Name:
Period:
Volcanism
Match the definition in Column A with the term in Column B.
Column A
Column B
________
1. Volcanic fragments thrown into air during a volcanic eruption
________
________
________
2. Internal resistance to flow
3. Intrusive igneous rock body
4. Opening in Earth's crust through which lava erupts
________
5. Bowl-shaped depression around a vent at the top of a
volcano
________
6. Depression that forms when the top or side of a volcano
collapses into the magma chamber
a. caldera
b. vent
c. viscosity
d. pluton
e. tephra
f.
crater
Compare and contrast each pair of related terms.
7. Caldera, crater
8. sill, laccolith
In the space at the left, write the word in parentheses that makes the statement correct.
____________________ 1. The hotter the magma or lava, the (greater, lower) is its viscosity.
____________________ 2. Lava that has low viscosity moves (slower, faster) than lava with
high viscosity.
____________________ 3. Temperature and pressure (increase, decrease) with depth
beneath Earth's surface.
____________________ 4. The temperature at which a substance melts (increases,
decreases) with the presence of water.
____________________ 5. Rhyolitic magma forms beneath (continental, oceanic) crust.
____________________ 6. Cinder-cone volcanoes have steep sides and are generally the
(largest, smallest) volcanoes.
____________________ 7. Volcanoes associated with (divergent, convergent) plate
boundaries form the Circum-Pacific and the Mediterranean Belts.
____________________ 8. (Laccoliths, Dikes) are plutons that cause overlying rocks to bow
upward.
____________________ 9. (Shield, Composite) volcanoes are made of basaltic lava.
____________________ 10. Most of the world's rift volcanism occurs at (divergent, convergent)
boundaries.
In the space at the left, write true if the statement is true; if the statement is false, change
the italicized word or phrase to make it true.
______________ 11. The fact that most of the rocks in Earth's lower crust and upper mantle do
not melt to form magma, even though the temperatures there are high enough, is explained by
the effect of water.
______________ 12. Rhyolitic magma-fueled volcanoes are especially explosive because
rhyolitic magma is highly viscous and contains a large volume of trapped gas.
______________ 13. The higher the silica content in lava, the higher the lava's resistance to
flow.
______________ 14. Many plutons formed as a result of mountain-building processes that
occurred along divergent plate boundaries.
______________ 15. The volcanoes in the Circum-Pacific Belt form as a result of magma rising
upward into faults and fractures that form as tectonic plates diverge.
Answer the following questions.
1. Compare and contrast magma and lava.
2. Contrast the three major types of volcanoes.
Thinking Critically
Answer the following questions.
1. For thousands of years, people have operated farms at the bases of active volcanoes in
spite of the risks. What might be the reason for this?
2. Pumice is an igneous rock. It is porous and floats on water. What conclusion can you
draw about the volume of gases present in the lava that forms pumice?
3. Why does lava containing large amounts of dissolved gases generally produce a more
violent explosion than lava that contains small amounts of dissolved gases?
Answer questions 1.4
1. How does magma move from a chamber deep within Earth to Earth's surface?
2. What is a mushroom-shaped pluton with a round top and flat bottom called?
3. What are sills and how do they form?
4. How do dikes form?