learning plate tectonics important
for this chapter and the coming chapters?
Section 9.2
Erupted materials
Write down information that you
feel is important
Different types of magma
What are some ways that magma could be
different?
Silica content
Gas content
Viscosity
Melting temperature
Conditions that lead to more
explosive eruptions
High silica content – they resist flow
viscosity the resistance of a liquid to flow
Higher gas concentration
Lower melting point
Location
Lava flows on land
Pahoehoe
smooth rope like lava
that flows very easily
Lava flows on land
AA
basaltic lava that cools
quickly into rough jagged
rock
Underwater lava flows
Pillow lava
rounded lumps of lava that crack forming pillow
shapes because of the drastic temperature
change in the ocean.
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Ash and rock fragments
Pyroclastic flow
A dense superheated
eruption of gases and
pyroclastic material.
Travels down hill at
speeds over 100
kilometers per hour.
Ash and rock fragments
Pyroclastic material
gases and solid
fragments of solid
rock that is ejected
from a volcano
Volcanic landforms
Section 9.3
3 types of volcanoes
• Shield volcano
• Cinder volcano
• Composite volcano
Shield volcano
Lava flows out of
the earth creating
a broad base and
gentle slopes
Cinder cone
Fragments of molten
rock pile up around
a volcanic vent
Composite volcano
Layers of material
accumulate around
a vent. A combination
of lava and ash are
deposited.
Other formations associated with
volcanic activity
Lahar
Fast-moving mud flow that is associated
with volcanic activity.
Caldera
Large crater at the top of a volcano.
Usually caused by a collapse in the
magma chamber.
Lava plateau
Large flat area where lava spills out onto
the Earth’s surface.