MIDTERM II 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.
WHAT THE EXAM WILL COVER: The exam will focus on marine sediments and the chemical and physical properties of seawater.
You will be responsible for the corresponding chapters from your textbook (Ch. 4 and 5).
WHEN THE EXAM WILL TAKE PLACE: The exam will be available in the CTC from Monday 11/2 through Wednesday 11/4.
Wednesday will be a late day with the commensurate $3 charge. You must take the exam during the scheduled time at the CTC
unless you have made other arrangements with Prof. Bunds.
INSURANCE: Insurance is due Wednesday 11/4. To be eligible for insurance points you must submit insurance to Prof. Bunds or the
College of Science and Health main office (one of the secretaries will put it in Prof. Bunds’ mailbox) by 3 pm Weds. 11/4.
Make yourself a photocopy of your insurance work and be sure to follow the directions to ensure you get full credit.
HANDOUTS: Where to find study guides and handouts on the web: http://research.uvu.edu/bunds
1. Marine Sediments
a. Why study seafloor sediments?
i. Hydrocarbons, Past climate – key to current, future climate trends, Sealife – past and present, Pollution, Study Earth’s
geologic system – where sediment goes; analogs for ancient sediments found on land today, etc., mineral resources,
curiosity
b. Sources of information on seafloor sediments
i. Dredging – big shovel,
ii. Gravity coring.
iii. Drilling. Fancy oil techniques. Expensive, but goes deep and can produce excellent intact samples
1) Deep sea drilling history: JOIDES – U.S. funded concerted effort to sample seafloor; 1963, DSDP – beginning of
actual concerted drilling; started in 1968, built the Glomar Challenger (could drill in 6000 m of water; documented
several key aspects of plate tectonics and seafloor spreading). Project became international in 1975 (W. Germany,
Japan, UK and USSR). Became ODP in 1983, with 20 participating countries. Ongoing.
iv. Seismic techniques, primarily of the type discussed earlier. Basic idea of the technique is to bounce or echo sound off
of the layers of sediment beneath the seafloor. This method is widely used, especially in the oil industry because it
provides information on broad areas of the seafloor, as opposed to drilling which only provides data on at a single spot.
c. What are sediments?
i. Material that has settled – in this case to bottom of seafloor
ii. Bits of rock (lithogenous) and organisms (biogenous) primarily. Some can be ‘chemical’ – precipitate from water
(hydrogenous). Get a mixture of lithogenous and biogenous pretty much everywhere – although often one dominates.
iii. Sediment can become lithified into sedimentary rock over time – usually with burial by more layers of sediment.
d. Where are sediments in the oceans? Can be grouped into those
i. close to the continents (Neritic deposits).
ii. deep ocean, relatively far from continents (Pelagic deposits)
e. Lithogenous sediment
i. Derived from mechanical weathering of rocks on continents.
ii. Much is transported long distances by rivers. Some by wind, glaciers. Wind gets very small particles of lithogenous
sediment to deep ocean areas.
iii. Distributed along and away from coasts by strong beach currents and turbidity currents.
iv. Tend to be rich in quartz because it is resistant to weathering and dissolution; most other minerals get dissolved before
they make it to the ocean.
v. Maturity. Rounding, sorting, quartz content.
vi. Lithogenous sediment dominates most neritic deposits, of which there are several types.
1) Beach. Consists of whatever is available. If there is a large river nearby, often has nice quartz-rich sand. Other
places its bare rock or gravel. Material is transported and weathered by waves, especially during storms.
2) Shelf deposits. Upper layers mostly left by rivers when sealevel was lower during last ice age. Sands, muds.
Layers underneath left in ocean tend to get finer-grained with distance from shore. Fine grained material is unable
to settle out of water where waves move water. Glacial deposits in some high latitude places.
3) Continental rise – formed by deposits from turbidity currents as discussed earlier. Graded bedding deposits –
coarse sands to muds.
4) Pelagic / Deep ocean –
a) Mostly very fine grained (clay sized) particles transported over ocean by winds. Called abyssal clay.
