Movie Showing: Tides Laboratory Animation and Discussion

1. Movie showing time WED. Oct. 20th 5.00 pm - end Room ES&T L1205 After seeing the movie there is going to be 20 min. of open discussion. You can bring your friends, wives, kids, etc. If you can let me know in advance.

2. New Homework: Tides Laboratory Complete and hand in exercises #1 #4 #5 #6 due next Friday

3. Animation of Tidal Elevations in the Pacific

4. TidesandTsunamis • Gravitational forces of moon and sun • Equilibrium theory of Tides • Dynamic theory of Tides (Reality): tidal patterns, confined basins • Tsunamis: generating forces • Effects of tsunamis • Warning systems, defenses

5. Equilibrium Theory Assumption Tides are always in equilibrium with the gravitational pull of the moon and Earth is a planet covered in water.

7. Gravity and centrifugal force(also called “tractive forces”) Equilibrium theory of tides Together:The earth-moon system

8. Tides: The moon and the sun together Spring tide Neap tide

11. semidiurnal + diurnal = composite

12. Dynamic Theory Needs to account for: Waves travel at a fixed waves speed There are continents and rotation

15. Tidal circulation • Tides progress around basins, counterclockwise in S hemisphere and clockwise in N hemisphere

16. Animation of Tidal Elevations in the Pacific

17. Inertia + continents cause the tidal motion on the planet to differ markedly from the “motion” of the forces. We can calculate the water motion knowing the forces, but we cannot say that the shape of the water is the same as the “shape” of the forces. For this reason tides must not be visualized as bulges standing under the sun and moon. But rather as very long waves over the sea forced by the gravitational-centrifugal forces associated with the moon-sun-earth system.

18. Tides in confined basins • Increase tidal range (the difference between high and low tide) • Examples --Bay of Fundy, Canada --Northern Gulf of California, Mexico • Tidal bores - wave of water moving upstream - result of high-tide crest entering confinced inlet

20. Bay of Fundy: map • 2.416

21. Bay of Fundy tides • Extreme tides (10m or more) found where small marine basin adjoins large ocean • Bay of Fundy, Nova Scotia • Gulf of California • (in most places, tides are 1 to a few meters in range)

22. Shock Waves and Tidal Bores are similar!

23. Tidal bore: Severn River, England • 2.452

24. Tidal ecosystems • Rise and fall of tides creates stressful environments for intertidal marine organisms

25. Tidal ecosystems • Others take refuge in tide pools, where water remains even at low tide

26. Tsunami • Japanese for harbor (tsu) wave (nami) • Caused by displacements of water • landslides into the sea • submarine earthquakes • submarine volcanoes • asteroid impacts • “Shallow-water” wave: disturbs water all the way to bottom

27. Tsunami of April 1, 1946 Earthquake triggers tsunami with devastating local and distant effects

28. The speed of the tsunami wave C = g d C = speed, g = acceleration due to gravity (9.8 m/sec/sec) d = depth (depth of Pacific ~4,600 m) C= (9.8 * 4,600) Speed = 212 meters per second; 472 mph Alaska to Hawaii in 5 hours!

29. Before… and after Locally, the tsunami washed away the 5-story lighthouse at Scotch Cap, Alaska

30. Hilo, Hawaii, 1946: Tsunami crossed the north Pacific to become one of Hawaii’s worst natural disasters

31. Hilo, Hawaii, 1946

32. Tsunami breaking over main pier in Hilo, 1946 This man did not survive

33. 1.5 hours 16.5 hours 8.5 hours 23.5 hours Chile earthquake, 1960numerical simulation of tsunami

34. Aftermath of local tsunami: Chiloe, Chile, 1960

35. Distant effects of the Chile earthquake: tidal wave aftermath, Hilo Hawaii

36. More tsunami damage in Hilo, 1960

37. Tsunamis: what can be done? • Early warning system for evacuation (if EQ is distant) • Coastal zoning. Get development out of the way. Example: Hilo, Hawaii • Defense. Protective walls. Example: Taro, Japan