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Name: ____________________________________
Notes:
1.
Introduction to Oceanography 112 - M. Yasuda
Due date:
February 26, 2015
Week 4 – Plate tectonics (cont.)
First Midterm on Thursday February 26th.
2.
No scantron required for the midterm. But BRING a few colored pencils. No calculators
allowed so all calculations will be longhand.
3.
ABSOLUTELY no late homework will be accepted after next Thursday, February 26 th as
described in the Syllabus.
4.
Things NOT to do during class – because it distracts you and/or your classmates from lecture.
a. Using cell phones under your desk
b. Leaving class regularly to use your cell phone, let me know if you have a special need, disrupts
others.
c.
Talking excessively during class.
d. Picking-up or dropping off homework at the front of class if you arrive late. Wait until break or
the end of class.
5.
Things to do and expect during a college class –
a. Try to recall most material discussed during the last class so that the next lecture builds
on existing knowledge and has more meaning for you.
b. Arrive on time nearly every class, even if it means adding cushion to your travel plans.
c.
Present your homework neatly. Staple your homework before coming to class so papers do
not get lost. Make sure pages are in order and use a reasonable standard of care.
d. Take the initiative to ask questions when you need clarification. Learning isn’t a passive
activity and you need a dedicated advocate, i.e. you.
e. Take the initiative to get to know other students during break, before class or at study
sessions and form a supportive network.
f.
Remember to pick up homework at the end of class if you arrive late. Otherwise, you won’t
get feedback in a timely way, particularly a week before a midterm.
Required reading for Weeks 3 and 4 (same as last week)
Textbook
Chapter 3 – Earth Structure and Plate Tectonics
Chapter 4 – Ocean Basins
Additional readings and video that may be useful to you
1. Online – This Dynamic Earth: The Story of Plate Tectonics – another presentation
http://pubs.usgs.gov/gip/dynamic/dynamic.html
2.
Plate tectonics
http://en.wikipedia.org/wiki/Plate_tectonics
3.
Seafloor Spreading with Bill Nye
https://www.youtube.com/watch?v=GyMLlLxbfa4
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Key diagrams
1.
Some of the animations I showed in class
http://earthguide.ucsd.edu/eoc/middle_school_t/t_tectonics/t_tectonics.html
Not all the links connect back to this page. So if you get lost go back in from the link above.
2.
Crustal Age
http://earthguide.ucsd.edu/eoc/teachers/t_tectonics/images/WorldCrustalAge.jpg
3.
Age of rocks around the globe
http://earthguide.ucsd.edu/eoc/teachers/t_tectonics/images/crustalage_lg.jpg
4.
Map of lithospheric plates (tectonic plates) – Flash animation with interactive layers
http://earthguide.ucsd.edu/eoc/middle_school_t/t_tectonics/p_map_plate_layers.html
5.
Map of lithospheric plates (tectonic plates) – Static (less info, but visible on iPad)
http://pubs.usgs.gov/gip/dynamic/slabs.html
6.
Plate reconstruction movie
http://earthguide.ucsd.edu/eoc/middle_school_t/t_tectonics/p_plate_reconstruction_blakey.html
Vocabulary list
1.
Continental shelf
2.
Continental slope
3.
Continental rise
4.
Oceanic islands
5.
6.
7.
Plateaus, guyots,
atolls
Hotspot
Mantle plume
Goals - Plate tectonics
Summarized on last week’s homework
Additional materials from lecture
2
8.
9.
Paleomagnetism
Paleomagnetic
anomaly
3
WEEK 4 – Homework
OCEA 112 – Memorie Yasuda
Name:
____________________________
A. Plate Tectonics Basics
1.
What key observations about the seafloor are explained by our current understanding of plate tectonics on
Earth?
a. The existence of relatively shallow mid-ocean ridges
b. The existence of craters on the Moon
c.
The overall slope of the seafloor
d. The existence of unusually deep and narrow trenches close to land
e. The overall age pattern of the seafloor
f.
The symmetrical pattern of paleomagnetic anomalies around mid-ocean ridges
g. The distinct age difference between continental and oceanic crust
2.
