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Earth Science
Chapter 18
Worksheet 1
Name ____________________________
Block ____________________________
Match the definitions to the correct word or term
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1. Plutons
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2. Dike
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3. Tephra
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4. Stock
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5. Hot spot
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6. Caldera
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7. Viscosity
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8. Composite volcano
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9. Vent
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10. Cinder-cone volcano
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11. Laccolith
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12. Pyroclastic flow
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13. Crater
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14. Batholith
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15. Shield volcano
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16. Sill
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17. Volcanism
____
____
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18. Flood basalt
19. Fissure
20. Conduit
A. Relatively small, mushroom shaped pluton that forms when
magma intrudes into parallel rock layers close to Earth’s surface
B. Coarse-grained, irregularly shaped, igneous rock mass that
covers at least 100km2
C. Pluton that forms when magma intrudes parallel rock layers
D. Steep-sided, generally small volcano that is built up by the
accumulation of tephra around the vent
E. Opening in Earth’s crust through which lava erupts and flows out
onto the surface
F. Bowl shaped depression that forms around the central vent at
the summit of a volcano
G. Rock fragments that are thrown into the air during a volcanic
eruption and fall to the ground
H. Intrusive igneous rock bodies formed through mountain-building
processes and oceanic-oceanic collisions
I. Pluton that cuts across preexisting rocks and often forms when
magma invades cracks in surrounding rock bodies
J. Broad volcano with gently sloping sides built by nonexplosive
eruptions of basaltic lava that accumulates in layers
K. A substance’s internal resistance to flow
L. Large, sloping volcano built by violent eruptions of volcanic
fragments and lava that accumulate in alternating layers
M. Irregularly shaped pluton that is similar to a batholith, but smaller
and cuts across older rocks
N. Swift-moving, potentially deadly clouds of ash, gas, and other
volcanic material produced by a violent eruption
O. Large crater that can form when the summit or side of a volcano
collapses into the magma chamber during or after an eruption
P. Unusually hot area in Earth’s mantle where plumes of mantle
material rise toward the surface
Q. Describes all the processes associated with the discharge of
magma, hot water, and steam
R. Huge amounts of lava that erupt from fissures
S. A long crack in Earth’s crust
T. A tubelike structure that allows lava to reach the surface
Circle the letter that corresponds to the correct answer
21. Which of the following does not play a role in magma formation?
a. Temperature
b. Pressure
c. Presence of water
d. Tephra type
22. Which of the following is true?
a. An increase in pressure results in a higher melting temperature of a dry substance
b. A decrease in pressure increases the temperature at which a dry substance melts
c. The addition of water increases the melting temperature of a substance
d. An increase in pressure decreases the melting temperature of a dry substance
23. Which of the following melts to form rhyolitic magma?
a. Continental crust
b. Oceanic crust
c. Oceanic sediment
d. The upper mantle
24. Which type of pluton is completely parallel to the rock layers into which it intrudes?
a. Dike
b. Sill
c. Laccolith
d. Stock
25. The Hawaiian volcanoes formed as a result of which of the following?
a. Divergence
b. A hot spot
c. Subduction
d. Subsidence
26. Which of the following is not true?
a. An increase in silica increases the viscosity of a magma
b. Andesitic magma has both an intermediate gas content and explosiveness
c. An increase in temperature increases a magma’s viscosity
d. Basaltic magma has a low viscosity and contains little gas
27. Which of the following has broad, gently sloping sides and a circular base?
a. Hot spot
b. Cinder-cone volcano
c. Composite volcano
d. Shield volcano
In the space at the left, write the word in parentheses that makes the statement correct
_______________
28. The hotter the magma or lava, the (greater, lower) is its viscosity
_______________
29. Lava that has low viscosity moves (slower, faster) than lava with high
viscosity
_______________
30. Temperature and pressure (increase, decrease) with depth beneath
Earth’s surface
_______________
31. The temperature at which a substance melts (increases, decreases) with
the presence of water
_______________
32. Rhyolitic magma forms beneath (continental, oceanic) crust
_______________
33. Cinder-cone volcanoes have steep sides and are generally the (largest,
smallest) volcanoes
_______________
34. Volcanoes associated with (divergent, convergent) plate boundaries form
the Circum-Pacific and the Mediterranean Belts
_______________
35. (Laccoliths, Dikes) are plutons that cause overlying rocks to bow upward
_______________
36. (Shield, Composite) volcanoes are made of basaltic lava
_______________
37. Most of the world’s rift volcanism occurs at (divergent, convergent)
boundaries
Circle T if the statement is true or F if the statement is false
T
F
38. 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
T
F
39. Rhyolitic magma-fueled volcanoes are especially explosive because rhyolitic magma is
highly viscous and contains a large volume of trapped gas
T
F
40. The higher the silica content in lava, the higher the lava’s resistance to flow
T
F
41. Many plutons formed as a result of mountain-building processes that occurred along
divergent plate boundaries
T
F
42. The volcanoes in the Circum-Pacific Belt form as a result of magma rising upward in
faults and fractures that form as tectonic plates diverge
Answer the following questions
43. Describe the three factors that affect the formation of magma
44. Discuss three ways in which magma affects the crust into which it intrudes
45. What is a volcanic crater, and how does it differ from a caldera?