Salt Lake Community College
Geography 1000 – Physical Geography
AJ Allred, Fall 2014
Student Name _____________________
Quiz 12 on Chapters 13-14
Notes to Landforms and Internal Processes
1. Tectonic plate boundaries which are ________ tend to produce island arcs.
a. divergent between continental plates
b. convergent between continental plates
c. divergent between oceanic plates
d. convergent between oceanic plates
e. All of the above produce island arcs.
Notes to Question 1. Tectonic convergence is a collision that causes solid Earth crust to buckle, warp, crumble,
sink or lift. When one plate is heavier than another, collision may result in “convergence subduction”. The remelting of subducted crust often leads to ‘leakage’ of molten rock back to the surface in a fan or arc of
volcanoes along the perimeter of the collision zone. Sub-ocean volcanoes associated with submarine crust (subocean) produce either islands that rise above sea level or seamounts that do not.
2. Utah geology is dominated by _____________________
a. basin and range formations on the western side of the state, and old sediments to the east in mesa and
scarp formations
b. basin and range on the eastern side and mesa/scrap formations to the west
c. a variety of younger igneous rocks in western Utah that host geothermal resources, and old
sediments in eastern Utah that contain vast amounts of fossil fuels
d. Answers ‘a’ and ‘b’ above are both true
e. Answers ‘a’ and ‘c’ above are both true
Notes to Question 2. Earth crust underlying the western United States is subject to compression and expansion
forces that cause folding, faulting, warping and rifting. Salt Lake City is one the eastern edge of the “basin and
range” pattern that goes all the way to California, consisting of a series of mountain ranges separated by valleys
for about 500 miles.
The eastern half of Utah consists mostly of ancient sediments layered with organic material that has morphed
into fossil fuels. (Note: Fossil fuels are classed as sedimentary because that is where they are formed;
however, it is easy to see that masses of ancient dead plants and animals have metamorphosed by heat and
pressure into something chemically distinct.)
So, eastern Utah is dominated by sedimentary sandstones and shales while western Utah is dominated by
younger volcanic rocks, some very recently placed. There is still a great deal of magmatic heat near the surface
in western Utah due to very recent volcanic activity. So, where water resources are available, geothermal
energy may be developed for a variety of uses.
3. Which of the following does not belong with the others?
a. Graben
b. Horst
c. Rift valley
d. Overthrust
e. Dike
Notes to Question 3. Graben and horst tend to go together. Where rifting or other faulting occurs, a graben
may appear as an upthrown ridge or block between two down-thrown or fallen grabens. Salt Lake’s “Point of
the Mountain” is a transverse east—west horst that is eroded enough to not be distinct.
A rift valley often develops when crustal mass is separating or pulling apart, allowing surface material to sink
into the space left by retreating margins. California’s “Death Valley” has rifted, or sunk enough to drop land
surfaces hundreds of feet below sea level. An over-thrust involves one land formation to push over the top of
another.
A dike is an intrusion or “finger line” of igneous magma that rises upward into an existing rock formation.
Plutonic, or sub-surface dikes may eventually be exposed on the surface if overlying layers erode away. The
large crystals in cooled plutonic magma are often harder than overlying sedimentary rock, so they may endure
the erosion process for a longer period of time than surrounding and overhead landforms.
4. For the mantle plume "hot spots" known as the Hawaiian Islands and Yellowstone Park, sliding
tectonic plates will result in these volcanic features someday being located ____________.
a. east of Hawaii and west of Yellowstone Park
b. west of Hawaii and west of Yellowstone Park
c. west of Hawaii and west of Yellowstone Park
d. east of Hawaii and east of Yellowstone Park
e. “Hot spots” or mantle plumes are unpredictable and move in any direction around the Earth.
