 The original extent of the glacier lake, once the glaciers disappeared, (the study of terminal glacial moraines) was about two to three times area of 2000 with extensions in the plain in three directions (Nurieux, Saint Martin du Fresne, Montreal).This explains the significant depth (42.9 m) and its configuration in the form of ice gorge east-west areas at risk of flooding towards the plain and Port areas moraines.Its scope was much larger and was marked by two arms of lakes and large marshes to unhealthy important work done in 1856.