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Student Notes—keep to study from!
Volcano:
an __________ in the earth’s surface through which lava, hot gases, and rock fragments ________
How do they form?
o
o
o
o
o
o
Magma ___________ miles below the earth’s surface slowly begins to _______ to the surface
As the magma rises it melts ________ in the surrounding rock
As more magma rises a ______________ forms as close as 2 miles below the surface (magma
chamber)
__________ from the surrounding rock causes the magma to ________ or _______ a conduit
(channel) to the surface where magma erupts onto the surface through a vent (opening)
The magma, now called lava, _______ up at the _________ forming a volcano
Often the volcano sides will be higher than the vent forming a depression called a _________
*Caldera: an unusually large crater or the remains when the cone collapses into its own magma
chamber
Anatomy of a Volcano
Cone: the ________ ground structure built from _____________________
Conduit: the path that magma takes from the ______________ to the _________
Magma Chamber: the reservoir located under the volcano where ________________ and
becomes the supply of magma/lava to build the volcano
Lava: molten, __________ rock on the surface of the earth
Parasitic Cone: a smaller secondary volcano built on the side of or near the main volcano, but
sharing the same _________ to the
magma chamber
Fumarole: a secondary vent that
emits only __________
Fissure: a long fissure (_______)
from which lava flows
Vent: ________ of the volcano,
through which lava, ash and gases flow
Take a minute to label the
parts on the diagram
(not all parts are shown)
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Types of Volcanic Eruptions—
Two factors determine the type of eruption
:
o
Amount of ___________ & other ________ in the magma
o
The ____________________________ of the magma
Explosive Eruptions
o
o
o
Trapped gases under ______ pressure will
violently explode when the magma reaches
the ___________ pressure of the surface.
Has ___________ magma is very _______
and _______ the vent causing the pressure
to build until it blows violently out the vent
The _________ water content of the
magma produces more water vapor which,
when mixed in granitic magma, produces
explosive eruptions
Quiet Eruptions
o
o
o
Low pressure gas
Has ____________ magma (is more fluid
and will flow instead of explode)
And has low _________ content
Examples: ______________________________
Examples: _______________________________
Composite
or strato
Shield
Cinder Cones
Types of Volcano Mountains
o
o
o
o
o
______________, steep-sided, loosely consolidated
Up to 1000 feet tall
Life span of a _______ years
Commonly built from gravel size lava rock fragments called _________
_________ eruptions, dangerous when close---High pressure gas bubbles
causes thick lava to explode into the air, lava begins to cool as it rises and
falls becoming very sticky
o When lava hits the ground it _____________ rather than flows
_____________ Viscosity
o This builds a steep cone with a small base
Sketch:
Large base, ______________, lava rock layers
A few ________ high
Life span of a __________ years or more
The lava is hot, thin, very _______, often __________.
____________ Viscosity
Example: Hawaiian Islands
Sketch:
o
o
o
o
Large mountain volcano often ___________, a few miles high
Life span of million years or more
Have alternating eruptions of _______and ________. The tephra
adds ______ to the volcano and the lava ______ the tephra together
and adds to the _______.
o Found mostly in __________ zones and have violent eruptions.
Examples: Mt Rainier, Mt Fuji, Mt Kilimanjaro
o
o
o
Sketch:
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Where do volcanoes occur?
Location
example
Divergent Boundaries: where plates move ________
Convergent Boundaries: where plates __________________
Hot Spots: plates riding over an especially hot place in the mantle
What comes out of volcanoes?
LAVA— 3 kinds:
Pahoehoe lava:
o
Cooler, _______, slow
moving
o
Hardens with a relatively
smooth surface
Aa Lava:
o Hot, thin, fast flowing
o Hardens with a rough,
jagged, sharp edge surface
Pillow Lava:
o Lava suddenly cooled by
_________
o Shows sack-like segments
(stuffed pillows)
o
Often has a _______ or
__________ appearance
Can you identify the kinds of lava from the pictures? Circle your choice below.
Picture 1:
Picture 2:
Picture 3:
Picture 4:
Pahoehoe/Aa/Pillow
Pahoehoe/Aa/Pillow
Pahoehoe/Aa/Pillow
Pahoehoe/Aa/Pillow
Tephra
o Basically, ______________ fragments. Also known as _____________ rock fragments.
o There are many different possible sizes, from very small (volcanic _______ or _______)
to much larger rocks (called volcanic _____________)
Lahar (mudflow): mixture of ______, _____________, and water flowing down river valleys
GASES
o
water vapor,_______________, nitrogen, ____________, hydrogen sulfide, _________
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Volcano Activity Levels (Stages)
Active (awake):
Has erupted within recent time and can erupt again at
Pre-eruption activities:
 Increase in ____________ activity
under the cone
 increase in temperature of cone,
 __________ of ice/snow in the crater
___________.



swelling of the cone
_________ eruptions
minor ______ eruptions
Dormant (sleeping):
 _____ eruption within recent times, but there is record of past
eruptions
 Can become ______ and erupt again after a “___________” period
 Example: Mt. Rainier
Extinct:
 No eruption within recorded history
 Not expected to ____________________
 Example: Mount Mazama (Crater Lake)
Mount Rainier
o The most _____________ volcano in the US
o The danger is mostly from ___________
traveling down river valleys at a speed of
25mph and destroying everything in its path
o 100,000 people live on the solidified mudflows
of previous eruptions
o The mountain is dangerously
_____________, a tall, steep heap of loose
rock held together by the force of gravity
and a cubic mile of glacier ice that could be
melted or shaken loose
o Lahar flows average every
________________ and have gone as far as
the Puget Sound lowlands
o Mount Rainier has erupted _____________
in the last 4000 years with the last eruption
200 years ago
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