1. Tides
Gravity- pull or attraction between objects; varies with mass of object
Centrifugal force- because the earth and moon are rotating simultaneously around a common center of mass, the water of the oceans shifts from the center of rotation, creating a 2nd tidal bulge on the side of the earth that faces away from the moon

2. Tides are generated by:
Gravitational pull of the moon and sun
Centripetal force of the rotating Earth
TIDES: Tides are the slow, periodic vertical rise and fall of the sea surface. They are usually described as being either diurnal or semi-diurnal. Diurnal tides have one high water and one low water in each lunar day (about 24.8 hours), while semi-diurnal tides have two high and two low waters in the same time period. While these tidal changes are easier to observe where land and water meet, they exist everywhere -- even in the middle of the ocean. Tidal ranges along the shoreline vary by location. For example, the tides in Canada's Bay of Fundy, an Atlantic Ocean inlet west of Nova Scotia, rise and fall as much as 50 feet, while the tidal range in Lake Superior is measured in inches.
High and low tides are the result of the attractive forces (gravitational pull) of the moon and sun on a rotating Earth.

3. Tides are generated by:
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
TIDES: Tides are the slow, periodic vertical rise and fall of the sea surface. They are usually described as being either diurnal or semi-diurnal. Diurnal tides have one high water and one low water in each lunar day (about 24.8 hours), while semi-diurnal tides have two high and two low waters in the same time period. While these tidal changes are easier to observe where land and water meet, they exist everywhere -- even in the middle of the ocean. Tidal ranges along the shoreline vary by location. For example, the tides in Canada's Bay of Fundy, an Atlantic Ocean inlet west of Nova Scotia, rise and fall as much as 50 feet, while the tidal range in Lake Superior is measured in inches.
High and low tides are the result of the attractive forces (gravitational pull) of the moon and sun on a rotating Earth.

4. GRAVITATIONAL & CENTRIPETAL
GRAVITATIONAL FORCE
CENTRIPETAL
The closeness of the moon to Earth (238,857 miles), and the distance to the sun (92,955,770 miles), accounts for the moon having a tide-raising force nearly 2.5 times greater than the sun. The position of these celestial bodies results in significant variations in pulling forces causing above or below normal tidal ranges.
The range between a high and a low tide is greatest when the sun, moon and Earth are in alignment. These are spring tides. When the sun and moon are at right angles to the Earth, their gravitational forces significantly reduce each other. This causes the neap tide, a period of decreased tidal range. The term neap is an acronym for near even as possible.
Bulges are about the same size
Tide-generating forces are a result of the gravitational attraction between the Earth, sun, and moon. It was not until Sir Isaac Newton (who lived from ) discovered the law of gravity that the effect of the sun and the moon on the tides was fully understood. All surfaces of the Earth are pulled toward the moon and sun. This force has little effect on land masses, but it does have a very great and obvious effect on the water of the Earth's oceans. Twice each month the tidal range reaches a maximum and these large tides are called the spring tides. Halfway through the monthly cycle the range is much smaller, and these weak tides are called neap tides.
As the moon rotates around the Earth, it pulls the water on the nearest side of the Earth outward into a bulge. A similar bulge on the opposite side of the Earth is caused by the water being thrown outward by the planet's spin. These two bulges travel around the globe, producing two high tides each day. During time of the new moon and full moon, when the sun and moon are in a straight line, their gravitational pull combine and produce spring tides; at this time the high tides are very high and the low tides are very low. When sun and moon are at right angles from the Earth, during the quarter phases of the moon, the gravitational pull on the oceans is less producing a smaller difference between high and low tide known as a neap tide.
Some locations have much bigger tides than others. Tidal ranges are usually small in the middle of the ocean but can be very large where tidal waters are funneled into a bay or river estuary. Hawaii has hardly any tidal range at all while the water in the Bay of Fundy, in Canada, has a range of about 40 feet.
GRAVITATIONAL & CENTRIPETAL

5. Tidal Cycles Diurnal Tide: 24 hr 50 min cycle
Semi Diurnal Tide: hr 25 min cycle
Mixed Tide: hr 25 min cycle
TIDES: Tides are the slow, periodic vertical rise and fall of the sea surface. They are usually described as being either diurnal or semi-diurnal. Diurnal tides have one high water and one low water in each lunar day (about 24.8 hours), while semi-diurnal tides have two high and two low waters in the same time period. While these tidal changes are easier to observe where land and water meet, they exist everywhere -- even in the middle of the ocean. Tidal ranges along the shoreline vary by location. For example, the tides in Canada's Bay of Fundy, an Atlantic Ocean inlet west of Nova Scotia, rise and fall as much as 50 feet, while the tidal range in Lake Superior is measured in inches.
High and low tides are the result of the attractive forces (gravitational pull) of the moon and sun on a rotating Earth.

