Download GS106_LABS_8to11

GS 106 LAB 8 Plate Motions
Name__________________________________
1. Tectonic Plates Use Fig. 16.8 in Lutgens and Tarbuck to answer the following:
How many plates are there? _________
Which plate is the smallest? ______________________ Which plate is the largest? _______________
Which plates are topped only by oceanic crust?
Which plate is topped mostly by continental crust? _____________________________
Which plates are topped by a mix of continental and oceanic crust?
2. Absolute & Relative Motion of Plates Use the handout provided in class.
Which plate two plates moving the fastest? Which direction are they moving?
_______________________________
_______________________________________
Which plate is moving the slowest? _________________
Describe the direction each plate is moving…..
Nazca __________
South American _________
African _____________ Indian ___________
Describe the motion of the North American Plate. _______________________________________
Most of the plates are moving towards one geographic area on the globe. Where is this? ____________
As the plates move along the surface of the Earth they often move relative to each other.
In some places plates move towards each other, this is a convergent boundary.
In some places plates move away from each other, this is a divergent boundary.
In some places plates slide past each other, this is a transform boundary.
What type of boundary occurs between the Pacific Plate and the Nazca Plate?
What type of boundary occurs between the Nazca Plate and the South American Plate?
What type of boundary occurs between the African Plate and the Indian Plate?
Hint: find a station on each plate, how is the distance between the two stations changing?
If it is decreasing it is a convergent boundary, if it is increasing it is a divergent boundary.
3. More Relative Motion Examine Fig. 16.8 in your text, again.
What symbol is used to indicate a divergent boundary?
What symbol is used to indicate a convergent boundary?
What symbol is used to indicate a transform boundary?
Check your answers to the last three questions in the previous section!
What type of plate boundaries occur along the west coast of North America?
Surprisingly different types of relative motion can form along a single boundary between two plates.
100 km
N
P LATE A
pppp PLATE B
Figure A
Above is a map view (bird's eye view) of a plate boundary. Plate A is topped by continental
crust. Plate B is topped by oceanic crust. Using the handout of the figure above cut along the
plate boundary (dotted line) separating Plate A from Plate B. Hold Plate A fixed (don’t move
Plate A), and move Plate B in the direction of the bold arrow.
Draw arrows showing the relative motion between the plates along each section of the plate
boundary. Draw three sets of arrows; one set for the E-W trending section, one set for the
NW-SE trending section, and one set N-S trending section.
What type of boundary occurs along the E-W trending section? _________________________
What type of boundary occurs along the NW-SE trending section? ______________________
What type of boundary occurs along the N-S trending section? ______________________
4. Earthquakes and Volcanoes at Plate Boundaries Use figures 16.8, 16.21 and 4.27.
Please circle all that apply!
What types of earthquakes occur along divergent boundaries? shallow
medium deep
What types of earthquakes occur along convergent boundaries? shallow
medium deep
What types of earthquakes occur along transform boundaries? shallow
medium deep
What type of boundaries do volcanoes occur along?
divergent convergent
transform
Examine Figure 16.22 which shows both a map view (bird’s eye) and cross section view (side) of
the Japan Arc.
What type of plate boundary occurs along the Japan Arc? convergent divergent
transform
Which two plates meet along the Japan Arc?
Of the two plates which meet at the Japan Arc…
which has more earthquakes? ________________ which has more volcanoes? ______________
How do the depths of earthquakes vary perpendicular to the Japan Arc?
Which plate is being subducted along the Japan arc? ____________________________
Examine the Tonga Arc! See figures 14.9, 16.8, 16.21 and 4.27.
What type of plate boundary occurs along the Tonga Arc? convergent
divergent
transform
Which two plates meet along the Tonga Arc? _________________________________________
Of the two plates which meet at the Tonga Arc…
which has more earthquakes? ________________ which has more volcanoes? ______________
How do the depths of earthquakes vary perpendicular to the Tonga Arc?
