The Worlds Lowest and Highest Tides Introduction To Tides Bay of Fundy Nova Scotia, Canada The Worlds Lowest and Highest Tides

Tides I. Definition: the periodic rise and fall of sea level A. measured relative to points on land B. highest level = high tide C. lowest level = low tide II. Occurrence: there are 2 high tides and 2 low tides each day.

Tides (cont.) III. Tidal Range: the difference in feet, or meters, between a high tide and the next low tide tidal ranges vary due to topography and latitude EX: low range: Gulf of Mexico tidal range is 1m high range: Bay of Fundy in Canada is as high as 15m

IV. Cause of tides A. Tides are caused by gravitational forces from the moon and the sun Gravity is a function of mass and distance C. The moon, which is much closer to the earth than the sun, exerts a stronger gravitational force on the oceans

IV. Causes of tides, cont. The force of gravity decreases with distance, so the moon exerts a stronger gravitational pull on the near side of earth, and a weaker gravitational pull on the far side. The oceans near the moon are pulled up towards the moon creating one tidal bulge. On the far side of the planet, the center of earth is pulled towards the moon resulting in the water on the far side being effectively left behind in a tidal bulge.

IV. Tidal Cycle a. The moon revolves around the earth at a rate of 12/day (1 revolution/month) b. The revolution is in the same direction as the earth’s rotation c. By the time the earth has completed one rotation, the moon has shifted 12 . So, it takes an extra 50 minutes for the moon to be in the same position relative to a point on earth. d. A tidal cycle is 24 hours and 50 minutes High and Low tides are 50 minutes later every day! Link to animation

V. The Sun’s Effect on Tides Because of its size, the sun exerts a gravitational force 180 times stronger than the moon! But, gravitational attraction decreases as the distance between bodies increases The sun’s influence on tides is much smaller than the influence of the moon The sun’s pull can either heighten the moon’s effect or counteract it depending on where the moon is in relationship to the sun.

V. The Sun’s Effect on Tides When the sun, moon and earth are aligned, the sun’s gravitational effect heightens that of the moon. High tides are higher and low tides are lower (large tidal ranges) These tides are called spring tides Spring tides occur at the new moon and full moon.

V. The Sun’s Effect on Tides When the sun’s gravitational effect is perpendicular to that of the moon, the sun’s gravity counteracts the effects of the moon The result is lower high tides and higher low tides (small tidal ranges) This occurs when the moon is in its first quarter and it’s third quarter These are called neap tides Link to animation

Full Moon 10/23 New Moon 10/8 1st Quarter 10/14 3rd Quarter 10/30

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