Transcript ESChap18Volcanoes

Volcanic Activity
Chap. 18
Notes:
Magma
Intrusive Activity
Volcanoes
Resources:
Section Assessments
Practice Test Questions
Magma
I. What it’s made of
I. What it’s made of
I. What it’s made of
A. Molten rock
I. What it’s made of
A. Molten rock
B. Suspended crystals of minerals
I. What it’s made of
A. Molten rock
B. Suspended crystals of minerals
C. Dissolved gases
I. What it’s made of
II. Factors that affect melting
rock
I. What it’s made of
II. Factors that affect melting
rock
A. Pressure
I. What it’s made of
II. Factors that affect melting
rock
A. Pressure
B. Temperature
I. What it’s made of
II. Factors that affect melting
rock
A. Pressure
B. Temperature
C. Water content
I. What it’s made of
II. Factors that affect melting
rock
A. Pressure
B. Temperature
C. Water content
D. A graph
What is the relationship between depth
and pressure?
For dry albite, the greater the depth the
_________ the melting temperature.
Which type of albite, wet or dry, tends to
melt at lower temperatures
I. What it’s made of
II. Factors that affect melting rock
III. Viscosity
Resistance to flow
I. What it’s made of
II. Factors that affect melting rock
III. Viscosity
A. Depends on _________
I. What it’s made of
II. Factors that affect melting rock
III. Viscosity
A. Depends on _________
B. Depends on _________
I. What it’s made of
II. Factors that affect melting rock
III. Viscosity
IV. Types of magma
I. What it’s made of
II. Factors that affect melting rock
III. Viscosity
IV. Types of magma
A. basaltic
B. andesitic
C. rhyolitic
Basaltic
Dark colored
Andesitic
Rhyolitic
Lighter colored
Basaltic
Andesitic
Low viscosity
Lighter colored
Intermediate
Dark colored
Rhyolitic
Higher viscosity
Basaltic
Andesitic
Low viscosity
Low silicon content
(about 50%)
Lighter colored
Intermediate
Dark colored
Rhyolitic
Higher viscosity
Higher silicon
(about 70%)
Basaltic
Andesitic
Low viscosity
Low silicon content
(about 50%)
Little dissolved gas
(1-2%)
Lighter colored
Intermediate
Dark colored
Rhyolitic
Higher viscosity
Higher silicon
(about 70%)
Higher amount of
trapped gas (4-6%)
Basaltic
Andesitic
Low viscosity
Low silicon content
(about 50%)
Lighter colored
Intermediate
Dark colored
Rhyolitic
Higher viscosity
Higher silicon
(about 70%)
Little dissolved gas
(1-2%)
Higher amount of
trapped gas (4-6%)
Less violent eruptions
More violent
eruptions
Basaltic
Andesitic
Low viscosity
Low silicon content
(about 50%)
Little dissolved gas
(1-2%)
Less violent eruptions
Lighter colored
Intermediate
Dark colored
Rhyolitic
Higher viscosity
Higher silicon
(about 70%)
Higher amount of
trapped gas (4-6%)
More violent
eruptions
Ex. Mt. Kilauea, Ex. Mt. St. Helens Ex. Yellowstone
Mt. Pu’ u O’o,
The End
Intrusive Activity
I. Plutons
Intrusive igneous rock bodies formed
under Earth’s crust
I. Plutons
A. Batholiths
Batholiths
Largest of the plutons (many
hundreds of kilometers)
Batholiths
Largest of the plutons (many
hundreds of kilometers)
Form inside mountains
Batholiths
Largest of the plutons (many
hundreds of kilometers)
Form inside mountains
Form coarse-grained rocks
Batholiths
Ex. Yosemite
I. Plutons
B. Stocks
Stocks
Like batholiths, but smaller
Irregular shape
I. Plutons
C. Laccoliths
Laccoliths
Intrude into rock layers
Form mushroom shaped plutons
Smaller than batholiths and stocks
Laccoliths
Ex. Bear Butte, SD
I. Plutons
D. Sills
Sills
Magma squeezes into cracks
Forms parallel to parent rock
May be cm. to hundreds of cm. thick
Sill
Ex. Palisades, NJ
I. Plutons
E. Dike
Dike
Like a sill but it cuts across rock layer
Transports magma
Dike
Ex. Radial Dike, NM
The End
Volcanoes
Krafla, Iceland
I. Parts of a volcano
I. Parts of a volcano
A. Vent
Opening in the Earth’s crust that carries
lava to the surface
I. Parts of a volcano
A. Vent
B. Crater
Bowl shaped depression at the top of a
volcano.
I. Parts of a volcano
A. Vent
B. Crater
Crater Lake, Oregon
C. Caldera
Volcanic depression that forms above the magma
chamber when the ground above sinks
How a caldera
forms
II. Types of Volcanoes
A. Shield Volcano
Mauna Loa, Hawaii
Broad, flat volcano that forms from
basaltic magma.
II. Types of Volcanoes
B. Cinder-Cone Volcano
Cinder Cone, California
Small, steep volcano that forms when ejected
material falls back near the volcano’s vent
II. Types of Volcanoes
C. Composite Volcano (Stratovolcano)
Java, Indonesia
Large, steep volcano composed of alternating
layers of lava and volcanic fragments.
Comparison of Volcano Types
III. Volcanic Material
III. Volcanic Material
A. Tephra
Rock fragments thrown in the air during a
volcanic eruption.
III. Volcanic Material
A. Tephra
1.
Dust - less than 0.25 mm
III. Volcanic Material
A. Tephra
1.
Dust - less than 0.25 mm
2.
Ash – less than 2 mm
III. Volcanic Material
A. Tephra
1.
Dust - less than 0.25 mm
2.
Ash – less than 2 mm
3.
Lapilli (little stones) – less than 64 mm
III. Volcanic Material
A. Tephra
1.
Dust - less than 0.25 mm
2.
Ash – less than 2 mm
3.
Lapilli (little stones) – less than 64 mm
4.
Volcanic block – large angular fragment
III. Volcanic Material
A. Tephra
1.
Dust - less than 0.25 mm
2.
Ash – less than 2 mm
3.
Lapilli (little stones) – less than 64 mm
4.
Volcanic block – large angular fragment
5.
Volcanic bombs – rounded blobs
III. Volcanic Material
A. Tephra
B. Pyroclastic flow
Clouds of gas, ash, and tephra that travel
rapidly down a volcano.
IV. Location of Volcanoes
IV. Location of Volcanoes
A. Convergent Boundaries
80% of volcanoes. These regions are the
Circum-Pacific and Mediterranean belts.
IV. Location of Volcanoes
A. Convergent Boundaries
B. Divergent Boundaries
Smaller percentage of volcanoes form here.
Most, except Iceland, are under the sea.
IV. Location of Volcanoes
A. Convergent Boundaries
B. Divergent Boundaries
C. Hot Spots
Unstable hot regions of the Earth’s mantle where
high-temperature plumes rise toward surface
Analyzing Hot Spots
The End
Section Assessments
Section Assessment – 18.1
 1. Match the magma types with their
A. intermediate viscosity
characteristics.
content, forms from oceanic
B basaltic