Notes to Question 4. Mantle plumes are relatively isolated, single points of rising magma that tend to be stable
in location, compared to crustal plates that slip or migrate across the surface of the Earth. The crust underneath
the Hawaiian Islands is moving westward, so the hot spot rising through the crust is located at the eastern edge
of the Hawaiian Island chain. The Hawaiian Islands will continue to move westward, and a new bulge of
magma is building on the sea floor east of the “Big Island”. Eventually, there is likely to be a new island in the
Hawaii chain.
The same pattern applies to Yellowstone Park, as the North American plate moves slowly westward, Earth crust
to the east will eventually slide over the hot spot. Yellowstone Park will eventually be located to the west.
In visualizing this movement, it may help to recall that New York is moving westward away from Paris, France
as the Atlantic Ocean grows larger due to mid-ocean rifting. So, over time the hot spot that underlies
Yellowstone Park will be intruding into crustal lithosphere that has moved over it from the east.
5. Which of the following is not true of ‘accrete terranes’ along the west coast of North America?
a. Plate tectonics moved them across ocean basins.
b. Dozens of them have been formed over millions of years.
c. They have gradually increased the size of North America.
d. They are the largest of all crustal plates.
e. They are made of rocks too lightweight or buoyant to subduct during tectonic collision.
Notes to Question 5. All of the above apply to accrete terrane, except that they are not particularly large,
certainly not as large as Earth’s major continents. They are best thought of as being islands that deform as they
collide with continental crust. Both sides of the collision are made of relatively lightweight crust, which is why
they are partially above sea level.
6. Which of the following is not true regarding volcanoes?
a. The "Big Island" of Hawaii is taller from sea floor to peak than Mt. Everest is from sea level to peak.
b. One of the hazardous stratovolcanoes in Hawaii is currently erupting.
c. Shield volcanoes are less associated with viscous silicates and gases than are stratovolcanoes.
d. Reversal of Earth's magnetic poles does not automatically cause a period of intense volcanic activity.
e. Utah has a number of potentially explosive stratovolcanoes along with cinder cones and flood basalt.
Notes to Question 6. The Hawaiian Islands rise from sea floor about 20,000 feet deep and then extend more
than 13,000 above sea level, making them the tallest mountains on Earth. Eruptions on Hawaii’s “Big Island”
are from immense shield volcanoes that are contain relatively less viscous or ‘sticky’ silicates and less dissolved
gases. The result is that shield volcanoes may be large in size, but tend to produce mild “flow” eruptions rather
than explosive “blow” eruptions.
7. The Himalaya, Earth’s tallest continental mountains above sea level, are being shaped by
__________________.
a. subduction and deformation that are typical of the "Ring of Fire"
b. massive transform or “slip—strike block faults that produce strong vertical thrusts
c. "Ring of Fire" volcanoes and earthquakes that spill over into the Indian Ocean
d. rifting and ridge formation that produce new crustal material
e. erosion and convergence
Notes to Question 7. Collision between lighter-weight continental crusts tends to produce convergence with
uplift as neither formation is prone to subduction and re-melting. Erosion plays an important role as well,
because tall mountains attract heavy snowfall that wears down steep landforms. The uplift caused by simple
convergence between Asia and the Indian sub-continent would exhibit much higher mountains were it not for
rapid erosion caused by solar forces acting with water.
The Himalayan mountains are not associated with volcanoes and lava. Transform quaking involves lateral,
horizontal movement, rather than vertical displacement. So, mountain-building is not typically involved with
slip—strike motion during transform quakes.
Rifting may produce new crustal material when upwelling of magma pushes landforms apart, such as along the
Atlantic mid-ocean ridge. However, this relatively heavier new crust is not known for producing island arcs
and/or tall mountains. Instead, this new crustal material moves laterally, or horizontally along the surface,
pushing continents apart rather than forming new ones.