An igneous rock is one that has formed by:
a. Cementation of pre-existing particles into a cohesive mass
b. Growth of solid crystals in water
c.
Solidification of molten rock such as lava or magma
3.
When we refer to the “age” of an igneous rock, it refers to the elapsed time since:
a. That rock landed on the Earth from outer space
b. That rock last solidified from a molten state
c.
Sediments piled up on the ground and formed a rock
4.
If enough time passes so that the entire Earth cools down and totally solidifies, plate motion would stop.
a. True
b. False
5.
Look at this diagram of mantle convection:
http://en.wikipedia.org/wiki/File:Oceanic_spreading.svg
The exact pattern of motion in the mantle isn’t well-defined yet. However there is little disagreement that it
moves very slowly in some way. The motion is thought to be convective. Convection is vertical motion
(motion against gravity) driven by differences in temperature where hot material lies below cooler material.
This condition exists inside the Earth where it tends to be hotter at greater depths.
Circle statements that are true about our current understanding of mantle convection and the diagram
cited above.
a. The parts of the mantle that are shown in orange are molten
b. Lava that erupts out of volcanic arcs at subduction zones originate in the outer core
c.
Mantle convection makes plates move by dragging overlying plates along with it
d. Mantle convection patterns may set the location of mid-ocean ridges
e. Mantle convection moves much more slower than the rate of plate motion
6.
For a continent to move, the plate on which it sits must change in overall size. The answer is not in the
book. You will have to think about this in your own mind.
a. True
b. False
______________________________________________________________________________________
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B. Just what is Plate Tectonics?
7.
As we used the term in class, the term “tectonics” refers to:
a. Processes within a planet that lead to development of a magnetic field
b. Processes within a planet that significantly shape its surface
c.
Processes that shape the surface by the action of running water
d. Mid-ocean ridges
e. Processes within a planet that operate on existing units called plates
8.
The tectonic activity on Earth is called “Plate Tectonics” because:
a. Tectonic processes operate on units called plates which are relatively thin and wide, like a dinner plate
b. Tectonic processes operate on continents which are relatively thin and wide like dinner plates
c.
All tectonic activity is called “Plate Tectonics” whenever and wherever it occurs on rocky planets
9.
Which of the following features are tectonic in origin?
a. Volcano
b. Valley cut by running water
d. Volcanic arc
e. Mid-ocean ridges
g. San Andreas Fault
c.
f.
Impact crater
Himalayas
10. Why is Olympus Mons so huge? Explain briefly.
Resource:
Martian volcano: Olympus Mons
http://mars.jpl.nasa.gov/gallery/atlas/olympus-mons.html
______________________________________________________________________________________
C. Plate margins vs. continental margins
Reference diagrams:
Lithospheric plates
http://earthguide.ucsd.edu/eoc/middle_school_t/t_tectonics/p_plates.html
All-in-one diagram that lets you compare location of different features we discussed
http://earthguide.ucsd.edu/eoc/middle_school_t/t_tectonics/p_ocean_closing.html
Layers of the Earth
http://earthguide.ucsd.edu/eoc/teachers/t_tectonics/p_layers.html
11. Which set of terms refers to continental margins?
a. Active and passive
b. Divergent, Convergent and Transform
12. A passive continental margin:
a. Sits somewhere in the interior of a lithospheric plate
b. Sits somewhere near or at the margin of a lithospheric plate
c.
Tends to have a narrow rather than wide continental shelf
d. Experiences earthquakes but not volcanism
e. Is not associated with earthquakes or volcanism
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13. Which term(s) mean the same thing as “margin” in our current usage of the term?
a. At a border
b. On the perimeter
c.
On the edge
14. Which of the following settings are passive continental margins?
a. San Andreas Fault
b. Aleutian Islands
c.
East coast of the U.S.
d. East coast of South America
e. Divergent margin
f.
Mid-ocean ridge
g. Himalayas
h. The Hawaiian (and Emperor) Seamount Chain
i.
Iceland
15. San Diego is:
a. Located on the Pacific Plate, west of the nearest plate margin
b. Located on the Pacific Plate, east of the nearest plate margin
c.
