Did You Know...?
The La Cloche Mountains we enjoy today are the eroded descendants of peaks once several thousand feet high. The white ridges and bluffs are made of fine-grained quartzite. This rock formed eons ago under an ancient sea, then was lifted when tectonic plates collided millions of years later.
The mountains started out as sediment. Starting about 2.5 billion years ago erosion ate into the massive heart of the Canadian Shield. Over hundreds of millions of years, sands, silts, and glacial debris settled in a vast sea south and east of the Shield. The deposits that would eventually rise to become the La Cloche range were very clean white-quartz sand that consolidated as marine sandstone. Over time, as the earth’s crust shifted, the sandstone was compressed and heated below the earth’s surface to become quartzite.
A period of folding and uplifting starting about 1.8 billion years ago exposed the quartzite and other types of metamorphic and sedimentary rocks that had been formed along the southern margin of the Canadian Shield. Over millions of years a complex mountain system emerged, with ridges and fault lines generally oriented east-west.
Locally these mountains extended from west of Espanola, to south of Sudbury, and northeast to Lake Wanapitei. Erosion and many periods of glaciation reduced these Pre-Cambrian mountains to the wrinkled terrain we see today. The white quartzite – harder and more weather-resistant than other rocks – allows the La Cloche Range to remain as the most distinctive feature of this ancient landscape.
This is a highly simplified description of the dynamic geologic history of our region. This area is one of very few in the world where a wide diversity of intricate Pre-Cambrian structures is exposed at the surface in close proximity. Several colleges hold geology field camps here each year, drawn to the varied and easily accessible bedrock.
Special thanks to Prof. Frank Fueten of Brock University for reviewing this article. Frank has been conducting research and leading field camps in La Cloche for more than 20 years.
