Let us begin with what causes tides and that is, of course, the gravitational pull of celestial bodies, specifically the sun and the moon. The moon is close to us (about 384,400 km away) and is about 75% responsible for the tide. The sun, although far larger than the moon, is 160 million km away and is responsible for about 25% of our tidal action.
The moon then goes around to a right angle with the earth again to the third quarter and we are back to neap tides.
Finally, the cycle is complete with a new moon once again. This lunar month is roughly 29 days.
To review, the tides are highest at the full and new moons. Not all full and new moons however are equal, there is one very important variable in all of this and that is the position of the moon in its orbit around earth. When the moon is closest to earth (perigee), the gravitational pull is stronger. When perigee occurs at a new or full moon, we have the huge tides – almost 14 metres (46 feet) at Hopewell Rocks and up to 16 metres (52 feet) at certain places in the Bay of Fundy. When the moon is farthest away from earth in its orbit (apogee), the gravitational pull is weaker. Even if this occurs at a new or full moon, the tides may be only average or perhaps slightly above average.
There you have it in the simplest way I know how to explain it; no doubt this raises many questions in your mind, but alas this is all (and perhaps more than) the space that I have been allotted.
About the Author: Paul Gaudet is the Interpretive Services Manager at the Hopewell Rocks. Images were provided by the Hopewell Rocks. TheHopewellRocks.ca