Post on 18-Dec-2015
transcript
Notes on “Waves & Tides”
Earth/Space
S.W.B.A.T.
• Describe wave formation• Distinguish between the movement
of water particles in a wave and the movement of the wave
• Explain how ocean tides form
Wave Characteristics
• Wave – a rhythmic movement that carries energy through matter and space
• Wind, earthquakes, landslides, the Sun & Moon (tides) all generate waves
Wave Characteristics
• Only the energy moves forward in a wave
• Water particles do not move forward unless a wave is breaking on shore
Wave Characteristics
• The crest, trough, wavelength and wave height describes a wave
• Crest – high point in a wave• Trough – low point
Wave Characteristics
• Wavelength – horizontal distance from crest to crest or trough to trough
• Wave height – vertical distance between crest & trough
Wave Characteristics
• Energy is transmitted through the water in 3-dimensions
• Orbital waves – water particles move in circles or orbits
• This allows energy transfer between liquids and/or gases
Water Orbital Wave Movement
Wave Characteristics
• Other wave characteristics include frequency and fetch
• Frequency – number of wavelengths that pass a fixed point over time
• Fetch – describes speed & constant wind direction over time and distance
Wave Characteristics
• Fetch can create huge waves
• Highest wave ever experienced at sea was over 112ft! (U.S.S. Ramapo 1933)
Wave Characteristics
• Rogue waves – rare and unpredictable ocean waves
• Wave heights are huge & damaging to ships
• Rogue waves are probably the result of extensive fetch and a combining of swells
Ocean Swells Can Combine to Form Larger Waves
Rogue Waves Can Occur in Non-Stormy Seas
Video (1:32) “Rogue Wave Hits Cruise Ship”
Tides
• Tides - gradual rise & fall (high & low) in sea level
• Tides can have a wave height of only 1-2 meters
• However - tide wavelength can be thousands of km long
Tides
• Tides are caused by the gravitational pull of the Sun & Moon
• The Moon exerts a stronger pull because it is closer to Earth
Tides Change as the Earth Rotates and the Moon Orbits the Earth
Tides
• Tidal range – difference between high & low tides
• As Earth rotates its surface passes through both high and low positions
• Most coastlines experience two high and low tides each day – depending on ocean basin shape & size
Mont-Saint-Michel - Normandy, France at High Tide
Mont-Saint-Michel at Low Tide - 13.5m Difference
Tides
• Extreme tidal ranges occur due to shoreline shape
• Bay of Fundy in Nova Scotia, Canada has a tidal range of 15m due to its funnel-like shape
Video (1:52) “Bay of Fundy’s Tides”
Tides
• Spring Tides – when the Moon, Earth & Sun line-up to produce even higher tides
• This happens about twice a month
Tides
• Neap Tides – when the Moon, Earth & Sun are at right-angles
• Gravity is nearly “canceled out” giving very little tidal pull
• This also happens about twice a month
Class Activity
• Many planets have more than one moon
• Explain what tides might be like if Earth had two moons