MEA Test 3

What are the differences in vertical and horizontal water movement under nodal lines and antinodal lines in a SW in this basin?

The node (or nodal line for a narrow-width basin) is where all the particle motion is horizontal (no vertical movement of surface); The antinode (or antinodal line for narrow-width basin) is where the surface of the SW and all the particle motion under the surface moves vertically. Between these two extremes, the particle motion is a combination of both movements.

What are wetlands and what is their relationship to estuaries?

Wetlands mitigate flooding by collecting runoff waters and REMOVE INORGANIC NITROGEN COMPOUNDS AND METALS FROM GROUNDWATER POLLUTED BY LAND SOURCES. Marine wetlands, (border estuaries and other shore areas protected from the ocean) are biologically productive areas delicately in tune with natural shore processes. The key to the effectiveness of marine wetlands is the natural circulation and flushing provided by the tides.

What phase of the sun and moon will produce a spring tide?

When the moon is either in the 1st or 3rd quarter of its distance around the earth and 90 deg out of phase, the tides produced will have a minimum tidal range, because each tide 'acts on its own' and is not additive. We call the maximum range tide spring tide (when moon and sun are aligned and tides are additive)

impact wave

(such as Tsunamis) may be generated on the water surface by earthquakes or any other forms of impact.

salt-wedge estuary

deep estuaries with a large volume of fresh water

What relationship do free waves and forced waves have to their generating force, and under what conditions may each of these classes of waves be found?

1. Free waves - run independent of their generating force (such as impact waves and swell) 2. Forced waves - are dependent upon their generating force for their continued existence (such as the tides). 3. Free/forced waves - are those being actively generated (in an intense storm for instance)

tidal range

The difference in hight between a LW and an adjacent HW

What is the relationship between beach slope and particle size on a beach?

direct relationship

What part do swash and backwash play in this relationship? What part does grain size play in this relationship (think void space)?

long grain sand - have a lot of void spaces, making sand more porous, so some of the water (especially in the backwash - because the water comes to a stop before running back down the beach) percolates beneath and moves back toward the ocean under the surface of the beach. This means that some of the sand moved up the beach by the swash stays there - it is not moved back in the backwash - and a larger equilibrium slope must be established before an equal amount of sediment can be returned in the backwash very fine sand - no appreciable void space - so all of the water and the vast majority of sand that runs up the beach in the swash, runs back down the beach in the backwash on top of the surface, and the equilibrium of the beach establishes a very small slope

Partially mixed estuary

relatively shallow, moderately high-volume estuaries in which the salinity increases from the head to the mouth at any depth

How does this decrease, and the resultant re-partitioning of energy from kinetic to potential, cause the wave height to increase.

According to linear wave theory, the total energy (TE) in a wave is equally partitioned between kinetic energy (KE) and potential energy (PE) in deep water, and wave energy travels at a group velocity. In an ocean wave, KE prop C and PE prop H. An energy balance can be expressed as: TE = KE (C) + PE (H). Waves slow when they shoal, and because KE prop C, KE also will decrease. Since TE is conserved (held constant), the decrease in KE results in a comparable increase in PE, so wave height is increased.

What is an estuary and what relationship does it have to movement and interaction of ocean water and fresh water?

An estuary is a semi-enclosed basin of water in which fresh water mixes with, and significantly dilutes, coastal water.

How do these man-made structures affect the movement of sand and change the erosion or deposition of sand in the dynamic zone?

Any structure in the dynamic zone that interrupts this natural flow will create problems downstream. As the longshore drift is interrupted, sand accumulates on the upstream side of the jetties, but erodes on the downstream side. The erosion on the downstream side results because the sand moved away from that part of the beach by a wave's action is not replaced by sand from the normal upstream flow.

There are two different tides with two highs and two lows per day -- They are: Equatorial Tides - where the two high and low tides have equal heights. Why are these tides produced when the moon is directly over the equator?

