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MIDTERM I STUDY GUIDE
GEOL 1080 INTRODUCTION TO OCEANOGRAPHY
FALL 2009
READ THIS FIRST: This outline is not meant to be fully comprehensive. This lists all the major topics we discussed in class, but it
does not completely cover everything involved with every topic, so use this as a guide to your notes, and to what to look at in
the text. The midterm will only test you on material that we have covered in class, although this guide includes material that we
probably won't get to in class.
WHAT THE EXAM WILL COVER: The exam will cover all lecture and textbook material through marine provinces (Chapters 1, 2, 3).
Other topics that we covered (see end of outline below) may also be included on the exam.
WHEN THE EXAM WILL TAKE PLACE
The exam will be available in the CTC Monday 9/28 through Wednesday 9/30. Note that on Wednesday you will be charged $3
by the CTC, and that the CTC requires a photo ID. You must take the exam during that time period unless you have made
other arrangements with Prof. Bunds.
INSURANCE: To receive maximum credit for insurance, it must be submitted by 4:00pm Wednesday 9/30, no exceptions, and should
be turned in to the College of Science and Health office (they’ll put it in my mailbox). Make yourself a copy before handing
in your insurance. Be sure to follow all the instructions for midterm insurance on the course syllabus.
HANDOUTS: Note that there are several useful handouts on the class website: A brief history of the Earth, The Earth’s interior
structure, Plate boundary processes, Illustrations of a subduction zone and divergent plate boundary. Be sure to have a look at
them.
1. INTRODUCTION
a. What is oceanography? The scientific study of all aspects of the oceans.
b. Why are people interested in the oceans?
i. Historically, for food, transportation, and curiosity
ii. More recently – 1930’s, people began exploring for and extracting petroleum from the oceans
iii. Military – especially beginning with WWII, huge military interest in the oceans. Submarine warfare in particular has
led to much exploration
iv. Today, food, hydrocarbon and mineral resources from the oceans are very important.
c. What are the oceans?
i. They cover 70.8% of Earth’s surface.
ii. How deep are they? (average 3.5 to 4.0 km deep; 2.2 – 2.5 miles; the deep oceans, which makes up much of the total
ocean area, average about 4.5 to 6 km depth (a bit less than 3 miles to about 4 miles deep).
iii. There are four principal oceans – but a fifth is usually named as well.
1) Pacific Ocean. Largest single geographic feature on the globe. Named by the mariner Ferdinand Magellan based
on smooth seas they encountered on it (Paci = peace).
2) Atlantic Ocean. Half the size of the Pacific. Named for the Atlas mountains in North Africa. Separates Old and
New worlds. Second largest.
3) Indian Ocean. About same size as the Atlantic, named for India.
4) Arctic Ocean. About 7% the size of the Pacific Ocean, has permanent layer of sea ice meters thick over much of it.
Named for the Big Dipper constellation, which is Ursa Major in Latin, which means Great Bear. Arktos is bear in
Greek.
5) Antarctic or Southern Ocean. Not so much a separate body of water, but a continuous band around the continent
of Antarctica; it consists of portions of the Pacific, Atlantic and India Oceans.
d. What are the scientific subdivisions of oceanography?
i. Geological oceanography, Chemical oceanography, Physical oceanography, Biological oceanography. Know the aspects
of oceanography that each subdivision covers.
ii. We study the oceans using the scientific method – observations (say pattern of earthquakes on earth) hypotheses,
theories
e. Some more questions about the oceans:
i. Has there always been water on the Earth’s surface? (No – but there has been since perhaps 3.8 billion years ago).
ii. Where did the water come from? (Volcanoes - large amounts of water are erupted in volcanic eruptions, and early in
Earth's history volcanism was probably much more frequent than it is today)
iii. Have the oceans always had the same shape (e.g., has there always been an Atlantic ocean?) (No - N. Atlantic began to
open about 190 Ma).
iv. Has anyone been to the ocean bottom? (Yes – indeed to a trench 10,912 m deep!)
v. Where and how deep are the deepest portions of the oceans? (Marianas trench, 11,022 m = 6.8 mi = 36,161 ft).
f. Scientific method – observations, hypotheses, theories etc.
