Volcanoes
Table of Contents
Volcanoes and Plate Tectonics
Properties of Magma
Volcanic Eruptions
Volcanic Landforms
Volcanoes
Volcanoes and Plate Tectonics
1. What is a volcano?
It is a weak spot in the crust where
molten material, or magma, comes to the surface.
2. A molten mix of rock-forming substances, gases,
and water from the mantle is referred to as ____.
Magma
3. When magma reaches the surface, it is called
______.
Lava
Volcanoes - Volcanoes and Plate Tectonics
Many of Earth’s volcanoes are located along the
boundaries of tectonic plates. The Ring of Fire is a
belt of volcanoes that circles the Pacific Ocean.
What other regions have a large number of
volcanoes?
Volcanoes
Volcanoes and Plate Tectonics
4. What is the Ring of Fire?
It is a major volcanic belt formed by
the many volcanoes that rim the Pacific
Ocean.
5. Where do most volcanoes form?
They form along diverging plate
boundaries such as mid-ocean ridges and
along converging plate boundaries where
subduction takes place.
Volcanoes
Volcanoes and Plate Tectonics
6.
Describe how volcanoes form along the mid-ocean
ridges.
Along the rift valley, lava pours out of cracks in
the ocean floor, gradually building new mountains.
7.
Volcanoes can form along diverging plate
boundaries on land.
True
8. Many volcanoes form near converging plate
boundaries where oceanic crust returns to the
mantle.
True
Volcanoes
Volcanoes and Plate Tectonics
9. How does subduction at converging plate
boundaries lead to the formation of volcanoes?
When the older, denser plate sinks beneath a
deep-ocean trench into the mantle, some of the
rock above the subducting plate melts and forms
magma. Because the magma is less dense than the
surrounding rock it rises toward the surface.
Eventually, the magma breaks through the ocean
floor, creating volcanoes
Volcanoes
Volcanoes and Plate Tectonics
*** Volcanoes can also form where oceanic
crust is subducted beneath continental
crust.
10. Volcanoes at boundaries where two
oceanic plates collide create a string of
islands called an ______.
Island arc
Volcanoes
Volcanoes and Plate Tectonics
11. What are three major island arcs?
They are Japan, New Zealand,
Indonesia, the Philippines, the Aleutians, the
Caribbean Islands
12.Types of plates that collide to form the
Andes Mountain on the west coast of
South America.
* A continental plate and an ocean plate
Volcanoes - Volcanoes and Plate Tectonics
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 beneath a trench. Rock above the plate
melts to form magma, which then erupts to the
surface as lava.
Volcanoes
at
converging
boundaries
Volcanoes - Volcanoes and Plate Tectonics
Hot Spot Volcanoes: Eventually, the Pacific
plate’s movements will carry the island of
Hawaii away from the hot spot. Which island on
the map formed first?
Volcanoes
Volcanoes and Plate Tectonics
13.What is a hot spot?
It is an area where material from within
the mantle rises and melts, forming magma.
14. How did the Hawaiian Islands form?
They formed over millions of years as
the Pacific plate drifted over a hot spot.
15. Hot spots form only under oceanic crust.
False
Volcanoes
End of Section:
Volcanoes and
Plate Tectonics
Volcanoes
Properties of Magma
Main Idea
Magma’s viscosity depends on…
Detail: Magma is made of elements and
compounds, among them silica.
Detail: Viscosity is a property of magma.
Detail: Viscosity depends on silica content
and temperature.
Volcanoes
Properties of Magma
1. A substance cannot be broken down into other
substances is called an _____.
Element
2. When frozen water melts, it is undergoing a
physical change.
True
3. Statements that indicate a chemical property.
• When paper is burned, it forms ashes.
• An iron chair will develop rust if oxygen
combines with the iron.
Volcanoes
Properties of Magma
4.
The greater the viscosity, the _____ a liquid flows.
The ______ the viscosity, the more easily a liquid
flows.
Slower
Lower
5. Liquids that can have a low viscosity.
• Milk
• Orange Juice
6. What two factors determine the viscosity of magma?
Temperature and silica content
Volcanoes
Properties of Magma
7. Statement that are true about silica.
• Silica makes magma thicker.
• Silica produces a light colored lava.
8. The rock ______ forms from light-colored
lava.
