Tides are generated by the gravitational pull of

Tides are generated by: • the gravitational pull of the moon and sun - moon has 2 x greater gravitational pull than the sun - sun is 10 million x more massive than the moon and is 390 times farther away • the centripetal force of the rotating earth Diurnal Tide: 24 hr 50 min cycle Semi Diurnal Tide: 12 hr 25 min cycle Mixed Tide: 12 hr 25 min cycle

Tides Moon Sun Moon Bulge of water Earth A. Gravitational pull Earth B. Centripetal force center of mass Moon Earth C. Gravitational pull & Centripetal force

• • • Description of tides High water: a water level maximum ("high tide") Low water: a water level minimum ("low tide") Tidal range: the difference between high and low tide Spring Tide: full moon and new moon (14. 77 days) Neap Tide: 1 st quarter and 3 rd quarter (14. 77 days) High tide Intertidal zone Low tide

full moon earth Spring Tide Highest high tide and lowest low tide new moon

1 st quarter moon earth 3 rd quarter moon Neap Tide

Tidal Patterns Semidiurnal tides- two high and two low per day; Cape Cod, MA (low latitudes) Diurnal tides- one high and one low per day; Mobile, AL (high latitudes) Mixed pattern tides- Two high and two low tides per day BUT with successive high tide levels that are VERY DIFFERENT from each other; Hawaii (mid latitudes) Type of tide depends on: • Position on the globe • Water depth • Contour- shape of ocean basins

Tidal Range 56 ft

Alma at High Tide Alma at Low Tide

La Rance tidal power plant at St. Malo, France.

Tidal Information http: //life. bio. sunysb. edu/marine bio/mbweb. html HAWAIIAN ISLANDS Mean Spring Mean Tide Station Latitude Longitude Range Level SAND ISLAND, MIDWAY ISLANDS 28° 12. 7' 177° 21. 6' 0. 8 1. 2 0. 6 Predictions Laysan Island 25° 46' 171° 45' 0. 7 1. 0 0. 4 Predictions East Island, French Frigate Shoals 23° 47' 166° 13' 0. 9 1. 4 0. 6 Predictions Nonopapa, Niihau Island 21° 52' 160° 14' 1. 0 1. 6 0. 7 Predictions Kauai Island Waimea Bay 21° 57' 159° 40' 1. 0 1. 6 0. 7 Predictions Port Allen, Hanapepe Bay 21° 54' 159° 35' 1. 1 1. 7 0. 7 Predictions NAWILI 21° 57. 4' 159° 21. 6' Predictions Hanamaulu Bay 22° 00' 159° 20' 0. 0 1. 2 1. 8 Predictions Hanalei Bay 22° 13' 159° 30' 1. 3 1. 8 0. 8 Predictions Oahu Island Haleiwa, Waialua Bay 21° 36' 158° 07' - - 1. 6 0. 7 Predictions Waianae 21° 27' 158° 12' 1. 2 1. 8 0. 8 Predictions HONOLULU 21° 18' 157° 52' 1. 3 2. 0 0. 8 Predictions Hanauma Bay 21° 17' 157° 42' 1. 3 1. 9 0. 8 Predictions Waimanalo 21° 20' 157° 42' 1. 1 1. 8 0. 8 Predictions MOKUOLOE 21° 26. 2' 157° 47. 6' 1. 2 2. 0 1. 0 Predictions Waikane, Kaneohe Bay 21° 30' 157° 51' 1. 4 2. 2 1. 1 Predictions