8. Which of the following features forms a flat or horizontal layer on top of Earth’s crust?
a. Dike
b. Laccolith
c. Sill
d. Batholith
e. Flood basalt
Note to Question 8. Dikes are vertical walls formed as rising magma cools along vertical cracks in overlying
rock. Laccoliths and batholiths are large masses of flat or horizontal igneous intrusions that formed in seams or
blisters in between layers of existing rock. Sills are small, horizontal formations of magma that also solidified
inside existing formations of existing dry rock.
In contrast to all of intrusive igneous features described above, flood basalts are created from very hot extrusive
magma that flows on the surface before cooling as extensive sheets or layers on top of existing surfaces.
9. A ____________ plate boundary is associated with lateral or horizontal slippage, conservation of
existing crust, and earthquake patterns like the San Andreas fault system.
a. convergent
b. fault scarp
c. divergent
d. subducting
e. transform
Note to Question 9. During convergence between plates made of differing density will tend to cause the heavier
plate to subduct or sink back into the molten asthenosphere where it remelts. A fault scarp is a vertical
formation where one face is higher than the adjacent face. Divergent boundaries can produce fault scarps.
Transform, (strike-slip) faults are horizontal or lateral in movement, not vertical, so fault scarps are not a typical
feature.
10. Which of the following is not a form of folding?
a. Anticline
b. Monocline
c. Over-turned fold
d. Syncline
e. Rift valley
Note to Question 10: Geological folds are similar to rumples in a blanket that has been pushed together. A dip
or low spot in a geologic layer is called a syncline and can sometimes collect fossil fuels like oil and natural gas
that sinks into these low areas. An anticline is a high spot or dome.
A rift valley is not a type of fold; instead, it is a rock formation or surface that has sunk due to thinning of
crustal material that is being pulled apart. As crustal material is pulled away from the middle, the thinning
interior breaks into blocks that tend to sink.
A fold may become so severe that it over-turns or folds over itself.
11. Which of the following statements about Utah’s Wasatch Front mountains is not true?
a. Mountains on the eastern side of Salt Lake valley are remnants of volcanoes that became dormant in
relatively recent geologic time.
b. Along Interstate 15 in south-central Utah are some genuine 12,000 foot tall stratovolcanoes.
c. Small cinder cones can be seen in the distance, west of I-15 in central Utah.
d. Utah geology east of Interstate 15, is dominated by sediments that often contain fossil fuels.
e. A large number of geothermal (hot water) sources exist along fault lines in western Utah's basin and
range country.
Note to Question 11: Mountains rising above the east side of Salt Lake represent major portions of the Wasatch
Fault, which is part of the Intermountain Seismic Belt that runs north and south for hundreds of miles, and
includes Yellowstone Park.
The Wasatch Fault zone is not formed by volcanoes, but by normal block faulting or “dip slip” movement. The
east-side block is rising relative to the “down-thrown” block that marks the valley floor. Fault scarps in
mountains above Salt Lake expose rock formations, such as granite, that were once buried deeply as plutonic
intrusions of magma that did not reach the surface before cooling and hardening.
There are some genuine stratovolcanoes in Utah, and some of the most prominent are the Tushar Mountains that
can be seen along the east side of Interstate 15 near Beaver and Manderfield. A large number of relatively tiny
cinder cones are scattered across much of southwestern Utah. These volcanoes and cinder cones are all
examples of extrusive magma that can erupt explosively at times.
Geothermal hot water can be found in countless Utah locations where water seeps into the ground far enough to
reach rocks that are still hot from Utah’s recently active volcanic past.
12. In the past 60 or so years, geologists reached agreement that the cause of plate tectonics is _________.
a. diastrophism
b. convection
c. sun spots
d. warping
e. uniformitarianism
Note to Question 12. Diastrophism is deformation of Earth’s crust. Diastrophism is a process, not a cause of
the process. Convection of hot, molten magma below the Earth’s crust is the cause of plate tectonics and
diastrophism. Warping is a form of crustal deformation.
