Oceanography 251 – Exam 3 Study Guide

What causes waves to form?

Key:

CHAPTER 8: WAVES 

CHAPTER 10: SEDIMENT TRANSPORT 

CHAPTER 11: OCEAN POLLUTION 

Study Guide Outline 

Vocabulary

CHAPTER 8: WAVES 

Waves: 

• Waves: representation of energy of the ocean

o All about energy! “water doesn’t move, energy does”

o Waves propagate energy:

▪ Kinetic: something moving from one place to another

???? Push wave down – moves water

▪ Potential: potential to do something

???? Lift surface of the ocean up

What are the two most common waves?

o * equilibrium is imperative for wave to occur! There is  not initial energy until…

▪ Disturbing force: “what causes waves to form” –

wind, tides (long waves,) seismic disturbance (when  

seafloor suddenly dropped down/changed, not very  

common,) impact

▪ Restoring force: “what causes waves to ‘continue,’  

and “push back” (think pendulum!) – gravity, surface  

tension (hydrogen bonding – attracted to each other,)  

Coriolis force (for jet streams)

o * all waves have both^ ! – D Force “kicks off” wave, R  Force allows for oscillation and “pushes back”

Waves (cont.) 

What is the energy from wind?

• Wavelength “L”: the horizontal distance between successive  crests

• Amplitude: the vertical distance of wave – half the distance  between crest and trough Don't forget about the age old question of Why are females more careful about mating?

• Crest: highest point of the wave

• Trough: lowest point of the wave

• Period: amount of time it takes for successive wave crests to pass  specified point  

• Speed: L/P (wavelength/time it takes to go that distance)  aka: wavelength/period

• Celerity: the speed of the progressing wave with respect to  stationary water  

• ‘Wave Steepness:’ Height/Wavelength

• Shallow-Water Waves: ‘D <L/20’ – when the water depth is less  than the wave base – speed (celerity) depends on depth! • Deep-Water Waves: ‘D>L/2’ – when the water depth is greater  than wave base – speed (celerity) depends on wavelength! • Transitional Waves: waves that have both deep and shallow wave characteristics – celerity depends on BOTH water depth AND  wavelength We also discuss several other topics like How are rare bases incorporated into trnas?

• Internal Waves: waves located at the thermocline (completely  submerged)

o As a result of ‘water + water interface’

o Cannot be seen

o Associated with the pycnocline

o Larger than surface waves

o Caused by tides, turbidity currents, winds, ships

o Possible hazard for submarines (as submarines like to reside  at the thermocline)

• Ocean waves: most common waves

o As a result of ‘water + ocean interface’

o Ex. surface waves

o Most common waves

o 1M high

▪ ‘Energy in Ocean Waves:’

???? most energy is at an average of 10-second time  

frame (aka: period = 10 seconds!) If you want to learn more check out Why are consumers so resistant to product placement?

???? waves transmit energy

• ex. cyclic motion of particles in ocean  

(results in circular orbit)

o > * diameter of orbital motion decreases with depth of water

o Wave Base: = ½ L (there is hardly any motion below the  wave base due to wave activity)

• Atmospheric Waves: waves present in the atmosphere o EX. successive lines of clouds

o As a result of ‘air + air interface’

Wind Forcing/Energy: 

• “Factors affecting wave height…”

o Wind speed

o Wind duration

o Fetch: distance over which wind blows Don't forget about the age old question of How does valence bond theory describe the bonding in n2?

• ‘Fully developed sea:’ maximum wave height, wavelength for  particular fetch, speed, and duration of winds at equilibrium  conditions

• Swell: uniform, symmetrical waves that travel outward from storm  area – long crests – transport energy long distances!

** Longer wavelength waves travel faster and outdistance  other waves!!!

Wave Interference Patterns: 

• Constructive Interference: in-phase wave trains with about the  same wavelengths

o (Wave Train: a group of waves with similar characteristics) • Destructive Interference: out-of-phase wave trains with about  the same wavelengths If you want to learn more check out What is the focus of medical geography as a field?

• Mixed Interference: two swells with different wavelengths and  different wave heights

Waves Breaking: 

• Surf Zone: zone of breaking waves near shore

o Spilling Breakers: occur at the gently sloping seafloor – wave energy is expended over longer distance – water slides  down front slope of wave

o Plunging Breakers: occur at the moderately steep seafloor  – wave energy is expended over shorter distance – results in  curling wave crest *best for board surfing! If you want to learn more check out How do officers behave under preventive patrol?

o Surging Breakers: occur at the steepest seafloor – energy  spread over shortest distance – waves break on the shore * best for body surfing!

