Transcript Living Things - Mountain View Middle School

Chapter 6 Volcanoes
Table of Contents
Chapter Preview
6.1 Volcanoes and Plate Tectonics
6.2 Volcanic Eruptions
6.3 Volcanic Landforms
6.4 California Geology
Chapter 6 Volcanoes
Chapter Preview Questions
1. Igneous rocks form when
a. sediment is compacted and cemented.
b. rocks are changed by heat and pressure.
c. sediment is heated and cooled.
d. lava and magma cool and harden.
Chapter 6 Volcanoes
Chapter Preview Questions
1. Igneous rocks form when
a. sediment is compacted and cemented.
b. rocks are changed by heat and pressure.
c. sediment is heated and cooled.
d. lava and magma cool and harden.
Chapter 6 Volcanoes
Chapter Preview Questions
2. Melted material that erupts from a volcano is called
a. magma.
b. sediment.
c. lava.
d. mica.
Chapter 6 Volcanoes
Chapter Preview Questions
2. Melted material that erupts from a volcano is called
a. magma.
b. sediment.
c. lava.
d. mica.
Chapter 6 Volcanoes
Chapter Preview Questions
3. Why do volcanoes erupt?
a. They are hot and fiery.
b. They form beneath the ocean floor.
c. Gases in magma expand as it rises to the surface.
d. Lava is a pure liquid.
Chapter 6 Volcanoes
Chapter Preview Questions
3. Why do volcanoes erupt?
a. They are hot and fiery.
b. They form beneath the ocean floor.
c. Gases in magma expand as it rises to the surface.
d. Lava is a pure liquid.
Chapter 6 Volcanoes
Chapter Preview Questions
4. Which of these does NOT rapidly change Earth’s
land surface?
a. earthquakes
b. mountain building
c. landslides
d. volcanic eruptions
Chapter 6 Volcanoes
Chapter Preview Questions
4. Which of these does NOT rapidly change Earth’s
land surface?
a. earthquakes
b. mountain building
c. landslides
d. volcanic eruptions
Chapter 6 Volcanoes
What causes volcanoes, and how do they change
Earth’s surface?
You know that if you want to open a
bottle of soda, you must do so
carefully. Otherwise, the soda might
spray out of the bottle as soon as you
loosen the cap. What causes the
soda to rush out with such force?
How is this similar to what happens
when a volcano erupts? Explain.
Chapter 6 Volcanoes
Use Clues to Determine Meaning
Unfamiliar words
Some volcanoes result from hot spots in Earthís mantle. A hot spot
is an area where material from within the mantle rises and then
melts. A volcano forms above a hot spot when the hot material
erupts through the crust and reaches the surface.
A hot spot in the ocean oor can gradually form a series of volcanic
mountains. For example, the Hawaiian Islands formed one by one
over millions of years as the Pacific plate drifted over a hot spot.
Example
Hot spot is
the subject of
the sentence.
Definition,
follows boldface
Explanation
Chapter 6 Volcanoes
Apply It!
Review the clues to the meaning of hot spot. Then complete the following.
1. What clue tells you that hot spot might be followed by a definition?
The term is in boldface and is the subject of the sentence.
2. What example helps you understand hot spots?
The Hawaiian Islands formed one by one over millions of years as the
Pacific plate drifted over a hot spot
Chapter 6 Volcanoes
End of Chapter
Preview
Describe what
happens along a fault
beneath Earth’s
surface when an
earthquake occurs?
How do volcanoes
change the land?
Volcanoes
Chapter 6 Volcanoes
Section 1:
Volcanoes and Plate
Tectonics
Where are most of Earth’s volcanoes found?
How do hot spot volcanoes form?
A volcano is a weak spot in the crust where molten
material, or magma, comes to the surface.
Magma is molten material that has not reached the surface and is
still underground.
Lava is molten material, or magma, that has reached the surface.
Ring of Fire is a major volcanic belt that rims or circles
the Pacific Ocean.
Island Arc is a string of islands formed by weak spots
or hot spots in the crust where magma burns through.
Chapter 6 Volcanoes
Volcanoes and Plate Boundaries
Volcanic belts form along the boundaries of Earth’s plates.
Chapter 6 Volcanoes
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.
Chapter 6 Volcanoes
Hot Spot Volcanoes
A volcano forms above a hot spot when magma erupts
through the crust and reaches the surface.
Chapter 6 Volcanoes
More on Volcanoes
Click the PHSchool.com button for an activity
about volcanoes.
Chapter 6 Volcanoes
End of Section:
Volcanoes and
Plate Tectonics
What causes volcanoes
to form at a spreading
boundary?
Where are most of
Earth’s volcanoes
found? Explain.
Describe the order of
parts through which
magma travels as it
moves to the surface.
Which is more likely to
be dangerous – a
volcano that erupts
frequently or a volcano
that has been inactive
for a hundred years?
Why?
Chapter 6 Volcanoes
Section 2:
Volcanic Eruptions
What happens when a volcano erupts?
What are the two types of volcanic eruptions?
What are a volcano’s stages of activity?
Volcanic
Eruptions
Chapter 6 Volcanoes
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.
Chapter 6 Volcanoes
Magma Reaches Earth’s Surface
Magma chamber is a
pocket beneath a
volcano where magma
is collected or stored.
Chapter 6 Volcanoes
Magma Reaches Earth’s Surface
Pipe is a long tube
inside a volcano that
connects the magma
chamber to the Earth’s
surface.
