Sunday, April 26, 2015

Geology of Mont-Royal : The Trenton Limestone Strata and the Monteregian Hills

Disclaimer: I am not educated in geology. I have simply gone searching for some information about a topic that caught my attention when I was wandering in Mont-Royal park.

Those who have had the pleasure of hiking in the Mont-Royal park may have noticed what I did on a recent trip: there are a large number of sedimentary rocks (rocks formed of layers of material which have gradually compressed together into stone) which have quite a distinctively striped appearance:

Sedimentary rock in Mont-Royal Park
Sedimentary rocks are usually only a relatively thin layer, formed by deposits on top of igneous or metamorphic rocks.

Some internet research and the very handy interactive park map available on the Les amis de la montagne website revealed that this particular sedimentary rock is apparently part of the Trenton limestone strata, which apparently formed approximately 450 million years ago (which would place its formation in the Paleozoic era). Unfortunately, I haven't yet been able to obtain any other information about the Trenton limestone strata at all. If anybody has more information about this rock formation, I would be delighted to hear from you!

It is my understanding that the Mont Royal was formed by magmic activity below the surface along the Great Meteor hotspot track which produced a number of upshoots of igneous rock, pushing the rock above it into hills and mountains.  The Monteregian hills are all considered to have been formed from the same magmic activity.

As near as I can tell without an expert to explain it to me, the Mont-Royal and other Monteregian hills were formed when a bunch of magma pushed up and lifted the sedimentary rocks above. The igneous rock that formed as a result of this activity is apparently less prone to erosion, and so as the land around eroded, these more durable hills made of igneous rock have remained.

So what began as idle curiosity about the striped rock I saw turned into a rather extensive crawl through Wikipedia and other sites, resulting in the discovery that the sedimentary rock that caught my attention in the first place was lifted up and now sits on the shoulders of igneous rock that formed below it. Cool.

I need to take a geology course.

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