GEOL 1080, Introduction to Oceanography, Midterm II Study Guide, Fall 2009, M. Bunds Instructor
page 1 of 7
b) Deep ocean currents apparently do not transport much if any sediment.
c) In places there is some glacial material that has been dropped by icebergs, which are pieces of glaciers.
Process is called ice rafting, and cobbles and boulders left in deep ocean in this way are called ‘dropstones.’
5) Lithogenous sediment does not dominate over biogenous sediment in much of the deep oceans.
f. Biogenous Sediment. From organisms. Macroscopic or microscopic; nearly all from microscopic
i. Two main types of microscopic – siliceous and calcareous. See handout
ii. Siliceous biogenous sediment consists of plankton tests (shells) made of silica (SiO2); zooplanktonic (Radiolarians)
and phytoplanktonic (diatoms) are the two main types of plankton that make silicic tests [know what both
zooplankton and phytoplankton are]. Oceans dissolve silica but only very slowly, so layers of sediment that consist
primarily of siliceous tests (siliceous oozes) can and do form where the productivity of radiolarians and/or diatoms is
great enough. Mass of all diatoms in the oceans probably equals or exceeds mass of all other organisms on Earth
combined! Siliceous plankton thrive in cold climates at high latitudes.
iii. Calcareous – tests made of calcite (CaCO3); zooplanktonic (foraminifera) and phytoplanktonic
(coccolithosphores). Oceans dissolve calcite below the calcite compensation depth (CCD – know about the CCD!!).
So calcareous oozes can only accumulate where oceans are shallower than CCD – primarily at the ridges. However,
calcareous oozes can be preserved as the seafloor ages and sinks below CCD if calcareous ooze is sealed from ocean
by more sediment (siliceous or lithogenous). Calcareous plankton thrive in warm climates – low latitudes.
iv. Uses of oozes: diatomaceous earth is used for filtration, as an abrasive, to absorb chemical spills and in chemistry.
Calcareous oozes are sources of chalk.
g. Hydrogenous sediment – sediment that precipitates from water. Examples are some limestones (only abundant type of rock
formed this way), manganese nodules and phosphates (both potentially important ores - someday).
h. Distribution of sediments and rates of sedimentation on seafloor
i. See table 4-4;
Sediment type and environment
Average deposition rate
Coarse lithogenous sediment – necrotic
environment
1 meter per thousand years
Biogenous ooze, pelagic environment
1 centimeter per thousand years
Abyssal clay (windblown lithogenous
sediment) – pelagic environment
1 millimeter per thousand years
ii. See figures 4-16; 4-17; 4-18; 4-19
iii. Global thickness of sediments– thickest near continents, on older seafloor. (Neritic deposits)
iv. Lithogenous sediments dominate near continents
v. Calcareous oozes tend to dominate on ridges, especially at low (warm) latitudes.
vi. Siliceous oozes tend to dominate in deep ocean
2. Seawater!
a. Atoms are the smallest particles that retain the characteristics of specific elements. They consist of:
i. Nucleus:
1) protons (+) charge, mass (of ‘1’)
2) Neutrons, no charge, mass (of ‘1’).
ii. Electrons: (-) charge (equal but opposite to proton), almost no mass. Electrons orbit around the nucleus in shells. It is
energetically favored for atoms to have full outer shells.
iii. In its neutral state an atom has the same number of electrons as protons and thus no net charge. If an atom obtains an
extra electron, the atom has net negative charge; if and atom gives up an electron, it will have a net positive charge.
