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• the gravitational pull of the moon and sun- moon has 2x 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 cycleSemi Diurnal Tide: 12 hr 25 min cycleMixed Tide: 12 hr 25 min cycle
Tides are generated by:
Sun
Earth
Earth
EarthMoon
Moon
Moon
Tides
A. Gravitational pull
B. Centripetal force
C. Gravitational pull & Centripetal force
center of mass
Bulge of water
• 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: 1st quarter and 3rd quarter (14.77 days)
Description of tides
Intertidal zoneHigh tide
Low tide
Spring TideHighest high tide and lowest low tide
full moon
new moon
earth
earth
3rd quarter moon
Neap Tide
earth
1st quarter moon
Tidal PatternsSemidiurnal 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
Alma at High Tide
Alma at Low Tide
La Rance tidal power plant at St. Malo, France.
http://life.bio.sunysb.edu/marinebio/mbweb.html
Tidal Information
HAWAIIAN ISLANDSMean Spring Mean Tide Station Latitude Longitude Range Range Level Predictions 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 NAWILIWILI 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