Midterm
The Oceans (OCEA-01)
Multiple choice. Please circle the letter that BEST describes the answer to the
question provided.
1. The lithosphere "floats" on the:
a) mesosphere
b) oceanic crust
c) aesthenosphere
d) outer core
2. During Alaska’s 1964 earthquake seismographers on the other side of the
Earth detected _______, which provided evidence that Earth contains a
liquid outer core.
a) compression and transverse waves
b) A transverse wave “shadow”
c) Aftershocks
d) transform boundaries
3. According to the Theory of Plate Tectonics, new oceanic crust is formed at
______ boundaries, and recycled back to the mantle at _______ boundaries.
a) convergent, divergent
b) transform, convergent
c) passive, active
d) divergent, convergent
4. Water that formed the Earth’s oceans came from:
a) degassing of the interior of the Earth through volcanism
b) comets made of frozen water that melted when they entered Earth’s
atmosphere
c) respiration of organic tissue which consumes oxygen and produces water
d) both a and b are thought to have been sources.
5. Ocean sediments are thickest at:
a) mid-ocean ridges
b) intraplate hot-spots
c) transform faults
d) continental boundaries
6. New oceanic crust is formed at:
a) mid-ocean ridges
b) transform faults
c) convergent boundaries
d) subduction zones
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7. In the lab, if energy is added to liquid water at 100˚C:
a) it will produce an increase in temperature.
b) it will be used to break hydrogen bonds and the liquid will change to vapor.
c) nothing will happen because the water is already at boiling temperature.
d) It will force latent heat to be released.
8. One nautical mile is equal to:
a) 1 ° of longitude at the poles
b) 2.1 statute miles
c) 1 minute of latitude anywhere on Earth
d) 1000 meters
9. Which ocean can be found in all longitudes?
a) Pacific
b) Atlantic
c) Indian
d) Southern
10. Which of the following did the Pacific Islanders not use for navigation:
a) Seawater properties
b) Migration paths of birds
c) The position of stars
d) Chronometers
11. Lost at sea, we notice that our watch (set to the time at the Prime Meridian)
says it’s 3:00PM when the sun is directly overhead (local apparent noon).
What is our approximate longitude?
a) 15° W
b) 45° W
c) 15° E
d) 35° E
12. What force is responsible for the formation of planets, solar systems, and
galaxies?
a) Coriolis
b) Gravity
c) van der Waals
d) Ionic
13. Nuclear fusion in the center of the Sun is responsible for:
a) formation of carbon atoms
b) growth of phytoplankton in the euphotic zone
c) liquid water on the surface of the Earth
d) all of the above
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14. Stanley Miller, testing a hypothesis about the origins of life, found that:
a) stromatolites increased atmospheric oxygen
b) continental rocks are older than oceanic rocks
c) Cell membranes are formed by sparking gaseous oxygen and methane
d) Water was a necessary ingredient
15. Calcium carbonate oozes may be the dominant sediment type:
a) on the abyssal plains
b) below surface waters that have high diatom populations
c) only above the carbonate compensation depth (CCD)
d) mainly below surface waters that are low in nutrients
16. N2 (nitrogen gas) is the most abundant gas in the atmosphere, but nitrogen
is often a limiting nutrient in the ocean because
a) few marine organisms can use N2 to build organic matter
b) N2 cannot easily diffuse down to depths where photosynthesis occurs
c) N2 has a very short residence time, so it is in low ocean concentration
d) all of the above
17. (T or F) During the process of coral reef formation, the first step is called an
atoll.
18. Convergence between continental and oceanic plates is responsible for
which geological feature?
a) back arc basin
b) Island chains like Hawaii
c) Volcanic mountains
d) mid-ocean ridges
19. On passive margins, sediments carried by turbidity currents mostly settle
out onto which marine province
a) continental shelf
b) continental slope
c) continental rise
d) abyssal plain
20. Neritic sediments are dominated by which type of sediment?
a) biogeneous
b) terrigeneous
c) cosmogeneous
d) hydrogeneous
21. Oceanic Abyssal Plains:
a) are flat and very deep, because the huge weight caused by high density of
oceanic basalt pulls them down over enormous space scales.
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b) are typically covered with neritic sedimentary deposits
c) are flat, because the endless rain of sediments covers up any volcanic
topography.
d) both b and c.