As the earth rotates around its axis, someone standing on the equator would detect two high water levels (HW) and 2 low water levels (LW) with the same height and with a tidal period of 12 hrs. 25 minutes.

mixed Tides - where the two highs that occur each day do not have equal heights. Why can we also call them tropical tides?

As you watch the moon rotate around the earth in its 29 day orbit, you see that the plane of its orbit is inclined with respect to the earths equatorial plane at an angle of 28.5 deg (declination angle). When the moon is inclined with respect to the equator at its max declination in either the N or S hemisphere, one bulge is primarily in the Southern hemisphere. This means that if you were standing on the earth at 28.5 deg N, you would see two highs, but these highs would not be the same height because of the location of the two bulges are not in the same hemisphere.

Why do we need at least a year-long tidal height record at a particular spot in the coastal ocean before we can determine the importance of the partial tides present at that location, and be able to accurately predict future tidal heights at that location.

Conditions during any one month would not be representative of the seasonal conditions found and averaged over a year and seasonal variations from year to year could affect how the partial tides are added together and the importance assigned to each tide. SO for the longer term, these short term variations would be filtered out, so you get a much better determination of the partial tides at that location.

What are wave rays (also called orthogonals) and how are they oriented with respect to the wave crest-lines?

Crest lines of the advancing wave train, but also orthogonal lines that are perpendicular to the crest-lines. We call these orthogonal wave rays (they are an artifact used in drawings that show refraction, but a very useful one for understanding how wave energy is focused and spread ou).

What are near-shore coastal geostrophic currents and how do they compare to well established ocean currents further offshore

CGC's are also driven by density - induced sloping sea surface, but the cause of the slope is quite different than for the ocean geostrophic currents.

As waves shoal (enter increasingly more shallow water), why does wave celerity decrease?

Celerity for shallow water waves is directly proportional to depth or change in the orbital progressive waves until the depth decreases below 1/2 their wavelength. Thereafter, as a train of waves shoal they will slow down. As the waves in the train shoal, they will begin to "crowd up" with the second wave closing on the first wave, etc. and the wavelengths (L) between successive crests will decrease.

What do we mean when we say a sea is fully developed.

For a given constant wind speed, if the depth, fetch and duration are large enough (greater than the minimum required values of each), the waves that constitute the 'sea' will reach what is called "Full development", where the largest of the waves in the 'sea' (with period Tp) cannot grow any larger and its wave height and wavelength have reached their full potential. This means that if a sea is fully developed for a given constant wind speed, it CANNOT continue to grow, even if the fetch or duration is more than the minimum required for full development.

high water/low water for diurnal tides

Diurnal tides have one HW and one LW per tidal day Semi-diurnal (semi-daily ) tides - There are two semi-diurnal tides and both have 2 HWs and two LW per tidal day. The period and range in these tides have the same definition for that of the diurnal tides, but the period is half as large.

For a given wind speed, how can wind duration and wind fetch limit the sea from reaching full development?

For full development, fetch and duration must be greater than or equal to the minimum required for full development. If water is too shallow, the wave steepness will grow more than is warranted by the fetch and duration, and the breaking criteria will be reached before the waves are fully developed.

How does the wave spectral-peak period, and the area under the curve of a wave energy spectrum (where wave energy is plotted as a function of wave period), grow as the wind speed, fetch, or duration increase?

Total wave energy in a sea is represented by the area under the spectral plot. This total energy is a measure of the energy of all waves of any size that make up the 'sea'. The predominant wave in a sea is represented by the period of the peak of the spectrum (Tp).

Why is a Tsunami always a shallow water wave?

Tsunamis have such long wavelengths that they are always shallow-water waves. The leading wave of the train created by seismic event will move with a celerity proportional to the water depth and generally in an excess of 700 km/hr, and will arrive at distant locations within a few hours. Since Tsunamis are surface waves, the main requirement for their generation is that the full force of the impact is applied to, and displace the water surface. At sea, Tsunamis have wave heights of only about 0.5 m. With such small heights and long wave lengths, Tsunamis are not noticed by someone on a ship in deep water.