2. EARTH HISTORY OVERVIEW
GEOL 1080, Introduction to Oceanography, Midterm I Study Guide, Fall 2009, M. Bunds Instructor
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a. How old is the Earth? (About 4.5 billion years). Remember this.
b. How did it form? Nebular hypothesis. Rotating cloud of gas condensed, coagulated into Sun with small planets orbiting it,
all of which are in the plane of the ecliptic except Pluto.
c. Oceans probably first formed by about 3.8 billion years ago.
i. When Earth and Sun first formed, gasses were stripped from surfaces of inner (rocky) planets. Too hot for liquid water.
ii. Volcanoes give off water when they erupt. Probably lots of volcanism early in Earth history, lots of water given off.
d. Whole Earth structure
i. Earth’s compositional layering: crust, mantle, core
ii. Earth’s mechanical layering: lithosphere (rigid outer shell!), asthenosphere, mesosphere, outer core, inner core
iii. lithosphere includes the crust and upper mantle.
3. Plate Tectonics basics
a. Basic concept of plate tectonics: the Earth has a thin, rigid outer shell – the lithosphere – that is broken into about 11 major
pieces that move relative to each other. Many interesting, important geologic phenomena occur at the boundaries between
the plates.
b. Know the 3 types of plate boundaries and the major things that happen at each boundary type, including the relative size of
the largest earthquakes that occur at each boundary type. Know an example of each type of plate boundary, and associated
volcano(s), earthquake fault, etc. (e.g., there is a convergent plate boundary along the coasts of Oregon and Washington,
which has caused the Cascade Volcanoes [including Mt. St. Helens] to form).
c. Plate tectonics is probably driven by convection in the mantle/asthenosphere; interior of the Earth is hot
d. The plates move inches per year, tens of miles per million years
e. hot spots – stationary spots of intense volcanic activity; plates move over them. Hawaii
f. Elevation of land and seafloor (concept of isostacy) –
i. The crust floats on the mantle (in an up and down sense, not in a moves through the mantle like a boat through water
sense)
ii. Less dense crust floats better and higher.
iii. The top surface of thicker crust will be higher than the surface of thinner crust.
iv. Continental crust is both less dense and thicker than oceanic crust.
v. Mid-ocean ridges exist because the oceanic crust near to a divergent plate boundary is younger, warmer and less dense
than the older oceanic crust further from the divergent plate boundary.
g. Be sure to realize that all ocean crust is made at divergent plate boundaries and that it all is very similar in composition
(basaltic). Without plate tectonics, there would be no ocean crust, and there wouldn’t be large ocean basins separated from
each other by continents – instead, there might be lots of small pieces of land and ocean scattered across the surface of the
Earth.
h. Seamounts and tablemounts
4. Plate Tectonics details
i. Driving forces (slab pull, ridge push, mantle convection)
ii. Locations of plate boundaries (i.e., the in class exercise)
iii. Plate boundaries on the west coast of North America
iv. San Andreas fault, Juan de Fuca plate, Cascade volcanic arc, sea floor spreading in the Gulf of California
v. Mid – ocean ridges; where they are, why the exist, etc.
vi. Seafloor magnetism
1) One of the key pieces of information that led to understanding of plate tectonics
2) Earth has a magnetic field, as if a giant bar magnetic were inside the Earth. Cause actually probably is convection in
iron – rich outer core.
3) Magnetic field has north and south poles, like a ‘regular’ magnet.
4) North and south magnetic poles have swapped positions many times in the Earth’s past. As if bar magnet inside
Earth suddenly rotated upside down.
5) When lava (or magma) cools and solidifies, it becomes weakly magnetized in the same direction as the Earth’s field
(at the time the lava solidifies). Sort of like inducing magnetism in a screwdriver. Some volcanic rock is
magnetized ‘normally,’ some is ‘reversed.’ Magnetism in old rocks is called paleomagnetism.
6) Ocean crust is mostly frozen lava/magma and is weakly magnetized either normally or reversed, depending on
Earth’s magnetic field when it formed.
