Practice Questions for Chapter 4
Geology 1200
Use these questions to test your understanding of Chapter 4.
A. Short answer:
1. When hot particles within a nuée ardente fall to the ground and stick
together, a welded _____ forms.
2. A flow of mud and pyroclastic material is called a ________.
3. A volcanic dome forms when rising ________ cools and hardens within a
volcano’s crater.
4. Pyroclastic materials that cool and solidify from lava ejected into the
atmosphere are called _________.
5. When basaltic lava erupts beneath the sea, it forms a ________ structure.
6. A volcano with a composite cone has layers of _______ and layers of
pyroclastic material within the cone.
7. Volcanoes that form on continent margins above subduction zones
typically have _______ silica than volcanoes in rift valleys.
8. Within a single lava flow in Hawaii, a'a' textured lavas are found ______
_______ from the vent than pahoehoe lavas.
9. Composite cones usually have __________ lava.
10. Volcanoes are created when molten rock escapes from the earth's interior
through surface openings called _________.
11. Contours are lines of equal ___________.
12. Steep slopes have contours ________
_________ than gentle slopes.
B. Match the terms
1. Shield Volcano
_____
a. magma chamber collapsed
2. Lahar ______
b. an andesitic, composite volcano
3. water vapor, carbon dioxide____
c. is silica-rich and/or cool
4. Nuée ardente ____
d. ropy lava
5. Pillows ____
e. has highly eroded slopes
6. Mount St. Helens _____
f. made of hot ash and gasses
7. Caldera _____
g. underwater lava structure
8. Very viscous lava
h. gasses expelled by volcanoes
9. Possibly extinct volcano
i. typical volcano type forming Hawaii
10. Pahoehoe
j. mudflow
C. True or False?
1. A very viscous magma tends to be less explosive. True or False?
2. The most quiet and least dangerous volcanic eruptions involve
glowing avalanches of volcanic rock fragments called Nuée ardente.
True or False?
3. Basaltic magmas are hotter than, and contain less silica than
andesitic magmas. True or False?
4. Basaltic magmas are less viscous than andesitic magmas and can
get to the surface more easily. True or False?
5. Magmas of gentle volcanoes have a higher silica content and a
higher viscosity than magmas of violent volcanoes. True or False?
6. Violent volcanoes often occur at convergent plate boundaries,
whereas gentle volcanoes often occur at divergent plate
boundaries. True or False?
7. Violent volcanoes are low in silica; gentle ones are high in silica.
True or False?
8. Tephra may consist of sizable blocks of solidified lava known as
volcanic bombs. True or False?
9. Pyroclastic eruptions usually occur along transform boundaries.
True or False?
10. Hawaiian volcanoes are thought to be formed by magma plumes
rising from deep in the mantle. True or False?
11. Lines of equal longitude run from the north pole to the south pole.
True or False?
12. The notation N40o 30' 30" marks a latitude in the southern
hemisphere. True or False?
13. In the northern hemisphere, latitudes increase toward the north.
True or False?
14. There are 60 minutes in a degree. True or False?
15. Fact: On a compass, a colored mark on the magnetized needle
points to magnetic North.
Question: if you face North, East is to your right (the sun rises near
there). True or False?
D. Multiple choice:
1. All of the following events could indicate an impending eruption
EXCEPT:
(a) discovery of new hot springs around the volcano.
(b) a measurable bulge or swelling of the volcano.
(c) swarms of small earthquakes in the region.
(d) a highly eroded, volcanic peak.
2. The principal factor(s) influencing upward magma migration before
cooling is (are):
(a) the magmatic water content.
(b) the magmatic gas content, combined with magma viscosity.
(c) the climate and temperature regime that affects the land surrounding
the volcano.
(d) the time since the last eruption, combined with the density of the
rocks overlying the volcano.
3. A volcano can release several kinds of gases into the air, but most of the
gas is:
(a) water vapor and carbon dioxide
(b) nitrogen and sulfur dioxide.
(c) sulfur dioxide and chlorine.
(d) nitrogen and carbon dioxide.
4. The term viscosity refers to:
(a) how heat and pressure influence a liquid’s gas content.
(b) a liquid’s resistance to flow.
(c) how dense a liquid is.
(d) how a liquid moves upward against gravity.
5. Of the following, the magma with the highest viscosity would have:
(a) a high silica content and high temperature.
(b) a high silica content and low temperature.
(c) a low silica content and high temperature.
(d) a low silica content and low temperature.
6. Compared to andesitic lavas, basaltic lavas tend to be:
(a) higher in viscosity and they retain dissolved gases.
(b) higher in viscosity but they easily release dissolved gases.
(c) lower in viscosity and they retain dissolved gases.
(d) lower in viscosity and they easily release dissolved gases.
7. Which of the following is LEAST likely to be a product of a basaltic
volcano?
(a) Columnar jointing.
(b) Nuée ardente.
(c) Pahoehoe lava flow.
(d) ‘A‘a lava flow
8. Which of the following is a likely product of an underwater basaltic
eruption?
(a) Nuée ardente
(b) Lahar
(c) Pillow lavas
(d) Pumice.
9. Felsic magmas with high water and gas content commonly form:
(a) pahoehoe.
(b) ‘a‘a.
(c) columnar jointing.
(d) pumice.
10. Which of the following is LEAST likely to be a product of a pyroclastic
volcano?
(a) Lahar.
(b) Nuée ardente.
(c) Volcanic bombs.
(d) Extensive lava flow.
11. On a map, a scale of 1:24000 means
(a) one inch on the map equals 24000 miles in the real world
(b) one inch on the map equals 24000 inches in the real world
(c) one inch on the map equals 24000 feet in the real world
(d) one inch on the map equals 24000 meters in the real world
E. Mixed Format
1. Examine
http://www.kean.edu/~csmart/Lectures/Igneous%20Rock%20Summary.doc
This must be printed out in landscape orientation. Note the differences in
the volcanic products of basaltic and andesitic and granitic volcanoes, AND
the differences between the plate-tectonic . Note that ivergent margin and
plumes are sources for basaltic magmas.