Exam 3 Flashcards
The depth below the surface where the circular orbits become so small that movement is negligible is called the
wave base
The uninterrupted distance over which wind blows without a change in direction
fetch
At the surface of the ocean the diameter of a wave orbital is equal to
wave height
Generally, the greater the speed, the greater the
wavelength
How do you calculate celerity?
L/T
restoring force for wind-generated waves
gravity
three factors that influence wave height
fetch, wind duration, and wind speed
the time between two successive waves is called the
period
What is the ratio of H:L
wave steepness
Wind waves grow from what types of waves?
capillary waves
In deep-water waves the water depth is greater than the ____ divided by 2.
wavelength
As a deep water wave approaches a shoreline and becomes a transitional wave, its wave height _____ and its wavelength _______.
increases; decreases
A Beaufort number of _____ is where we would begin to see the formation of whitecaps in the ocean.
3
If we see orbital movement of water at a pynocline we are looking at _____ waves.
internal
Waves in the surf zone begin to behave like shallow-water waves when _____.
wave depth = wavelength/20
Wave formed on a river by a flood current.
tidal bore
The angular distance of the Sun or the Moon above or below the Earth’s equatorial plane is called the ______?
declination
When the Earth is at its greatest distance from the Sun, it is said to be at _____.
aphelion
The difference between centripetal forces and gravitational forces is called the _____.
resultant force
A neap tide has _____ tidal range.
low
There is constructive interference between the lunar and solar tidal bulges during _____ tides.
spring
The center of mass of the Earth-Moon system is called the ______.
barycenter
Which of the following would you expect to find on a summertime beach?
a wide, sandy berm
The section of the coast that is exposed at low tide and submerged at high tide is called the _____.
foreshore
Isostatic movement of a coastline might occur due to
removal of a big glacier in the area
Eustatic changes in sea level might include
increased glacial melting due to the climate change
Which of the following is found at a depositional shore?
deltas
Which of the following is designed to prevent or retard shoreline erosion?
seawall, beach nourishment, groin
In terms of erosion protection from wave action, seawalls
lead to erosion of sediment on their seaward sides
Sediment is supplied to the coastal zone by
rivers, coastal erosion, local biological activity
regular, long-period waves that have sorted themselves based on speed
swell
If you have a moon that is 7 days old (past new moon) what type of tide would we experience?
neap tide
If you took a series of salinity measurements and found that salinity was constant at all depths in a particular estuarine location, you are probably in which kind of estuary?
vertically mixed
_______ force - ________ force = ________ force
centripetal, gravitational, resultant
A full lunar tidal cycle is _____ than a solar day.
+50 minutes
A solar day is ____ than a full lunar tidal cycle.
-50 minutes
If the mainland is connected to an island by a sand ridge, we would term that feature a
tombolo
Why do waves converge on headlands?
wave refraction
A tide that occurs when a spring tide corresponds with the moon in perigee is termed a
proxigean tide
4 types of armoring
groins, jetties, breakwaters, seawalls
Groin definition and the problem with it
armoring built perpendicular to the beach which is made of large blocky/rocky material. Traps the sand and builds up the beach in the north, but causes erosion below it. Slosh, backwash moves in the south direction - lose sand south
jettie
type of hard stabilization build in pairs - go long ways and have done major stabilization and they have caused massive buildup because they fill area with sediments and sand
sea wall
remove beach as water strikes sea wall it is eroding sand below sea wall and it will collapse. Wave activity will undermine sea wall, so it will have to continually be repaired. Loses beach for public.