___
crust and oceanic sediments
B. low viscosity and gas content,
A andesitic

___
forms from rocks in the upper
mantle

___
C rhyolitic
C. high viscosity, forms from
continental crust materials
Section Assessment – 18.1
2. What would be the likely effect if the volcano at
Yellowstone National Park were to erupt? Why?
It would most likely be a devastating eruption
because it would be fueled by rhyolitic magma,
which has a very high viscosity and gas content.
Section Assessment – 18.1
3. Identify whether the following statements are
true or false.
______
true It is unlikely that Mount Kilauea in Hawaii
will explosively erupt.
true Wet granite will melt at a lower temperature
______
than dry granite.
false A liquid with a high viscosity will also have a
______
high flow rate.
true
______ Major eruptions of Mount St. Helens in
Washington state and Mount Fuji in Japan
would probably be similar in nature.
Section Assessment – 18.2
1. Match the following terms with their
A. a pluton that forms when
definitions.
___
D batholith
___
B stock
___
E laccolith
___
A sill
___
C dike
magma intrudes parallel to
layers of rock
B. an irregularly shaped pluton
that is similar to a batholith but
smaller in size
C. a pluton that cuts across
preexisting rocks
D. an irregularly shaped pluton
that covers at least 100 km2
E. a mushroom-shaped pluton
with a round top and flat bottom
Section Assessment – 18.2
2. How do sills and laccoliths differ?
Sills and laccoliths both result from magma
intrusions that are parallel to existing rock.
Laccoliths push the overlying layers upward,
creating a distinct mushroom-shape when they
cool and solidify. Sills are generally thinner and
do not cause a noticeable bump in the surface.
Section Assessment – 18.2
3. What surface feature are batholiths most
associated with?
Batholiths are found at the cores of many of
Earth’s mountain ranges.
Section Assessment – 18.3
1. Match the following terms with their
A. an opening in the crust from
definitions.
which lava flows
___
A vent
___
C crater
___
D tephra
___
E pyroclastic flow
___
B caldera
B. depression caused by a
collapsed magma chamber
C. a bowl-shaped depression
around an opening in the crust
D. volcanic materials that are
thrown into the air during a
volcanic eruption
E. a cloud of rapidly moving,
extremely hot volcanic material
Section Assessment – 18.3
2. How can chains of volcanoes that form over a
hot spot track plate movement?
The hot spot is in a fixed location. All of the
volcanoes in the chain were over the hot spot
when they formed. The volcanoes’ movement
and the direction of the chain’s alignment
indicates the movement of the plate.
Section Assessment – 18.3
3. Identify whether the following statements are
true or false.
______
true Many cinder-cone volcanoes are less
than 500 m high.
______
false Volcanism is more common along divergent
boundaries as compared to convergent boundaries.
______
false The Mediterranean Belt is also known as the
“Ring of Fire”.
______
true It can be 700ºC in the center of a pyroclastic flow.
The End