Friday, June 19, 2015

Derby - a town in the shire

Low Tide in Derby

Derby is a town in the Kimberley shire of Western Australia that has a tidal range of 35 feet. I took a look at the google street view, but I was unable to find Hobbiton anywhere. If you can find it, let me know.

So how can the tidal range be 35 feet (vertical)? In the open ocean, the vertical tidal range is only about 2 feet. Does the moon's lovely attraction pull harder on the water in some areas of the Earth? To find out what's going on we can take a look at the Bay of Fundy. It has the highest tidal range in the world at 53 feet.

There's a whole page explaining why Bay of Fundy tides are the highest. Basically, the bay acts as a funnel with a natural oscillation period of between 12 and 13 hours. This happens to match up with the Atlantic ocean tide flooding which occurs every 12 hours and 26 minutes. This results in resonance just like pushing on a swing does for the swinger. If you changed the shape of the bay, the tides wouldn't be as high.

The Derby visitor centre has plenty of other beautiful stuff about Derby on it. My favorite thing about the place is the Boab Prison Tree. I just love crazy looking trees:

Boab Prison Tree

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