Alternatives to armoring?
construction restrictions, relocation, beach replenishment
sun’s declination to earth
23.5 degrees
declination of moon to earth
28.5 degrees
apogee
point at which moon is furthest from earth in its orbit
perigee
point at which moon is closest to earth in its orbit
tidal range is ______ at perigee
highest
Apogee has what affect of GF
decrease
perigee has what affect on GF
increase
aphelion
sun is furthest from earth in its orbit
periphelion
sun is closest to earth in its orbit
center around which the tide rotates
amphidromic point
connects all locations that are experiencing high tide at one time; can be strange in shape but it has to do with the basin
cortidal lines
tidal datum
reference point for the tidal height; not always at sea level
diurnal
one high and one low tide per day
semidiurnal
2 high, 2 low tides a day
mixed
2 high, 2 low tides a day - tidal range is different - common
when water is moving out of the system; can be very strong; tides near shore; leads toward low tide
ebb tide
when water is moving into the system; tides near shore; leads toward high tide
flood tide
little movement
slack tide
most extreme tides - location
Bay of Fundy, Nova Scotia - 15m
How do we predict tides?
relative distance, position of moon, declination, where are the amphidromic points
What influences predicted tides?
weather patterns, storm surge, tsunami, strong on-shore winds, high and low pressure systems, strong wind patterns
proxigean tide
spring tide at perigee; every 1.5 years; can cause coastal flooding
spring tide
full moon; new moon; when tidal range is greatest
neap tide
moon is at a right angle; low tidal amplitude; tidal range is at its lowest
Nadir
point that earth is furthest to the moon; lowest gravitational forces
Zenith
point that earth is closest to the moon; high gravitational forces
gravitational force arrows point where
toward the center of the moon
centripetal force arrows
center seeking; what keeps planet in orbit; same at all points; points straight
resultant force
Fg - centripetal force ; this is what impacts tides; vectors point towards zenith or nadir; top and bottom arrows point into the center of earth
tidal period
12 hours and 25 minutes
lunar day
24 hours and 50 minutes
solar day
24 hours
syzygy
when earth, moon, and sun system are aligned; creates high tidal amplitudes; highest highs and lowest lows; during spring tides
what is the average tidal range in Jax
3-6m
disturbing force
whatever caused the wave to form; wind, body, pretty much anything
Where are ocean waves formed?
air-water interface
Where are atmospheric waves formed?
between 2 air masses of differing densities
Where do internal waves form?
water-water interface
What causes internal waves?
tides, turbidity currents, ship movements
- high density bottom water and low density surface water
wave base
point at which there is negligible water movement due to depth ; 1/2(L) - tells u depth of ocean that will be impacted
Stoke’s Drift
slight movement of water forward along the path of the energy transmission
How do we classify waves?
disturbing force, are they still under disturbing force, what restores them, wavelength
5 types of waves in increasing order
- capillary wave
- wind waves
- seiche - long period waves that rock back and forth
- tsunami
- tide
free wave
wave that is no longer under the force that created it ; tsunami
forced wave
type of wave that is still under disturbing force ; tide
deep water wave
waves that are found at a depth greater than 1/2 (L)
when steepness is greater than _____ what happens
1/7 < H/L
unstable and breaks - white caps
Beaufort Wind Scale
wind scale and state of the sea; 0-12 ; 0 is flat ass calm; 12 is hurricane; 3 presence of white caps
wave trains
free waves; group velocity is very slow; form series of rounded swells coming from offshore storm; progress forward, lose leading wave, gain new wave at the end of the train ; overall celerity of the group Cg = C/2
constructive wave interaction
come together in phase and build each other up. 1m crest meets 1m crest = 2m crest
destructive wave interaction
if out of phase, they will cancel
1mcrest meets .5m trough = .5m wave
mixed wave interaction
waves of different lengths and heights; form rogue waves
rogue waves
very dangerous, randomly large, rare waves coming in and against a powerful current; horn of Africa
wave refraction
bending of waves as they approach shore; regions that hit shallow water first, slow down allowing rest of wave to catch up
wave defraction
waves move around an obstruction; as waves strike the object they bend around the region, makes crossing area for waves beyond the island; lots of erosion
wave reflection
wave strikes barrier, bounces back - may form standing wave ; oscillate around node
