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95) Volcanoes formed from silica-rich magma
A) have gently sloping surfaces that give them the appearance of a shield.
B) are highly explosive and dangerous.
C) are associated with midocean ridges.
D) are associated with rift zones.
96) The eventual catastrophic eruption of Mount Saint Helens was
A) a total surprise.
B) within only a few days of the first earthquake.
C) not preceded by any physical activity.
D) related to seafloor subduction at the west coast of North America.
97) A cinder cone is formed from relatively ________ viscosity magma with a ________ gas
content.
A) high; high
B) high; low
C) low; high
D) low; low
98) Lava plateaus, such as the Columbia River Plateau, are formed from ________ magma
which has a ________ viscosity.
A) granitic; high
B) granitic; low
C) basaltic; high
D) basaltic; low
99) Composite cones have steep slopes and experience ________ eruptions because they are
composed of ________ magma.
A) mild; mafic
B) mild; felsic
C) violent; mafic
D) violent; felsic
100) Increased seismicity in Colorado, New Mexico, and Oklahoma has been linked to
A) a rift valley hot spot in the mid-continental region.
B) injection wells associated with hydraulic fracturing.
C) a continental plate-continental plate subduction zone.
D) a strike-slip fault.
13.2 True/False Questions
1) The topography of Earth's surface has had relatively little influence on human activities and
culture.
2) The average elevation of all Earth's surface is slightly above sea level at this time in Earth's
history.
3) Modern technologies, such as GPS, LiDAR, and radar are important tools for studying the
Earth's topography.
4) The first order of relief is the most detailed order and includes mountains, cliffs, valleys, hills,
and other landforms.
5) The Alps are examples of the second order of relief.
6) Landscapes are grouped into orders of relief by scale, from continents and ocean basins to
individual landforms.
7) The measurement of land elevations relative to sea level is known as hypsometry.
8) The relief from the Earth's highest point to its lowest point is approximately 50 km (31 mi).
9) The Earth's landscapes are generalized to 12 topographic regions, each defined based on
specific, statistical criteria.
10) Extensive plains are found in North and South America, Asia, and Australia.
11) Whereas mountains occur on every continent, depressions (basins) only occur in Asia and
Africa.
12) Cratons are generally of low elevation and old in age.
13) A continental shield is a large region where a craton is exposed at the surface.
14) Terranes refer to the topography of a tract of land.
15) Terranes often differ in rock composition and structure from the continental plate to which
they accreted.
16) Geologically speaking, the continents began forming relatively recently.
17) Shortening or folding of the crust is produced by strain caused by tension.
18) Folding occurs when rocks are deformed as a result of compressional stress and shortening.
19) Oil and gas tend to concentrate in the low areas of a fold; i.e., near the bottom of a syncline.
20) Compressional forces associated with converging plates produce blocks that move upward
relative to the footwall block; this is called a thrust or reverse fault.
21) In a normal fault, the hanging wall drops (moves downward) relative to the footwall.
22) In a normal fault, the hanging wall drops (moves downward) relative to the footwall.
23) A normal fault is associated with compressional stress.
24) In a reverse fault, the hanging wall moves upward relative to the footwall.
25) A thrust fault is associated with compressional stress.
26) The San Andreas fault is principally the result of compressional stress.
27) The Basin and Range Province of the interior western United States is a type of horst-and-
graben topography.
28) A playa is a dry lakebed characterized by an area of salt crust left behind by evaporation of
water.
29) An orogeny is usually caused by large-scale deformation and uplift of crust.
30) Orogenesis may begin with the capture of migrating terranes.
31) Orogens are markably well correlated with the plate tectonics model.
32) I an oceanic plate-continental plate collision, denser continental crust dives beneath oceanic
crust.
33) Oceanic trenches form when one oceanic plate collides with another oceanic plate.
34) The Appalachian Mountains are older than the Rocky Mountains.
35) The Sierra Nevada and Grand Tetons are examples of tilted-fault block mountain systems.
36) Some aftershocks rival the main shock in magnitude.
37) Prior to the invention of seismometers, damage to terrain and structures and severity of
shaking were used to assess an earthquakes size.
38) All earthquakes re-rated using the moment magnitude scale have been rated higher than they
had been rated using the Richter scale.
39) Amplitude is the height of a seismic wave and is directly related to the amount of ground
movement.
40) The Richter scale replaced the moment magnitude (M) scale for measuring earthquake
magnitude.
49
41) An earthquake with a high rating on the moment magnitude scale can receive a low rating on
the Mercalli scale.
42) The elastic-rebound theory explains what happens to the Earth's plates during an earthquake.
43) Paleoseismology estimates expected earthquake activity based on past earthquake activity.
44) A seismic gap refers to ruptures in the land surface that result from an earthquake.
45) Radon gas emissions and changes in the magnetic field are some of the phenomena that often
occur prior to a quake.
46) History seems to teach us that humans are generally unable or unwilling to perceive hazards
in a familiar environment.
47) Scientists have been able to accurately forecast earthquakes for approximately a decade.
48) The Hawaiian Islands are near one end of a hot-spot track that stretches to Alaska.
49) A tall, conically-shaped volcanic peak is generally the result of effusive eruptions.
50) Explosive eruptions produce composite volcanic peaks and few lava flows.
51) Felsic magma produces more violent eruptions that mafic magma.
52) Crater Lake in southern Oregon is an example of a caldera.
53) An active volcano is one that has erupted at least once in the last 25 years.
54) Earthquakes associated with human activity, such as waste water injection wells, are known
as induced seismicity.
55) Human populations are growing in areas prone to seismic activity and near active volcanoes.
13.3 Essay Questions
1) Describe the three orders of relief and give one example of each.
2) Describe the typical formation and characteristics of a continental shield.
3) Discuss the process and causes of folding, and distinguish between anticline and syncline.
4) Draw and label a simple sketch showing common folded landscape features.
5) Describe the creative forces and typical characteristics of the three major types of faults.
6) Draw and label a simple sketch showing the three major types of faults.
7) Draw and label a diagram of the three types of convergent plate boundaries and their typical
orogenies.
8) Define and distinguish between the following: epicenter, focus, foreshock, aftershock.
9) What are the different ways of measuring the intensity and/or effects of earthquakes? Which
do you think is best, and why?
10) Describe various volcanic landforms.
11) Compare and contrast explosive and effusive eruptions. Include their locations, the chemical
composition of the magma, and the landforms they typically produce.
12) Discuss why short term predictions of earthquakes are not yet entirely reliable, while
volcanoes are more easily predicted.
13) What were the important effects of the 1991 Mount Pinatubo eruption?
14) Discuss the seismic hazards in your area. Are these tectonically driven or induced seismicity.