• Shoaling Water: water becoming gradually more shallow o When deep-water waves encounter shoaling water less than  half their wavelength, they become transitional waves. 

• “as a deep-water wave becomes a shallow-water wave…” o wave speed decreases

o wavelength decreases

o wave height increases

o wave steepness increases

▪ when steepness is greater than or equal to 1/7, the  

wave breaks

Wave Refraction: 

• Waves rarely approach shore at a perfect 90 degree angle • As waves approach shore, they bend so wave crests are nearly  parallel to shore 

• Wave speed is proportional to the depth of water (shallow-water  wave!) 

• Different segments of the wave crest travel at different speeds o Results:

▪ Wave energy is unevenly distributed on shore!

???? More energy released on headlands

???? > As opposed to bays: where energy is more  

dissipated

???? can be seen with…

• Orthogonal Lines: “wave rays,” are drawn  

perpendicular to wave crests

• Wave Reflection:

o Waves and wave energy are bounced back from barrier

o Reflected wave can interfere with next incoming wave

o With constructive interference, can create dangerous plunging  breakers

Tsunamis: 

• Seismic sea waves

• Originate from sudden seafloor topography changes:

o Earthquakes = most common cause

o Underwater landslides

o Underwater volcano collapse

o Underwater volcanic eruption

o Meteorite impact (splash waves)

• Long wavelengths (> 200km or 125 miles)

• Behave as a shallow-water wave

o Encompasses entire water column, regardless of ocean depth o Can pass undetected under boats in open ocean

• Speed is proportional to water depth!

o Aka: very fast in the open ocean

• Highly destructive – sea level can rise up to 40m when a tsunami  reaches shore

o EX. Indian Ocean Tsunami, Japan Tsunami

• Tsunami Warning Systems:

o Pacific Tsunami Warning Center: ‘PTWC,’ located in  Honolulu, Hawaii, uses seismic wave recordings to forecast  tsunami

o Deep Ocean Assessment and Reporting of Tsunami: ‘DART,’ system of buoys that detect pulse of tsunami passing o Tsunami Watch: issued when potential for tsunami exists o Tsunami Warning: unusual wave activity verified

▪ Evacuates people/moves ships from harbors

CHAPTER 8: WAVES COMPLETE 

CHAPTER 10: SEDIMENT TRANSPORT: 

Erosion and Deposition: 

• Erosion: sand being removed

Beaches: 

• Beach: interface between land and water (coast)

• The beach is a dominant coastal feature

• Wave activity continually modifies the beach/coastal areas o Sea level changes affect the coast!

▪ Globally, sea level is rising! 

???? > people are trying to keep the water from  

moving inland – resulting in various coastal  

stabilization attempts which have created  

temporary solutions that can become problematic  

with time

• Beach (cont.) : from land not impacted by water, out to deep  water where there is not a free transport of sediment (aka: a bar) • > Bar: accumulation of sediment offshore (parallel to the beach!) • Berm: region above the high tide (but still affected by the ocean!)  Sand movement along beach:

• Two major types:

o Perpendicular to shoreline (toward and away)

▪ Swash: water rushes up the beach

▪ Backwash: water drains back to the ocean

o Parallel to shoreline (up-coast or down-coast)

▪ Longshore Current: net motion of beach that  

transports material on long face of the beach

“Summertime Beaches:” 

• light wave activity (“quiet time” – low energy!”

• wide, sandy berm

• steep beach face

• swash dominates

• longshore bars are not present

• generally milder storms

“Wintertime Beaches:” 

• heavy wave activity (high energy!)

• backwash dominates

• sediment moved away from shore

• narrower beach

• flattened beach face

• longshore bars are present

• stormy weather

Longshore Current:

• “zigzag” movement of water along shore (surf zone)

• travel at speeds up to 4km (2.5mph)

• can transport huge amounts of sediment

• parallel motion of water along shoreline

• always in the direction of the waves! 

Longshore Transport:

• Only occurs in the shallow water of surf zone

• Transports beach sediment in same zigzag fashion, in the same  direction of the longshore current

• Beaches sometimes called “rivers of sand”

• Millions of tons of sediment moved yearly

• Direction of transport changes due to wave approach

o ** In general, net sediment movement is southward  along the Atlantic and Pacific coasts of the U.S.

“Two Major Types of shores…”

Erosion Shores: emerging coastlines resulting in well-developed cliffs – existing where tectonic uplift of coast occurs (won’t spend too much time on  these!)  

