Friday 19 April 2013

The Petitcodiac Bore

Next weekend, the last in April, DauII and I are off to Merrie Engalond for a family knees-up.  My beloved and colorful brother-in-law is turning 60 and his friends-and-relations have organised a party on the banks of the Severn.  I'm assuming that they have arranged the time so that we can view the Severn Bore. I hasten to explain that this is not the B-in-L's nick-name.  When we scrabbled enough money to go partners with the bank on buying a house for the first time I announced the event with a picture of a swinging pub-sign featuring a pig's head and the motto "Ad signum verris oppressus" which Google refuses to translate as at the sign of the crushing boar.  But not everyone will suffer, let alone celebrate being named for a form of Piggie: too much frightening baggage from reading Lord of the Flies as a child.

Au contraire, the Severn Bore is a spectacular tidal phenomenon, similar in its cause to a tsunami.  After the recent events in Fukushima, we all know the word tsunami and deprecate calling it a tidal wave.  But perhaps a word of explanation of how it happens might be in order.  In an earthquake a huge amount of rock is shifted a comparatively small distance.  If the rock is near or under the sea, that small movement is transmitted to a huge amount of water locally setting up a small wave which travels outwards.  It might be only a few centimeters high but as it approaches land and the sea gets shallower, those few centimeters, spread over a large area, build up into several meters spread over a small area and still travelling.  The collision with the shallowing seas also slows the wave down from a zippy 800km/hr to the relentless and inexorable thing that we saw on the news from Japan two years ago.  A tidal bore, such as the Severn's, happens because the tide, a volume of moving water that puts the largest tsunami in the ha'penny place, gets increasingly constrained by certain estuaries as it moves upstream against the current.  You can surf the Severn Bore.

I have seen the Petitcodiac Bore!!!  I beg to suggest, ladies and gentlemen of the jury, that there are not more than a handful of people in Ireland this morning who can make such an extravagant claim.  Quite possibly, I am the only one.

The Petitcodiac is a short river in New Brunswick Canada that debouches into the head of the Bay of Fundy, which has among the most extreme tides on the planet.  The Bay opens to the West and is funnel-shaped, just like the Severn, only much bigger.  So it scoops up and constrains a lot of water as the earth turns.  At the head of the bay lies Moncton NB, astride the Petitcodiac.  Sometime in the early 1980s, as part of my PhD research at Boston University, me and my mentor were in Moncton for a tuthree days.  One afternoon we decided to walk across the 1km of tidal slobs to the Southside suburbs.  You couldn't even see the river from downtown Moncton, just acres of mud with some reeds and spartina near the dry land.  ANNyway, as we trudged across the bridge, the river itself became visible at the bottom of its canyon of gloop and as it became visible, a wave came round the corner travelling upstream.  It looked like the wash of a steamer but there was no boat.  The whole show lasted about 2 minutes.  Because we were both scientists, we were able to work out what we had seen before we got to the Southern shore.  Like most people who aren't completely indigent we whisked back to Moncton in a taxi when we'd exhausted the data and delights of Riverview NB.

So what are the odds?  What do you have to have 'achieved' to become a member of the Irish chapter of the Petitcodiac Bores? - we meet for luncheon in the Railway Hotel, Carlow on the 3rd Friday of the month? 
You have to have been to Moncton.
You have had to have a reason to go to the much smaller Riverview suburbs.
You have to have made the trek on foot...
...during the 2-3 minutes twice a day (during one of which it's probably dark) when the bore is visible.
You have to look down.

Come on, it's lonely eating on my own.

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