oceanography final
What are isostatic changes in sea level and how are they different than eustatic changes in sea level?
-due to an increase or decrease in the height of the land
Be able to identify the following words (1-8) with their respective definitions (A-H) (see list on pp. 170): 1. Dunes 2. Overwash fans 3. Backshore 4. Foreshore 5. Beach Face 6. Nearshore or Surf Zone 7. Sand Bar 8. Offshore A. Area from the low tide shoreline to the high tide shoreline B. Area between the low tide shoreline and where the breakers form C. Linear ridges of unconsolidated wind-blown sand D. Area of the continental shelf seaward of the breakers of surf zone E. Fan shaped accumulations of sand on the landward side of dunes F. Flat area from high tide shoreline to coast G. Linear ridges of unconsolidated sand in the nearshore zone H. Sharply inclined surface between the berm and low tide terrace Page 242 and top panel of Figure 5.18
1. C 2. E 3. F 4. A 5. H 6. B 7. G 8. D
Why are so many barrier beaches located along the east coast of the U.S.? Slide 20 in lecture notes.
1. wide relatively shallow region off shore (i.e. wide continental shelf) 2. lots of sediment 3. relatively low wave activity compared to Pacific
You should be able to calculate the water depth that waves of a given length will begin to bend or refract towards the coast (see text box in bottom figure on pp. 175). (Example: Waves with a length of 30 m will begin to refract or bend towards the coast in a water depth of:
15 m , D= L/2
Be able to pick out the top reasons for why deltas like are subsiding so quickly. They are the following: 1. The delta is compacting under its own weight. 2. Dams have reduced the sediment supply to the delta. 3. Levees along the river have restricted the transport of sediment from the main river to the flood plain. 4. Natural subsidence is being exacerbated by oil and fluid extraction from the delta.
2. dams have reduced the sediment supply to the delta 4. natural subsidence is being exacerbated by oil and fluid extraction from the delta (land subsidence) 1. compacting under its own weight
You should be able to calculate the wave length for waves that begin to refract at a certain water depth (Example: If waves being to refract in a water depth (D) of 10 m then the length for these waves (L) is?
20m, wave base (D) = L/2 so L= 2D
After a storm you observe marsh peat on the front beach face of a barrier island. How does this provide evidence for a shoreward migration of the barrie?
??
What is Eustatic Sea Level Change?
Any uniformly global change of sea level - includes impacts from thermal expansion and ice melt
Why do we say that barrier beaches represent an example of a dynamic coastline?
Beaches are dynamic because they are constantly changing their form and position in response to things like wind, waves and sediment supply. Deltas are another example of a dynamic coastline.
Where are the two primary ice sheets which contain over 99% of freshwater ice located
Greenland and Antarctic Ice Sheets contain over 99% of the freshwater ice on earth
Be able to identify the following coastal environments in Figure 5.15 on page 241 of readings: • A. barrier island, B. spit, C. delta, D. estuary (for drowned river valley case), E. lagoons (behind spits and barrier islands), and F. tidal inlet
LOOK
Be able to identify where marshes and mudflats typically develop in the figure (i.e. behind barrier islands and spits, as well as within estuaries and deltas).
LOOK
Be able to sketch how a wave's path will change as it enters shallow water. See slide 14 and 16 in lecture notes.
LOOK
Finally, be able to identify the direction of long-shore drift given a dominant direction of approaching swell and/or the geometry of a spit (i.e. the tip of spits typically point towards the direction of long-shore drift transport).
LOOK
On the top figure on pp. 249 (Fig. 5.25) be able to identify the areas where wave energy is focused and dispersed along a coastline, as well as the areas of erosion and deposition.
LOOK
Using Figure 5.17 on page 243 be able to identify the following features for a beach profile: A. foreshore, B. backshore, C. low tide terrace, D. beach face, E. berm, F. sand bar, G. surf zone (near shore), H. offshore, and I. Dune
LOOK
What is a tombolo?
a ridge of sand joining the mainland to an island
How does wave refraction tend to bend waves as they approach shore? For example: Wave refraction tends to bend waves so that they are: a. nearly parallel to shore b. nearly perpendicular to shore c. away from headlands.
a. nearly parallel to shore
Be able to define and explain the cause of longshore drift.
along coast transport of sand on in surf zone due to breaking waves (river of sand)
Define the following: Barrier Beach, Barrier Spit and Barrier Island.