Located on the North American Plate
d. Located on the Nazca Plate
16. The closest plate margin to Grossmont College is:
a. The San Andreas Fault
b. The continental shelf to the west
17. All mid-ocean ridges are:
a. Divergent plate margins
b.
Convergent plate margins
c.
Transform plate margins
18. The San Andreas Fault is a:
a. Divergent plate margin
b.
Convergent plate margin
c.
Transform plate margin
19. The Himalayas formed:
a. After closure of the ocean that existed between Asia and India
b. Before closure of the ocean that existed between Asia and India
20. The North American plate consists of:
a. Continental Crust
b.
Oceanic crust
c.
Mantle
21. Name a features at a real-world location that is an example of each of these types of plate margins:
a.
Ocean-Ocean Divergent Plate Margin
______________________________________
b.
Cont.-Cont.Divergent Plate Margin
______________________________________
c.
Ocean-Ocean Convergent Plate Margin
______________________________________
d.
Ocean-Cont. Convergent Plate Margin
______________________________________
22. The San Andreas Fault is a transform fault because:
a. It exhibits opposite motion on either side of the fault
b. It causes earthquakes and is considered a natural hazard
c.
It is arranged in a particular way relative to certain tectonic features of the Earth
d. It is a strike-slip type of fault
23. What lies at or near the ends of the San Andreas Fault?
a. Mid-ocean ridges
b. Trenches
c.
24. Which place is always a convergent plate margin?
a. Subduction zone
b. Seafloor Spreading Center
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Subduction zones
25. What kind of forces occur at a divergent margin?
a. Compression
b. Tension
c.
Vertical
______________________________________________________________________________________
D. Paleomagnetic Anomaly Pattern
A paleomagnetic anomaly pattern is the same thing as the magnetic seafloor pattern discussed in class.
The term “paleo” refers to something that is old or from the past. Since the magnetic seafloor pattern involves
sections of seafloor that were magnetized long ago, it is a “paleomagnetic” pattern. The pattern is also said to
be an “anomaly” pattern. An “anomaly” is something that is unexpected, deviates from average, or not normal.
Since the paleomagnetic pattern in the seafloor reveals sections of seafloor that are magnetized in a direction
that is not normal, i.e. reversed, the pattern is said to be anomalous. Thus many scientists and texts will use
the term paleomagnetic anomaly pattern to refer to the magnetic stripes of the seafloor.
Explore this interactive diagram first:
Make your own magnetic stripes
http://earthguide.ucsd.edu/eoc/middle_school_t/t_tectonics/p_paleomag.html
If you tap the square block with the image of the Earth’s magnetic field on it, you will be able to change the
Earth’s magnetic field from Normal to Reversed. Try this and see how this affects the magnetization pattern
of the seafloor.
Try changing the speed or rate of seafloor spreading and see how this affects the magnetization pattern of the
seafloor.
26. What generates the Earth’s magnetic field?
a. The liquid outer core
b.
c.
The solid mantle
d.
e. Continental crust
f.
The solid inner core
The partially molten asthenosphere part of the mantle
Oceanic crust
27. When the North magnetic pole is at the North Pole, as it is today, the magnetic field is considered to be in
its:
a. Normal state
b. Reversed state
28. The width of a paleomagnetic stripe is detected by a device towed by a ship. The device is called a:
a. Multibeam sonar
b. Magnetometer
c.
Satellite altimeter
29. The width of a paleomagnetic stripe is wider when:
a. The magnetic field was in a particular state, normal or reversed, for a longer period of time
b. Seafloor spreading is taking place at a faster rate
30. If no seafloor spreading occurs or if the rate is nearly zero:
a. There would few to no paleomagnetic stripes on the seafloor
b. There would be many more paleomagnetic stripes on the seafloor
31. That the paleomagnetic stripes on the seafloor are symmetrical tells us that:
a. Seafloor spreading takes place, producing seafloor to both sides of mid-ocean ridges
b. Continental drift does not take place because there are no traces of continents moving through
oceans
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32. The pattern of magnetic stripes around the East Pacific Rise is:
a. The same as that around the Mid-Atlantic Ridge
b. Is unique for each mid-ocean ridge
______________________________________________________________________________________
E. Crust vs. Lithosphere
33. Below any sediment cover, what kind of material makes up the seafloor?
a. Continental crust
b. Oceanic crust
c.
