Come for the Whales, Stay for the Tides
June 14, 2023
By: Madison Malloy
Sitting at the base of the Bay of Fundy, St. Andrews is no stranger to large tides. The Bay of Fundy sees tides up to 16 metres high, and here in St. Andrews, our tides can rise as high as 8.5 metres (Government of Canada, 2023)! In order to appreciate what causes this phenomenon, we must understand how the Sun and Moon influence tides, as well as the special characteristics of the Bay of Fundy.
How frequent are tides? (National Oceanic and Atmospheric Administration [NOAA], 2013)
The largest tidal force is the gravitational pull of the Moon on the Earth, which pulls the water towards the Moon, forming a bulge. On the other side of the earth, a bulge of approximately equal size is formed from inertia, the opposing force to gravity (NOAA, 2005). In the image above, this is represented by the high tides on either side of the equator, and low tides at both of the poles.
We must also consider the secondary tidal force of the Sun on the Earth. Despite the Sun being around 400 times bigger than the Moon, it has a lesser impact on the tides because it is much, much farther away (Britannica, n.d). The gravitational pull from the Sun creates a smaller bulge in addition to the one from the Moon. Instead of thinking of the tides as going up and down, you can think of the Earth as rotating in and out of these stationary bulges every day.