Rhyolite
9. Low-silica magma forms rocks like ____.
Basalt
Volcanoes - Properties of Magma
What type of magma would have a higher
viscosity? Explain:
Volcanoes
Properties of Magma
Volcanoes
Properties of Magma
10.What happens to the viscosity as
temperature increases?
It decreases.
11. Hot fast moving lava is called ____.
pa hoe hoe
12. Cool, slow moving lava is called ____.
aa
Volcanoes
Properties of Magma
13.Chart:
High viscosity Magma is usually lower
in temperature and/or has a higher silica
content. Low viscosity magma usually has a
higher temperature and/or a lower silica
content.
A. Low
B. Lower
C. Higher
D. Lower
Volcanoes
Properties of Magma
13. e.
State the relationship between temperature and silica content
in magmas that have high viscosity and magmas that have
low viscosity.
The lower the temperature and the higher the
silica content of magma, the higher the viscosity. The
higher the temperature and the lower the silica content
of magma, the lower the viscosity of the magma.
Volcanoes
End of Section:
Properties of
Magma
Volcanoes
Volcanic Eruptions
What You Know
1. Lava flows out of a volcano.
2. Eruptions are not all the same.
3. Some volcanoes are dormant.
Volcanoes
Volcanic Eruptions
1. Magma forms in the lithosphere.
False-- asthenosphere
2. Liquid magma rises until it reaches the surface,
or until it becomes trapped beneath layers of rock.
True
3. Features that all volcanoes share.
A pocket of magma beneath the surface
A crack at the surface
Volcanoes - Volcanic Eruptions
4. A volcano
forms where
magma breaks
through the
Earth’s crust and
lava flows over
the surface.
a.
b.
c.
d.
Pipe
Crater
Vent
Magma chamber
Volcanoes
Volcanic Eruptions
5. What is a lava flow?
It is the area covered by lava as it pours out
of a vent.
6. Where does a crater form?
At the top of the volcano around the central
vent.
7. The pipe of a volcano is a horizontal crack in the
crust.
False – it is a long tube in the ground that
connects the magma chamber to the Earth’s
surface.
Volcanoes
Volcanic Eruptions
8. Complete the flowchart about how magma moves
through a volcano.
Lava flow
a. Crater
b. Vent
c. Pipe
d. Magma chamber
e. What does the graph show about where magma goes
after it leaves the pipes?
It goes to the vent.
Volcanoes
Volcanic Eruptions
9. Sentences that describe the best model of a
volcano erupting.
• Carbon dioxide dissolved in soda pop rushing
out when a soda pop is opened.
10. What happens during a volcanic eruption?
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
11. What factors determine the force of a volcanic
eruption?
The main factors are the magma’s silica content
and viscosity.
12. A volcano erupts quietly if it’s magma is thick
and sticky.
False -- explosively
13. Volcanic ash:
C- is made up of fine particles as small
as a grain of sand.
Volcanoes
Volcanic Eruptions
14. Cinders:
A- are pebble-sized particles.
15. Bombs:
B- are particles ranging from the size of
a baseball to the size of a car.
16. What is a pyroclastic flow?
It is an explosive eruption that hurls out a
mixture of hot gases, ash, cinders, and bombs.
Volcanoes
Volcanic Eruptions
17. Volcanic eruptions cause damage only when they are
close to the crater’s rim.
False
18. What kinds of damage can volcanoes cause?
Volcanic ash can bury entire towns. If it becomes wet,
the heavy ash can cause roofs to collapse. Eruptions can
cause landslides and avalanches of mud, melted snow and,
rock.
Volcanoes
Volcanic Eruptions\
19.The activity of a volcano may last from
less than a decade to more than 10
million years.
True
20.Most long-lived volcanoes erupt
continuously.
False
Volcanoes
Volcanic Eruptions
21. Complete the compare/contrast table.
a. An extinct volcano is very unlikely to erupt ever
again.
b. An active volcano is erupting or showing signs
that it will soon erupt.
c. A dormant volcano is no longer active, but may
become active again.
d. Rank the volcanic stages from least likely to
erupt to most likely to erupt:
extinct, dormant, active
Volcanoes - Volcanic Eruptions
Within the last 150 years major volcanic
eruptions have greatly affected the land and
people around them.
Volcanoes
Volcanic Eruptions
22. The length of time between eruptions of a dormant
volcano is always less than a thousand years.
