Maine- Tides, and a Jellyfish

2024 April 7

One thing that we noticed right away in Bar Harbor was that the docks were – unusual. Like this one, where you can see this sloping ramp running down from a main dock, to a lower one. You can also see that the foundation of the main dock is water-stained to a considerable height, it looks like about 7-8 feet above the waterline. It turns out that the lower dock floats, and the reason it does this is that the tides in Maine are very substantial [1]. By having the docks float up and down like that, they can handle the tides very well.

The big tides in Maine mean that the beaches are a lot more, I guess I’d say “vegetated” than we’ve seen elsewhere. The large daily changes in water levels mean that the various types of seaweed get well watered twice a day, and so they never dry out. This rocky beach here is a good example.

Incidentally, that big rock is frankly pretty enormous, and even so it is clear that the water comes way up the beach and still goes high enough to half-immerse it. Here’s a closer view, so you can see the two people standing behind it for scale.

It has been there for a while. Even the crashing waves of the sea apparently don’t budge it any more, and so it is still approximately where it was when the melting glaciers dumped it there thousands of years ago.

One of the features of Bar Harbor is the Bar, which is totally immersed at high tide, but at low tide is practically a highway out to Bar Island.

Notice I am not calling it a “sandbar”. And that’s because it isn’t. It is more of a gravel bar. Some of the stones in this next picture were the size of my fist.

When this is immersed, the water runs deep enough over it that some fairly large marine life can get stranded when the tide goes out. Like this one:

We weren’t quite clear on what this was at first, the most similar thing I had ever seen was the placenta after one of our cows had given birth. It was about the right size, too:

But eventually, we realized that this is what a large jellyfish looks like when it gets stranded. I don’t know what kind it is, because frankly one blob of jelly looks a lot like another and its distinguishing features (the tentacles) were pretty much hidden. At any rate, I am glad we didn’t try to move it, as I understand jellyfish stings are often quite painful.

So, I have scads of pictures because there were lots of things scurrying, creeping, oozing, or just hanging out on the bar. Next time, I think we will have a look at the crabs.


[1] This is quite unlike other beaches we have been at over the years. To start with, Lake Superior (and the other great lakes) effectively have no proper tides at all, the water just gets pushed up on the beach by the wind sometimes. When we went to Sanibel Island in Florida, they also had pretty much negligible tides. In Tasmania and the northeast coast of Australia, the tides were a few feet, but only really noticeable on broad tide flats where tiny changes in depth made for big changes of the shoreline. But Maine, well. That’s another story altogether.

Here’s an interesting map showing the range of tides in various places in the world, where dark red to black are where the tides are largest. You may notice that most coastlines have pretty moderate tides, but some places really get it. And, if you look up by the coast of Maine, you can see that it is nearly black. It’s too bad this map isn’t higher resolution, if it was we could see up into the Bay of Fundy. That is north of Maine and gets some really outrageous tides, with the range from the lowest low to the highest high being 52 feet (!)

When I originally stumbled across this map years ago, I wasn’t even looking for tide ranges. It seems that there used to be an ice hockey arena here in Houghton that was called The Amphidrome (which burned down years ago and was replaced by a building currently named Dee_Stadium). The weird thing was that nobody seemed to know why it was named that, or what “amphidrome” even meant. So, I went and looked it up, and found this Wikipedia article about Amphidromic_points, which had that map. See, if you look at that map, the white lines show places that experience tides at the same time. And these lines meet up at points which are marked as deep blue, indicating that they have essentially no tide. These points are the “amphidromic points”, and they occur because of the resonant characteristics of their ocean basins. So places near the amhidromic points tend to have negligible tides, while places further away often have massive tides, particularly if the coastline tends to funnel the tide into a small area. The tide essentially rotates around these points as the oceans slosh about in their basins.

So what does this have to do with hockey rinks? As far as I can tell, not a thing. I guess that when he built it, James Dee just heard the term “Amphidrome” somewhere, thought it sounded cool, and named it that without much concern with what it actually meant.

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