Page 39 - A Geology Walk up the Clyburn Valley

ISSUE : Issue 67

Published by Ronald Caplan on 1994/8/1

And these minerals grow under different pressure and temperature conditions. And when the pressure changes rapidly--in oth? er words, when the magma rises up inside the crust of the earth--then one mineral or the other will be preferentially crys? tallized. And when we see the plagioclase being crystallized around the pink potas? sium feldspar, we know that that was asso? ciated with the magma rising. Some of these boulders, I think have got a lot of rapakivi in them. And some of them have just got one or two. So when you get this colour zoning in it, you know that you're dealing with magma that was rising up in the crust, slowly.... (A lot of this we're not seeing because these have been here long enough so that moss, lichen, and everything else that dis? colours or covers it, is taking place, as well.) Exactly. You've got to look for a fresh surface. And since these boulders have been lying around here for a couple of thousand years, they don't have any fresh surfaces left. Unless they crack open..,. (And what we're looking at here--it's kind of a field of fallen boulders that have fal? len off of Franey.) Exactly. The bottom of a scree slope.... These are gravity deposits. These are rocks which fell off the top. Now, the reason that they fell is probably because during the wintertime the water would percolate down in the cracks in the rock, and then it would freeze. And when water turns to ice, of course, it expands. And it basically just wedges the rock off, very gradually, piece by piece. They come cascading down the face of the mountain when it melts away again in the spring.... What we're going t' base of the slope, quite some distance The river, as you to the far side of all the way to the So we're not going We'll see a little here. And then we brooks that feed into it, from here on up. But I think this is the last that we'll see of the river.... Watch on the right as we go around the bend...for the scree slope.... We're right under Beinn Franey. We can see it through the trees... . We're standing at the bottom of the scree slope. The scree is the name that's given to all these boulders and--I don't think there's o do is walk along the And we're going to be s away from the river. go upstream, is away out the valley from now on, very end of the trail, to see the river again, bit of a backwater 11 cross a couple of the 9 slope • -boulders that fell off Franey Mountain anything smaller than a boulder here--all these boulders that have fallen off the edge of the mountain. In fact, looking at it from here, there's a definite possibility that this whole face is one enormous landslide. VOLUME ONE BOOKSTORE Bag No. 200 Port Hawkesbury Centre Port Hawkesbury, N. S. BOE 2V0 Phone (902) 625-1514 Wilson Timmons Res.: 345-2387 Phoebe Timmons Res.: 863-1825 133 Church St. Antigonish Shopping Centre Antigonish, N. S. B2G 2E3 Phone (902) 863-4112 VOLUME TWO BOOKSTORE Super>'u IMVJJ;JNJf:fiT.7J:l Welton St., Sydney King St., North Sydney Paint St., Port Hawkesbury Kings Rd., Sydney River Reserve St., Glace Bay Stellarton St., New Glasgow

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