Geology
Mont Saint-Hilaire is one of the Monteregian Hills, a group of erosional remnants of intrusive mountains spreading across southern Quebec. It is composed of three distinct plutonic intrusions that formed during the Cretaceous Period between 133 and 120 million years ago. Like the other Monteregian Hills, Mont Saint-Hilaire forms part of the Great Meteor hotspot track, which was created when the North American Plate slid over the New England hotspot. During this time, melting occurred, creating subsurface magma intrusions. Erosion of the surrounding softer sedimentary rocks revealed the more resistant rocks of Mont Saint-Hilaire.
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