7) Normally and reverse magnetized regions of oceanic crust occur in stripes that are parallel to and symmetric about
mid – ocean ridges.
5. Marine Provinces – The oceans can be divided into provinces based on ocean depth and proximity to a continent. The major
provinces are continental margins, deep-ocean basins and mid-ocean ridges
a. First: Bathymetry – depth + measurement (of seafloor) – the depth of the seafloor
i. Old method of determining bathymetry was sounding
GEOL 1080, Introduction to Oceanography, Midterm I Study Guide, Fall 2009, M. Bunds Instructor
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1) HMS Challenger did first systematic soundings – 492 around the globe during a 3.5 year voyage around 1872.
Showed that seafloor is not flat.
ii. Sonic techniques. Precise techniques and widespread use of the method in 1960’s allowed compilation of quality
bathymetric maps at that time. Side-scan sonar allows mapping of wide swaths with a single pass. Still making
detailed seafloor maps.
iii. Harry Hess. Geologist and Navy officer, collected sonar information from ship he commanded in WWII Pacific
Theater, which led to his discovery of guyots (tablemounts) and mid-ocean ridges. He is the originator of the sea-floor
spreading concept.
b. Continental margins – a continental margin is the edge of a continent; the transition from continent to ocean. There are two
types - passive and active
i. Passive – Passive margins are imbedded within the interior of a lithospheric plate; no active plate boundary exist along
the continental margin. This is an important point: many continental margins do not coincide with a plate boundary.
1) Consist of shelf, shelf break, slope and rise
a) Shelf – essentially flooded continent. Shallow water, and only very gently sloping
b) Break – boundary between shelf and slope; ‘break in slope’
c) Slope – relatively steeply sloped; ‘edge’ of continent
d) Rise – gently sloped area oceanward os slope; on oceanic crust; created by sediment that has slid off the
continent(mostly left by turbidity currents)
2) East coast of U.S. is a prime example of a passive margin.
ii. Active – Occur where a plate boundary coincides with a continental margin.
1) two types – convergent and transform.
2) West coast of Americas is example
3) Active margins consist of a narrow shelf, steep slope, and a trench if there is a subduction zone
iii. Submarine canyons and turbidity currents.
c. Deep Ocean Basins - beyond (oceanward) the continental rise. Three main subzones – abyssal plains, volcanic peaks,
trenches
i. Abyssal Plains, know where they are, why they are flat plains, and how deep they are on average.
ii. Abyssal Hill Regions – similar to abyssal plains but thin sediment, and thus dominated by abyssal hills. Pacific.
iii. Trenches. Deep, linear troughs along convergent plate margins (with oceanic lithosphere).
Trench
Average width [km]
Depth [km]
Slope [degrees]
Length [km]
Aleutian
50
7.7
17.1
3700
Peru – Chile
100
8
9.1
5900
Japan
100
8.4
9.5
800
Philippine
60
10.5
19.3
1400
Mariana
70
11
17.4
2550
d. Mid-ocean Ridges; where, what, how deep. Know names of some segments
i. Pillow basalts
ii. Hydrothermal vents (e.g., black smokers)
iii. Ridge is cut by transform faults and fracture zones.
6. GIS and GPS
a. Geographical Information Systems – software for storing, retrieving, analyzing, viewing and communicating information that
is tied to locations on Earth. Very common and important in business, industry, government and more. Google Earth is
GIS; navigation and maps on your Iphone or in your car are GIS. GIS is used to prepare weather maps. See your notes for
more information.
b. Global Positioning System – a system that uses 24+ satellites to provide locations for users. Car nav systems, many cell
phones and of course purpose-built GPS units use this system. Unto itself, it only provides locations. GPS is often
integrated with GIS, but not always by any means.
7. Very Near Infrared (VNIR)
a. Commonly used (along with regular infrared) to image aspects of the Earth’s surface such as vegetated areas, damp areas,
urbanized areas, mineral deposits, ground temperatures, cloud heights , flooded areas and more.
b. Utilizes electromagnetic radiation that is just slightly longer in wavelength than light that is the color red. A sensor detects
the wavelengths of infrared, just as our eyes detect wavelengths of light (which we see as different colors) then a computer
translates the wavelengths into colors we see, creating a ‘false color’ image.
c. We looked at a neat false color VNIR image of the area burned in a very large fire just north of Los Angeles this September.