Wave dispersion is directly proportional to wave celerity. For deep water, therefore, does wavelength or water depth govern wave dispersion?

Wavelength

Contrast and compare salt marshes and mangrove swamps

salt marshes - are filled with a variety of grasses and are found from the equator to as high as 65 deg. latitude. mangrove swamps - restricted to latitudes below 30 deg. Once mangrove swamps colonize an area, they normally outgrow and replace marsh grasses.

Distinguish between erosional shoreline features (sea caves, sea arches, stacks and wave-cut bench or terrace) and depositional shoreline features (barrier islands, bay barrier, spit and Tombolo).

sea caves - the initial "burrowing into rock" on side of headland sea arches - when caves on both sides of the headland meet stacks - when arches collapse wave-cut bench or terrace -underlies the sand of the beach and shore regimes barrier islands - when sediments are deposited parallel with the shoreline and which produces a Lagoon bay barrier - if the spit spans between two jutting sides of an embayment spit-where sediments are deposited from a jutting point of land along the direction of the longshore drift which may eventually result in a bay barrier Tombolo - when a spit extends between an island and the land

Wind fetch

the distance over which the wind blows

What period and phase conditions between Tc and the TPF are required for the seiche to be enhanced to produce a free/forced standing wave called a resonance tide?

If Seiche has been set up by the wind with a Tc very nearly the same as the period of the forced SW (TPF) and most importantly, if Tc and the period of the TPF are in phase, then a small amplitude Resonance SW may be set up in a basin. In other words, Resonance SW is a Seiche that is "boosted" at just the right moment by the TPF to enhance its motion, and as a result, cause it to last longer and/or be larger than a totally free SW not so enhanced.

Explain how you would set up an experiment to determine Min. Duration for a fixed wind speed.

If our goal is to measure minimum duration required for full development, we must place our wave gauge at a distance at least as great as the theoretical minimum fetch required for full development. Assume first that you place a single wave gauge at a fetch that is greater than or equal to the minimum required fetch. Assume, initially there is no wind and no resulting waves and that the experiment begins when the wind begins to blow offshore and reaches a constant speed. You also would plot spectral growth, but NOW as a function of time, not distance.

During the passage of the moon in its orbit around the earth, the tides may alternate between being equatorial tides and tropical tides. How does the theory explain these changing tides and there different heights?

The changes in the tidal range (the difference in water height between HW and an adjacent LW) that occurs with a periodicity of about 2 weeks ( a fortnight). These tides result when we combine the tides produced by the moon and the sun.

The wave celerity of each of these two types of waves is a function of different variables - what are they?

Celerity is directly proportional to either L or T and water depth.

How is the diurnal inequality of a tropical/mixed tide defined?

Difference between the heights of the 2 hight waters (the HHW and the LLW)

Vertically mixed estuary

Generally shallow, low-volume estuaries that are well mixed vertically, and stratified horizontally

Highly -stratified (fjord) estuary

deep estuaries with net flows much like that of the slightly stratified estuary, but where the mixing is from the deeper ocean water up into the surface water, which creates a horizontal surface water salinity gradient that increases toward, and equals that of the ocean at the head.

wind wave

generated when wind blows across the water surface and momentum is transferred from the wind to the water.

wind duration

how long the wind blows.

What two forces are in equilibrium in this theory?

1. Gravitational attraction - the moon and the sun have on the water of the earth. G, the moon's gravitational force, will attract every part of the earth's surface depending on the distance of the moon from that part with G vectors on the earth pointing toward the center of the moon. The magnitude of the vector forces are inversely proportional to the square of the distance from those points to the center of the moon, and will tend to pull the water "toward the moon". 2. Centrifugal force - set up by the earth-moon system and the earth-sun system each rotating around a common center of mass. Created when a mass moves around a center of rotation. It is equal at all points on the center of the earth.

