Download Volcanic Eruptions On a separate sheet of paper, explain what an

Volcanic Eruptions
On a separate sheet of paper, explain what an active volcano is and how it affects Earth’s
surface.
145C
Name
Date
Class
Volcanic Eruptions
Understanding Main Ideas
Answer the following questions on a separate sheet of paper.
1. Why does magma in the mantle rise through the crust above it?
2. As magma rises toward the surface, what happens to the gases in it?
Why?
3. Contrast the silica content of magma in quiet and explosive
eruptions.
4. How does an explosive eruption produce pyroclastic flow?
5. Identify two hazards of a quiet volcanic eruption.
6. Describe the stages of volcanic activity.
Building Vocabulary
Label the figure below with the names of a volcano’s parts.
9.
8.
10.
7.
11.
145D
Name
Date
Class
Volcanic Eruptions
Read the passage and study the table. Then use a separate sheet of paper to answer the
questions that follow the table.
Pegmatites
Can you imagine a mineral crystal as big as a truck? Such crystals do exist. They sometimes are found
in pegmatites, which are a type of mineral deposit. Pegmatites form from low-viscosity, watery magma.
Viscosity refers to a fluid’s resistance to flow. High-viscosity magma is thick and flows slowly.
Low-viscosity magma is thin and flows more quickly.
As magma cools and starts to harden beneath Earth’s surface, the magma that’s left becomes more and
more watery. This extra water lowers the viscosity of the magma, which makes it more fluid. In some
cases, the last magma to harden can have a large amount of water in it. In the more watery magma,
atoms are able to move long distances. These atoms become concentrated in the water magma and
combine to form large crystals. Some of these large crystals found in pegmatites include gems and rare
elements.
Some Important Pegmatites in the United States
Location
Characteristic
Black Hills, South Dakota
Contains crystals more than 10 m long
Petaca, New Mexico
Contains the mineral uraninite, an ore of uranium
Oxford County, Maine
Deposit is mined to obtain lithium, a rare mineral
Kings Mountain, North Carolina
Includes gem-quality minerals, such as aquamarine
1. What effect does water have on the viscosity of magma?
2. How do the crystals in pegmatites form?
3. According to the table, which pegmatite in the United States contains
uranium ore?
4. Which pegmatite has a lot of aquamarine, a valuable gem?
5. Why are pegmatites important to society?
145E
Name
Date
Class
Volcanic Eruptions
Write the letter of the correct answer on the line at the left.
1.
Which of the following is an opening
through which molten rock and gas leave a
volcano?
A pipe
B magma chamber
C crater
D vent
2.
A volcano erupts quietly if its
magma is which of the following?
A cool
B solid
C low in silica
D high in silica
3.
What do geologists call a volcano that is
not likely to erupt ever again?
A extinct
B dormant
C sleeping
D active
4.
From what kind of lava does
pahoehoe form?
A cool
B runny
C thick
D slow-moving
Fill in the blank to complete each statement.
5. A(n)
lava that pours out
of a volcano.
is the spread of
6. The elements oxygen and silicon form
magma.
, a material found in
7. Geologists say a volcano is
future.
if it is expected to awaken in the
8. A mixture of hot gases, ash, cinders, and
bombs that erupt explosively are called a(n)
flow.
9. Geologists classify volcanic eruptions as
quiet or
.
10. A(n)
pocket of magma beneath the
surface.
is a