A Lesson on Tides

This is our last day on the shores of the Bay of Fundy for this part of our trip. The tides here just fascinate me; as I’ve said, these are the highest tides in the world.

We took a short drive to Wassons Bluff. There a trail takes you down to a small beach near cliffs where tens of thousands of dinosaur bones have been found.

It’s a very pretty place in the vicinity of Two Islands.

While Bud wandered over to look for fossils I became fascinated with the tide, which was now coming in.

Tides are caused by the gravitational pull of the moon, and to a lesser extent, the sun, on the water in the oceans. How high a tide is at any place depends on how the water is pulled against the land. In places where there is a large continental shelf the water piles up. In places where the continents restrict the flow of water the water piles up. Both of those things happen at the Bay of Fundy, but there is another contributor. Water sloshes in the bay just like it will in a basin if you tip it. How fast it flows from end to end depends on the size of the basin. It just so happens that water sloshes in Fundy Bay in about 13 hours. The tidal cycle is twelve and a half hours. So as water is moving either into or out of the bay from sloshing, the moon gives it another pull, amplifying the movement.

And that movement is astonishing. This is a one minute video I took of the tide coming up on a rock. It may seem like a slow video, but what you are seeing is the actual rise of the tide, the water was otherwise still. At the end of the minute I looked closely at the depth of water on the seaward edge of the rock. It was at least an inch deep. An inch in a minute. That’s five feet in an hour!

And this is happening all across this huge bay. That’s an almost unimaginable amount of water moving.

People get stranded along these shores all the time. Rescuers are dispatched in boats to save them. It’s already happened twice this season at this campground.

Now I can see how strandings happen. You are wandering about looking for fossils or taking pictures…

and a half an hour later, half your beach is gone!

We stayed where we had a path up, but many people walk along the base of the rock cliffs and if they misjudge they are stranded.

That’s why there is a sign with the current tide times posted at the beach entrance here.