• EX. U.S. Pacific Coast

Depositional Shores: gradually subsiding shores resulting in barrier islands  and sand deposits

• EX. South Padre Island = Barrier Beach

>Depositional Shores: 

• Naturally occurring features:

o Bay barrier: “bay mouth bar,” seals off a lagoon from the  ocean

▪ Low energy environment (aka: deposition)

o Tombolo: “tied island,” a sand bar that connects an island to  the mainland  

▪ As a result of reduction in wave energy (“because they  are in the shadow of wave energy”

▪ Breakwater Feature: “human version of tombolo,”  

aka: man-made island

o Barrier Islands: “barrier beach,” long offshore sand deposits  that parallel the coast

▪ Protects land behind it – creates shallow lagoon

o Spit: connects at one end to the mainland and hooks into a  bay at the other

o Delta: as a result of the deposition of sediment carried by the  flow of water located at the “mouth” of a body of water - an  area of land in which a river divides into smaller rivers,  

emptying into a larger body of water  

Barrier Islands/Beaches (Cont.)

• Sediment deposits that stretch offshore (not ideal for building  because it is fragile, exposed to wind, etc.)

o * prime location for hurricanes because subject to great  forces: floods, extreme winds, etc. 

• extremely long offshore deposits of sand parallel to the coast • do not exist along erosional shorelines

• protect mainland from high wave activity

• appear to have developed at the end of the last ice age 18,000  years ago… Formation:

o Beach > dunes > marsh & tidal flat > lagoon >> mainland ▪ Ocean beach: closest part of the island to the ocean

▪ Dune: stabilized by grasses; protect lagoon from strong  storms

▪ Barrier Flat: a grassy area that forms behind dunes

▪ High and low salt marshes: biologically productive  

wetlands

???? Generate ‘Peat deposits’ or ‘peat bed’ of  

decaying organic matter – prime indicator that  

this is taking place! *(can’t produce peat in the  

ocean because there’s too much turbulence)

▪ Lagoon: water between barrier island and mainland

• Progression (retreating) of barrier beaches:

o Older peat deposits found on ocean beach

o Migrate landward overtime due to rising sea levels

>Changing sea level: 

• Two major processes can change sea level:

o Local tectonic processes:

▪ EX. pacific coast of US is currently being uplifted

▪ Isostatic adjustments: rebound of Earth’s crust after  removal of heavy loads or sinking with application of  

heavy loads

???? Ice-loading from glaciers during ice ages

o Global changes in sea level:

▪ Ice ages lock seawater up in ice (glaciation) – sea level  goes down

▪ Ice melting after an ice age (deglaciation) – sea level  

rises 

▪ Thermal expansion/contraction of seawater:

???? Physical property of water: warmer water  

expands and cooler water contracts (roughly  

2m per 1 degree C, change in temperature)

▪ Glaciation Cycles: from 2 million to 10000 years ago,  a series of ice ages affecting Earth

???? Sea level was at least 120m below today’s sea  

level (* if all remaining ice on Earth melted today, 

sea level would rise another 70m!) 

???? Globally averaged temperatures = .6C warmer  

over last 130 years

???? Sea level rose 10-15cm over past 100 years

Hard Stabilization: 

• Structures built to decrease coastal erosion and interfere with sand  movement - also called ‘armoring of the shore’

• Often results in unwanted outcomes:  

o EX. some structures may accidentally increase wave erosion • Four major types:

o 1. Groins and groin fields

o 2. Jetties

o 3. Breakwaters  

o 4. Seawalls  

• 1. Groins and Groin Fields:

o Built perpendicular to the beach (often made of rip rap, or  large block material)

o Traps sand upcoast, which can cause erosion downstream of  the longshore current

o May necessitate a Groin Field: a series of groins built along a  beach

o Sand is distributed differently, but no additional sand is on  the beach

• 2. Jetties:

o Built perpendicular to shore

o Built in pairs (to create channel)

o Built to protect harbor entrances: EX. Santa Cruz Harbor, CA • 3. Breakwaters:

o Built parallel to a shoreline

o Designed to protect harbors from waves

o Can cause excessive erosion, requiring dredging to keep area  stable  

▪ EX. Santa Barbara between 1931 and 1949, breakwater  disrupted longshore transport of sand

• 4. Seawalls:

o Destructive to environment

o Designed to armor coastline and protect human developments o One large storm can remove beach

o Wave actively eventually undermines seawall structure; need  continual repair or will collapse

Alternatives to hard stabilization:

• Three major alternatives:

o Construction restrictions:

▪ Simplest alternative

▪ Limit building near shorelines

▪ Paradoxically, national flood insurance program  

encouraged construction

o Beach replenishment:

▪ Sand added to beach/longshore current

▪ Expensive; costs between $5 and $10 per cubic yard

▪ Sand must be dredged from elsewhere

o Relocation:

▪ Moves structures rather than protect them in areas of  

erosion

CHAPTER 10: SEDIMENT TRANSPORT COMPLETE 

CHAPTER 11: OCEAN POLLUTION 

Oil in the Marine System: 

• Oil Spills:

o Transportation spills, shipping, oil rigs, etc.

