2014 Exam #3 Study Guide

8/10/2019 2014 Exam #3 Study Guide

1/7

STUDY GUIDE FOR EXAM #3

DIRECTIONS: Following is a list of topics that you should understand for the exam. When

studying the topics, make sure you understand them a bit more than as basic facts. Use your

notes from class, the lecture slides, and your book to study this material. The internet can be a

great source to get more general information, but use it wisely.Notethat there may be othertopics from your class notes that are not in this study guidebest advice is thatyour lecture

notesandslides should remain the primary study tool.

PRIMARY PRODUCTION:

Primary production: rate at which energy is stored by an organism through formation of

organic matter (C-based compounds) using energy derived from:

-

Chemosynthesis (know where this occurs)

- Photosynthesis (know where this happens and what the limiting factors are)

o Photosynthetic organisms include plants, algae, bacteria (know examples)

o Examples of phytoplankton, and what shells are composed of

o

Global distribution of chlorophyll in the oceans: what does this tell us? Whereare these concentrations greatest and why?

o 99% of ocean productivity (~1/2 of world productivity) occurs in


2/7

Controls on the size of waves:

- wind speed, wind duration, fetch all of these are required to build large waves

Speed of waves:

deep-water waves(deep water is defined as being > 1/2 the wavelength of the wave)

-

does not interact with seabed- speed is a function of wavelength, where speed = wavelength wave period

shallow-water waves

(shallow water is defined as being < 1/20 the wavelength of the wave)

o wave interacts strongly with seabed because water depth is shallow

o speed is controlled only by water depth, where speed =(gravity x depth)

o (ie., in shallow water, speed of any wave is a function of water depth)

Wave groups 'surf beat'

- because the speed of deep-water waves is controlled by their wavelength, waves ofsimilar sizes tend to get grouped together (ie., packages of bigger waves and smaller

waves)

- these 'groups' form larger waves called 'surf beat', which travel at 1/2 the speed of the

individual waves in the package

- the leading wave in the wave package does more work and slowly disappears, whereas

the rear wave has excess energy and grows to form a new wave at the back of the

package this is how the individual waves move 'through' the package, from back to

front

- at the beach, the individual waves break and disappear, but the 'surf beat' reflects off the

beach and can now move along the beach due to wave refraction

- 'surf beat' is hard to see, but it does most of the work along beaches, so is a veryimportant process. If you've been at the beach and seen the water run far up onto the

beach without really seeing any big wave, then that is 'surf beat' a low but very long

wave.

Wave interference

- water waves waves are just like other waves (e.g., sound) in that two or more can

interact to become larger or smaller this is called interference

o constructive interference is when two waves are 'in phase', meaning the

crests and troughs of one wave 'lines up' with another, making the crests

higher and the troughs lower (hence, overall wave height greater)

o

destructive intereference is when two waves are 'out of phase', meaning the

crest of one wave 'lines up' with the trough of another, thereby canceling out

the crest and trough (hence, overall wave height is greatly reduced)

NOTE: tides give a great example of constructive and destructive interference. (1) both

the Moon and Sun produce their own tidal bulge (wave) on Earth; (2) as the Earth,

Moon, and Sun move into and out of alignment with one another, the corresponding


3/7

Solar and Lunar tidal waves move into and out of phase; (3) this is the Spring Neap

tidal cycle every two weeks; (4) Spring tides are large because Earth, Sun, Moon are

aligned, so tidal bulges are in phase and result in constructive interference; (5) Neap

tides are small because Earth, Sun, Moon are at right angles to each other, making the

tidal bulges out of phase, thus destructive interference.

Global wave energy

- the energy of wind waves is greatest during the winter season at high latitudes this is

because the temperature gradient between the pole and tropics is greatest during

winter, thus driving stronger winds, thus generating larger waves

Wave refraction

- only relevant to a shallow-water waves because shallow-water waves interact with

the seabed, thus are influenced by water depth

- speed of shallow wave = square root of gravity x water depth so the part of a wave in

shallower water will slow down, the part of the wave in the deeper water will be faster

consequence is that waves refract (bend) around seafloor topography

Breaking waves at the beach

- again, waves break because the slow in shallow water, the wave energy is compressed

upwards into the wave crest, the orbitals become flattened

- as wave height increases, the wave becomes unstable and breaks

- IMPORTANT: most of the energy that the wave was transporting is now transferred into

moving water (ie., the 'surf' that rushes onto the beach), carrying with sands that

resuspended into the water by the wave interacting with the seabed.

Longshore transportmovement of sand along a beach due to the angled approach of

waves- wave washes up the beach at an angle, then drains straight back down the beach due to

gravity so sand carried by this across-and-down the beach wave motion is

transported along the beach this is not the main mechanism for longshore transport

TIDES & TSUNAMI

Tides

Equilibrium Theory

A tidal bulge is a product of two forces: the centripetal force between Earth and

Moon and the gravitation force between the Oceans and Moon. The centripetal force is

constant at all points on Earth, but the gravitational force is stronger on the side of Earthfacing the Moon, causing the oceans to bulge out, and the gravitational force is weaker on

the other side of Earth, causing the ocean to bulge away from the Moon. In this way, there

are two tidal bulges on Earth, hence the typical two tidal cycles each day.

Gravitational Force is a function of the size of the two attracting bodies (ie., the Earth

and either the Sun or Moon) and the distance (squared) between those bodies. So, even


4/7

though the Sun is 27,000,000 times bigger than Moon, the Moon is 387 times closer and

ends up being twice as important to tides than the Sun.

Remember: the tidal bulges are fixed toward the Moon and Sun, and then the Earth rotates

'underneath' these tidal bulges causing ocean water levels to rise and fall.

