Introduction To Tides

Bay of Fundy

Nova Scotia, Canada

The Worlds Lowest and

Highest Tides

TidesI. 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. Tidal Ranges: the difference in feet, or meters, between a high tide and the next low tide

A. 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

III. Causes

A. gravitational attraction between the Earth, Moon, and Sun

B. gravitational attraction decreases as the bodies involved move farther apart from each other

C. the Moon and Earth both orbit around a common point (in the center of the Earth)

1. each experiences gravitational and centrifugal forces that are unbalanced - as such the water on the Earth’s surface sloshes toward the unbalanced side of the pattern created by the Earth-Moon orbit.

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D. The Sun’s Influence

1. the Sun’s influence is smaller than the moon - although the Sun is much larger than the Moon, it is much farther away - recall III. b.

2. solar influence - called solar tides, depend on the phase of the moon.

3. large tidal ranges - called Spring Tides - occur when the moon is either full or new - these phases of the moon occur when the Sun, Moon, and Earth are aligned

4. small tidal ranges - called Neap Tides - occur when there is a first or third quarter moon - during these phases the Sun, Moon, and Earth form a right angle!

5. Spring and Neap tides alternate every two weeks - on average, spring tides are three times higher than neap tides

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