▪ [EX. Exxon tanker in Alaska – boat accident – released  

large amount of oil into high energy environment with  

coarse sediment – affected marine life, fisheries, etc.]

???? had a slower recovery time in comparison to  

recovery time in Gulf of Mexico, as a result of  

metabolic rate of oil-eating bacteria. -- because  

the water was too cold for bacteria to  

thrive/function

o > ** aka: it is harder for colder environments to  

recover from an oil spill as opposed to warmer  

environments!

o * Oil is more buoyant and calmer than surrounding  water! (result of the suppression of capillary waves, as a  

result of oil reacting to water’s hydrogen bonding)

▪ EX. Oil spills as a result of tanker – oil enters at surface 

???? Initially remains on top of the water but  

eventually gains density and sinks to bottom of  

the ocean affecting deep water marine life as well

▪ EX. Oil spills as a result of deep–water rig/pipe – oil  

enters at seafloor under very high pressure  

** “2010 Deep-water Horizon Spill – 5 million barrels – 210 million gallons  AKA: largest accidental oil spill!”

** “1991 Saudi Arabia, Kuwait – Oil terminals/tankers – 240 million gallons  AKA: largest (intentional) oil spill!” - (as a result of war)

Oil in the Marine System (cont.) 

Oil: a natural compound part of the ecosystem as a result of decay,  controlled by bacteria

• Natural seeps: 47%

• Human sources: 53% (tankers/rigs/petroleum consumption) o > Petroleum Consumption:  

▪ EX. getting oil changed: some left in bottle – thrown out  – will eventually leak – will rundown – reach river –

eventually runs off into ocean

▪ OR: direct dumping into drainage/sewage

> Ocean Dumping/Sewage:

• EX. Evolution of “New York Bight Sludge Sight” – (dumping sight) • Creates productivity in low-energy environment – accelerates  photosynthesis in an environment that is unable to keep up • * Efforts to counteract dumping have been made/have provided for  improvement (especially in US!)

o Beaches are cleaner now than ever

▪ EX. Est. dumping restrictions – “loosen” the further you  get away from shore – but still have had a significantly  

positive impact

o Poorer nations cannot say the same… – the greater the  poverty, the greater the pollution

> Plastics: 

• EX. water bottles, toothpaste, fleece jackets (from just washing  your fleece and releasing plastic fibers)

o >these microplastics are confused with food – consumed by  organisms, which in turn affects the entire food chain

• vast majority of marine debris

o 80% of marine debris from land sources (most of it is plastic) • not readily biodegradable

• entangle fish, marine mammals, and birds

• plastic bags choke turtles – mistake them for jellyfish

• some plastics attract poisons, EX. DDT, PCB’s

• floating plastics photodegrade – break into smaller pieces • plastic particles are significantly increasing

• regions of floating trash – Eastern Pacific Garbage Patch Non-Point-Source Pollution/Trash:

• Aka: not from underwater pipelines, EX. storm drains

• EX. trash, road oil, pesticides/fertilizers… 

• > Nutrient loading from fertilizer run off: 

o Dead Zones: low-oxygen areas where life (fish/typical sea  life) cannot survive, caused by excessive nutrient pollution  that depletes the environment’s oxygen - as a result of the  pollutants (nitrates) in fertilizers being “run off” into rivers,  lakes, oceans, etc.

▪ EX: along the East Coast, Gulf of Mexico, Great Lakes – the second largest dead zone in the world is in the U.S.  

in the northern Gulf of Mexico

Urban Run-off: either wet weather (rainwater) or dry weather (water  waste) that flows from urban landscapes carries pollutants of various kinds  into storm drains, sewage systems, and receiving waters.

Potential Solutions for Ocean Pollution: Bioremediation Bioremediation: the use of either naturally occurring or deliberately  introduced microorganisms or other forms of life to consume and break  down environmental pollutants, in order to clean up a polluted site.

• Cost effective, sustainable, natural approach to cleaning up  contaminated sites – biological agents include: bacteria, microbes,  fungi, and other organisms of their enzymes.