Basalt
d. Andesite or Granite
34. How does oceanic crust differ from continental crust?
a. Continental crust is thinner than oceanic crust
b. The base of continental crust sits lower into the underlying mantle
c.
The average rock type differs
d. Mechanical properties differ
35. Which layer constitutes (makes up) the vertical extent of a plate?
a. Crust
b. Lithosphere
36. What defines the lithosphere?
a. It behaves in a brittle manner by breaking like ceramic material under stress
b. It behaves in a plastic manner by deforming without breaking under stress
c.
Rock type
d. Presence of Andesite
37. What is the average thickness of a plate?
a. 5-7 km
b. 100 m
c.
100 km
d.
6,371 km
38. Where is the eastern margin of the South American Plate?
a. Coast of Brazil
b. Coast of Ecuador
c.
Mid-Atlantic Ridge
d. East Pacific Rise
39. Where is the eastern margin of the continent of North America?
a. East coast shoreline
b. Continental shelf break off the east coast
c.
Mid-Atlantic Ridge
40. What is the typical depth of the continental shelf break? _____________________
41. What is the average depth of the ocean? _____________________
______________________________________________________________________________________
F. Key process #1 – Seafloor spreading
42. Seafloor spreading takes place at:
a. Trenches
b. Mid-ocean ridges
c.
Hawaii
43. Seafloor spreading:
a. Produces most new land areas
b. Produces new seafloor
c.
Changes the shape of the seafloor to the extent that surrounding continents are moved aside
d. Destroys old seafloor
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44. In overall area, the Atlantic is now:
a. Growing
b. Closing
c.
Staying the same size
45. The Atlantic Ocean began opening within a continent, like the East African Rift is doing today. The
Atlantic began opening:
a. ~20,000 years ago
b. ~180 million years ago
c.
2.1 billion years ago
46. Continents have been around the Earth’s surface for a long time, for billions of years, But the entire
seafloor is very young. Why do old pieces of continent exist for much longer spans of time? Explain
briefly.
47. Seafloor at the top of MORs is:
a. Relatively new
b.
Old
48. As magma is injected in to cracks in the MOR, it solidifies and is then pulled apart, with half moving to one
side and the other half to the other side. As new magma makes it to the surface, the process repeats itself,
leaving a seafloor paved with stripes of progressively older rock away from mid-ocean ridges.
If seafloor spreads in one direction at a rate of 5 cm a year, What width of seafloor would be “paved” in 20
million years time? Show your calculations.
49. As the northernmost segment of the East Pacific Rise (in the Gulf or California/Sea of Cortez) spreads,
what is it doing to the Pacific Plate west of the San Andre\as Fault?
a. Making it move to the northwest\
b. Making it move to the southeast
50. Which ocean(s) are producing new seafloor?
a. Pacific
b. Atlantic
51. Which ocean(s) are losing area (shrinking) over time?
a. Pacific
b. Atlantic
______________________________________________________________________________________
G. Key process #2 – Subduction
52. Which features are associated with subduction?
a. Mid-ocean ridge
b. Trench
d. Fracture zone
e. Transform fault
g. Island arc
c.
f.
Accretionary prism or wedge
Volcanic arc
53. What is the depth range of most earthquakes on the planet?
a. Within the lithosphere
b. Within the upper 100 km
c.
Within brittle rock
d. Within partially molten rock
54. In a subduction zone, earthquakes occur at progressively and unusually deep depths.
a. True
b. False
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55. What is the source of magma in a volcanic arc?
a. The molten outer core
b. Hotspot under the lithosphere
c.
Partial melting of a subducting plate
56. What hazards are associated with subduction zones?
a. Hurricanes
b. Tsunami
c.
