Hurricanes and Tsunamis – Flashcards
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Biggest Hurricane
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Galveston, TX 1900
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Most Expensive Hurricane
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Katrina in 2005, $81 billion
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Why has property damage gone up so much since 2000?
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More people moving to the coast
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Which NWS office handles hurricanes?
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NHC
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Hurricane definition
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No. hemisphere tropical cyclone, it's a low pressure sys that forms in the tropics or subtropics and is accompanied by t-storms organized into rainbands
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In no. hemisphere, trop cyclones have...
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counter-clockwise rotation at low levels and clockwise rotation at high levels
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Classifications for Tropical Storm (sustained wind speed)
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1. Tropical depression-max winds of 38 mph 2. Tropical Storm-max wind at 39-73 mph 3. Hurricane-max wind 74 mph 4. Major Hurricane-max winds of 111 mph
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When does NHC name a storm?
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formation of tropical storm
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How do tropical storms form?
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*pre-exist disturbance (spin & flow) *80 deg ocean water *light winds (no vert wind shear) *300 mi away from the equator *atmo that cools at higher levels *moisture in atmo to fuel t-storms
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Saffir-Simpson Hurricane Scale
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Cat 1 = 74-95 mph Cat 2= 96-110 mph Cat 3 = 111-129 mph* Cat 4 = 130-156 mph* Cat 5 = 157+ mph* *=major
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What kills a hurricane?
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vertical wind shear, cooler water, dry land (no moisture source)
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What are impacts of hurricanes when they make landfall?
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storm surge heavy rainfall-flooding tornadoes high winds
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What are Category 5 Hurricanes?
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Labor Day 1935, Andrew 1992, Camille 1969, Katrina 2005
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What is main hurricane threat to coast?
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Storm surge
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What is main hurricane threat inland?
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Flooding
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"Cape Verde"
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large clusters of t-storms off of Africa coast turn into hurrianes
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Easterly Waves
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90% of storms come from disturbances off the African coast
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Hurricane Season
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June 1 thru Nov 30, but biggest threat is Aug thru Oct when water is warmest
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Where would you go to be free of hurricanes?
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Equator
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Hurricane Features
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Eye Eye Wall - strongest winds Rainbands (spirals) can spawn tornadoes
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What 2 things drive storm surges?
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lower pressure and wind
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Which is worse for surge, gradual or steep slope?
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Gradual slope
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How do hurr winds affect a 30-story building?
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1 category stronger
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What part of hurricane is most dangerous?
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Right-front quadrant (strong winds, poss. tornadoes)
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What determines where the storm may threaten land?
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Prevailing steering current and time of year
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storm surge
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abnormal rise in sea level generated by a hurricane or other intense storm over and above the predicted or normal astronomical tide
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Storm surge is result of...
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winds shoving ocean water and low pressure of the eye
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Surge inundation is affected by...
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bathymetry (underwater topography) and slope of continental shelf (shallow or steep)
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Storm surge causes...
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structural damage, beach erosion, damage to coastal hwys, marinas and boats
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SLOSH
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Sea, Lake, Overland Surges from Hurricanes-computerized model dev by NHC estimates storm surge height from historical, hypothetical or predicted hurricanes
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SDP
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SLOSH Display Program-determines who is at risk and should evacuate. Includes directions of motion, landfall loc, intensity, storm sizes and fwd speeds
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Hurricane Local Statement
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local WFO & NHC: areas affected, watch/warn in effect, rec precautionary actions, surge and tide info, present winds, onset, tornado
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Storm Surge Products
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SDP, MEOW (Max Envelope of Water), MOM (Max of Maximums) and P-SURGE (Probablistic Storm Surge)
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Right-front Quadrant is important because
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tornadoes possible here, wind speeds are greatest in this area
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Flooding more likely when
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recent heavy rains, bands of rain stay over the same area, large storm
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Tropical Storm Watch
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trop storm force winds (39-73) are poss. in next 48 hrs
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What is an emergency manager's biggest headache when evacuating?
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tourists (unprepared)
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Decision Arc
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boundary that helps determine when you should make the decision to evacuate
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NWS issues
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HWO NWS Forecast Inland watch/warn HLS
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NHC issues
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Coastal Watch/Warning Surface Wind Field Storm Surge Prob Wind Speed Prob Track Forecast Cone Forecast Discussion Trop Cyclone Public Advisory Trop Wx Outlook
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Tools used to observe trop cyclones
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Satellites, buoys, dropsondes, radar and ASOS
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Vulnerability Analysis
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id areas, population and facilities in harm's way
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Behavior Analysis
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an understanding of residents' attitudes and the potential evac response, including residents, visitors, tourists and special needs-most important portion of HES
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Post-Storm Analysis
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what people actually did in response to an approaching storm
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Transportation Analysis
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sig # of cars have to move on the roads in a relatively short time - alleviate congestion of community in evacuating
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Hurricane Evacuation Studies
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help communities dev evac zones, probable effects of hurricanes, assess impacts from storm surge and winds and sheltering
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Hazard Analysis
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primary goal is worst-case storm surge (also looks at other hurricane hazards)
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TDR
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Technical Data Report contains final findings of the specific analyses from the HES
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Storm Surge Atlas
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visualize storm surge inundation
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Evacuation Zones
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evac zones defined using potential surge vulnerability and info from HES
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Evacuation Clearance Times
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calculated by time (in hrs) required to get residents out of storm-surge vulnerable areas to a place of safety
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HURREVAC
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Hurricane+Evacuation, a software program designed by Sea Island Software for FEMA to help visualize evacuation timing
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When should evacuation start?