Atoms not in base state are called ions
iv. bonding: atomic bonding results from interactions between electrons of neighboring atoms. The electrons interact
because it is energetically favored for atoms to have full outer shells. Consequently, atoms can give away or take
electrons and then bond because of their resulting net charges (ionic bonding), or because atoms share electron(s) to
produce a single full shell that surrounds both atoms (covalent bonding).
b. Elements
i. Atoms naturally come in 92 main varieties. These are the naturally occurring elements. The difference between atoms
of different elements is the number of protons in the nucleus. The number of electrons or neutrons in atoms of the
same element can vary. E.g., all Carbon atoms have 6 protons, but some have 6 neutrons, a few have 7, and a very few
have 8 (these are the three isotopes of carbon). Similarly, the number of electrons varies, and in fact the same atom can
give up and take electrons easily and repeatedly. The number of protons is the basic control on the chemical and
physical behavior of an atom.
c. The water molecule
i. What is the water molecule?
1) H2O
GEOL 1080, Introduction to Oceanography, Midterm II Study Guide, Fall 2009, M. Bunds Instructor
page 2 of 7
2) The smallest amount of water you can have (definition of a molecule).
3) Two hydrogen atoms bonded to an oxygen atom by sharing of electrons.
ii. Geometry and bonding of the water molecule.
1) Both H atoms are on the same side of the O atom! – 105o angle between the H atoms.
2) Covalent bond between H and O.
a) Covalent bonds result from sharing of electrons; each H atom shares its electron with O.
b) Covalent bonds are a very strong type of chemical bond.
i) Ionic bonds (see above)
iii. Polarity of the water molecule. The end of the water molecule on which the H atoms reside has a net (+) charge; the O
end has a net (–) charge. This is because the electrons that are shared between each H and O atom are not evenly
shared – they spend more time around the O atom than the H atom. The polarity of the water molecule gives water its
special qualities and is very important.
iv. Interactions between water molecules - they are attracted to each other because they’re dipolar
1) The connection between water molecules is called a hydrogen bond. Do not confuse this with the covalent bond
between H and O within and individual water molecule.
2) These hydrogen bonds are much weaker than the covalent bonds that hold individual water molecules together.
3) This attraction between water molecules creates surface tension. Causes drops to form, water to bead-up on some
surfaces; lets water stick-up a bit above the top of a glass.
4) This attraction gives water the remarkable properties that are described below.
v. Water as a solvent
1) Why is water such a good solvent? (the ‘Universal Solvent’).
a) Many materials are ionically bonded, and even many of those that are covalently bonded show some polarity.
b) Water is strongly polar, can latch onto edges of polar solids, and breaks them apart
c) Dissolved substances become hydrated, and are held ‘in solution’ in the water.
d) Water can dissolve more of more materials than any known solvent; hence its name ‘The Universal Solvent.’
e) 3.5% of ocean mass is dissolved substances = 50 quadrillion tons = 50x1015 tons = 100x1018 pounds
f) But why doesn’t water dissolve oil better? Oil is highly nonpolar. To a certain extent, organisms evolved that
way to prevent us from getting dissolved by water.
vi. Water’s (Remarkable) Thermal Properties
1) Water is remarkable in that it stays solid and liquid to high temperatures (considering its low molecular mass), and
in that can hold very large amounts of heat - in two ways. Its ability to hold heat energy greatly influences ocean
circulation, weather & climate, and daily and yearly ocean temperature changes – hence it influences life greatly.
2) First some background ideas and terminology: (know these)
a) Heat
b) Temperature .
c) calorie
d) States of matter – solid, liquid, gas (at least the ones we need to know here)
Distance between
Motion of
Temperature
State
Bonding
between
Molecules
molecules
(relative to
molecules
other states)
Solid
Strong
Close, in contact
Vibration, but
Low
no real
displacements
accumulate
between atoms
or molecules
Liquid
Weak
To
None
In contact
3. Gas
4. None
5. Very far apart
Vibration and
moderate lateral
displacements
between atoms
6. Rapid lateral
motion and
vibration
Medium
7. High
1) Freezing and Boiling Points of water
a) Definitions of melting/freezing and boiling/condensation
i) When enough heat energy is added to a solid, it melts. The temperature at which this happens is called the
melting point or melting temperature.