Which plate is being subducted along the Tonga arc? ____________________________
Draw/sketch a simple two dimensional cross section (a slice down through the Earth)
perpendicular to the Tonga Arc. Label the following: Pacific Plate, Australian-Indian Plate,
Tonga Trench. Show the plate boundary extending underground. Label the plate boundary.
Show earthquakes along the plate boundary as stars. Show the locations of volcanoes on the
surface as triangles.
Use figures 14.9, 16.8, 16.21 and 4.27 to find three places oceanic crust and continental crust
collide at convergent boundaries.
Generalize form these examples; which type of crust does not subduct? oceanic
continental
What are two differences between continental and oceanic crust which could explain why one
type of crust does not subduct?
5. Reexamine the Figure A on page 2 showing the imaginary plate boundary.
Are earthquakes produced any where along the plate boundary? YES
NO
If yes, indicate the location of the earthquakes on Figure A. Use different symbols for different
earthquake depths. Use an x to mark the location of shallow earthquakes. Use a square to mark
the location of medium depth earthquakes. Use a circle to mark the location of deep earthquakes.
Are volcanoes produced any where along the plate boundary? YES
NO
If yes, indicate the location of the volcanoes with triangles on Figure A.
6. Changes in Plate Sizes and Boundaries: Use Fig 16.8 and the absolute motion handout.
Is the Philippine Plate growing, shrinking or staying the same size? How can you tell? (explain
your reasoning!)
Is the African Plate growing, shrinking or staying the same size? How can you tell? (explain
your reasoning!)
Is the mid Indian Ridge separating the African and Indian plates stationary or moving? If it is
moving describe its motion (i.e. which direction is it moving?) Explain your reasoning!
GS 106 LAB 9 -Metamorphic Rocks
Name__________________________________
Comparing Protoliths and Metamorphic Rocks
During metamorphism rocks are subjected to increased temperature and/or pressure and/or are infiltrated
by fluids. In response to these changes the minerals in the rock recrystallize while remaining solid (i.e.
they don't melt!), this changes the appearance of the rock and transforms the starter rock (the protolith)
into a metamorphic rock. Metamorphic recrystallization can produce several types of changes including;
changes in grain size, changes in grain shape, changes in the minerals present and changes in layering.
Amazingly these changes usually occur with very little change in the chemical composition of the rock
(i.e. no atoms are removed or added to the rock), what happens is that the atoms in the rock are
rearranged destroying existing crystal structures and creating new crystal structures (i.e.
recrystallization). Compare the following protoliths with their metamorphosed counterparts and describe
the changes produced by metamorphism.
1. Sandstone (protolith) (gray box 2, red dot)
vs. Quartzite (metamorphosed sandstone) (blue box 5, gold dot)
a) Touch the sandstone and quartzite, they should feel different. Describe their different 'feels'.
b) Examine the grains in the sandstone and quartzite using a hand lens.
Make a sketch of the grains in each rock as you see them through the hand lens; draw several grains
(ten or so) showing how they meet along their edges, please draw the grain boundaries clearly!
Sandstone
Texture?
Quartzite
interlocking
fragmental
interlocking
fragmental
c) Describe in words the change in the shape of the grains.
d) The sandstone is made of mostly one mineral; what is that mineral? ____________________
e) The quartzite is also made mostly of one mineral. Describe this mineral and identify.
2. Limestone (protolith) (gray box 1, orange dot) vs.
Marble (metamorphosed limestone) (blue box 6, blue dot)
a) The limestone is made of mostly one mineral; what is that mineral? ____________________
b) The marble is also made mostly of one mineral. Describe this mineral and identify.
c) What type of fossils are in the limestone? _____________________________
d) Are there any fossils in the marble?
yes
no
(circle correct response)
e) What happened to the fossils during metamorphism?
3. Basalt (protolith) (red box 9)
vs Serpentinite (metamorphosed basalt) (blue box 1, black dot)
a) What is the grain size of the basalt? fine
medium
coarse (circle correct response)
b) What is the grain size of the serpentinite? fine
medium
coarse (circle correct response)
c) The serpentinite is made mostly of the mineral serpentine. Describe the color, luster, cleavage and
hardness of serpentine.
d) The chemical composition of serpentine is Mg6Si4O(OH)8.
