Notes on Waves Tides EarthSpace S W B
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 112 ft! (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 12 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. 5 m Difference
Tides • • Extreme tidal ranges occur due to shoreline shape Bay of Fundy in Nova Scotia, Canada has a tidal range of 15 m 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
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