CHAPTER 11: OCEAN POLLUTION COMPLETE 

 EXAM III: CHAPTER 8, 10, 11: COMPLETE

11/7/16 4:46 PM

11/7/16 4:46 PM

Oceanography 251 – Exam 3 Study Guide

Key:

CHAPTER 8: WAVES 

CHAPTER 10: SEDIMENT TRANSPORT 

CHAPTER 11: OCEAN POLLUTION 

Study Guide Outline 

Vocabulary

CHAPTER 8: WAVES 

Waves: 

• Waves: representation of energy of the ocean

o All about energy! “water doesn’t move, energy does”

o Waves propagate energy:

▪ Kinetic: something moving from one place to another

???? Push wave down – moves water

▪ Potential: potential to do something

???? Lift surface of the ocean up

o * equilibrium is imperative for wave to occur! There is  not initial energy until…

▪ Disturbing force: “what causes waves to form” –

wind, tides (long waves,) seismic disturbance (when  

seafloor suddenly dropped down/changed, not very  

common,) impact

▪ Restoring force: “what causes waves to ‘continue,’  

and “push back” (think pendulum!) – gravity, surface  

tension (hydrogen bonding – attracted to each other,)  

Coriolis force (for jet streams)

o * all waves have both^ ! – D Force “kicks off” wave, R  Force allows for oscillation and “pushes back”

Waves (cont.) 

• Wavelength “L”: the horizontal distance between successive  crests

• Amplitude: the vertical distance of wave – half the distance  between crest and trough

• Crest: highest point of the wave

• Trough: lowest point of the wave

• Period: amount of time it takes for successive wave crests to pass  specified point  

• Speed: L/P (wavelength/time it takes to go that distance)  aka: wavelength/period

• Celerity: the speed of the progressing wave with respect to  stationary water  

• ‘Wave Steepness:’ Height/Wavelength

• Shallow-Water Waves: ‘D <L/20’ – when the water depth is less  than the wave base – speed (celerity) depends on depth! • Deep-Water Waves: ‘D>L/2’ – when the water depth is greater  than wave base – speed (celerity) depends on wavelength! • Transitional Waves: waves that have both deep and shallow wave characteristics – celerity depends on BOTH water depth AND  wavelength 

• Internal Waves: waves located at the thermocline (completely  submerged)

o As a result of ‘water + water interface’

o Cannot be seen

o Associated with the pycnocline

o Larger than surface waves

o Caused by tides, turbidity currents, winds, ships

o Possible hazard for submarines (as submarines like to reside  at the thermocline)

• Ocean waves: most common waves

o As a result of ‘water + ocean interface’

o Ex. surface waves

o Most common waves

o 1M high

▪ ‘Energy in Ocean Waves:’

???? most energy is at an average of 10-second time  

frame (aka: period = 10 seconds!)

???? waves transmit energy

• ex. cyclic motion of particles in ocean  

(results in circular orbit)

o > * diameter of orbital motion decreases with depth of water

o Wave Base: = ½ L (there is hardly any motion below the  wave base due to wave activity)

• Atmospheric Waves: waves present in the atmosphere o EX. successive lines of clouds

o As a result of ‘air + air interface’

Wind Forcing/Energy: 

• “Factors affecting wave height…”

o Wind speed

o Wind duration

o Fetch: distance over which wind blows

• ‘Fully developed sea:’ maximum wave height, wavelength for  particular fetch, speed, and duration of winds at equilibrium  conditions

• Swell: uniform, symmetrical waves that travel outward from storm  area – long crests – transport energy long distances!

** Longer wavelength waves travel faster and outdistance  other waves!!!

Wave Interference Patterns: 

• Constructive Interference: in-phase wave trains with about the  same wavelengths

o (Wave Train: a group of waves with similar characteristics) • Destructive Interference: out-of-phase wave trains with about  the same wavelengths

• Mixed Interference: two swells with different wavelengths and  different wave heights

Waves Breaking: 

• Surf Zone: zone of breaking waves near shore

o Spilling Breakers: occur at the gently sloping seafloor – wave energy is expended over longer distance – water slides  down front slope of wave

o Plunging Breakers: occur at the moderately steep seafloor  – wave energy is expended over shorter distance – results in  curling wave crest *best for board surfing!

o Surging Breakers: occur at the steepest seafloor – energy  spread over shortest distance – waves break on the shore * best for body surfing!

• Shoaling Water: water becoming gradually more shallow o When deep-water waves encounter shoaling water less than  half their wavelength, they become transitional waves. 

