Transcript Volcanoes - TEMSScience8

Volcanoes
Table of Contents
Volcanoes and Plate Tectonics
Properties of Magma
Volcanic Eruptions
Volcanic Landforms
Volcanoes - Volcanoes and Plate Tectonics
Volcanoes and Plate Boundaries
Volcanic belts form along the boundaries of Earth’s plates.
Volcanoes - Volcanoes and Plate Tectonics
Volcanoes and Plate Boundaries
Volcanoes often form where two oceanic plates collide or
where an oceanic plate collides with a continental plate. In
both situations, an oceanic plate sinks through a trench.
Rock above the plate melts to form magma, which then
erupts to the surface as lava.
Volcanoes - Volcanoes and Plate Tectonics
Hot Spot Volcanoes
A volcano forms above a hot spot when magma erupts
through the crust and reaches the surface.
Volcanoes - Volcanoes and Plate Tectonics
Asking Questions
Before you read, preview the red headings. In a graphic
organizer like the one below, ask a where, what, or how
question for each heading. As you read, write the answers to
your questions.
Questions
Answers
Where are volcanoes
found?
Most volcanoes are found
along plate boundaries.
What are hot spots?
A hot spot is an area where
material from deep within the
mantle rises and then melts,
forming magma.
Volcanoes - Volcanoes and Plate Tectonics
More on Volcanoes
Click the PHSchool.com button for an activity
about volcanoes.
Volcanoes
End of Section:
Volcanoes and
Plate Tectonics
Volcanoes - Properties of Magma
Magma Composition
Magma varies in composition
and is classified according to the
amount of silica it contains. The
graphs show the average
composition of the two types of
magma. Use the graphs to
answer the questions.
Volcanoes - Properties of Magma
Magma Composition
Reading Graphs:
Study both graphs. What
materials make up both types
of magma?
Silica, other oxides, and other
solids.
Volcanoes - Properties of Magma
Magma Composition
Reading Graphs:
Which type of magma has
more silica? About how much
silica does this type of
magma contain?
Rhyolite-forming magma;
about 70 percent.
Volcanoes - Properties of Magma
Magma Composition
Estimating:
A third type of magma has a
silica content that is halfway
between that of the other two
types. About how much silica
does this type of magma
contain?
About 60 percent
Volcanoes - Properties of Magma
Magma Composition
Predicting:
What type of magma would
have a higher viscosity?
Explain.
Rhyolite-forming magma
would have higher viscosity
because it is higher in
silica.
Volcanoes - Properties of Magma
Identifying Main Ideas
As you read the section “Types of Viscosity of Magma,” write
the main idea in a graphic organizer like the one below. Then
write three supporting details that further explain the main
idea.
Main Idea
Magma’s viscosity depends on its physical and chemical properties.
Detail
Detail
Detail
Magma is made of
elements and of
compounds, among
them silica.
Viscosity is a
property of magma.
Viscosity depends
on silica content and
temperature.
Volcanoes - Properties of Magma
Links on the Properties of Magma
Click the SciLinks button for links on the
properties of magma.
Volcanoes
End of Section:
Properties of
Magma
Volcanoes - Volcanic Eruptions
Magma Reaches Earth’s Surface
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.
Volcanoes - Volcanic Eruptions
Composite Volcano Eruption Activity
Click the Active Art button to open a browser window and
access Active Art about composite volcano eruption.
Volcanoes - Volcanic Eruptions
Kinds of Volcanic Eruptions
Within the last 150 years, major volcanic eruptions have
greatly affected the land and people around them.
Volcanoes - Volcanic Eruptions
Using Prior Knowledge
Before you read, look at the section headings and visuals to
see what this section is about. Then write what you know
about volcanic eruptions in a graphic organizer like the one
below. As you read, write what you learn.
What You Know
1.
2.
3.
Lava flows out of a volcano.
Eruptions are not all the same.
Some volcanoes are dormant.
What You Learned
1.
2.
3.
Magma rises toward Earth’s surface through a pipe that leads to a
vent.
Differences in gas and silica content cause some eruptions to be
explosive and others to be quiet.
Dormant volcanoes can become active at any time.
Volcanoes
End of Section:
Volcanic
Eruptions
Volcanoes - Volcanic Landforms
Landforms From Lava and Ash
Volcanic eruptions create landforms made of lava, ash, and
other materials. These landforms include composite
volcanoes, shield volcanoes, cinder cone volcanoes, and
lava plateaus.
Volcanoes - Volcanic Landforms
Landforms From Lava and Ash
A caldera forms when an
volcano’s magma chamber
empties and the roof of the
chamber collapses. The
result is a large, bowlshaped caldera.
Volcanoes - Volcanic Landforms
Landforms From Magma
Features formed by magma include volcanic necks, dikes,
and sills, as well as batholiths and dome mountains.
Volcanoes - Volcanic Landforms
Batholiths
A batholith is a mass of rock formed
when a large body of magma cools
inside the crust. Several large batholiths
form the core of mountain ranges in
western North America. Half Dome in
Yosemite National Park, California, is
part of the Sierra Nevada batholith.
Volcanoes - Volcanic Landforms
Outlining
As you read, make an outline
about volcanic landforms that
you can use for review. Use
the red headings for the main
topics and the blue headings
for the subtopics.
Volcanic Landforms
I. Landforms From Lava and Ash
A. Shield Volcanoes
B. Cinder Cone Volcanoes
C. Composite Volcanoes
D. Lava Plateaus
E. Calderas
F. Soils From Lava and Ash
II. Landforms From Magma
A. Volcanic Necks, Dikes and
Sills
B. Dikes and Sills
C. Batholiths
D. Dome Mountains
III. Geothermal Activity
A. Hot Springs
B. Geysers
C. Geothermic Energy
Volcanoes - Volcanic Landforms
Links on Volcanic Effects
Click the SciLinks button for links on volcanic effects.
Volcanoes
End of Section:
Volcanic
Landforms
Volcanoes
Graphic Organizer
Volcanic
mountains
include
Shield
volcanoes
Composite
volcanoes
Cinder
cones
produce
produce
produce
Lava
Lava and
ash
Ash, cinders,
and bombs
Volcanoes
End of Section:
Graphic Organizer