GEOL 1080, Introduction to Oceanography, Midterm II Study Guide, Fall 2009, M. Bunds Instructor
page 3 of 7
ii) When enough heat energy is removed from a liquid, it will freeze. The temperature at which this happens
is called the freezing point or freezing temperature. The freezing point always exactly equals the
melting point. This temperature is 0oC (32oF) for water at sealevel. [oF = oC x 9/5 + 32].
iii) Similarly, when enough heat energy is added to a liquid, it boils. The temperature at which this happens is
called the boiling point or boiling temperature.
iv) When enough heat energy is removed from a gas, it will condense. The temperature at which this happens
is called the condensation point or condensation temperature. The condensation point always exactly
equals the boiling point. This temperature is 100oC (212oF) for water at sealevel.
b) Water has very unusually high melting and boiling points for its molecular weight. This is because it is
(di)polar and forms hydrogen bonds that tend to keep it as a solid or liquid. If it wasn’t polar, it would freeze
at –90oC [-130oF] and boil at –68oC [-90oF]. Note that not only are these temps lower, but that the range
over which it would be liquid is much less. If water wasn’t polar, all water on Earth would be gaseous and
the skiing would suck!
2) Water’s Heat Capacity
a) The heat capacity of a substance is the amount of heat that is required to raise the temperature of 1 gram of a
substance by 1oC. [1 g is ~1/28 oz; 1oC = 1.8oF].
b) So a substance with a large heat capacity can absorb large amounts of heat without its temperature changing
much. A substance that gets hot readily when heat is added has a low heat capacity.
c) Q- Name substances with high and low heat capacities. A- Think of the microwave (e.g., butter vs. water).
Most all oils and metals have low heat capacities.
d) Water has a heat capacity of 1 calorie; nearly all other substances have lower heat capacities. This is because
hydrogen bonds must be broken to get the water molecules moving and that takes lots of heat energy.
Remember, temperature directly measures the movement of molecules/atoms in a substance.
3) Water’s Latent Heat of Melting and vaporization.
a) It takes lots of energy to break hydrogen bonds and transform water from solid to liquid or liquid to gas. These
are the latent heats of melting and vaporization.
b) The amounts of energy required are 80 calories for melting (to melt 1 gr of ice; more technically, to transform
1gr of ice to water at 0oC), and 540 calories for vaporization (to boil 1 gr of water; more technically, to
transform 1gr of water to vapor at 100oC)
c) Called latent because it is hidden. Adding heat, but temperature is not being raised. Heat energy is going into
the change in state of the water (from liquid to gas or from solid to liquid).
d) The energy (latent heat energy, that is) is available to be given back: during condensation and freezing,
identical amounts of heat energy are released.
e) Evaporation vs. Vaporization. The transformation of a substance, such as water, from a liquid to a gas at a
temperature less than its boiling point is call evaporation.
i) Latent heat of evaporation. More energy is required to evaporate water than to vaporize it (because the
water is cooler). For example, 585 calories of heat energy is required to evaporate 1 gr of water at 20oC
[68oF]. The amount of latent heat required for evaporation depends upon the temperature at which the
evaporation occurs.
ii) An important consequence of the latent heat required for evaporation is the strong cooling effect on the
remaining water when water evaporates. (The latent heat of evaporation is provided by a decrease in the
temperature of the water that remains as a liquid).
iii) If water is evaporated in one place and then condenses elsewhere, a large amount of heat is transported.
ii. Water Density (liquid - solid)
1) With cooling, liquid water becomes slightly more dense from 100oC down to 4oC (about 212oF to 39oF). So it
contracts and takes up less volume.
2) Between 4oC and 0oC, waters density decreases slightly. It expands slightly. So at 4oC, water attains its maximum
density.
3) Freezing causes water to become significantly less dense – the change is about 9%. (note that freezing occurs at less
than 0oC for saline water, i.e., seawater).
d. Salinity
4) Refers to total amount of dissolved solid material in the water. Solid material only; does not refer to gases, some of
which are dissolved into seawater.
5) Refers to all water – really is no such thing as natural pure water.