Spring-Neap tidal cyclessee previous section on wave interference

Amphidromic systemsA wave generated by the tidal bulge rotates to the right (No.

Hemis) due to Coriolis, and like a reversed ocean gyre, it 'runs' counterclockwise around

the ocean basins about every 12.5 hours.

-

There are 5 major amphidromic systems in the world one each in the Atlantic and

Indian oceans, and three in the Pacific the amphidromic systems and their

interactions are very a complex and you don't need to worry about them any more

than I discuss here.

Tide height (or tidal range)remember that tides are shallow-water waves everywherein the oceans. Thus, their speed is controlled by water depth, and therefore they slow

down when they move onto the continental shelf (where water depth go from >1000 m

deep to


5/7

o contributions to the natural environment nutrients, ocean chemistry,

habitats

o economic/human benefits yield oil, gas, minerals; trap some contaminants

o scientific benefits archives of Earth history preserve records of biology,

chemistry, circulation of oceans, as well as processes on land and global

climate- size categories of sediments (sand, silt, clay)

o importance of size in terms of settling velocity

o what this means for the energy needed to transport sediments by wind and

water

Types of ocean sedimentsterrigenous, biogenic, hydrogenic, cosmogenicknow what

is deposited where and why

-

terrigenous/lithogenous sediments major sources

o importance of river sediments nutrients to coast, coastal landforms

o importance of wind-blow sediment nutrients to open ocean (iron very

important)- biogenic sediments major types, carbonate and siliceous

o sources of biogenic sediments plankton in open ocean (know which species

has shells composed of silica vs calcium carbonate); corals, shellfish in

coastal regions

o carbonate sediments what are the controls on their distribution in the

oceans? (Carbonate compensation depth)

o siliceous sediments what are the controls on their distribution in the

oceans?

- hydrogenic sediments deep-sea vent metal sulfides (black smokers, chimneys);

evaporite salts (remnants of small, dried ocean basins)

- cosmogenic sediments ash, shocked quartz, and tecktites formed by collisions withmeteorites

General distribution of ocean sediments

-

continental margins have most sediment, mostly derived from rivers and, at high

latitudes, also glaciers

-

open ocean, away from continental influence, are mainly wind-blown terrigenous

sediments (clays) and siliceous and carbonate biogenic sediments

-

the distribution of open ocean sediments reflects oceanographic processes, such as

upwelling (for siliceous seds), deep-ocean circulation (for carbonate seds)

Paleoceanography- First, recognize that the paleoceanography lecture was merely looking at the history

of the same processes you already know from our tectonics, atmosphere, ocean

circulation, and sediment lectures so, this is where understanding these processes,

not memorizing them, will really benefit you.

- I do not expect you to know all of the details and complexities of our

paleoceanography lecture


6/7

-

I do expect you to know the major transitions that the Earth has undergone in the

past 70 millions years (ie., transition from Greenhouse to Icehouse)

-

important stable oxygen isotopes 18O/16O, analyzed from water, ice, air, carbonate

(plankton, corals, cave deposits), is useful for determining 1) air and ocean water

temperature and 2) volume of water stored as ice on land.

-

For questions that I ask on paleoceanography, I will provide the necessarybackground information then, I will expect you to be able to respond with an

informed manner ie., if I explain an event/situation to you, you can respond with

how/why it works based on your understanding of basic earth/ocean/atmosphere

processes.

Oceanography of Tennessee

This lecture was intended to give you a broader understanding of the environment in

which you currently live, and how that environment has changed over time. I dont expect

you to remember the specifics of this lecture other than the following major points:

1.

There are 3 main physical provinces that make up Tennessee (know what they are).2. 450 Million years ago, the climate was much warmer than today, and the landform that

will become Tennessee was located near the Equator and at that time it was a shallow

ocean.

3.

Trilobites, brachiopods, crinoids, molluscs (gastropods - snails), bryozoans, and

cephalopods dominated the ocean life at that time. The death and accumulation of these

organisms resulted in extensive limestone (calcium carbonate) deposits.

4. Plate tectonics over the next few million years uplifted the limestone deposits of the

shallow sea so that it now sits well above sea level.

5. These limestone deposits can be seen in the many road cuts around Nashville and

central Tennessee.

BEACHES, COASTS, DELTAS, AND ESTUARIES

50% of the worlds population lives within 100 miles of a coast

-

Know beach zones and barrier island structure (nearshore, foreshore, backshore,

dunes, backbarrier environments)

-

Major controls on coastlines

-

Passive vs active margins, what kind of coastline youd expect

-

Significance of high or low sediment supply (from rivers) to coastal ocean

- What causes variation in sea level?

o Volume of water contained in the ocean basins (glacial vs interglacial periods)

o

Thermal expansion of watero Rate of sea-floor spreading

-

How has sea-level changed in last 20,000 years? Why?

- Transgression (i.e., retreat) of barrier islands with sea-level rise

-

Beach profile during summertime vs wintertime (sediment storage of sand in offshore

bars during the winter)

-

Sand dunes, where sediment comes from, importance

-

Waves move sediment alongshore, tides move sediment inland and offshore.


7/7

-

Barrier island length relationship with tidal range

- Coastal protection structures: groins, seawalls, breakwaters, jetties; impacts on

longshore transport

Estuaries where rivers meet the sea if the sediment supply is low

Deltas where rivers meet the sea if the sediment supply is higho Louisiana delta built from several lobes of sediment that have been deposited

by the Mississippi delta over the past 7,000 years

o Currently in a state of deterioration, mostly due to anthropogenic (man-made)

alteration

Estuarine sediment maximum

Documents

2014 Exam #3 Study Guide