PlateTectonics_Packet_Review
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University of North Carolina, Chapel Hill *
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Course
101
Subject
Geology
Date
Dec 6, 2023
Type
docx
Pages
4
Uploaded by BrigadierBuffalo1397
Plenge Sp21 GEOL 101
Name
Poojha Palle
Look in your text (Section 2.6 and Chapter 4) to help!
Part A – Earth’s Layers
1.
Tectonic plates are lithosphere.
What 2 compositional layers are components of the lithosphere?
Oceanic crust & continental curst
2.
The lithospheric plates are floating on the asthenosphere.
How is the asthenosphere mechanically
different from the lithosphere?
The asthenosphere is more ductile, which is what allows the lithosphere to move on top.
3.
How are the continental crust and the oceanic crust different in terms of density and thickness?
(select 1)
a.
Oceanic crust is thicker and denser
b.
Oceanic crust is thinner and denser
c.
Oceanic crust is thinner and less dense
d.
Oceanic crust is both thicker and less dense
4.
Why is the oceanic crust, but not continental crust, subducted at convergent boundaries?
Because oceanic crust is denser, and hence sinks beneath lighter continental crust.
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Part B – Divergent Boundaries and Seafloor Spreading:
This diagram shows a divergent boundary in oceanic crust with arrows indicating relative motion.
5.
Where is the oldest crust found?
(select 1)
A
B
C
6.
If each plate is moving at a rate of 2 cm
per year, ~ how long did it take for Rock C
to reach its current location?
(select 1)
0 years
2 years
4 years
8 years
7.
What is the age of the rocks at location B?
(select 1)
0 years
2 years
4 years
8 years
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1
Plenge Sp21 GEOL 101
Name
Poojha Palle
This map of the Atlantic Ocean shows seafloor age with a black and white color scale.
8.
Draw a line along the divergent boundary.
9.
When did the Atlantic Ocean begin to form?
~154 million years ago
10. When the divergent boundary initially
formed, was oceanic crust present at the
boundary?
Explain your answer and describe
how the boundary might have looked upon
initial formation.
No, when the boundary initially formed,
magma rises from the mantle causing crust
to fracture and spread apart. After the
magma has cooled, it becomes the youngest
oceanic crust at the boundary.
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11. This diagram shows a cross-section of a divergent boundary.
Which choice best describe the age
and magnetic orientation of the crust at locations
X
and
Y
?
(select 1)
a.
Crust
at location
X
is younger than the
crust at location
Y
. Both locations have
the same magnetic orientation.
b.
Crust at locations
X
and
Y
is the same
age. Both locations have the same
magnetic orientation.
c.
Crust at locations
X
and
Y
is the same
age. Location
X
has normal magnetic
orientation and location
Y
has reversed
magnetic orientation.
d.
Crust at location
X
is older than the crust at location
Y
. Location
X
has reversed magnetic
orientation and location
Y
has normal magnetic orientation.
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2
Plenge Sp21 GEOL 101
Name
Poojha Palle
Part C – Subduction at Convergent Plate Boundaries
The cross section below shows a subduction zone at an ocean-continental convergent boundary.
The
ocean surface is indicated by a dashed line.
12. On the diagram,
a.
Draw arrows showing which way the plates are moving
b.
Label every feature that geologists can see on the Earth’s surface relating to plate tectonics.
(A feature is something you can see and not something that is happening.)
13. Is subduction visible at a subduction zone boundary?
If yes, what would you see?
If no, how can
you infer that subduction is occurring?
Subduction is not blatantly visible, but one can tell it’s happening because of the seismic activity
and volcanism that result from one plate subducting under another—one can also see
topographical features like trenches and mountain formation in continents.
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14. The diagram to the right is
also an ocean-continental
subduction zone.
Based
on what you know about
movements along a
subduction zone, where
was
in the past?
A
B
C
D
E
same place
15. Where will
be in the future?
A
B
C
D
E
same place
16. Where does lava for subduction-zone volcanoes come from?
e.g. what’s melting? Why is it hot?
Lava comes from the magma rising to the surface due to “partial melting” that occurs as old
oceanic crust is subducted—because fluid is added to mantle, lighter magma forms and rises
above subduction zones to produce volcanoes. Magma is hot because it comes from the mantle.
-----------------------------------------------------------------------------------------------------------------------------------------------
Part D – Transform boundaries
volcano
Subduction zone –
oceanic trench
3
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Plenge Sp21 GEOL 101
Name
Poojha Palle
17. How can transform boundaries be identified in near mid-ocean ridges?
At these ridges, transform boundaries cause certain areas of the divergent boundaries to elongate
horizontally. This is why there are certain sections of the ridge are faulted.
18. How can transform boundaries on land be identified?
Land transform boundaries can be identified by linear valleys, small ponds, and breaks in linear
formation (which is noticeable in orchards or farmland). Shallow earthquakes also occur here.
4