6. High water: a water level maximum ("high tide")
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: 1st quarter and 3rd quarter (14.77 days)
Intertidal zone
High tide
Low tide

7. The monthly tidal cycle (29½ days)
About every 7 days, Earth alternates between:
Spring tide
Alignment of Earth-Moon-Sun system (syzygy)
Lunar and solar bulges constructively interfere
Large tidal range
Neap tide
Earth-Moon-Sun system at right angles (quadrature)
Lunar and solar bulges destructively interfere
Small tidal range

8. Earth-Moon-Sun positions and the monthly tidal cycle
Spring Tide
Highest high tide and lowest low tide
Neap Tide
Moderate tidal range

9. Flood tide directs water landward; Ebb tide directs water seaward
TIDAL CURRENTS: The rise and fall of the tide is accompanied by the horizontal flow of water called a tidal current. The usual terms used to describe the direction of this horizontal movement are ebb and flood. Ebb currents occur when tidal currents are moving away from the coast. Flood currents move toward the coast. In a purely semi-diurnal current, the flood and ebb each last about 6 hours. Speed of tidal currents depends upon the shape and dimensions of the harbor, coastal areas and ocean bottom. The configuration also influences vertical range of the tide itself. Under certain conditions, tidal currents can move more than 10 knots.

11. Type of tide depends on: Position on the globe Water depth
Tidal Patterns
Semidiurnal tides- two high and two low per day; Cape Cod, MA (high latitudes)
Diurnal tides- one high and one low per day; Mobile, AL (low 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)
Countor- can distort the rotary motion of circular waves
Additional distortions occur near the equator where coriolis deflection changes direction, and along continental margins around large islands, where the sea bottom is shallow and the water is lowed down. These combined effects result in considerable variation in the type of tide and the tidal range along the world’s coastlines
Shouldn’t the tides be 12 and 24 hours?
Explanation: after 1 earth day, the moon has moved slightly forward in its orbit, so an additional 50 minutes or so is necessary for a spot on the earth to region its postion relative to the moon each day.Hence, the high tide and low tide shift forward each day
Type of tide depends on:
Position on the globe
Water depth
Contour- shape of ocean basins

14. Tidal Range
56 ft
6 ft

15. The Bay of Fundy: Site of the world’s largest tidal range
Tidal energy is focused by shape and shallowness of bay
Maximum spring tidal range in Minas Basin = 17 meters (56 feet)

16. Alma at High Tide
Alma at Low Tide

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

18. Tidal bore = a true tidal wave
Wall of water that moves upriver
Caused by an incoming high tide
Occurs in some low-lying rivers
Can be large enough to surf or raft

19. Corals exposed to air at extreme low tide

20. Tidal Information http://life.bio.sunysb.edu/marinebio/mbweb.html
HAWAIIAN ISLANDS
Mean Spring Mean Tide         Station Latitude Longitude Range Range Level Predictions
SAND ISLAND, MIDWAY ISLANDS 28° 12.7' 177° 21.6' Predictions
Laysan Island 25° 46' 171° 45' Predictions
East Island, French Frigate Shoals 23° 47' 166° 13' Predictions
Nonopapa, Niihau Island 21° 52' 160° 14' Predictions
Kauai Island Waimea Bay 21° 57' 159° 40' Predictions
Port Allen, Hanapepe Bay 21° 54' 159° 35' Predictions
NAWILIWILI 21° 57.4' 159° 21.6' Predictions
Hanamaulu Bay 22° 00' 159° 20' Predictions
Hanalei Bay 22° 13' 159° 30' Predictions
Oahu Island
Haleiwa, Waialua Bay 21° 36' 158° 07' Predictions
Waianae 21° 27' 158° 12' Predictions
HONOLULU 21° 18' 157° 52' Predictions
Hanauma Bay 21° 17' 157° 42' Predictions
Waimanalo 21° 20' 157° 42' Predictions
MOKUOLOE 21° 26.2' 157° 47.6' Predictions
Waikane, Kaneohe Bay 21° 30' 157° 51' Predictions

21. Inquiry Which has the greatest tidal effect– sun or moon?
Where is the greatest tidal range located?
Which lunar phase produces moderate tides?
How is a tidal bore created?