An astrobleme is a scar on the surface of a planet or a natural satellite made by a meteorite, asteroid or comet upon impact. This scar can be expressed by a simple bowl-shaped crater for smaller meteorite impacts, or a more complex morphology for major impacts. For the latter, the isostatic compensation causes instantaneous feedback from the bottom of the crater during its recess. The impact structure is then said complex or multi- ring.
To demonstrate the existence of a meteorite crater, scientists have only two criteria. One is visible to the naked eye: the shatter cones. The other is only visible with a polarizing microscope at high magnification: Planar Deformation Features or PDF in crystals.
The Charlevoix crater was unearthed in 1965 by Jehan Rondot during a geological mapping campaign. He had observed rocks in St- Hilarion that appeared to have shatter cones. This observation was confirmed in 1966 by a geologist familiar with meteorite impacts. Since this discovery, shock cones and PDFs have been observed at several locations in Charlevoix, indicating beyond doubt the nature of the mechanism responsible for this landscape.
The Charlevoix astrobleme is a complex structure of about 56 km in diameter. The event would have occurred there about 340 million years ago. The current topography reflects the post- impact readjustment, especially with a large rise in the bottom of the crater at the height of Les Éboulements and arched valleys of Du Gouffre River and La Malbaie River.
For those interested in learning more about the Charlevoix astrobleme, know that a dedicated observatory has mounted an interesting exhibition. It is, however, only available during summer at the Old Clubhouse of the Manoir Richelieu, on the same site as the astronomy observatory. This organization has also developed with our help a geological journey that will be enhanced over the years.
We now think of offering a summer activity of a day to our customers of Sablon so they can become “Geologist for a Day” and learn about the geology of Charlevoix. Interested parties are requested to follow us on our website.