Why is an ocean wave described as being an orbital progressive wave, and what is the path of water particles at and below the surface as this wave passes?

ocean surface waves propagate horizontally along the air-sea boundary. They are orbital because, as the wave form passes a certain point, the water particles under the wave move with orbital paths. They are are progressive because the wave more moves (progresses) horizontally from one location to another.

What is the "American Mediterranean"?

Marginal sea. It includes the four basins of the Caribbean sea and the Gulf of Mexico. The Caribbean Sea is set off from the Atlantic ocean by an island arc called the Antillean Chain. Much of the water that circulates through the American Mediterranean comes from the S. Equatorial Currents. It leaves the Caribbean and enters the Gulf of Mexico through the Yucatan Straits. Some of this water circulates in a clockwise gyre in the Gulf, and then joins other water flowing directly through the Yucatan Straits, and out through the Florida Straits as the Florida Current. The Florida current joins with the remainder of the water from the N.Equatorial current that flows east of the Caribbean in the Antilles Current to form the Gulf Stream north of around Jacksonville, FL. Sometimes, the flow through the Yucatan Straits forms a CW looping current in the eastern end of the Gulf of Mexico. Occasionally, this Loop Current will intensify and turn with such a sharp curve as the current approaches the Florida Straits, that a clockwise rotating rig and warm core eddy is broken off.

Explain how you would set up an experiment to determine Min. Fetch. for a fixed wind speed

If our goal is to measure the minimum fetch required for full development, we must allow the wind to blow at least as long as the theoretical minimum duration required for full development. To see how this is done for wave fetch, consider the following set-up. The figure on the left is a plan view of the coast and the ocean. The figure on the right is a plot of the progressive growth of the wave spectra for a n increasing fetch. As you can see, six wave gauges (1-6) are located at increasing fetches away from a straight coastline. Then, for a steady wind that blows directly offshore for a long period of time, we measure wind-wave growth at each gauge and compare their wave-energy spectra, where the numbers correspond to the wave gauge from which the measurements are being made. The spectra will not continue to grow for any fetches longer than the minimum required for full development. And it also will NOT decrease for fetches longer than the minimum required for full development.

Contrast and compare jetties, groins, breakwaters and seawalls?

Jetties - artificial barriers attached ("anchored") to, and extending out from land into the longshore drift and include: breakwaters - made of rock rick-rack that cause incoming waves to break and dissipate their energy. A breakwater interrupts the longshore drift and prevents the movement of any sand directly along the beach at its location, groins - low-lying structures that stick out into the ocean and interrupt, but do not prevent the movement of all sediment tethered float breakers - dissipates wave energy without interrupting the flow of sand. sea walls - are rigid and solid structures generally built parallel with the shoreline, and are used as a last act of desperation when everything else had failed.

What two ways can the density slope that drives the current be established?

when strong southerly or southwesterly winds blow north along the Oregon coast, Ekman transport toward shore causes water to pile-up along the coastline, creating a slope gradient toward the ocean 0 this alone could cause this current. During the rainy season, runoff from major rivers in that region, swollen by heavy precipitation west of the coastal rang of mountains, can create a freshwater wedge that could also alone cause this current. combined, these processes create a stronger low density slope that extends away from the coastline toward the ocean

Define and explain what is meant by the equilibrium of a beach?

when the sand moved up-slope in the swash establishes an equilibrium with the sand moved down-slope in the backwash (ie the backwash returns as much sand as that moved toward shore by swash)

What are the names of the four major classes of estuaries (by origin), and what are their characteristics?