The basalt is made up mostly of olivine, pyroxene and feldspar
do any of these minerals contain an OH group? (see Figure 2.16 in your text!)
yes
no
e) Was basalt exposed to water when it was metamorphosed to form serpentinite? Explain your
reasoning!
g) The basalt is unlayered while its metamorphosed equivalent (the serpentinite) is layered. How did the
layers in the serpentinite form?
4. Progressive Changes During Metamorphism
As temperature and/or pressure increase many metamorphic rocks will go through a series of changes.
For example when a mudstone is metamorphosed it is first converted to a slate, then a phyllite, then a
schist, and finally to a gneiss. Describe the changes in grain size, layering and mineralogy which
accompany these changes in rock type.
Describe Changes in
Grain Size
Describe Changes in
Describe Changes in
Minerals Present
Layering
Shale
(gray box 4)
to Slate
(blue box 4)
Slate
(blue box 4)
to
Phyllite
(blue box 3)
Phyllite
(blue box 3)
to
Schist
(blue box 2)
Schist
(blue box 2)
to
Gneiss
(blue box 9)
Generalizations based on table above (circle correct statement)
During progressive metamorphism grain size tends to: decrease or increase or stay the same?
During progressive metamorphism layering tends to become: thinner or thicker or stay the same?
5. Unknowns Describe each unknown and then name the unknown using figure 7.10 in your text.
Unknown #2 BIG BLUE BOX
grain size:
fine
layering: none
schistossity
gneissic banding
slatey cleavage
medium
coarse
How many different minerals can you identify? ______
Describe each and try to identify.
rock name: ________________________
Unknown #12 cardboard box
grain size:
fine
layering: none
schistossity
gneissic banding
slatey cleavage
medium
coarse
How many different minerals can you identify? ______
Describe each and try to identify.
rock name: _________________________
Unknown #9 BIG BLUE BOX
grain size:
fine
layering: none
schistossity
gneissic banding
slatey cleavage
medium
coarse
How many different minerals can you identify? ______
Describe each and try to identify.
rock name: ________________________
Unknown #25 cardboard box
grain size:
fine
layering: none
schistossity
gneissic banding
slatey cleavage
How many different minerals can you identify? ______
Describe each and try to identify.
rock name: _________________________
medium
coarse
GS 106 LAB 10 Geologic Dating
Name__________________________________
1. Relative Dating
R
A
P
E
L
F
H
D
G
S
Using the geologic principles discussed in chapter 18 of Lutgens and Tarbuck deduce the
sequence of geologic events recorded in the cross section above. List the events from
youngest to oldest along with the geological principle(s) used to place the event in
sequence. Rock units R, P, D, L, and E are sedimentary, while units A and F are igneous
extrusive and units S and G are igneous intrusive. The line H is a fault.
GEOLOGIC EVENT
GEOLOGIC PRINCIPLE(S) UTILIZED
_________________________
__________________________________
_________________________
_________________________________
_________________________
_________________________________
_________________________
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_________________________
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_________________________
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_________________________
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_________________________
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_________________________
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_________________________
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_________________________
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_________________________
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_________________________
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_________________________
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_________________________
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2. Grand Canyon Geology
The visually magnificent Grand Canyon is a classic geologic locality where the deep
down cutting of the Colorado River has exposed layer after later of sedimentary rock.
You will examine a geologic map of the Grand Canyon to learn about geologic time
periods and unconformities.
Examine the map
Different colors represent different sedimentary rock units. A key is provided which gives
the names and ages of the sedimentary rock units.
What is the name of the pale blue map unit which covers most of the map?
Find the Colorado River, what is the color of the map unit exposed at the bottom of the
canyon? What is the name of this unit?
Notice how the map units create stripes parallel to the river. This pattern is controlled by
the orientation of the rock layers. Are the rock layers horizontal or vertical?
What would the map look like if the rock layers were oriented in the direction which you
didn’t choose above?
