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Slide 2 Slide 3 A Wave is a rhythmic movement that carries energy through matter or space. In oceans, waves move through seawater Slide 4 Waves Caused by: Wind Earthquakes Gravitational force of the Moon and Sun. Slide 5 Crest highest point of a wave Trough lowest point of a wave Wave Height vertical distance between the crest and the trough Wavelength horizontal distance between two crests or two troughs Still-Water Line - The level of the ocean if it were flat without any waves. Slide 6 Wave Period - The time it takes for two successive waves to pass a particular point. For example, it you are standing on a pier and start a stopwatch as the crest of a wave passes and then stop the stopwatch as the crest of the next wave passes, you have measured the wave period. Wave Frequency - The number of waves that pass a particular point in a given time period. Amplitude - The amplitude is equal to one-half the wave height or the distance from either the crest or the trough to the still-water line. Slide 7 Wavelength Wave Height Crest Trough Still Water Wave Parts Slide 8 Wave Movement When a wave passes through the ocean, individual water molecules move up and down but they do not move forward or backward. http://www.classzone.com/books/earth_science/ terc/content/visualizations/es1604/es1604page0 1.cfm?chapter_no=visualization Slide 9 Wave Movement When a wave breaks against the shore, the crest outruns the trough and the crest collapses. Called a breaker. Slide 10 Waves Caused by Wind When wind blows across a body of water, friction causes the water to move along with the wind. Wave height depends on 1. Wind speed 2. Distance over which the wind blows called fetch 3. Length of time the wind blows Slide 11 Slide 12 Slide 13 Slide 14 Ocean Tides Slide 15 High and Low Tide Slide 16 The rise and fall in sea level is called a tide. One low-tide/high-tide cycle takes about 12 hrs and 25 min. Tidal range is the difference in ocean level between high-tide and low-tide Long wavelengthsup to 1/2 the circumference of the earth Slide 17 What is the Tidal Range? HT = 30 ft, LT = 20 ft HT = 30 ft, LT = 20 ft HT = 20 ft, LT = 12 ft HT = 20 ft, LT = 12 ft HT = 50 ft, LT = 20 ft HT = 50 ft, LT = 20 ft Slide 18 TIDE TERMS TO KNOW Flood tidewhen water level is rising Ebb tidewhen water level is falling Slide 19 Its the Moons Fault Primary factor that controls the rhythm and height of the tides Primary factor that controls the rhythm and height of the tides 2 tidal bulges due to gravitational attraction 2 tidal bulges due to gravitational attraction Side of Earth closest to moon - seawater drawn towards moon. Side of Earth closest to moon - seawater drawn towards moon. Opposite side - bulge produced away from the moon. Opposite side - bulge produced away from the moon. Timing of tides is related to the Earths rotation, and the rotation of the moon around the Earth. Timing of tides is related to the Earths rotation, and the rotation of the moon around the Earth. Slide 20 Gravitational Effect of the Moon Two big bulges of water form on the Earth: one directly across from the moon another on the exact opposite side As the Earth spins, the bulges follow the moon. Slide 21 G Slide 22 Slide 23 Moon and Centrifugal Force Centrifugal force is equal to the gravitational attraction of the Moon, but operates in the opposite direction Causes an opposing bulge on Earths surface away from the Moon Slide 24 The opposing gravitational and centrifugal forces create two tidal bulges GC C = Centrifugal ForceG = Gravitational Attraction Slide 25 Spring Tides Occur at New Moon and Full Moon phases every 14-15 days Earth, Moon, and Sun aligned Moon tidal bulge adds to Suns Higher high tides Lower low tides Slide 26 Neap Tides Occur at 1 st quarter and 3 rd quarter phases Earth, Moon, and Sun at right angles Moon tidal bulge subtracts from Suns Lower high tides Higher low tides Slide 27 Slide 28 Types of Tides Spring: new and full moon Neap: 1 st and 3 rd quarters Slide 29 TYPES OF TIDES 1.DIURNAL TIDES: 1.DIURNAL TIDES: one high and one low water tidal per day. Northern Gulf of Mexico and SE Asia. Geometric relationship of sun and moon to locations on the Earths surface creates three different types of tides. Slide 30 2. SEMI-DIURNAL TIDE: Two high and two low waters per tidal day. Two high and two low waters per tidal day. Common on Atlantic coasts of the United States and Europe. Common on Atlantic coasts of the United States and Europe. Slide 31 3. MIXED TIDES: two cycles daily, but the two high tides reach different heights and the two low tides drop to different levels two cycles daily, but the two high tides reach different heights and the two low tides drop to different levels West coast of Canada and the US. West coast of Canada and the US. Slide 32 Slide 33 Tides Around the Globe Slide 34 TOPEX/Poseidon Accurate global maps of tides, can now be predicated with an accuracy of 2cm. Data used for study of ocean circulation. Level of accuracy necessary to understand many oceanic processes. Slide 35 Slide 36 What is a tidal bore? A wall of water that moves up certain low-lying rivers due to an incoming tide. form when an incoming tide rushes up a river river is flowing in the opposite direction. Tidal bore develops a steep forward slope due to rivers resistance Slide 37 Slide 38 Slide 39 Bay of Fundy, Nova Scotia, Canadalow tide Slide 40 Bay of Fundy, Nova Scotia, Canadahigh tide Slide 41 Slide 42 Slide 43 Slide 44