1. Coastal plain estuaries - formed at the end of the last ice age when rising seawater flooded existing river valleys. Ex: Chesapeake bay 2. Fjords - glaciated U-shaped valleys with steep walls. Usually, the glacial deposit pushed ahead by the advancing glaciers creates a shallow sill near the ocean entrance. Fjords are common along Norwegian and Canadian coasts. 3. Bar -built or barrier island estuaries - barrier islands that are separated from land by a shallow lagoon. They are formed by the creation of sand bars parallel with the shore, usually adjacent to slow flowing rivers that discharge freshwater into the coastal waters. The Outer banks of NC 4. Tectonic estuaries - caused by earthquakes, San Francisco bay

Explain the differences between waves classed as deep or shallow water waves, including how the shape of the water particle orbital paths differ.

1. Deep - (d>= 1/2 L). Ocean waves are unaffected by water depth. The diameter of the orbital paths of water particles under these waves decreases as depth increases below the surface and shrinks to 0 at d=1/2L. Wave celerity is directly proportional to either wavelength or wave period. Waves with longer wavelengths will travel faster than waves with shorter L or T. 2. Shallow - (d<=1/20 L ). Ocean waves are only under the control of water depth and the orbits are elongated ellipses with a major axis in the horizontal direction and the minor axis in the vertical direction. Only the minor axis decreases as depth below the surface increases so that near the bottom, the water motion is only horizontal and water particles move back and forth with the passage of a wave. Wave celerity is directly proportional to depth. This means that as water depth decreases, waves slow down.

Under what conditions are they formed with wave-current interaction?

According to non-linear ocean wave theory, large waves from storms that run directly into a strong oncoming current will steepen and actually gain energy from the current. Also, according to the theory, waves that run with a current will lose energy and those that cross a current will be refracted, but will otherwise be unaffected.

Define the Characteristic Period (Tc) for this type of basin?

Tc is the characteristic period of the free SW - this means that every time a basin is "excited" by the wind and a SW is produced, it will oscillate with the same characteristic period.

How long do these currents last?

The Davidson current IS NOT permanent. The dominant wind usually from the northeast, creating upwelling, and only during the rainy season do you get significant runoff

What relationship do white-caps have to the energy put into the sea by the wind?

These open-ocean, deep-water breakers are NOT caused by decreasing water depth, but because the waves have reached full development and are already as steep as they can be, so the excess energy must be dissipated.

high-high water, low-low water, high-low water, low-high water for mixed or tropical tides

They are found when the moon is around 28 deg above or below the equator. Mixed tides also have 2 HWs and 2 LWs per day, but they are not the same height. This tide has four tidal ranges and each HW and LW have different names.

What is the major difference in the movement of water in a breaking wave as compared to water movement in the same wave before it breaks?

Just as it begins to break and the water particles changes from their orbital paths to a more horizontally-oriented translational path that hurls the water toward the beach as swash.

How do dispersing waves sort themselves out, so that "order" is created from "chaos"?

Longer waves run faster than shorter waves ( because celerity of a deep water wave is directly proportional to length or period). Longer waves outrun the shorter waves and order is created out of chaos. This sorting of waves by wavelength is called wave dispersion.

What is longshore drift, and how is it related to longshore currents?

Near-shore currents may distribute some of this sediment to the edge of the shelf break and onto the slope, but most sediments are distributed in the surf zone by waves as longshore drift. Much more important for understanding marine depositional coasts, is that wave action also will pick up sediment that will be moved by the longshore currents. The movement of sand by these is called longshore drift.

Who formulated the Equilibrium theory and what are the theory's simplifying assumptions

Newton. A perfectly spherical earth covered with water, but with no basins nor continents, nor bottom friction)

How are they formed by constructive interference of two or more wave trains.

Rogue waves are thought to occur when the period of arriving waves are harmonics (1/4; 1/2; etc.) of the period of the predominate wave and when all the crests arrive together, suddenly producing a constructed wave that is the sum of the heights of all the waves that are interfering.

What are Rogue waves?

Rogue waves are unpredictable and very damaging. With maximum heights of around 30 meters, or 100 ft), they get their name form the sudden way in which they seem to appear. They are thought to be caused by wave current interaction and constructive interference.