Earthquakes
57. Which of these hazards is not associated with a transform plate margin?
a. Hurricanes
b. Tsunami
c.
Earthquakes
58. The rim of this ocean is called the “Ring of Fire”
a. Pacific
b. Atlantic
c.
d.
Volcanoes
d.
Volcanoes
Indian
______________________________________________________________________________________
H. The Hawaiian-Emperor Seamount Chain
59. The islands and seamounts of the Hawaiian-Emperor Seamount Chain may have formed at:
a. A convergent plate margin
b. An active plate margin
c.
A hotspot underneath the lithosphere
d. A hotspot inside the lithosphere
e. A plate in the interior of the Pacific Plate
f.
A mid-plate location
g. A mid-ocean ridge
h. An asteroid impact site
60. Which of these chains of volcanoes is/are age-progressive?
a. Hawaiian-Emperor Seamount Chain
b. Volcanoes in the Andes
c.
Volcanoes along the Mid-Atlantic Ridge
61. The oldest feature of the Hawaiian-Emperor Seamount Chain is:
a. The seamount closest to the Aleutian Trench
b. The Big Island of Hawaii
c.
The bend in the seamount chain
62. If you have a plate moving southward over a hotspot, in which direction will the oldest volcanoes lie?
a. North
b. South
c.
East
d. West
63. Although not absolutely true, a hotspot is generally thought to be fixed in its position (i.e. does not move
inside the Earth) relative to the overlying plate.
a. True
b. False
64. The older seamounts are more submerged because:
a. They continually erode as they age
b. The seafloor on which they sit continually sinks as it ages
c.
Sea level is rising
65. Which of these statements are true?
a. Most of the seafloor was produced at mid-ocean ridges, at a depth of about 2,700 mbsl
b. Most seafloor becomes progressively deeper as it gets older
c.
The seafloor is relatively shallow at mid-ocean ridges relative to locations to either side
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66. Which statements are true about volcanoes that make up the Hawaiian-Emperor Seamount Chain?
a. They are mostly composed of basalt
b. Eruptions are more hazardous than volcanoes at subduction zones
c.
Their lava is more viscous than at Mt. St. Helens
d. The piles of lava that make up each seamount are shorter in overall height than volcanoes in the
Andes
e. The overall shape of the seamounts is shield shaped rather than cone-shaped
67. Which material has exited to the surface of the Earth?
a. Lava
b. Magma
FYI: Read about the next seamount on the way - Loihi
http://www.huffingtonpost.com/2014/06/28/loihi-hawaii-mission_n_5535439.html
______________________________________________________________________________________
I. Essay
68. Copy or scan a copy of your essay answer to Question #34 from last week’s homework
– the question about the map of San Diego Bay.
Redo your essay in light of what we discussed in class last week and comments I wrote on your essay.
Staple both the new and old essay to your homework.
Checklist:
1. Does your essay clearly and concisely communicate the question you’re addressing?
Does it present your conclusion or assertion with respect to that question?
Did you address the question at hand?
To be concise means to use as few words as possible, in contrast to being wordy and using too many
words.
To be clear means to choose, arrange and craft words in a way that lets a reader know exactly what you
mean to tell them.
2.
Does the content help to explain or support your assertion? Is your thinking logical?
Be your own editor. Remove extraneous thoughts and make sure you have all the necessary pieces
to explain your train-of-thought to someone who is not reading your mind. There is a common
tendency to include a laundry list of somewhat related knowledge. If something doesn’t have a
purpose in explaining or supporting your assertion, throw it out. Part of editing includes ruthlessly
removing extraneous content. Sometimes it’s difficult to part with what you wrote. The upside? The
more extraneous stuff you toss, the less stuff you need to cite or be sure about.
On the other hand, you must address all key points. Omission of key points is a weakness. For
example, let’s say you write a book about Ways People Travel in the 20th Century, and you include
chapters about walking, planes, trains, bicycles and buses. Forgetting to include a section about
automobiles would be a major error because of its omission. Address key points even if it adds
words.
3.
Does the content flow nicely when you read it back?
Take the time to reread your essay after letting it sit a day.
______________________________________________________________________________________
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