The rift system trends northeast and southwest and forms a half-graben that links the Ottawa-Bonnechere and the Saguenay grabens.
The rift system extends more than 1,000 km (620 mi) along the Saint Lawrence valley from the Ottawa – Montreal area.
[1] Two significant historically active seismic zones occur along this system associated with northwest trending intersecting graben structures.
Seismic studies indicate a crustal convergence across the Saint Lawrence valley of about 0.5 mm (0.020 in) per year.
You can help Wikipedia by expanding it.This article about a specific United States geological feature is a stub.