Explain why wavelength (L) also decreases during shoaling.

Shoaling waves crowd up and L decreases.

Which of these two waves occurs most frequently and which does the most overall damage on an annual basis?

Storm surges occur more frequently and are more damaging.

tidal period

The time between two adjacent HWs or LWs

What causes the brine pools in the Red Sea, and how does the circulation with the Indian Ocean contribute?

The basin that forms the Red Sea is being created by the separation of the Arabian Peninsula from the African mainland because of plate movement (that also created the great African Rift Valley). It is separated from the Gulf of Aden and the Indian Ocean by a narrow strait and a shallow sill of only 125 m in depth, but has a depth of over 2300 m at its deepest point.

What is meant by the dynamic zone of the shoreline?

The dynamic zone of a beach includes all of the shore and coastal areas that are affected in any way by breaking waves, including those parts that are covered with water during a hurricane storm surge.

Contrast and compare the way that waves change direction during reflection, refraction and diffraction?

Reflection - waves that encounter a solid vertical surface (such as a seawall) will abruptly change direction, and if they hit at an angle, without much loss of energy. Angle of incidence (Xi) is equal to the angle of refraction (Xr). Sometimes reflection can crated dangerous conditions when the reflected waves interferes constructively with an incoming wave, creating a wedge with nasty characteristics. Very large waves, may reflect a good portion of their energy off the continental shelf and slope, even though the wave also will break as surf in shallow water. Diffraction - Involves bending of wave rays, but now that bending is around corners or edges of solid objects such as breakwaters, other harbor structures, or islands, and is not the result of changes in wave celerity as a result of changes in depth. When striking the edge of a solid surface, any point on a wave may be the source from which energy can propagate in all directions. Refraction - waves also may bend as they shoal (because C prop d) if they approach the beach at an angle. At some distance away from the coast the crest-lines may approach at an angle of more than 45 degrees, but as they get closer to shore they appear to bend so that the crest-lines are more parallel with the coastline by the time they reach the surf zone. Sometimes they bend (refract) around a point of land, because the portion of a crest-line that reaches shallow water first is slowed (remember c prop d), but the portion still in deeper water continues at its regular celerity .

What is the loop current in the Gulf of Mexico, and how is it associated with the Florida Current?

The Florida current joins with the remainder of the water from the N.Equatorial current that flows east of the Caribbean in the Antilles Current to form the Gulf Stream north of around Jacksonville, FL. Sometimes, the flow through the Yucatan Straits forms a CW looping current in the eastern end of the Gulf of Mexico. Occasionally, this Loop Current will intensify and turn with such a sharp curve as the current approaches the Florida Straits, that a clockwise rotating rig and warm core eddy is broken off. This Loop Current was the source of very warm water continually supplied to the easter portion of the Gulf that allowed hurricanes crossing west over Florida to explode from a Category 2 to a Category 5 storm in 12-16 hrs.

How does wave interference occur, and what is the difference between constructive and destructive interference?

In a large storm, component waves of many different wavelengths and directions are being generated simultaneously and they combine, by the process of interference, to create "sea", a very chaotic state of the sea surface that has no discernible organization. Destructive interference - where crests and troughs arrive out of phase, canceling each other out Constructive interference - where crests and troughs are in phase and reinforce each other.

Explain why and how this process increases the wave steepness parameter, H/L, and why we call H/L > 1/7 the breaking criteria?

Therefore, because H increases and L decreases, H/L will increase doubly fast, and in theory when the breaking criteria (H/L>1/7) is exceeded, the wave will break with its swash rushing onshore.

Why is a seiche a free standing wave?

Therefore, these free SWs are "tuned" to their basin, and, using the name given to such waves by the Swiss, are called Seiche.

How 'big' are the waves when the sea is fully developed and in what way may the wave steepness parameter, H/L, be used to explain this 'bigness'.