barrier beach - narrow beach and dunes parallel to the coastline separated from the mainland by a body of water or wetland barrier spit- barrier beach attached at one end to land barrier island- barrier beach not attached to land
What are beach cusps and how are they formed?
beach cusps- ridges of beach material extending seaward from the beach face with intervening troughs --- formed by rip currents
What is a breakwater and what is its purpose?
breakwater- hard structure built parallel and near to shore purpose- prevent and protect anchorage from effects of weather and longshore drift
Similar to the in class investigation be able to identify the salinity depth-profile at the three different positions up an estuary (at the mouth, in the middle and at the landward end of the estuary).
check on slide 4 lecture 21
How does a coastline's shape typically evolve over time and why?
costal straightening - erosion of headlands and deposition in bays served to straighten coast over time
Be able to provide the definition for a Delta and where they occur
delta- accumulation of sediment at the mouth of a river where: at the mouth of a river
What are embayments and pocket beaches? Is wave energy focused or dispersed here and does this promote deposition or erosion?
embayments: bays between headlands (wave energy dispersed here, causes deposition) pocket beaches : beach formed due to wave dispersion in an embayment
what is an estuary?
estuaries are bodies of water and their surrounding coastal habitats typically found where rivers meet the sea
Be able to identify the areas of sediment accumulation and erosion for groins and jetties in relation to the direction of longshore drift.
groins- short structure build perpendicular to coast to trap sand jetty- long structure built perpendicular to coast to protect harbor of channel
Define and provide examples of both hard and soft stabilization?
hard stabilization: groin, jetties, breakwater, seawall soft stabilization: beach nourishment?
What is a headland? Is wave energy focused or dispersed their and does this promote deposition or erosion?
headland- -part of coast that extends further into sea -wave energy focused here -causes erosion
What is subsidence? When it occurs do you observe relative sea level rise or fall?
land subsidence- sinking of land resulting in a rise in sea level
Be able to define Overwash and Overwash Fans and explain their role in building the back side of a barrier beach system.
overwash- one way flow of water and sediment over the crest of the beach overwash fans- primary mechanism for building a barrier beach
What is beach nourishment?
process of dumping or pumping sand from elsewhere onto an eroding shoreline
At what depth do waves begin to refract? At what depths do waves begin to transport sediment?
refraction only happens when waves approach shore at an angle, at shallow water
Define shoreline regression and transgression and know which commonly occurs during times of both sea-level rise and sea level fall.
regression- oceanward migration of the shoreline - common during a FALL in sea-level transgression- landward migration of the shoreline - common during a RISE in sea-level
What is a rip current and how are they identified?
rip current- strong narrow off-shore current of water typical speed of a rip current: .5 to 2.0 m/s identified- ??
Be able to identify the likely source for sediment to a barrier spit like the one shown in Q1 of Investigation 5.3 (pg. 267).
rivers and erosion from cliff
Describe the seasonal changes for a typical beach on in the northeast.
small summer waves use up their energy shifting the sand back and forth on the beach face larger winter storm waves sometimes shift the beach sand to offshore bars then the waves spend their energy eroding the bedrock and widening the wave cut terrace
Be able to distinguish between the winter and summer beach profiles shown on Figure 5.18 on pp. 243 of readings. During which season (summer or winter) is the net movement of sand landward and during which is the movement offshore? During which season do near-shore sand bars tend to form?
summer beach profile- -gentle, fair weather waves move sand shoreward - net movement of sand in onshore - summer beach is piled high with sand winter beach profile - winter storms wave move sand seaward - net movement of sand is offshore - nearshore sand bars tend to protects the coast by dispersing wave energy
What is thermal expansion and how important a roll has it played in rates of sea level rise over the last few decades?
thermal expansion- tendency of matter to change in volume in response to a change in temperature importance??
What is uplift? When it occurs do you observe relative sea level rise or fall?
uplift- Rise in sea floor that results in a Fall in sea level
What is swash?
uprush of water onto beach by wave
What is the difference between wave refraction (top paragraph pp. 248), wave diffraction (bottom paragraph pp. 248) and wave reflection (2nd paragraph pp. 248)?
wave refraction- bending of waves due to changing depth which changes wave speed wave diffraction- propagation of a wave around an obstacle wave reflection- reflect off a rigid structure like a seawall or the hull of a ship with a little loss of energy- may collide with on-coming waves to create larger waves and greater turbulence by way of constructive interference