Geology 101 Name:
Midterm Exam
Please put your name on this page as well as the scantron sheet, and make sure you sign the honor pledge at the end. Answer the questions on both this copy and the scantron sheet. Good luck!
1) Around the earth, there
are numerous volcanic chains called “volcanic arcs”. These arcs are typically associated
with
A)
plate collision
B)
subduction
C)
spreading centers
D)
hot spots
E)
A and D
2) Which of the following
magma properties cause eruptions to be more explosive?
A)
silica content
B)
volatile content
C)
viscosity
D)
all of the above
3) Pillow basalt forms under
which of the following circumstances?
A)
homogeneous shrinkage after the lava flow has stopped moving.
B)
eruption while underwater
C)
eruption associated with continental hot spots
D)
basaltic eruptions on flanks of composite volcanoes
E) minor basaltic eruptions associated with much larger rhyolitic eruptions
The following 3 questions refer to the map below of the Hawaiian Islands. The numbers refer to ages or rock (in Ma).
4)
In which direction is the Pacific Plate moving?
A) towards the northeast
B) towards the southeast
C) towards the southwest
D) towards the northwest
E) there is not enough information to tell.
5) Towards the northwest, the
island chain becomes submerged as a series of seamounts. Why do they become submerged?
A)
The older part of the hot spot was less active.
B)
Lack of new lava flows increases a given island’s viscosity.
C)
Transition of the hot spot into a subduction zone pulls the islands underwater.
D)
Lack of new lava flows allows coral reef growth to effectively push the island
underwater.
E)
The seafloor subsides as it moves away from the hot spot.
6) What is Loihi?
A)
A growing seamount off the northwest coast of the Big Island of Hawaii.
B)
A growing seamount off the southeast coast of the Big Island of Hawaii.
C)
The oldest rock in non-submerged the Hawaiian Islands.
D)
A basaltic mudflow.
E)
A chaotic flow of cinders.
7) Many basaltic
lava flows change from pahoehoe to aa because
A)
lava flows tend to get broken up by earthquakes after they cool.
B)
atmospherically–derived silica, added to an active lava flow, causes it
to increase its viscosity.
C)
atmospherically–derived silica, added to an active lava flow, causes it
to increase its viscosity
D)
cooling of an active lava flow causes it to increase its viscosity.
E)
cooling of an active lava flow causes it to decrease its viscosity.
8) The distance from the
earth’s surface to the center of its core is about
A)
6000 km.
B)
1000 km.
C)
100 km.
D)
12,000 km.
E)
24,000 km.
The following 6 questions relate to the diagram below:
9) Notice the labels a, b, c
at the plate boundaries. Which of
the following label descriptions is correct?
A)
a is a spreading center; b is a subduction zone; c is a mid-ocean ridge
B)
a is a spreading center; b is a transform fault; c is a subduction zone
C)
a is a transform fault; b is a subduction zone; c is a spreading center
D)
a is a transform fault; b is a convergent boundary; c is a subduction zone
E)
a is a subduction zone; b is a transform fault; c is a spreading center.
10) How
many lithospheric plates does the diagram show?
A)
3
B)
5
C)
1
D)
12
E)
8
11)
At which location could you find the youngest oceanic lithosphere?
A) w
B)
x
C)
y
D)
z
E)
the only oceanic lithosphere on this map is east of the plate boundary at
“c”.
12) Which
of the following hazards are not associated with the Cascade volcanoes?
A)
ash fall
B)
ash flow
C)
lahar
D)
tsunami
E)
pyroclastic flow
13) During an earthquake on a
fault at point “EQ”, which type of seismic wave would reach Seattle
first?
A)
P waves
B)
S waves
C)
P and S waves would arrive simultaneously; it’s the tsunami that would
arrive first.
D)
S waves, because P waves could not propagate through water.
E)
P waves, but only because S waves could not propagate through water.
14) True/False: the two boxes
at “#14” show the correct direction of movement on the adjacent
fault.
A)
True
B) False
15) Lahars are probably the biggest hazards of the Cascade
Volcanoes because
A) the Cascades are largely underlain by a broad
shield of basalt.
B) the Cascadia subduction zone is capable of
generating large-magnitude earthquakes.
C) the Cascade volcanoes are capable of generating
great volumes of ash.
D) most Cascade volcanoes are covered by glaciers.
E) Lahars constitute a threat only when volcanoes erupt under water.
16) What is the most
significant difference between andesite and rhyolite?
A)
Grain size
B)
Silica content
C)
one is igneous, the other metamorphic
D)
one is igneous, the other sedimentary
E) both are igneous, but one is volcanic, the other intrusive.
17) What is the dominant rock
type in the Yellowstone caldera?
A)
Rhyolite
B)
Andesite
C)
Basalt
D)
Komatiite
E)
Granite
18) What happens when two
continental plates meet at a convergent margin?
A)
The older continental plate will subduct beneath the younger one.
B)
The younger continental plate will subduct beneath the older one.
C)
Niether plate will subduct; the result will be a plate collision and major
mountain-building.
D)
The result is plate re-organization leading to continental rifting.
E)
The margin changes to a transform fault.