6) Seawater averages 3.5% salinity. 96.5% pure.
a) Commonly measured in parts per thousand instead of percent, which is parts per hundred. So salinity of seawater
commonly reported as 35‰ instead of 3.5%.
b) Varies from 33 to 38‰ in open ocean.
c) 6 elements account for 99% of the tds. Know these 6 elements and be able to list them in order of relative
abundance (don’t need to know each one’s exact concentration).
GEOL 1080, Introduction to Oceanography, Midterm II Study Guide, Fall 2009, M. Bunds Instructor
page 4 of 7
d) Minor constituents; know that the abundances of these are measured in parts per million and even parts per billion,
and know the names of the important abundant ones. Know what parts per million means.
e) Principle of constant proportions – total salinity varies, but ratio of the major dissolved constituents is virtually
Constituent
Cl- (Chloride)
Na+ (Sodium)
SO42- (Sulfate)
Mg2+ (Magnesium)
Ca2+ (Calcium)
K+ (Potassium)
Total
Concentration (‰)
Ratio of constituent to total salts
19.3
10.7
2.7
1.3
0.41
0.38
34.79
55
30.6
7.7
3.7
1.1
1.1
99.3
identical everywhere. This implies that the oceans are well mixed and that variations in salinity result from
addition or removal of pure water. Know this idea.
7) Origin of salinity
a) Water on land dissolves rocks to limited extent, carries material to oceans. Water is evaporated from oceans, leaves
dissolved solids behind.
b) Some comes from waters that circulate at mid-ocean ridges
8) Variations in salinity
a) Fresh water - Decent tap water contains < 0.8‰, good tap water is < 0.6‰ and good bottled water is < 0.3‰.
b) Great Salt Lake is about 280‰ – about 9 times more saline than typical seawater.
c) Varies between 33 and 38‰ in open ocean
i) As low as 10‰ and as high as 42‰ in some area. Influx of ‘fresh’ river water, removal of water by evaporation
causes the variations (see Principle of Constant Proportions).
ii) High salinity at low latitudes (high evap.); low salinity where lots of river run-off (Alaska).
iii) In general, salinity is a balance between addition and removal of dissolved solids, and addition and removal of
pure water. Very constant over time – only minor variations in total salinity.
d) Variations with depth
i) Below about 1 km depth, salinity is very consistent worldwide: evaporation and runoff don’t effect deep ocean.
ii) But at high latitudes relatively low salinity at surface, whereas at low latitudes relatively high salinity at surface.
iii) Depth range over which there is gradient from surface conditions to stable depth conditions is called the
halocline.
iii. Seawater density
1) Depends upon temperature and salinity; temperature is by far most important.
2) Understand and be able to sketch the figures on page 155 of text.
3) Three distinct zones with depth at low to mid - latitudes, where surface water is warmer and lower density than deeper
waters.
a) Mixed surface layer
b) Upper water zone. Not mixed and does not mix with the deep water below
c) Deep water below 1000m – fairly homogenous in temperature and salinity, but does not mix with water above.
iv. Transmission of light through seawater
1) Know what electromagnetic radiation is.
2) Light does not penetrate very deep – 45% makes it to 1m; 16% makes it to 10m; only 1% makes it to 100m. If you want
to photosynthesize, live near the surface!
3) Blue light penetrates best; hence water free of particulate matter and plankton looks blue.
4) Particulate matter and plankton scatter yellow-green light, making water look more that color where they are abundant.
v. Sound transmission in seawater
1) Sound travels quickly and efficiently (less decrease in volume as it travels) in water. 1450 m/s (4750 ft/s). four times
faster than in air.
2) Velocity of sound travel through water increases with temperature, salinity, and pressure.
3) Sound waves refract (the direction of travel changes/bends) when their speed changes as they pass through water with
different characteristics (see 2 above). Refraction causes waves to bend towards areas where they travel more slowly.