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by the time 39-mph winds of a powerful hurricane intersect the decision arc and completely by the time these trop storm-force winds come ashore
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Because of uncertainty, the NHC...
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must place larger areas under watch and warning than will actually experience winds that high
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Do you feel impacts of hurricane outside the forecast error cone?
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yes
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TAFB
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Tropical Analysis and Forecast Branch, sub-unit of NHC, provides tropical ocean forecasts
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HSU
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Hurricane Spec Unit-prepares forecast dissemination
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HLT
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Hurricane Liaison Team facilitates comm. betw NHC and public officials (FEMA-sponsored)
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Which agency has responsibility for trop storms when out to sea?
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NHC handles out at sea
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After NHC issues forecast...
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WFO customizes forecast to local conditions and anticipated storm effects
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HES
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Hurricane Evac Studies - guide to help decision-making: established evac zones, hurricane effects, storm surge impacts and appropriate sheltering
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Planning tools for hurr. decision making
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Hurricane Evac Studies (HES) Tech Data Report (TDR) Post-Assessment
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Tsunami
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great wave
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What is the main cause of a tsunami?
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A vertical displacement of water
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What triggers a tsunami?
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Earthquakes (most common) 8.0+ Subaerial Landslide Submarine Landslide Volcano eruption Meteorites Meteotsunami
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NOAA-operated office to monitor tsunamis
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Tsunami Warning Center (operated by geologists)
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Bathymetry
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underwater topography
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for every mb drop,...
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the water can come up a cm
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Tectonic Boundaries
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Convergent (most likely cause) subduction zone Divergent Transform (Strike-slip fault-oblique)
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What happens with Convergent Boundary quake...
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2 plates come together, typically oceanic and continental plates and the denser oceanic plates sinks below the less dense continental plate
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Which boundary produces the largest earthquakes and tsunamis?
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Convergent - Subduction zone
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Earthquakes occurring closer or farther from surface creates a bigger earthquake?
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Closer to the surface results in bigger earthquake
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Wave height = ?
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2x amplitude
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deep water waves are caused by
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wind
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depth vs. wavelenth of a shallow water wave
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depth is less than 1/20 of their wavelength
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Wave height is based on...
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energy; more height = more energy
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Describe what happens when a wave enters shallow water.
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speed slows down, particle motion increases and wave height increases
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Speed is _____________ of wavelength with a shallow water wave.
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independent
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Who issues Tsunami Warnings?
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Tsunami Warning Center
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Tsunami Products
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Warning - highest level Watch-uncertain of the events to come Advisory-non life threatening Info Statement-"there's been a major earthquake...more info to come"
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obliquity
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strike-slip faults with vertical component
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Factors that determine strength of tsunami
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amount of seafloor displacement length of rupture zone depth of water above the seafloor displacement duration of the earthquake magnitude of earthquake
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Tsunami can appear at shore as...
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drop or rapid rise in sea level
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Tsunami waves can arrive w/crest or trough first...
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crest first appears as a rising tide or tidal bore (stepped walls of water) and trough first causes sea to withdraw from coast
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tsunami waves are primarily waves of ____ in open ocean
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energy
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A zone struck by a tsunami with many islands will...
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be less significant
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wavelength
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distance between two successive wave crests
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wave amplitude
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1/2 the wave's height
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period
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the time between the passing of 2 crests
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frequency
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number of wavelengths that pass a fixed point
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deep water waves
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distance to the ocean bottom is greater than the wavelength and have heights proportional to their energy
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water molecules of deep water waves
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have circular orbits and gradually decrease in diameter with depth
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Tsunami waves are...
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shallow water waves
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shallow water waves have wavelengths
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much greater than their depth
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Shallow water waves, wave speed _________, while particle speed _____________, and wave height _______________
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slows, increases, increases (energy needed for run up on shore)
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tsunami waves are much __________ than the depth of ocean
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longer (and low amplitude)
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tsunami (shallow) waves' wind speed is ________ of wavelength or height
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independent
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moving particles of a tsunami wave become
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the wave's current running up shore
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seamount
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edge of a continental shelf