8. Arctic Sea Ice
GEOL 1080, Introduction to Oceanography, Midterm I Study Guide, Fall 2009, M. Bunds Instructor
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a. We looked at maps that show extent of ice this year and in past summers
b. Monitored since 1979 by satellite
c. Less in 2007 summer than ever measured at any time
d. Significantly less than average this year
e. Positive feedback to warming: warming causes sea ice to melt, with less sea ice more sunlight is absorbed so water and
ground heat up more(ice is very reflective and keeps things cooler), global warming is increased.
9. Gas Shale
a. U.S. has large reserves, especially in the Northeast
b. Natural gas is: relatively plentiful, clean burning (makes half the CO2 of coal, and virtually no toxic pollutants). Its also
expensive to transport
c. Shale is very impermeable, so if you simply drill a well straight into it, very little gas (or oil) will be able to percolate thru the
rock and into the well. The solution is directional drilling and hydrofracting. See your class notes for more info and a
sketch.
10. Hurricanes (more on hurricanes later in the semester)
a. Hurricanes, Typhoons and Tropical Cyclones are all the same type of storm but are given different names in different parts of
the world.
b. Formation
i. Near equator, but not nearer than 300 miles
ii. Warm water – 80oF
iii. Little or no wind shear
iv. A trigger – thunderstorms, ripples in atmospheric flow
v. They rapidly weaken over land, because their energy source is warm water.
c. Rotation
i. Spin results from the Coriolis effect.
ii. All hurricanes that occur north of the equator and spin counter-clockwise. Typhoons and cyclones can occur south of the
equator, where they spin clockwise. The winds in N. Hem. hurricanes blow roughly in a counterclockwise circle
around the hurricane
d. Intensity
i. Based on sustained wind speed (winds sustained for at least one minute)
ii. If winds must be greater than 74mph (if less it’s a tropical storm)
iii. Category 5 is the largest, with winds over 155 mph.
iv. Have had two category 5’s strike North America already this season; first time on record that’s happened.
e. Hazards
i. Storm Surge
1) This is the biggest threat
2) It’s an effective, temporary rise in sea-level caused by the intense wind blowing water towards land.
3) Low pressure in the eye contributes a little
4) Very large hurricanes can cause 30 feet of storm surge
5) Surge is most pronounced on the side of the eye where winds are blowing onshore (usually the north/east side in
North America)
ii. Wind
1) Hazardous and expensive
2) Strongest near the eye
iii. Inland flooding from rain
1) Hurricanes can produce 20” of rain in a day or two in inland areas, causing intense flooding, landslides, etc. (Utah
averages around 20” or precipitation in an entire year).
f. Ike
i. Struck Houston area on 9/13; eye passed right over Galveston and Houston
ii. Extensive damage along coastline – some towns/neighborhoods virtually totally destroyed
iii. Up to about 15 foot surge, highest just northeast of Galveston Island and Bay
iv. Strong category 2, but very large for a 2 so power was more like a 3
Second, here are some study questions.
If you want to turn these in as part of you r insurance work, please be sure to answer them on separate sheets of paper and
staple everything together!
1.
What are the three main subdivisions of Oceanography?
2.
What percentage of the Earth is covered by oceans?
3.
Explain what an ocean basin is, and why they exist on Earth.
GEOL 1080, Introduction to Oceanography, Midterm I Study Guide, Fall 2009, M. Bunds Instructor
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4.
Draw a picture that is a side view of an entire ocean basin. Include a passive continental margin with its major parts on one
side, an active margin on the other, deep ocean, a ridge, etc. Clearly label the depth of the ocean over the deep ocean, ridge,
etc.
5.
How wide are ocean trenches?
6.
Why are there deep ocean trenches?
7.
Name the 5 major oceans of the world.
8.
How old is the Earth?
9.
About how long has there been water, and probably oceans, on Earth?