4) Temp, salinity and pressure combine to create a low velocity horizon at about 1000 m depth – called the ‘SOFAR’
channel [Sound Fixing and Ranging].
a) Sound gets trapped in this layer/channel due to refraction.
b) Causes sound to be able to travel and be heard at large distances. May be used by marine animals like whales.
c) Has been used to estimate average temperatures of oceans, because sound velocity varies with water temperature.
GEOL 1080, Introduction to Oceanography, Midterm II Study Guide, Fall 2009, M. Bunds Instructor
page 5 of 7
vi. Calculation of mass of seawater dissolved constituents.
1) Calculation of the mass of a dissolved constituent in water is important. The ability to do simple calculations is
important.
2) To calculate the mass of, for example, gold in a quantity of seawater you can do the following
a) Calculate the volume of seawater in question; the formula is Volume = length x width x depth = area x depth. In the
case of calculating the volume of all the world’s oceans, its expedient to calculate the surface area of the entire earth
using the formula for area of a sphere (A=4 x pi x r2) and then multiply by the fraction of Earth’s surface area that’s
covered by oceans (0.718), which will give you the surface area of the oceans; multiply by average depth and you
have an estimate of the volume of the oceans..
b) Calculate the mass of the water volume in question using the formula mass = Volume x density
c) Calculate the mass of the constituent in question by multiplying the total mass of the seawater in question by the
fraction of that mass that is the constituent in question; a formula for this looks like massconst. = masssw x fconst.
vii. USS Indianapolis
1) Ill – fated heavy cruiser from WWII. It delivered the atomic bomb to Tinian Island and then on its return to Leyte was
sunk by a Japanese submarine; the ship went down in approximately 12 minutes.
2) Due to a flaw in the Navy’s ship-tracking system its sinking went unnoticed for days.
3) 1196 men were on board; approximately 300 went down with the ship; of the approximately 880 that made it into the
water, 321 survived to be rescued beginning on August 2. 5 more men perished after being rescued.
4) Many had no lifejacket, and only a few life rafts were freed before the ship sank. Deaths were caused by exposure, lack
of food and water, desquamation and shark attacks. It is unknown how many men were killed by sharks, but rescuers
directly observed men being attacked by sharks.
5) The fictitious character Quint (Robert Shaw) in the film Jaws is a survivor of the USS Indianapolis and he gives a
moving monologue in which he describes the horror of the experience.
6) The Discovery Channel show Ocean of Fear is a documentary on the incident and includes interviews with survivors.
Second, here are some study questions.
If you want to turn these in as part of you r insurance work, be sure to answer them with complete sentences on separate
sheets of paper and staple everything together!
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
What are the two main types of sediment in the oceans, and what is the origin of the material in each type?
From where does most lithogenous marine sediment come, and how does it get to the oceans?
Why is quartz an abundant mineral in lithogenous sediment?
What is the most abundant type of life on Earth?
What is the CCD, where is it, and why does it exist?
Do calcareous oozes exist below the CCD, and if so why?
Which type of biogenic ooze can accumulate in the deep ocean?
List three industrial/human uses of diatomaceous Earth.
On average, how fast do biogenic oozes accumulate on the seafloor?
On average, how fast does lithogenous sediment accumulate on the continental shelf?
How does most lithogenous sediment get to the deep oceans in neritic environments?
Is there lithogenous sediment in the pelagic environment, and if so how does it get there, and what is its grain size?
What does zooplankton mean? Name a calcareous and a siliceous zooplankton.
What does phytoplankton mean? Name a calcareous and a siliceous phytoplankton.
What types of sedimentary rock result from siliceous oozes?
What types of sedimentary rock result from calcareous oozes?
What is the difference between sediment and sedimentary rock?
Explain how sedimentation processes and the types (and amounts) of sediment formed differ between continental margin and
deep ocean areas. What do we call the areas near continental margins and deep ocean?
In relation to continental margins and the deep ocean, where is oil found (and where has it formed in the past)?
How do the atoms of different elements differ from each other?
Can the number of electrons in a Carbon atom vary?
Do all Carbon atoms have the same number of neutrons?
How do covalent bonds differ from ionic bonds?
