These piles dot the northern half of Thunder Bay near Alpena. Each circle is roughly 15 meters (49 feet) in diameter and some contain lumps of coal.
 Coal Piles
Image courtesy of Thunder Bay 2010 Expedition, NOAA-OER. Download image (jpg, 51 KB).

These piles dot the northern half of Thunder Bay near Alpena. Each circle is roughly 15 meters (49 feet) in diameter and some contain lumps of coal.

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