10. From where did the water of the oceans probably originally come?
11. What is the deepest into the oceans that any human has ever gone? When was this done?
12. How old and where is the oldest ocean crust on Earth?
13. From where did the water of the oceans probably originally come?
14. Draw a picture that shows the main compositional and mechanical layers of the Earth, and label the thickness of the layers.
15. What is the difference between the crust and the lithosphere? Answer this in terms of how they spatially relate to each other
and how they are defined in relation to the Earth’s other mechanical and compositional layers.
16. What type of plate boundary has the largest earthquakes? Which boundary type has medium sized earthquakes? Name a place
on the earth with the type of plate boundary that has the really huge earthquakes.
17. List at least three geologic observations or phenomena that are explained by the theory of plate tectonics (such as the way the
North and South American and African coastlines fit together like pieces of a jigsaw puzzle).
18. Sketch a side view of a subduction zone, like we did in class. Include and label the important features that we discussed in
class (crust & lithosphere, ocean, subducting plate, overriding plate, trench, volcanic arc (continental or oceanic), location and
magnitude of earthquakes and where crust & lithosphere are destroyed and recycled into the mantle).
19. Sketch a side view of a divergent plate boundary, like we did in class. Include and label the important features that we
discussed in class (crust & lithosphere, ocean, mid-ocean ridge, axial valley, location and magnitude of earthquakes and where
new crust and lithosphere is created).
20. Name three examples of mid-ocean ridges. Name and give the location of three trenches.
21. What are mid-ocean ridges and why do they exist along divergent plate boundaries? In your answer, be sure to fully explain
what special characteristics of the young crust along divergent boundaries create ridges there, and how the young crust changes
and moves as it ages. Name an example of a mid-ocean ridge.
22. List and explain the 3 probable driving forces for plate tectonics, using sketches.
23. Explain the probable origin of the Earth’s magnetic field.
24. Explain what a magnetic reversal is.
25. Explain the evidence that the Earth’s magnetic field has reversed in the past.
26. Explain how reversals of the magnetic field are recorded in oceanic crust and how the patterns of magnetized crust relate to sea
floor spreading. A sketch will aid your answer.
27. What types of rock composes most of seafloor crust?
28. What type of basalt flow or formation commonly forms at mid-ocean ridges (and underwater in general)?
29. What is a scientific hypothesis?
30. How does a scientific hypothesis become a theory?
31. What is a hot spot?
32. Explain why the oceans contain ridges.
33. Who was Harry Hess? What did he do, and what did he discover?
34. Draw a side view of a continental margin. In your sketch include and label the shelf, shelf break, slope and rise.
35. Explain what a continental margin is.
36. Briefly explain the difference between a passive and an active continental margin. Give at least one example of each.
GEOL 1080, Introduction to Oceanography, Midterm I Study Guide, Fall 2009, M. Bunds Instructor
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37. How does the continental rise form?
38. How can one tell that ancient sedimentary rock layers may have been deposited by turbidity currents?
39. How do submarine canyons form?
40. What are abyssal plains, where are they, how do they form, and why do they tend to exist in some oceans but not others?
41. Why, in some parts of the oceans, are there abyssal hill provinces instead of abyssal plains?
42. What are typical depths of abyssal plains, deep sea trenches, mid ocean ridges, and continental shelves?
43. Briefly explain standard sonar and side-scan sonar techniques.
44. Explain what seamount and tablemounts are, as well as how they form.
45. Explain what atolls are and how they form.
46. On what basis are hurricanes categorized (i.e., as a 1, 2, 3, 4, or 5)?
47. What are the three main types of hazard that hurricanes pose, and which historically has been the most deadly?
48. Compare typhoons, cyclones and hurricanes.
49. Which way do hurricanes rotate, and in which direction to the winds rotate or spin around a hurricane in the northern
hemisphere?
50. Explain storm surge, including its causes, size, and locations relative to the eye of a hurricane where it usually is most extreme.
51. Be sure that you are familiar with the following concepts from class: GIS, GPS, NOAA, NWS, NHC, VNIR, arctic sea ice, gas
shale; see the notes on these topics in the outline above.
GEOL 1080, Introduction to Oceanography, Midterm I Study Guide, Fall 2009, M. Bunds Instructor
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