What type of bond exists between the hydrogen atoms and oxygen atom in a water molecule? Is this a strong bond?
Draw a water molecule; be sure to get the positions of each atom correctly and include the charge distribution on the molecule.
Are water molecules attracted to each other? Why or why not?
GEOL 1080, Introduction to Oceanography, Midterm II Study Guide, Fall 2009, M. Bunds Instructor
page 6 of 7
27. What kinds of substances is water particularly good at dissolving (think in terms of electric charges and types of bonds)?
Why?
28. Sketch a sodium chloride crystal and some water molecules and explain how water dissolves it.
29. Describe freezing, melting, condensation and boiling, and give the points (temperature) of each for water.
30. What is the heat capacity of a substance (i.e., describe the concept)? What is the heat capacity of water (i.e., a number – with
units!)?
31. Relative to other substances, does water have a high or low heat capacity? Why?
32. Describe a way that water’s heat capacity impacts surface temperatures on Earth.
33. What is latent heat? Why is it called latent? What is the latent heat of vaporization of water (give a number and units)?
34. What is the difference between the latent heat of vaporization and latent heat of condensation in water (there is a distinction)?
35. Explain how ice keeps a beverage cold, using your knowledge of heat capacity and latent heat.
36. What is the difference between boiling and evaporation?
37. Is water vapor in your kitchen visible?
38. What is the density of a substance?
39. Sketch (neatly) a graph of pure water’s density vs. temperature. At what temperature does water attain its maximum density?
40. How might the behavior of water differ if the hydrogen atoms were attached on directly opposite sides of the oxygen atom (i.e.,
all three atoms were in a line)? [There should be several parts to this answer – water’s solvent properties, heat capacity, latent
heats, density, melting and vaporization points].
41. Explain what is meant by the salinity of seawater.
42. What is the average salinity of seawater? Be sure to give the salinity in the standard units, using standard notation.
43. What is the origin of most of the salinity of seawater?
44. List, in order of decreasing concentration, the 6 most abundant constituents of the salinity of seawater.
45. What is the typical range in salinity of seawater in the open ocean?
46. Explain the principle of constant proportions. Be sure that you understand this concept.
47. In some parts of the oceans, the salinity is less than average; name 3 causes of this decreased salinity and explain what factor
all 3 causes have in common.
48. In what parts of the oceans (where on Earth) is salinity typically less than the average value?
49. In some parts of the oceans, the salinity is greater than average; name a cause of this increased salinity.
50. In what parts of the oceans (where on Earth) is salinity typically greater than the average value?
51. What are the typical concentrations of the minor constituents of seawater salinity (i.e., in what units are they usually reported)?
52. Graph typical ocean water temperature vs. depth for both high and low latitudes. Label all the key elements of the graph.
53. Graph typical ocean water salinity vs. depth for both high and low latitudes. Label all the key elements of the graph.
54. Graph typical ocean water density vs. depth for both high and low latitudes. Label all the key elements of the graph, including
the three horizons of low latitude water.
55. Calculate the mass of magnesium in a bay with dimensions 20 km long by 5 km wide by 50 m deep. Assume the bay contains
seawater of average salinity. The concentration by weight of magnesium in seawater is given in a table above. Show all your
work.
56. Calculate the mass of water (i.e., perfectly pure H2O) in all the oceans. Show all your work.
57. Calculate the mass of gold in Lituya Bay, Alaska. Assume that the water in Lituya Bay is average seawater. Lituya Bay’s
dimensions are approximately 12 km by 3 km by 200 m deep. The concentration of gold, by weight, in average seawater is
approximately 0.001 ppb (parts per billion, i.e., (0.001/1,000,000,000)). Now answer the following question: How much gold
is there by in Lituya Bay if the salinity of the water in the bay is only ½ average seawater, but it abides by the principal of
constant proportions? Show all your work.
GEOL 1080, Introduction to Oceanography, Midterm II Study Guide, Fall 2009, M. Bunds Instructor
page 7 of 7