GEOLOGY
News
In Charlevoix, the earth’s mantle of Precambrian rocks was subjected to violent convulsions. More than two billion years old, Precambrian rocks are the oldest on the planet. At depths of more than 20 kilometres, metamorphic rocks were subjected to enormous pressure and intense heat. Of all the metamorphic rocks, gneiss is the most remarkable. It is very hard and comes in many colours that can be seen on the bare flanks of mountains: the range of colours are diverse: white, grey, yellow, pink or black. Among intrusive rocks, anorthosites are the hardest and are found in Saint-Urbain where they have been mined for a few years for iron and titanium. As for quartzites around La Galette, on the Petit-Parc road, these are sedimentary rocks. Today, they are mined for silica. The most common varieties are flint and sandstone.
A billion years ago, continents were not separated and it appears that the Laurentian Mountains were created by a collision between the Quebecia Block and the Canadian Shield. Geologically, Ile-aux-Coudres is part of the southern shore of the St. Lawrence River. The Logan fault travels along the north shore and separates the two shores.
350 billion years ago, a meteorite with a two-kilometer diameter fell on Charlevoix at a speed of ten kilometres per second. As a result, the Mont des Éboulements was created by the central upheaval caused by the enormous forces delivered by this impact. Among the nine craters of meteoric origin known in Quebec, it is the biggest after the Manicouagan crater, 56 kilometres in diameter. The smallest and most recent, a deep lake, is called the Chubb crater and was painted by René Richard about fifty years ago during a scientific expedition lead by the well-known professor, botanist and ethnologist Jacques Rousseau. The crater measures three kilometres in diameter and is only one million years old. It is located in Ungava, about a hundred kilometers west of Kangiqsujuak, a village located on the shores of the Hudson Strait.
According to Jehan Rondot, in his book entitled Géomorphologie de l’astroblème de Charlevoix, published by the Quebec Ministry of Energy and Resources, « among meteorite craters, the Charlevoix crater is the only one that has to this day a very visible multi-ringed basin with a central uplift, very close to the morphology of lunar craters ». In his book, the Astroblèmes du Québec et des Environs, he mentions that « the impact origin of the Charlevoix crater was realised after the discovery of many shatter cones in the area, obviously caused by an extremely powerful collision». Further on, the author states that Charlevoix, because of its particular location and easy access, reveals unique and precious data on the formation of astroblemes.
In Eastern Canada, Charlevoix is well-known as having regular seismic activities. Small earthquakes happen very often and it would appear that special conditions of underground water circulation and the presence of deep intrusions weaken the complex fault system in the region. Between 1663 and 1925, six important earthquakes ranking above 6 on the Richter scale shook the region. This should have a bearing on land management and construction and development standards.