19) What happens when two
oceanic plates meet at a convergent margin?
A)
The older oceanic plate will subduct beneath the younger one.
B)
The younger oceanic plate will subduct beneath the older one.
C)
Niether plate will subduct; the result will be a plate collision and major
mountain-building.
D)
The result is plate re-organization leading to oceanic rifting.
E)
The margin changes to a transform fault.
20) What happens when a
continental and and oceanic plate meet at a convergent margin?
A)
The continental plate will subduct beneath the oceanic one.
B)
The oceanic plate will subduct beneath the continental plate.
C)
Niether plate will subduct; the result will be a plate collision and major
mountain-building.
D)
The result is plate re-organization leading to continental rifting.
E)
The margin changes to a transform fault.
21) Many cinder cones show an
evolution in which they start off violently, then calm down with effusive lava
flows, and finally stop erupting.
This evolution is best explained by which of the following factors?
A)
the site of volcanic activity moves off the hot spot.
B)
gradual decrease in the amount of magma available.
C)
gradual decrease in the amount of volatiles available.
D)
gradual decrease in the amount of silica available.
E)
gradual increase in the amount of silica available.
22) Which of the following
hydrothermal features are present in Yellowstone?
A)
geysers
B)
hot springs
C)
fumaroles
D)
A, B, C
E)
A, B only
23) Evidence that Yellowstone
will one day be covered by basalt flows comes from what line(s) of evidence?
A)
to the southwest, the hot spot track is now covered by basalt.
B)
the hot spot in Hawaii is entirely basalt.
C)
today’s hydrothermal activity is markedly low in silica.
D)
we can see that basalt dominates the Cascades, even though stratovolcanoes are
the most obvious.
E)
B and D
24) The dominant rock type of the Sierra Nevada Range in
California is granite. This is
significant because
a)
it indicates that the
bedrock of the Sierra Nevada was accreted.
b)
it indicates that
metamorphism of the Sierra Nevada occurred slowly.
c)
it indicates that much
of the Sierra Nevada formed during the Paleozoic.
d)
it indicates that the
Sierra Nevada initially formed near a subduction zone.
e)
All of the above.
25) Continental accretion occurs by which process (es)?
A) rifting
B) subduction
C) hot spot activity
D) intrusion
E) b and c
The following 2 questions refer to the diagram
below. The diagram shows an
intrusive body invading bedded sedimentary rock.
26) The feature at location A
is called
A)
pluton
B)
sill
C)
dike
D)
xenolith
E)
batholith
27) Chilled margins
A)
typically form in country rock adjacent to the cooling intrusion.
B)
typically form near the intrusion’s margins, adjacent to the country
rock.
C)
are marked by extra-large crystal sizes.
D)
are most prevalent along plate boundaries at northern latitudes.
E)
B and C
28) Most typically, silicic
igneous rocks.
A) contain more iron and
magnesium than intermediate rocks.
B) are lighter in color than
mafic rocks.
C) are darker in color than
mafic rocks.
D) are found in oceanic
crust.
E) are denser than mafic rocks.
29) In 1926, Alfred Wegener
proposed Continental Drift, the idea that the continents are mobile and had
once fit together. Which of the
following were among his lines of evidence?
A) fossil land-based animal species in South America
and Africa
B) some continents fit together like pieces in a
jigsaw puzzle.
C) magnetic “stripes” on the sea floor
symmetrical about mid-ocean ridges.
D) A and B only
E) A, B, and C
30) Wegener’s proposal
of continental drift, however, was not well-received until the 1960s. Why?
A)
His evidence was based on weak data overall.
B)
His evidence had numerous small mistakes, which cumulatively pointed to major
contradictions.
C)
He forgot to offer donuts to his colleagues.
D)
He failed to recognize intrusive bodies in the Sierra Nevada of California.
E)
There was no known mechanism for moving continents.
31) Cleavage in minerals
refers to
A)
a tendency to break in an irregular pattern
B)
a tendency to break along planes of weakness
C)
the sharpness of edges between crystal faces
D)
the development of distinct crystal faces
E)
how easy it is to scratch the mineral
32) Explosive or voluminous
eruptions may cause the volcano to collapse upon the floor of the (now empty)
magma chamber, producing a broad depression termed a _____
A)
crater
B)
lahar
C)
caldera
D)
fissure
33) Marine magnetic anomaly
belts are widest when or where _____
A)
continents are joined to form supercontinents
B)
sea floor spreading rates are relatively rapid
C)
sea floor spreading rates are relatively slow
34) Volatiles refer to
substances that
A)
crystallize most rapidly out of a magma
B)
melt immediately upon contact with a hot body of magma
C)
have a tendency to evaporate and are stable as gases.
D)
sink to the bottom of magma chambers
E)
make up the fine-grained portion of a porphyritic volcanic rock.
35) Which of the following
best describes the make-up of Tectonic plates?
A) continental lithosphere only
B) oceanic lithosphere only
C) either oceanic or continental lithosphere, or a
combination of both.
D) either oceanic or continental lithosphere, but not
both.
Honor Pledge:
On my honor, I have not given nor received any help on this exam.
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