Examine Cross Section B
What is the total thickness of the horizontal sedimentary units? __________________
What is the top most horizontal sedimentary unit? ________________________
During which geologic time period did the top most unit form? ____________________
What is the bottom most horizontal sedimentary unit? ________________________
During which geologic time period did the bottom most unit form? _________________
What is the name of the unit labeled Pc?
When did it form?
What is the name of the unit labeled Ph?
When did it form?
Are any time periods missing between the deposition of units Pc and Ph? yes
If yes, what periods?
no
What type of depositional contact occurs between units Pc and Ph?
conformity angular unconformity
disconformity
nonconformity
What is the name of the unit labeled Dtb?
When did it form?
What is the name of the unit labeled Cm?
When did it form?
Are any time periods missing between the deposition of units Dtb and Cm? yes
If yes, what periods?
no
What type of depositional contact occurs between units Dtb and Cm?
conformity angular unconformity
disconformity
nonconformity
What type of depositional contact occurs between the Tapeats Sandstone and the Vishnu
Schist? conformity angular unconformity disconformity
nonconformity
Examine Cross Section D
What type of depositional contact occurs between the Tapeats Sandstone and the preCambrian sediments?
conformity
angular unconformity
disconformity
nonconformity
Examine Figure 18.6 In Your Text
Which is older the Vishnu Schist or the Zoroaster Granite? How can you tell?
Is the metamorphism of the Vishnu Schist the oldest event recorded in the Grand
Canyon? If there is an older event what would it be?
Examine Figure 18.6 in your text. How many periods of uplift and erosion are recorded
in this cross section of the Grand Canyon? Identify each!
GS 106 LAB 11 Absolute Dating
Name__________________________________
1. Radioactive Decay
1) Complete the data table below using the coin flip data we generated in class.
2) Plot the number of parents, the number of daughters, and the number of parents
plus daughters against the number of half-lives using the attached graph paper.
DO NOT CONNECT THE DOTS! Instead draw a smooth best fit curve through
each set of data points. A smooth best fit curve will come as close as possible to
the data points while staying as smooth as possible. Make sure to label the axes
and provide a key identifying the data points.
# of half lives
0
1
2
3
4
5
6
7
8
# of parent
(p)
# of daughter
(d)
p+d
% p remaining
0
1
2
3
4
5
6
7
2. Absolute Dating
1. On the attached graph draw a curve showing how the percentage of parent remaining
decreases as the number of half lives passed increases.
2. The mica muscovite (KAl3Si3O10(OH)2) is often present in granite. What process forms
the muscovite grains in granite?
3. Some of the potassium in muscovite is the isotope
40K which is radioactive. What is the half life of 40K? ___________________________
4. When geologists analyze muscovite in granites they find minute quantities of 40Ar
even though no 40Ar was present in the grain when it formed (see formula). What process
forms this 40Ar?
5. A geologist analyzes a tiny flake of muscovite from a granite from Northern Ontario
Canada and finds it to contain 2,000,000,000 atoms of 40K and 8,000,000,000 atoms of
40Ar.
a) How many atoms of 40K were in the muscovite when it formed? __________________
b) What percentage of the initial 40K atoms still remain? _________________________
c) How many half lives have passed? ________________
d) How old is the muscovite grain? __________________________
e) How old is the Canadian granite? __________________________________
6. A geologist analyzes a tiny zircon grain from a granite pebble in a conglomerate from
the San Bernardino Mountains in California and finds it to contain 7,000,000,000 atoms
of 235U and 3,000,000,000 atoms of 207Pb.
a) How many atoms of 235U were in the zircon when it formed? ______________
b) What percentage of the initial 235U atoms still remain? ______________
c) How many half lives have passed? ______________________
d) What is the half life of 235U? ___________________________
e) How old is the zircon grain? __________________________
f) How old is the conglomerate? __________________________________
Radioactive Decay Plot
100
90
Percentage of Parent Remaining
80
70
60
50
40
30
20
10
0
0
1
2
3
4
Number of Half Lives
5
6
7
8
16