22. If winds all across the United States are blowing to the NORTH, which coast
will experience Ekman Upwelling?
a) West Coast
b) East Coast
c) Gulf Coast
d) Hidden Coast
23. The deepest parts of the oceans, whether pelagic or benthic, have which of
the following prefixes?
a) abyssal
b) hadal
c) bathyl
d) methyl
24. A sapropel is:
a) a type of unicellular algae
b) a submarine avalanche
c) a sedimentary deposit composed of >90% organic matter
d) a type of ocean current
25. In order for a hurricane to form, the following conditions must be met
except:
a) water temperatures in excess of 25oC
b) swift horizontal surface winds
c) an atmospheric disturbance
d) an atmosphere that cools with altitude
26. True or false.
Warm core rings are found to the north of the Gulf Stream.
27. At a passive plate boundary between oceanic and continental crust, which
plate will be subducted?
a) oceanic
b) continental
c) neither
d) the older plate
28. You are determining the depth of water under your ship with an
echosounder. Given that the speed of sound in seawater is 1500 m/s, after a
“ping”, you wait 10 seconds to hear the echo. How deep is the water?
a) 1500 m
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b) 15000 ft
c) 15000 m
d) 7500 m
29. Water from the Pacific Ocean is brought up from 4000 m depth is brought to
the surface in a pressure-tight container. When the bottle is opened at the
surface, what is a potential observation?
a) beautiful green color due to living diatoms
b) fizz as CO2 escapes to the atmosphere
c) suction as CO2 rushes into the water
d) chunks of ice from depth
30. Two waters with the following characteristics mix:
Water Mass 1: ρ = 1.027 g/cm3, Temp = 1°C, Salinity = 34.1
Water Mass 2: ρ = 1.027 g/cm3, Temp = 5°C, Salinity = 35
What is the density of the resulting water?
a) 1.027 g/cm3
b) greater than 1.027 g/cm3
c) less than 1.027 g/cm3
d) need more information
31. Which chemical species would you expect to most clearly not exhibit a
nutrient type depth profile in the ocean?
a) Nitrate (NO3-)
b) Phosphate (PO4)
c) Sodium (Na+)
d) Calcium (Ca2+)
32. In the Atlantic Ocean, salinity is higher at mid-latitudes than at the Equator
because:
a) Evaporation occurs more rapidly at mid-latitudes
b) Evaporation at the Equator is balanced by high levels of precipitation
c) There is more precipitation at mid-latitudes
d) There is more river runoff at the Equator than at mid-latitudes
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Part 2: Definitions (10 pts). Choose any 5 of the following 8 words or terms
listed on this page and the next page and give a brief but complete definition in
the space below. Sketches are acceptable.
guyot
Ooze
van der Waals forces
Barrier reef
shelf break
density stratification
Trade Winds
coccolithophore
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Part 3. SHORT ANSWERS
Remember to fill in your name and Section TA above!!!
(There’s a list of words to use to fill in the short answers on the last page)
(3 pts) You are out on the ocean and decide to look at density profiles while you’re
out there (without TV you might as well do some science!). During collection of the
density profile, you collect additional data (see the figures below). In each profile, you
note a rapid change of the measured parameter with depth. Please label the
following 3 graphs with the appropriate oceanographic associated with the change:
Part 2: SHORT ANSWERS continued
Remember to fill in your name and Section TA above!!!
(6 pts) While steaming to the deep ocean, the echo-sounder has recorded the
following:
Label all major features
(A-D) below:
A___________________
B___________________
A
B
C
C___________________
D___________________
D
What kind of margin is
this?:_______________________________________
Which types of plates (2) are meeting?
(4 pts) Your group collects an interesting length of sediment from the bottom of
Monterey Canyon, which had graded bedding (see figure below).
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This type of bedding is created by a seafloor avalanche called a: ____________
The layering of the strata tells us something about their age. Which strata is the
youngest (top or bottom)?: ______________
Use the Hjulstrom diagram (on last page) to answer
the following questions. In the middle stratum, the largest
sediment grains are 10 mm in diameter.
This size of sediment grain (according to the diagram)
is called a: ______________
The speed of the water during the “avalanche” must have
been great enough to at least roll those sediments along
the bottom.
The current speed must have been greater than:
________________________________(units of cm/s)
HJULSTROM DIAGRAM
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