Like weather phenomena, convection is the rise of higher-temperature substance over cooler substance: higher
temperature means relatively more kinetic motion. As kinetic motion causes molecules to push apart from each
other, lower density and relatively lighter weight result, allowing warmer material to rise over cooler material.
Sun spots can affect Earth weather, but not magma motion. Uniformitarianism is the concept that processes that
occurred in the past continue into the present. Understanding the past is a key to understanding the present and
the future.
13. California’s famous San Andreas fault system is known for everything below except ____________.
a. high-magnitude earthquakes that could kill or injure thousands of people
b. transform fault movement that is gradually moving the Los Angeles region northward to San
Francisco and then on to Alaska
c. being any part of the high Sierra Nevada mountains
d. fault movement that cracks sidewalks and breaks water lines over time
e. being part of the “Pacific Ring of Fire”
Note to Question 13: All of the options are true except being part of the Sierra Nevada mountains. The San
Andreas is mostly transform, or slip-strike movement that does not create significant vertical scarp faces.
A portion of energy released by San Andreas fault movement occurs as “creep” or slow quaking that gradually
cracks sidewalks and other infrastructure. Unfortunately, some build-up of tectonic stress is not relieved by
small, slow or gradual movements. So, severe quaking has occurred in the past and expected in the future
anywhere along the hundreds of miles of the San Andreas fault system.
14. Which of the following statements accurately describes the relationship between quake magnitudes?
a. An earthquake of M 7.2 releases 64 times as much energy as a quake of M 6.0.
b. Energy released by a M 6.0 quake is 10 times greater than from a quake of 5.0.
c. Ground shaking doubles with each whole number increase in quake Magnitude, e.g. 6.0  7.0.
d. Ground shaking is not related to energy release, because land forms and buildings vary too widely
from place to place.
e. A quake of M 6.0 releases 1/32 as much energy as a quake of M 5.0.
Note to Question 14: Each whole number increase in Magnitude (M) represents a 32-fold increase in energy
release. An incremental increase of 0.2 in Magnitude represents a doubling of energy release.
So, a quake of 7.2 releases 32 times more energy for the whole number increase between 6.0 and 7.0, and then a
further doubling of energy release for the 0.2 additional increment.
Ground shaking varies widely, based on a wide variety of factors such as soil and rock qualities, steepness and
stability of terrain and the quality and height of buildings. Even so, ground shaking tends to vary inversely with
distance: the closer to an epicenter, the more likely that shaking will be worse than at locations further away.
Compare this explanation to Question 15 below.
15. Which statement below most accurately describes earthquakes along fault zones?
a. A fault scarp is most likely to appear at the epicenter of an earthquake.
b. Ground shaking will always be worse at the fault scarp than anywhere else.
c. Earthquakes always create a fault scarp or fault line that is visible on the ground.
d. Fault scarps along the Wasatch Fault are located directly above quake epicenters.
e. A quake epicenter is always located directly above the focus or hypocenter of a quake.
Note to Question 15. A variety of earthquake fault zones can occur: normal, reverse, transform, thrust and so
on. Even normal block faults that produce high mountains along Utah’s Wasatch Front have a slope or fracture
line that moves away from the hypocenter. So, a fault scarp at the surface, if there is one, is likely to be
somewhere other than directly above the focus of the quake. In many cases, a quake is from a “blind” fault that
does not show a surface rupture anywhere.
By definition, a quake occurs at a focal location that is also called a hypocenter. The epicenter of a quake is
simply whatever location is on the surface directly above where the quake occurred.
Ground shaking during a quake can vary widely from place to place and can be very hard to predict for any
Magnitude of quake. Water bodies, rock density and hardness and a host of other factors affect how energy
waves are propagated away from a hypocenter. By definition, an epicenter is relatively close to a hypocenter or
focus by being directly above; however, conditions at the epicenter may be much more stable (or less stable)
than locations further away. Because energy does dissipate with distance, naming a quake epicenter is still a
useful way of identifying where quaking and quake damage may be most significant.