Anyone who has ever spent the day at a beach will know that the sea is not static.
Indeed, over 24 hours a shoreline can change dramatically as the gravitational interaction between Earth, the Moon and the Sun dictates the ocean tides. But are other large bodies of water on Earth subject to tides as well?
Well, technically the answer is yes, because everything, even solid land, believe it or not, experiences the tidal pull from our cosmic neighbors. However, it all comes down to proportions. Because lakes are so much smaller in volume and also self-contained – unlike the oceans which are interconnected – the level of water displacement is far smaller.
For instance, according to NOAA, the most powerful spring tides in the Great Lakes in North America (which combined contain over 20 per cent of all the world’s fresh water) amount to a mere five centimeters (two inches) at most. Therefore, in smaller bodies of water, the lake tides are simply too minuscule for us to notice.
Something often mistaken for tidal movement is a seiche, or standing wave, which can reach several meters in height. These waves are caused by strong winds or extreme changes in pressure and rebound back and forth in an enclosed or semi-enclosed body of water, much like the sloshing motion you often see in your bathtub.
Depending on the scale of the lake or bay, the high and low points of the seiche can be up to seven hours apart, hence why many mistake this phenomenon for tides.