EOSC 114: Tsunami Learning Goals
EOSC 114: Tsunami Learning Goals 1. Identify key properties of waves
2. Use these properties to determine wave speed and behavior in either shallow or deep water
3. Explain how waves move matter and energy
4. Describe the forces that generate waves, eliminate waves, and return the ocean to a flat, undisturbed surface
5. Explain the factors that determine the roughness of the sea
6. Describe how waves interact; explain constructive and destructive interference 7. Describe wave refraction, seiche (standing waves in enclosed or semi-enclosed bodies), and resonance; how do these affect the coast and people?
8. Relate wave interference and resonance to marine hazards
Crest Trough Wavelength Amplitude Wave Height Period Frequency Speed Deep water: when waves are at depth equal or deeper than L/2do not feel the bottom, move in circles --longer wavelength travel faster than shorter wavelengths b/c dispersive (depend on L) Shallow water: waves are at depth higher than L/20feel bottom, move in ellipses --all shallow waves travel at same speed at same depth Matter (water particles)does not transport matter, particles just move in circle/ellipses, no net movement Energyonce wave breaks, energy becomes KE in surfKE moves water up beach, transported into PE on beach (effectively “absorbed” by the beach, stored as PE) Generating force: -Wind -Tsunami, landslides, volcanoes, storm surges -Gravitational attraction, Earth rotation Restoring force: surface tension, gravity “Sea State” (ocean condition/roughness): -Speed -Fetch (area of uninterrupted wind blown) -Duration (time wind blown over fetch) Constructive interference: additive Deconstructive interference: subtract Wave refraction: -near coast, side of wave closest to coast slows more than rest, causing refraction. -refraction also causes shore straightening by eroding headlands (land that sticks out) and filling in embayments (curved parts) with the eroded sediment Seiche: resonating wave in (semi-)enclosed body of water Wave interferenceconstructive interference of 2 wave trains can cause rogue waves (often by Cape of Good Hope, South Africa); very unpredictable and dangerous
EOSC 114: Tsunami Learning Goals
9. Explain how a tsunami compares with other ocean waves
10. Discuss why tsunami come ashore so violently
11. Describe how tsunami form and how they are detected
12. Identify tsunami warning signs, and know how to respond 13. Describe how storm surges are generated
14. Identify where and how the maximum surge occur in a hurricane
15. Define wave breaking and determine when a wave will break 16. Explain differences between surging, plunging, and spilling breakers
17. Predict the type of breaking wave that will be found on a given beach 18. Describe how coastlines affect waves, and how waves affect coastlines
Resonanceseiches resonate within contained areas, cause repeated damage -much longer wavelength L -shallow-water wave -very fast -large period -When tsunami waves are shoaling (slow down, shorter wavelengths while approaching shore), energy is build up. All the energy in the water hits shore very fast and with lots of momentum Earthquake/volcanic eruptions, or rapid addition of masses (landslides, meteors, icebergs) -detected by tsunameters (DART buoys in water) that measure small tsunami waves -PTWS(pacific tsunami warning system)earthquake hits, seismographs read magnitude, anticipate tsunamiread tsunami dangerrelay to dissemination points to public -Water level of shore decreases Storm surge: bulge of water, behaves like shallow-water wave Generated by 2 processes together: winddriven surge by hurricane winds+ pressure surge (from eye of storm) Maximum: during high tide (height of tide adds) On the right side of the hurricane eyewinds + pressure surge in same direction When the wave height is too tall, it will collapse at a point where H/L >1/7 and break, turn into surf 1. Spilling breakers formed with flat ocean bottom; gentle, spread energy over wide area 2. Plunging breakersformed with moderately steep ocean bottom; semi-dangerous, for expert surfers 3. Surging breakersformed with very steep ocean bottom; very dangerous b/c energy released in sudden bursts; energy reflected back in water Type of breaking wave on beach is the same (same floor steepness), but surf differs due to wavelength, height, and energy. Water affects Coastline: water “swash” and “backwash” move particles up and down, sideways,causing “longshore drift”, making barrier islands &tombolos
EOSC 114: Tsunami Learning Goals
19. Compare and contrast the effects of artificial barriers such as groins, seawalls, and other structures, on coastal processes
Coastline affects Waves: the coast shape can affect refraction of waves, ie. redirecting through small channels Groins: wall built perpendicular to beach; due to longshore drift, one side accumulates sediment and other side is eroded Jetties: pair of walls build perpendicular to permanently allow entrance to inlet; accumulation & erosion similar to groin occurs Breakwater: barrier built parallel to beach to stop wave action; causes accumulation of sand behind breakwater, and erosion on unprotected side b/c blocks longshore drift Tethered-float breakwater: steel balls floating in water break wave action without affecting longshore drift
20. List 2 causes of eustatic changes in sea level
21. List 2 causes of regional (or local) changes in sea level 22. Relate these changes to risks for coastal communities
Seawall: barrier build inland (not on coast) to protect community of wave energy. Not good b/c encourages erosion of beach, increased water depth and therefore bigger wavespositive feedback cycle (bigger waves = bigger seawall = deeper erosion = bigger waves) 1. Change volume of water in ocean basin a) glacier/ice caps melting/forming b) water density changes (ie. water warms, volume increases, density decreases) c) liquid going between land and ocean 2. Change in volume of ocean basin/ - local temperature increase (ie. northern BC warming faster than global average) - mountains, proximity to ocean -low areas will be submerged in water -more erosion of coast -changes to agriculture/aquaculture -change groundwater quality -damage ecosystems, habitats -economic damage, cultural damage
2. Use these properties to determine wave speed and behavior in either shallow or deep water
3. Explain how waves move matter and energy
4. Describe the forces that generate waves, eliminate waves, and return the ocean to a flat, undisturbed surface
5. Explain the factors that determine the roughness of the sea
6. Describe how waves interact; explain constructive and destructive interference 7. Describe wave refraction, seiche (standing waves in enclosed or semi-enclosed bodies), and resonance; how do these affect the coast and people?