False– it is unknown
23. Why might people living near a dormant volcano
may be unaware of the danger?
The time between volcanic eruptions may span
hundreds to many thousands of years.
24. Sentences true about predicting volcanic eruptions.
• Geologists are more successful in predicting volcanic
eruptions than earthquakes.
• Geologists cannot predict what type of eruption a
volcano will produce.
Volcanoes
End of Section:
Volcanic
Eruptions
Volcanoes
Volcanic Landforms
I.
Landforms From Lava and Ash
A.
B.
C.
D.
E.
F.
Shield Volcanoes
Cinder Cone Volcanoes
Composite Volcanoes
Lava Plateaus
Calderas
Soils from Lava and Ash
Volcanoes
Volcanic Landforms
II. Landforms from Magma
A. Volcanic necks
B. Dikes and Sills
C. Batholiths
D. Dome Mountains
III. Geothermal Activity
A. Hot Springs
B. Geysers
C. Geothermal Energy
Volcanoes - Volcanic Landforms
Volcanic activity is responsible for forming lava
plateaus.
Volcanoes
Volcanic Landforms
1. List four landforms created from lava and ash.
a. shield volcanoes
b. cinder cone volcanoes
c. composite volcanoes
d. lava plateaus
2. Sentences true about shield volcanoes.
• They form from many thin layers of lava.
• They result from quiet eruptions.
3. The Hawaiian Islands are cinder cone volcanoes.
False – shield volcanoes
Volcanoes
Volcanic Landforms
4. Name two examples of composite volcanoes.
• Mount Fuji in Japan
• Mount St. Helens in Washington State.
5. A composite volcano has both quiet and
explosive eruptions.
True
6. Shield volcano:
E- is a gently sloping mountain formed
by repeated lava flows.
Volcanoes
Volcanic Landforms
7. Cinder cone volcanoes:
C- Cone-shaped mountains formed
from ash, cinders, and bombs were once.
8. Composite volcano:
B- A mountain formed by lava flows
alternating with explosive eruptions is a.
9. Lava plateau:
A- is a high, level area formed by
repeated lava flows.
Volcanoes
10. Caldera:
D- is a hole left by the collapse of a
volcanic mountain.
11. When volcanic ash breaks down, it releases
_____ and, _____ both of which are needed by
plants.
Potassium
Phosphorus
Volcanoes
Volcanic Landforms
12. List five features formed by magma.
a. volcanic necks
b. dikes
c. sills
d. batholiths
e. dome mountains
Volcanoes - Volcanic Landforms
1 The top of a composite volcano explodes.
Lava flows partially empty the magma
chamber.
2 The roof of the
magma chamber
collapses, forming
a caldera
Volcanoes - Volcanic Landforms
Magma that hardens beneath the surface may
form volcanic necks, dikes, and sills. A dike
extends outward from Ship Rock, a volcanic
neck in New Mexico.
What is the difference between a dike and a sill?
Volcanoes
Volcanic Landforms
13. Complete the Venn Diagram:
• A dike forms across rock layers.
• A sill forms between rock layers.
• Both a dike and a sill forms from magma.
14. A mass of rock formed when a large body of
magma cools inside the crust is called a ______.
Batholith
15. What is an example of a batholith in the United
States?
The Sierra Nevada Mountains in California.
Volcanoes - Volcanic Landforms
Batholiths
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
16. A dome mountain forms when rising magma is
blocked by horizontal layers of rock.
True
17. Some types of volcanic activity do not involve
the eruption of lava.
True
18. When groundwater is heated by a nearby body
of magma rises to the surface and collects in a
natural pool, it is called a ____.
Hot springs
Volcanoes
Volcanic Landforms
19. A fountain of water and steam that erupts from
the ground is referred to as a ____.
Geyser
20. How can geothermal energy be converted to
electricity?
Steam from underground is piped into
turbines. Inside a turbine, the steam spins a wheel.
The moving wheel in the turbine turns a generator
that turns mechanical energy into electrical energy.
Volcanoes
Volcanic Landforms
• Key Terms:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
Magma
Crater
Silica
Pahoehoe
Aa
Geyser
Volcano
Lava
Active
Caldera
Extinct
Batholith
Dike
Sills
Volcanoes
End of Section:
Volcanic
Landforms