• “as a deep-water wave becomes a shallow-water wave…” o wave speed decreases

o wavelength decreases

o wave height increases

o wave steepness increases

▪ when steepness is greater than or equal to 1/7, the  

wave breaks

Wave Refraction: 

• Waves rarely approach shore at a perfect 90 degree angle • As waves approach shore, they bend so wave crests are nearly  parallel to shore 

• Wave speed is proportional to the depth of water (shallow-water  wave!) 

• Different segments of the wave crest travel at different speeds o Results:

▪ Wave energy is unevenly distributed on shore!

???? More energy released on headlands

???? > As opposed to bays: where energy is more  

dissipated

???? can be seen with…

• Orthogonal Lines: “wave rays,” are drawn  

perpendicular to wave crests

• Wave Reflection:

o Waves and wave energy are bounced back from barrier

o Reflected wave can interfere with next incoming wave

o With constructive interference, can create dangerous plunging  breakers

Tsunamis: 

• Seismic sea waves

• Originate from sudden seafloor topography changes:

o Earthquakes = most common cause

o Underwater landslides

o Underwater volcano collapse

o Underwater volcanic eruption

o Meteorite impact (splash waves)

• Long wavelengths (> 200km or 125 miles)

• Behave as a shallow-water wave

o Encompasses entire water column, regardless of ocean depth o Can pass undetected under boats in open ocean

• Speed is proportional to water depth!

o Aka: very fast in the open ocean

• Highly destructive – sea level can rise up to 40m when a tsunami  reaches shore

o EX. Indian Ocean Tsunami, Japan Tsunami

• Tsunami Warning Systems:

o Pacific Tsunami Warning Center: ‘PTWC,’ located in  Honolulu, Hawaii, uses seismic wave recordings to forecast  tsunami

o Deep Ocean Assessment and Reporting of Tsunami: ‘DART,’ system of buoys that detect pulse of tsunami passing o Tsunami Watch: issued when potential for tsunami exists o Tsunami Warning: unusual wave activity verified

▪ Evacuates people/moves ships from harbors

CHAPTER 8: WAVES COMPLETE 

CHAPTER 10: SEDIMENT TRANSPORT: 

Erosion and Deposition: 

• Erosion: sand being removed

Beaches: 

• Beach: interface between land and water (coast)

• The beach is a dominant coastal feature

• Wave activity continually modifies the beach/coastal areas o Sea level changes affect the coast!

▪ Globally, sea level is rising! 

???? > people are trying to keep the water from  

moving inland – resulting in various coastal  

stabilization attempts which have created  

temporary solutions that can become problematic  

with time

• Beach (cont.) : from land not impacted by water, out to deep  water where there is not a free transport of sediment (aka: a bar) • > Bar: accumulation of sediment offshore (parallel to the beach!) • Berm: region above the high tide (but still affected by the ocean!)  Sand movement along beach:

• Two major types:

o Perpendicular to shoreline (toward and away)

▪ Swash: water rushes up the beach

▪ Backwash: water drains back to the ocean

o Parallel to shoreline (up-coast or down-coast)

▪ Longshore Current: net motion of beach that  

transports material on long face of the beach

“Summertime Beaches:” 

• light wave activity (“quiet time” – low energy!”

• wide, sandy berm

• steep beach face

• swash dominates

• longshore bars are not present

• generally milder storms

“Wintertime Beaches:” 

• heavy wave activity (high energy!)

• backwash dominates

• sediment moved away from shore

• narrower beach

• flattened beach face

• longshore bars are present

• stormy weather

Longshore Current:

• “zigzag” movement of water along shore (surf zone)

• travel at speeds up to 4km (2.5mph)

• can transport huge amounts of sediment

• parallel motion of water along shoreline

• always in the direction of the waves! 

Longshore Transport:

• Only occurs in the shallow water of surf zone

• Transports beach sediment in same zigzag fashion, in the same  direction of the longshore current

• Beaches sometimes called “rivers of sand”

• Millions of tons of sediment moved yearly

• Direction of transport changes due to wave approach

o ** In general, net sediment movement is southward  along the Atlantic and Pacific coasts of the U.S.

“Two Major Types of shores…”

Erosion Shores: emerging coastlines resulting in well-developed cliffs – existing where tectonic uplift of coast occurs (won’t spend too much time on  these!)  