Wave steepness of an ideal wave is measured by the "steepness parameter", H/L which increases as H increases and/or as L decreases. When H/L > 1/7, waves become too steep and unstable, so they break; therefore, H/L>1/7 is called the breaking criteria. As wind speed increases, full development results in larger and larger values of H and L and requires longer and longer minimum fetches and durations. For full development, fetch and duration must be greater than or equal to the minimum required for full development. Full development at a given wind speed will not remain full developed if wind speed increases.

In what zone (and how close to shore) are longshore currents found, and how are they created by ocean waves?

Waves that approach a shoreline at an angle and then break the surf zone will produce a longshore current. It is created when these waves break, and the water continues to rush up the beach (at the same angle as the wave's approach) as swash, but when it stops, the water runs back down the beach along the greatest slope as backwash, being pulled by gravity. This swash/backwash motion will result in a zigzag movement of the water with a net direction that is the same as the approaching waves and which will produce a longshore current.

Combined Effects of the Moon and Sun (with fortnightly period of 14 days). How does the sun's tide-producing force combine with the moon's tide-producing force to create this twice monthly tide?

When the sun and moon are lined up on the same axis through the center of the earth, either with the moon on the same side as the sun (a new moon) or on the opposite side from the sun (a full moon), the tides produced by each will be additive. This will produce a new bulge that is the sum of the moon's bulge and the sun's bulge producing a maximum tidal range.

Under what depth and shoreline conditions are wave rays focused by refraction and toward what shoreline depth do the wave crest-lines (or wave rays) bend?

When wave trains approach an irregular coastline, the portion of the wave train that first encounters the shallow water of the headland will slow and both the crest-lines and the wave rays will turn toward the headland and the waves will quickly break in the headland surf zone. that portion on either side of the headland will continue for some time at its deeper water celerity without refracting. Often, there are bays between two headlands. Note that if we advance the waves toward shore, the wave rays will bend "toward" shallow water (toward the headlands) and away from the bay. During this refraction into the bay, the area between two wave rays and two adjacent wave crests increases. Therefore, the wave energy per unit area is greatly decreased when the train enters the surf zone of the bay.

The Equilibrium theory cannot be used to explain diurnal tides (that have only one high and low per day ), but it can give us insight into tides that have two highs and two lows in a day, and into combined tides produced by the sun and the moon: Tides with 12 hr 25 min. periods. Explain why the semi-diurnal period is not 12 hr (the earth rotates once around its axis in 24 hrs, doesn't it?)Use example given in lessons about why lunar tide is 24 hrs 50 min (and divide it by half)

While the earth was making one complete CCW revolution (24 hrs in solar day), the moon also was moving CCW around the earth, so to come again under the moving maximum bulge, the earth has to rotate an additional 50 minutes - the lunar day (and half of 24 hr 50 min is 12 25).

Distinguish between offshore, nearshore, and foreshore

foreshore = the part of the shore between the high-tide and low-tide shorelines that is submerged and uncovered repeatedly by the tides) Nearshore - region between the low tide shore line and the low-tide breaker line offshore - everything seaward of the low-tide breaker line

What about a neap tide?

minimum range tide (when the moon and sun are 90 deg out of phase and acting independently)

What are partial tides, and how do they compare with component waves found in "sea".

that the actual tide at a location (analogous to the "sea" in an active wind-wave generation field) is composed of a number of component waves of different periods called Partial Tides.

Antillean chain

includes islands of Cuba, Hispaniola, Puerto Rico, Jamaica, and the Greater and Lesser Antilles).

