Volcanoes
Table of Contents
Essential Question: How Does A Volcano
Erupt?
What happens when a volcano erupts?
What are the stages of Volcanic activity?
6.2
Volcanic Eruptions
Pgs 200-207
Vocabulary 6.2
1. Magma Chamber- The pocket beneath a volcano where magma collects.
2. Pipe- A long tube through which magma moves from the magma chamber to
Earth’s surface.
3.
4.
5.
6.
Vent- the opening through which molten rock and gas leave a volcano.
Lava flow- the area covered by lava as it pours out of a volcano’s vent.
Crater- a bowl-shaped area that forms around a volcano’s central opening.
Silica- a material found in magma that is formed from the elements oxygen and
silicon; it is the primary substance of Earth’s crust and mantle.
7. Pyroclastic flow8. Dormant-Not currently active but able to become active in the future (as a
volcano)
9. Extinct-A volcano that is no longer active and unlikely to erupt again.
Pearson
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Online Interactive Activity
What Happens When a Volcano Erupts? Pg. 200
Inside a Volcano
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All volcanoes have a pocket of magma
beneath the surface, called a magma
chamber, where the magma collects.
Magma moves upward through a pipe, a
long tube that extends from Earth’s crust up
though the top of the volcano, connecting the
magma chamber to Earth’s surface.
Molten rock and gas leave the volcano
through an opening called a vent.
A lava flow is the spread of lava as it pours
out of a vent.
A crater is a bowl-shaped area that may
form at the top of a volcano around the
central vent.
Volcanoe
Fig. 1 Volcanic Eruptions pg. 201
Inside a Volcano
A volcano is made up of many different parts. Place each word in its proper place in
the diagram
2 Types of Volcanic Eruptions pg. 202
During an eruption, dissolved gases trapped in the magma expand,
form bubbles, and exert great force.
When a volcano erupts, the force of the expanding
gases pushes magma from the magma chamber through
the pipe until it flows or explodes out of the vent.
Geologists classify volcanic eruptions:
1. as quiet
2. or explosive.
Whether an eruption is quiet or explosive depends in part on the
magma’s silica content and whether the magma is thin and
runny or thick and sticky.
Volcanic Eruptions pg. 202
The “Wakulla Volcano” was a column of smoke that was last seen near
Tallahassee in 1886. (no volcanic activity in FL for millions of years)
DO THE MATH!! Volcanic Eruptions pg. 202
Magma Composition
Magma varies in composition. It is
classified according to the amount of
silica it contains. The less silica that the
magma contains, the more easily it flows.
1. What materials make up both types?
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2. Which type of magma has more silica?
How much silica does this magma contain?
__________________________________
3. Which of these magmas do you think
might erupt in a dramatic explosions? Why?
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Quiet Eruptions pg. 203
Silica
is a material found in magma that forms from the elements
oxygen and silicon.
Characteristics of a quiet eruption:
A volcano erupts quietly if its magma is hot or low in silica. The
gases in the magma bubble out gently. The lava oozes quietly
from the vent and can flow for many kilometers.
Characteristics of an explosive eruption:
A volcano erupts explosively if its magma is high in silica.
Trapped gases build up pressure until they explode. The
erupting gases and steam push the magma out with incredible
force. Both kinds of eruptions can cause damage far from a
crater’s rim.
Volcano Hazard pg. 205
Volcanoes can cause great damage far from a
crater’s rim.
Quiet eruption= lava flows, setting fire to
everything in its path. They can cover large
areas with thick layer of lava.
Explosive eruption= Dangerous chemicals are
belch out from the volcano- such as hot rock
and ash.
A pyroclastic flow is a mixture of hot gases,
ash, cinders, and bombs that flow down the
sides of a volcano when it erupts explosively.
Landslides of mud, melted snow, and rock
can also form from an explosive
eruptions.
Did You Know?
Stromboli volcano lies on an island off
the coast of Italy. The volcano has
been erupting almost constantly
for at least 2,400 years! Expanding
gases dissolved in magma cause
the eruption to be nearly constant.
What are the Stages of Volcanic Activity? Pg. 296
Geologists often use the terms active, dormant, or extinct to
describe a volcano’s stages of activity.
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An active, or live, volcano is one that is erupting or has
shown signs that it may erupt in the near future.
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A dormant, or sleeping, volcano is a volcano that scientists
expect to awaken in the future and become active.
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An extinct, or dead, volcano is a volcano that is unlikely to
ever erupt again.
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Hot-spot volcanoes may become extinct once they drift away from
the hot spot
Geologist use special instruments to detect changes in the
volcanoes.
For example:
Tiltmeter- detects slight surface changes in elevation and tilt
caused by magma moving ground.
Geologist also monitor: gases escaping from the volcano, small
earthquakes before eruption, and rising temperatures in
underground water.
Fig. 5. Volcanic Eruptions pg. 206
Cascade Volcanoes
The Cascade volcanoes have
formed as the Juan de Fuca
plate sinks beneath the
North American plate.
1. Circle the 3 volcanoes
that appear to be the
most active.
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______________________
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2. Why migh geologists still
consider Mount Jefferson
to be an active volcano?
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Volcanic Eruptions pg. 207
Magma at Mount Rainier
Mt. Rainier
Mount Rainier is part of the Cascade volcanoes.
All past eruptions of Mount Rainier have included
ash and lava.