• EX. U.S. Pacific Coast

Depositional Shores: gradually subsiding shores resulting in barrier islands  and sand deposits

• EX. South Padre Island = Barrier Beach

>Depositional Shores: 

• Naturally occurring features:

o Bay barrier: “bay mouth bar,” seals off a lagoon from the  ocean

▪ Low energy environment (aka: deposition)

o Tombolo: “tied island,” a sand bar that connects an island to  the mainland  

▪ As a result of reduction in wave energy (“because they  are in the shadow of wave energy”

▪ Breakwater Feature: “human version of tombolo,”  

aka: man-made island

o Barrier Islands: “barrier beach,” long offshore sand deposits  that parallel the coast

▪ Protects land behind it – creates shallow lagoon

o Spit: connects at one end to the mainland and hooks into a  bay at the other

o Delta: as a result of the deposition of sediment carried by the  flow of water located at the “mouth” of a body of water - an  area of land in which a river divides into smaller rivers,  

emptying into a larger body of water  

Barrier Islands/Beaches (Cont.)

• Sediment deposits that stretch offshore (not ideal for building  because it is fragile, exposed to wind, etc.)

o * prime location for hurricanes because subject to great  forces: floods, extreme winds, etc. 

• extremely long offshore deposits of sand parallel to the coast • do not exist along erosional shorelines

• protect mainland from high wave activity

• appear to have developed at the end of the last ice age 18,000  years ago… Formation:

o Beach > dunes > marsh & tidal flat > lagoon >> mainland ▪ Ocean beach: closest part of the island to the ocean

▪ Dune: stabilized by grasses; protect lagoon from strong  storms

▪ Barrier Flat: a grassy area that forms behind dunes

▪ High and low salt marshes: biologically productive  

wetlands

???? Generate ‘Peat deposits’ or ‘peat bed’ of  

decaying organic matter – prime indicator that  

this is taking place! *(can’t produce peat in the  

ocean because there’s too much turbulence)

▪ Lagoon: water between barrier island and mainland

• Progression (retreating) of barrier beaches:

o Older peat deposits found on ocean beach

o Migrate landward overtime due to rising sea levels

>Changing sea level: 

• Two major processes can change sea level:

o Local tectonic processes:

▪ EX. pacific coast of US is currently being uplifted

▪ Isostatic adjustments: rebound of Earth’s crust after  removal of heavy loads or sinking with application of  

heavy loads

???? Ice-loading from glaciers during ice ages

o Global changes in sea level:

▪ Ice ages lock seawater up in ice (glaciation) – sea level  goes down

▪ Ice melting after an ice age (deglaciation) – sea level  

rises 

▪ Thermal expansion/contraction of seawater:

???? Physical property of water: warmer water  

expands and cooler water contracts (roughly  

2m per 1 degree C, change in temperature)

▪ Glaciation Cycles: from 2 million to 10000 years ago,  a series of ice ages affecting Earth

???? Sea level was at least 120m below today’s sea  

level (* if all remaining ice on Earth melted today, 

sea level would rise another 70m!) 

???? Globally averaged temperatures = .6C warmer  

over last 130 years

???? Sea level rose 10-15cm over past 100 years

Hard Stabilization: 

• Structures built to decrease coastal erosion and interfere with sand  movement - also called ‘armoring of the shore’

• Often results in unwanted outcomes:  

o EX. some structures may accidentally increase wave erosion • Four major types:

o 1. Groins and groin fields

o 2. Jetties

o 3. Breakwaters  

o 4. Seawalls  

• 1. Groins and Groin Fields:

o Built perpendicular to the beach (often made of rip rap, or  large block material)

o Traps sand upcoast, which can cause erosion downstream of  the longshore current

o May necessitate a Groin Field: a series of groins built along a  beach

o Sand is distributed differently, but no additional sand is on  the beach

• 2. Jetties:

o Built perpendicular to shore

o Built in pairs (to create channel)

o Built to protect harbor entrances: EX. Santa Cruz Harbor, CA • 3. Breakwaters:

o Built parallel to a shoreline

o Designed to protect harbors from waves

o Can cause excessive erosion, requiring dredging to keep area  stable  

▪ EX. Santa Barbara between 1931 and 1949, breakwater  disrupted longshore transport of sand

• 4. Seawalls:

o Destructive to environment

o Designed to armor coastline and protect human developments o One large storm can remove beach

o Wave actively eventually undermines seawall structure; need  continual repair or will collapse

Alternatives to hard stabilization:

• Three major alternatives:

o Construction restrictions:

▪ Simplest alternative

▪ Limit building near shorelines

▪ Paradoxically, national flood insurance program  

encouraged construction

o Beach replenishment:

▪ Sand added to beach/longshore current

▪ Expensive; costs between $5 and $10 per cubic yard

▪ Sand must be dredged from elsewhere

o Relocation:

▪ Moves structures rather than protect them in areas of  

erosion

CHAPTER 10: SEDIMENT TRANSPORT COMPLETE 

CHAPTER 11: OCEAN POLLUTION 

Oil in the Marine System: 

• Oil Spills:

o Transportation spills, shipping, oil rigs, etc.