How are waves classified by period and what are their principle generating and restoring forces? (5)

The principle generating forces and principle restoring forces change as the period of waves increase. Principal generating forces: moon and sun, earthquakes, volcanoes, landslides, storms, wind. Restoring forces: Coriolis/friction, gravity, surface tension 1. smallest waves - capillary waves (period <0.1 seconds). The surface is restored by surface tension. They are generated as the wind begins to blow. 2. Gravity waves - (T = 1 - 30 seconds). Generated by wind storms and restored by gravity. 3. Infra-gravity waves - generated by strong storms and restored mostly by gravity. Period around 1 min. 4. Long waves - (period > 5 min). Generated by intense storms and by earthquakes, and restored by gravity and the Coriolis force. 5. tides - (periods 12 - 24 hours). Generated by the sun and moon and restored by bottom friction and Coriolis force.

When do "white-caps" (the breaking of waves in deep water) form during the growth of a fully-generated sea?

Even after the seas are fully developed, the wind may continue to transfer momentum to the ocean but, because the waves cannot grow any larger (they are fully developed), the excess energy supplied by the wind MUST BE DISSIPATED. This is accomplished through the turbulent breaking of the waves, which dissipates the excess energy and creates "white caps."

In how many ways does Storm Surge differ from a Tsunami?

Intense cyclones at sea have very low pressure centers around which the storm winds blow. This low pressure creates a "hill" of water on the surface that moves with the storm. This hill and the water in the right front quarter of the store being pushed by the winds in the same direction the store is moving create a high water surge that can exceed 10m. Storm surge is more like a very fast rising tide, that quickly reaches its peak and then stays there until the storm moves well onshore.

What does the theory predict about the movement and accumulation of water on the earth as a result of these bulges and the moon's movement around the earth?Why are there two water "bulges" found on the earth in line with the position of moon above the earth?

The Gravity force vectors point directly toward the center of the moon with magnitudes that are inversely proportional to the square distance from those points to the center of the moon and will tend to pull the water toward the moon. Therefore, at all points on the earth closest to the moon will have the largest G, and those farthest from the moon will have the smallest G. The centrifugal force vectors are all equal in length and are pointing in the same direction away from the moon. By vector addition, we end up with short vector tractive forces on the surface of the earth that point both toward z on the moon side of the earth-moon axis and toward N on the opposite side of the earth from z. These forces are in equilibrium and together result in TPF. TPF is inversely proportional to the cube distance between the attracting masses, the distance between masses becomes more important than the size of the masses. The closeness of the moon the the earth means that the moon's TPF is twice that of the sun. THE RESULTING TRACTIVE FORCES CAUSE THE WATER ON OUR FRICTIONLESS SPHERICAL EARTH TO MOVE TOWARD BOTH POINTS N AND Z, SO WE GET 2 "BULGES" ON OPPOSITE SIDES OF THE EARTH. The bulge on the side of the earth nearest the moon (zenith) is primarily the result of the moon's gravitational attraction. The bulge on the opposite side of the earth (N) is primarily the result of the centrifugal force of the earth-moon system.

Contrast and compare sea and swell.

The first swell to arrive at some distant point will be the longest and as the storm gets closer, the wavelength (or period) of the arriving swell will decrease and wave height will increase(because as the progressively shorter waves arrive the energy per unit area increases - the wave energy is concentrated in a smaller area between crest lines and wave rays).

Dynamic Theory How do the assumptions for this theory differ from those of Equilibrium Theory.

The key dynamic theory of tides is that the tides are really just very long waves. This means that we can treat tides as we would long waves and assume that the actual tide at a location is composed of a number of component waves of different periods called partial tides.

How does a coastline differ from a shoreline?

The shoreline is defined as the water's edge, which moves back and forth, up and down the shore, with the tide. The coastline is the demarcation line (the landward limit) of the effect of the highest storm waves on the shore (and in which marine flora and fauna are found)

Why is a SW produced by the TPF called a forced wave?

The tide producing force may cause very small-amplitude forced SWs with semi-diurnal periods. Most of these are insignificant (with a range usually measured only in centimeters). Free - A strong wind blowing for a long period of time in a constant direction along the long axis of a narrow enclosed basin (such as a continental lake) will push the water to one end. this wind set up may create a small amplitude free SW.