Chapter 7-Study Questions
Multiple Choice:Select the best answer to complete the
statement.
___1. Which of the following is NOT a primary factor that
affects the viscosity of magma?
a. composition b. age c. temperature
d. dissolved gases e. a and b
___2. Which one of the following provides the force that
propels molten rock from the vent of a volcano?
a. basalt b. lapilli c. escaping gases d. viscosity
e. silica
___3. What is the most abundant gas found in magma?
a. oxygen b. hydrogen c. nitrogen d. methane
e. water vapor
___4. The Hawaiian Islands consist primarily of what type of
volcanic cone?
a. shield b. composite c. pyroclastic d. cinder
e. laccolith
___5. Intrusive igneous bodies that cut across existing
sedimentary beds are said to be _____.
a. concordant b. parallel c. homogenous
d. disinclined e. discordant
___6. Tabular igneous intrusive bodies formed when magma is
injected along sedimentary bedding surfaces are _____.
a. dikes b. sills c. batholiths d. laccoliths e. stocks
___7. Igneous intrusive bodies with a surface exposure of more
than 100 squarekilometers (40 square miles) that frequently
make up the cores of mountain systems are _____.
a. dikes b. sills c. batholiths d. laccoliths e. stocks
___8. The area commonly called the Ring of Fire surrounds the
_____.
a. United States b. Atlantic Ocean c. Mediterranean Sea
d. Indian Ocean e. Pacific Ocean
___9. Volcanoes located within the ocean extrude lavas that are
primarily of ____ composition.
a. rhyolithic b. granitic c. andesitic d. basaltic
e. gabbroic
___10. Subduction zone volcanism in the ocean produces a
chain of volcanoes called an island _____.
a. reef b. arc c. group d. string e. system
True/False
___11. Basaltic lava with a surface of rough, jagged blocks is
called aa lava.
___12. Although volcanic eruptions from a central vent are most
familiar, by far the largest amounts of volcanic material are
extruded from fractures in the crust called fissure eruptions.
___13. Sills are sheetlike intrusive igneous bodies that form when
magma is injected into fractures that cut across rock layers.
___14. Most of Earth’s more than 800 active volcanoes are
near divergent plate margins.
___15. Rising plumes of hot mantle material produce
intraplate volcanic regions a few hundred kilometers across
called hot spots.
___16. The greatest volume of volcanic rock is produced along
the oceanic ridge system.
___17. Shield volcanoes represent the most violent type of
volcanic activity.
___18. Pyroclastic flows consist largely of ash and pumice
fragments produced when silica-rich magma is extruded.
___19. Volcanoes that extrude lava that has a high silica
content are generally located landward of the continental
margins.
___20. Most of the 800 known active volcanoes are located
along the mid-ocean ridge.