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> Issue 67 > Page 34 - A Geology Walk up the Clyburn Valley

Page 34 - A Geology Walk up the Clyburn Valley

Published by Ronald Caplan on 1994/8/1 (229 reads)

water level were to rise. There are a couple of old stumps lying on it, but ob? viously they haven't been there for very long. They must get washed on down in the spring floods. Even a whole tree up there at the beginning of it. If you look at the size of some of those boulders--the larger ones are getting up to being about 18 inches across. Most of the larger ones are about a foot across. The kind of river current that would be needed to move these boulders is really quite surprising. The water would be flow? ing down there at a rate of some 60 to 80 kilometres an hour. It certainly is trav- • elling down there. 'sv| ACCESS OPENING THE DOOR TO FINANCIAL SEGORITY AND PEACE OF MINO. AvaUable to ages 50-85 DRUKER INSURANCE AGENCY LTD. 363 Chariotte St., Sydney 562-5504 Toll Free In Nova Scotia and PEI: 1-800'61-3500 (FAX 564-5053) ' BLUE CROSS" But the shape is even more interesting. The bar itself is totally flat across the top. And that tells us that the boulders were be? ing swept along the top of the bar. And then they were tum? bling over the front of it. You see, it's fairly steep in the front--the downstream side. And the boulders would be tumbling down the side of that bar-- over the sides as well as down the front of it. The whole thing is very streamlined-- very hydr??dynamic in its shapes. But right at the bot? tom of it, there's some sand. Now, if the current was mov- ling at some 50 or 40 knots, then you would expect that sand to get washed away to- CELLULAR KING We've got you covered! Authorized MT&T; Mobility Dealer Call Wes THE CELLULAR KING for all your Cellular and Paging Needs Authorized Dealer for: • NOKIA • AUDIOVOX • NOVATEL Welton St. -PULSAR Sydney, N.S. B1P5R2 Bus.: 562-6222 Cell.: 565-6003 Fax: 562-6335 tally. And around the front of the bar, it has been washed away. But on the sides it hasn't. And that tells us there must have been a little back eddy in there. So that the water would have been flowing over the top of the bar, pouring off the'sides, rolling the boulders down with it. They, of course, would roll down under gravity. And at the bottom, there were these little dead spots where the water wasn't flowing fast at all. And the fine-grain sand was accumulating right there. That's a neat example of the boulder bar actually pushing its way out over the sandbar, which probably was there before the boulder bar started to get developed. Of course, what you always wonder is, why is the boulder bar right there? And not 10 metres nearer us, or 10 metres upstream, or whatever. I wonder if that big stump had anything to do with it. The big dead tree that's lying above--or that's just been beached on the bar. I've never been here in the spring runoff. I'd love to see it--it must be really a tremendous force. Oh, it must be a fantas? tic sight, to watch it roaring its way down here. I would expect that this road is probably flooded during the height of spring runoff as well.... All the bars in the middle of the river-- even the ones that are built out from the edge of the river--are the same. Some'11 be connected to the bank, and some of them will be as islands in the bank, if the river forks around about them. (And am I correct that what looks like dry islands have the riverbed flowing through and under them?) The water is flowing un? derneath, but underneath at river level today. Later on in the summer as the bar? rens begin to dry up up on top, the river flow gets really, really low. Some of the places where today there's just water flowing over the riffles--over these sto? ny, bouldery patches where you could walk across the water--those would dry up to? tally. But the water is still flowing, down underneath, in the riverbed itself. KEDDY'S Sydney Hotel 600 KING'S RD., SYDNEY, N.S. 214 ROOMS Air Conditioned • Colour Cabie TV Indoor Recreation Facility- • ?Pool "Sauna ? Whirlpool Bath Entertainment & Dancing at lUORV'S LOUNGE KEDDY'S FAMILY RESTAURANT 7 A.M. to 9 P.M. Licensed Dining • Daily Features
Cape Breton's Magazine
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