▪ [EX. Exxon tanker in Alaska – boat accident – released  

large amount of oil into high energy environment with  

coarse sediment – affected marine life, fisheries, etc.]

???? had a slower recovery time in comparison to  

recovery time in Gulf of Mexico, as a result of  

metabolic rate of oil-eating bacteria. -- because  

the water was too cold for bacteria to  

thrive/function

o > ** aka: it is harder for colder environments to  

recover from an oil spill as opposed to warmer  

environments!

o * Oil is more buoyant and calmer than surrounding  water! (result of the suppression of capillary waves, as a  

result of oil reacting to water’s hydrogen bonding)

▪ EX. Oil spills as a result of tanker – oil enters at surface 

???? Initially remains on top of the water but  

eventually gains density and sinks to bottom of  

the ocean affecting deep water marine life as well

▪ EX. Oil spills as a result of deep–water rig/pipe – oil  

enters at seafloor under very high pressure  

** “2010 Deep-water Horizon Spill – 5 million barrels – 210 million gallons  AKA: largest accidental oil spill!”

** “1991 Saudi Arabia, Kuwait – Oil terminals/tankers – 240 million gallons  AKA: largest (intentional) oil spill!” - (as a result of war)

Oil in the Marine System (cont.) 

Oil: a natural compound part of the ecosystem as a result of decay,  controlled by bacteria

• Natural seeps: 47%

• Human sources: 53% (tankers/rigs/petroleum consumption) o > Petroleum Consumption:  

▪ EX. getting oil changed: some left in bottle – thrown out  – will eventually leak – will rundown – reach river –

eventually runs off into ocean

▪ OR: direct dumping into drainage/sewage

> Ocean Dumping/Sewage:

• EX. Evolution of “New York Bight Sludge Sight” – (dumping sight) • Creates productivity in low-energy environment – accelerates  photosynthesis in an environment that is unable to keep up • * Efforts to counteract dumping have been made/have provided for  improvement (especially in US!)

o Beaches are cleaner now than ever

▪ EX. Est. dumping restrictions – “loosen” the further you  get away from shore – but still have had a significantly  

positive impact

o Poorer nations cannot say the same… – the greater the  poverty, the greater the pollution

> Plastics: 

• EX. water bottles, toothpaste, fleece jackets (from just washing  your fleece and releasing plastic fibers)

o >these microplastics are confused with food – consumed by  organisms, which in turn affects the entire food chain

• vast majority of marine debris

o 80% of marine debris from land sources (most of it is plastic) • not readily biodegradable

• entangle fish, marine mammals, and birds

• plastic bags choke turtles – mistake them for jellyfish

• some plastics attract poisons, EX. DDT, PCB’s

• floating plastics photodegrade – break into smaller pieces • plastic particles are significantly increasing

• regions of floating trash – Eastern Pacific Garbage Patch Non-Point-Source Pollution/Trash:

• Aka: not from underwater pipelines, EX. storm drains

• EX. trash, road oil, pesticides/fertilizers… 

• > Nutrient loading from fertilizer run off: 

o Dead Zones: low-oxygen areas where life (fish/typical sea  life) cannot survive, caused by excessive nutrient pollution  that depletes the environment’s oxygen - as a result of the  pollutants (nitrates) in fertilizers being “run off” into rivers,  lakes, oceans, etc.

▪ EX: along the East Coast, Gulf of Mexico, Great Lakes – the second largest dead zone in the world is in the U.S.  

in the northern Gulf of Mexico

Urban Run-off: either wet weather (rainwater) or dry weather (water  waste) that flows from urban landscapes carries pollutants of various kinds  into storm drains, sewage systems, and receiving waters.

Potential Solutions for Ocean Pollution: Bioremediation Bioremediation: the use of either naturally occurring or deliberately  introduced microorganisms or other forms of life to consume and break  down environmental pollutants, in order to clean up a polluted site.

• Cost effective, sustainable, natural approach to cleaning up  contaminated sites – biological agents include: bacteria, microbes,  fungi, and other organisms of their enzymes.

CHAPTER 11: OCEAN POLLUTION COMPLETE 

 EXAM III: CHAPTER 8, 10, 11: COMPLETE

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