3 types of breakers and characteristics
- spilling - JAX, gradual slope, long distance, East Coast
- plunging - steep slope, short distance, West Coast
- surging - very steep, very short distance
tsunami
seismic sea waves that move quickly and have extremely long wavelengths; caused by tectonic events; common in Pacific
shore
zone that lies between the low tide line and the highest area on land affected by strorm waves
coast
extends inland as far as we have ocean related features
coastline
region between the coast and the shore
backshore
upper region of the shore that is above high tide line
foreshore
part of shore that is exposed at low tide and exposed at high tide
shoreline
water-land interface; moves
nearshore
extends low tide shoreline to low tide breaker line
offshore
zone beyond breakers
longshore drift
movement of sediments parallel to shore driven by wave energy; longshore current (flow of water) moves particles up (angular) (swash) and straight back (flow) moving it in the direction of the current
summer beach
wide, sandy berm; light wave activity, backwash not significant; swash pushes particles up but backwash doesnt necessarily bring it all back ; NO LONGSHORE BARS
winter beach
heavy wave action; backwash dominates; narrow beach; longshore bars present
headlands have waves crashing on it called
defraction
barrier islands
extremely long offshore deposits of sand that run parallel to coast; protect mainland from high wave activity; temporary features that developed about 18,000 years ago at the end of the last ice age
Offshore bar theory
barrier island formation - waves crashing into the shadows build up sand and begin building the sand bar; sand bar will emerge and form barrier island
Spit accretion theory
barrier islands formed from sediment from longshore drift. Drift accumulates to form spit or strip of land connected to mainland that juts out of land connected to mainland that juts out into the water.
Submergence theory
water moves in on coastal ridges and separates them from the mainland
what kind of barrier island migration is happening now
transgressive migration - island moves back toward mainland - sea level rising
deltas
deposition of materials deposited at the end of the river; form in low energy areas; currents not too strong; broad continental shelf
Arcurate Delta
Ganges River; river mouth arches out into the sea and the river splits many times
Cuspate Delta
Ebro River; juts out arrowlike, does not carry a lot of sediment
Bird’s Foot Delta
Mississippi; a lot of deposition and so the river juts out into the sea or gulf; carries a lot of sediment
3 types of coral reefs and their descriptions
- atoll - specialized type of island found in the tropics; form from volcanic island
- fringing - found against shoreline; grows seaward from shore
- barrier - usually a lagoon that is separating the reef from the shoreline
how do atolls form?
- on an active volcano, coral growth starts to builds up close to the shore
- As the volcano becomes inactive and sinks, coral builds up more over time.
- Eventually, island sinks below sea level but a thick section of coral builds up to stay close to surface, creating the atoll.
mangrove
type of halophyte (tolerant to salinity); 3 kinds black, red, white
mangle
dense growth of mangroves
overwash islands
dominated by red mangroves; surrounded by estuary or lagoonal water; excellent for bird habitat
mangrove fringe
found along shoreline; protect shoreline and reduce erosion; dominated by red mangroves
coastal plain estuary
Chesapeake Bay; formed when ancient glaciers melted and some of the streams and rivers covered with water as sea level rose - lots of volume
fjord estuary
Glacier Bay; glacially carved; northern habitats where rocky coastlines are - glaciers melted sea water floods in; deep and steep
bar built estuary
used to be St Johns; sand bars or barrier islands build up by ocean currents and waves create protected area fed by smaller streams and rivers
tectonic estuary
San Francisco Bay; formed where tectonic activity sunk the land or the land is sliding by itself
vertically mixed
same salinity from surface to bottom but transition of salinity from fresh at the head to more saline at the mouth; shallow, low volume
slightly stratified
salinity increasing from head to mouth; more saline at bottom than top; tend to be a little deeper
Highly Stratified
deep deep, upper layer salinity increasing from head to mouth- surface waters low in salinity but marine at bottom
salt wedge
high volume; lots of water coming out of head which forms a freshwater lens over the more saline water
mixing salinity dependent on what 3 characteristics
shape of basin, river volume, range of tides