Chapter 6 Volcanoes
Magma Reaches Earth’s Surface
Vent is an opening
through which molten
rock and gas leave the
volcano.
Chapter 6 Volcanoes
Magma Reaches Earth’s Surface
Lava flow is the area
covered by lava as it
pours out of a vent.
Chapter 6 Volcanoes
Magma Reaches Earth’s Surface
Crater is a bowlshaped area that may
form at the top of a
volcano.
Chapter 6 Volcanoes
Magma Reaches Earth’s Surface
Pahoehoe is a very thin,
fast moving lava.
Pahoehoe contains low
amounts of silica, which
gives it it’s thinness. When
Pahoehoe hardens, it
forms wrinkle and ropelike rock formations.
Pahoehoe is hotter than
Aa.
Chapter 6 Volcanoes
Magma Reaches Earth’s Surface
Aa is a very thick, slow moving lava.
Aa contains high amounts of silica,
which gives it it’s thickness. When
aa hardens, it forms a rough surface
consisting of jagged (sharp) lava
chunks.
Chapter 6 Volcanoes
Magma Reaches Earth’s Surface
Pyroclastic flow is
an explosive
eruption that
includes hot gases,
cinders (volcanic
ash), and bombs
(volcanic rocks).
Chapter 6 Volcanoes
Composite Volcano Eruption Activity
Click the Active Art button to open a browser window and
access Active Art about composite volcano eruption.
Chapter 6 Volcanoes
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.
Chapter 6 Volcanoes
Magma Composition
Reading Graphs:
Study both graphs. What
materials make up both types
of magma?
Silica, other oxides, and other
solids.
Chapter 6 Volcanoes
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.
Chapter 6 Volcanoes
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
Chapter 6 Volcanoes
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.
Chapter 6 Volcanoes
Kinds of Volcanic Eruptions
Within the last 150 years, major volcanic eruptions have
greatly affected the land and people around them.
Deadly Eruptions
Chapter 6 Volcanoes
Stages of Volcanic Activity
Active volcanoes are considered “live” meaning that it is erupting,
or has shown signs that it may erupt in the near future
Mount Shasta
Lassen Peak
Chapter 6 Volcanoes
Stages of Volcanic Activity
Dormant volcanoes are considered “asleep” or “sleeping bears”
meaning that they may become active in the future
Long Valley
Craters
Chapter 6 Volcanoes
Stages of Volcanic Activity
Extinct volcanoes are considered “dead” meaning that it is
unlikely that they will erupt again
St. Lucia
Auckland
Chapter 6 Volcanoes
End of Section:
Volcanic Eruptions
Chapter 6 Volcanoes
Section 3:
Volcanic Landforms
What landforms do lava and ash create?
How does magma that hardens beneath the
surface create landforms?
Types of Volcanoes
Chapter 6 Volcanoes
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.
Chapter 6 Volcanoes
Landforms From Lava and Ash
Composite Volcanoes have quiet eruptions that alternate
with explosive eruptions, forming layers of lava and ash.
Cotopaxi, Ecuador
Mayon, Philippines
Chapter 6 Volcanoes
Landforms From Lava and Ash
Shield Volcanoes have quiet eruptions and have gentle
slopes, which are not steep.
Mauna Loa, Hawaii
Erta Ale, Ethiopia
Chapter 6 Volcanoes
Landforms From Lava and Ash
Cinder Cone Volcanoes have explosive eruptions of ash,
cinders, and bombs that form a cone-shaped hill.
Mount Etna, Italy
SP Crater, Arizona
Chapter 6 Volcanoes
Landforms From Lava and Ash
Lava Plateaus are formed from runny lava (pahoehoe) that
cools in flat sheets of rock. Over time these layers form high
plateaus.
Steamboat Rock,
Washington
Hawaii
Chapter 6 Volcanoes
Landforms From Lava and Ash
Calderas are formed when a magma chamber is emptied
after an eruption and the volcano mountain collapses into the
empty space creating a crater.
Aniakchak, Alaska
Crater Lake, Oregon
Chapter 6 Volcanoes
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.
Chapter 6 Volcanoes
Landforms From Magma
Features formed by magma include volcanic necks, dikes,
and sills, as well as batholiths and dome mountains.
Chapter 6 Volcanoes
Landforms From Magma
Batholiths
Chapter 6 Volcanoes
Landforms From Magma
Volcanic Necks
Chapter 6 Volcanoes
Landforms From Magma
Dikes
Chapter 6 Volcanoes
Landforms From Magma
Sills
Chapter 6 Volcanoes
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.
Chapter 6 Volcanoes
Links on Volcanic Effects
Click the SciLinks button for links on volcanic effects.
Chapter 6 Volcanoes
End of Section:
Volcanic Landforms
Chapter 6 Volcanoes
Section 4:
California Geology
How does plate tectonics help to explain
features of California’s geology?
Chapter 6 Volcanoes
Plate Tectonics and California
The movements of three plates have shaped the geologic
features of California over millions of years.
Chapter 6 Volcanoes
Plate Tectonics and California
Many geologic processes
worked together to form
California’s landscape
of volcanoes, faults,
mountain ranges, and
basins.
Chapter 6 Volcanoes
End of Section:
California Geology
Chapter 6 Volcanoes
Chapter 6 Volcanoes
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