8. Relate wave interference and resonance to marine hazards
Crest Trough Wavelength Amplitude Wave Height Period Frequency Speed Deep water: when waves are at depth equal or deeper than L/2do not feel the bottom, move in circles --longer wavelength travel faster than shorter wavelengths b/c dispersive (depend on L) Shallow water: waves are at depth higher than L/20feel bottom, move in ellipses --all shallow waves travel at same speed at same depth Matter (water particles)does not transport matter, particles just move in circle/ellipses, no net movement Energyonce wave breaks, energy becomes KE in surfKE moves water up beach, transported into PE on beach (effectively “absorbed” by the beach, stored as PE) Generating force: -Wind -Tsunami, landslides, volcanoes, storm surges -Gravitational attraction, Earth rotation Restoring force: surface tension, gravity “Sea State” (ocean condition/roughness): -Speed -Fetch (area of uninterrupted wind blown) -Duration (time wind blown over fetch) Constructive interference: additive Deconstructive interference: subtract Wave refraction: -near coast, side of wave closest to coast slows more than rest, causing refraction. -refraction also causes shore straightening by eroding headlands (land that sticks out) and filling in embayments (curved parts) with the eroded sediment Seiche: resonating wave in (semi-)enclosed body of water Wave interferenceconstructive interference of 2 wave trains can cause rogue waves (often by Cape of Good Hope, South Africa); very unpredictable and dangerous
EOSC 114: Tsunami Learning Goals
9. Explain how a tsunami compares with other ocean waves
10. Discuss why tsunami come ashore so violently
11. Describe how tsunami form and how they are detected
12. Identify tsunami warning signs, and know how to respond 13. Describe how storm surges are generated
14. Identify where and how the maximum surge occur in a hurricane
15. Define wave breaking and determine when a wave will break 16. Explain differences between surging, plunging, and spilling breakers
17. Predict the type of breaking wave that will be found on a given beach 18. Describe how coastlines affect waves, and how waves affect coastlines
Resonanceseiches resonate within contained areas, cause repeated damage -much longer wavelength L -shallow-water wave -very fast -large period -When tsunami waves are shoaling (slow down, shorter wavelengths while approaching shore), energy is build up. All the energy in the water hits shore very fast and with lots of momentum Earthquake/volcanic eruptions, or rapid addition of masses (landslides, meteors, icebergs) -detected by tsunameters (DART buoys in water) that measure small tsunami waves -PTWS(pacific tsunami warning system)earthquake hits, seismographs read magnitude, anticipate tsunamiread tsunami dangerrelay to dissemination points to public -Water level of shore decreases Storm surge: bulge of water, behaves like shallow-water wave Generated by 2 processes together: winddriven surge by hurricane winds+ pressure surge (from eye of storm) Maximum: during high tide (height of tide adds) On the right side of the hurricane eyewinds + pressure surge in same direction When the wave height is too tall, it will collapse at a point where H/L >1/7 and break, turn into surf 1. Spilling breakers formed with flat ocean bottom; gentle, spread energy over wide area 2. Plunging breakersformed with moderately steep ocean bottom; semi-dangerous, for expert surfers 3. Surging breakersformed with very steep ocean bottom; very dangerous b/c energy released in sudden bursts; energy reflected back in water Type of breaking wave on beach is the same (same floor steepness), but surf differs due to wavelength, height, and energy. Water affects Coastline: water “swash” and “backwash” move particles up and down, sideways,causing “longshore drift”, making barrier islands &tombolos
EOSC 114: Tsunami Learning Goals
19. Compare and contrast the effects of artificial barriers such as groins, seawalls, and other structures, on coastal processes
Coastline affects Waves: the coast shape can affect refraction of waves, ie. redirecting through small channels Groins: wall built perpendicular to beach; due to longshore drift, one side accumulates sediment and other side is eroded Jetties: pair of walls build perpendicular to permanently allow entrance to inlet; accumulation & erosion similar to groin occurs Breakwater: barrier built parallel to beach to stop wave action; causes accumulation of sand behind breakwater, and erosion on unprotected side b/c blocks longshore drift Tethered-float breakwater: steel balls floating in water break wave action without affecting longshore drift
20. List 2 causes of eustatic changes in sea level
21. List 2 causes of regional (or local) changes in sea level 22. Relate these changes to risks for coastal communities
Seawall: barrier build inland (not on coast) to protect community of wave energy. Not good b/c encourages erosion of beach, increased water depth and therefore bigger wavespositive feedback cycle (bigger waves = bigger seawall = deeper erosion = bigger waves) 1. Change volume of water in ocean basin a) glacier/ice caps melting/forming b) water density changes (ie. water warms, volume increases, density decreases) c) liquid going between land and ocean 2. Change in volume of ocean basin/ - local temperature increase (ie. northern BC warming faster than global average) - mountains, proximity to ocean -low areas will be submerged in water -more erosion of coast -changes to agriculture/aquaculture -change groundwater quality -damage ecosystems, habitats -economic damage, cultural damage
