New England's Dark Day - Cause

Cause

The likely cause of the Dark Day was smoke from massive forest fires. When a fire does not kill a tree and the tree later grows, scar marks are left in the growth rings. This makes it possible to approximate the date of a past fire. Researchers examining the scar damage in Ontario, Canada, attribute the Dark Day to a large fire in the area that is today occupied by Algonquin Provincial Park.