Ancient glaciers eroded many of the valleys, creating space for the lakes as they melted at the end of the last Ice Age, approximately 8,000 b.c.
The valleys were created by the last ice age.
mnli hypothesis: The valleys were created by the last ice age. premise: Ancient glaciers eroded many of the valleys, creating space for the lakes as they melted at the end of the last Ice Age, approximately 8,000 b.c.