Saturday, March 24, 2012

The rocks of Rockcliffe

Driving eastward round the bends of the Rockcliffe Parkway this morning I was aware of the crumbling shale cliffs (on my right) and the cliff edge over the river (on my left) that's presently being reinforced with a retaining wall, and not a moment too soon, because the sidewalk on that side looks as if it threatens to subside into the river. The ice builds up on these surfaces in winter and the pavement heaves and generates potholes in the early spring. Cyclists, beware!–– before the holes are filled in, the roads round here are full of hazards.

A geological assessment of Manor Park mentions the ...
...vertical cliff along Rockcliffe Parkway where it curves up escarpment west of the Ottawa-New Edinborough tennis courts: Cross-beds are inclined at low angles to the main, near-horizontal bedding to form wedges that are visible from the pathway across the road ...
Further down the page, the geologist reminds us that at one time there was a sea, rather than a river, here:
... limestones were deposited in a shallow (mainly < 10 m) sea on a continental shelf, or within an intracontinental basin. The limestones vary from fine-grained to coarsely crystalline and include accumulations of shell or skeletal fragments broken by wave action and marine currents.
So this is how this part of the world would have appeared during the retreat of the glaciers in the Paleozoic era; what is now Canada's National Capital Region was once under the western end of the Champlain Sea:

The thought of that big melt puts our present day springtime thaws into perspective!

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