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A lost world underground

Mark Vancleave

Feb. 06, 2013

Follow University of Minnesota researcher Greg Brick on a tour of the hidden world of Minnesota caves. French explorers, including Pierre-Charles Le Sueur, mined the caves for saltpeter, the main ingredient in gunpowder until World War I. Story by Rebecca Harrington: http://www.mndaily.com/2013/02/06/u’s-cave-diver

Brick prepares to descend a snow-covered slope to an entrance of Miles Cave on Monday, Feb. 4, 2013, beneath Hastings, Minn. Brick has explored around 100 caves as part of his research on saltpeter.

University of Minnesota researcher Greg Brick examines the roof of Miles Cave on Monday, Feb. 4, 2013, beneath Hastings, Minn. Brick has been exploring caves for his research since 2004.

Brick slides through the narrow "coon crawl," named after the large amount of raccoon remains there, in Miles Cave on Monday, Feb. 4, 2013, beneath Hastings, Minn.

The skeletal remains of a raccoon lay on the floor of Miles Cave on Monday, Feb. 4, 2013, beneath Hastings, Minn. Raccoons and other cave-dwelling animals contribute to elevated levels of nitrates, through both their droppings and decomposing bodies.

Brick looks out from the mouth of Miles Cave on a ravine carved by the Vermillion River on Monday, Feb. 4, 2013, beneath Hastings, Minn.

Brick carefully navigates an icy cliff to reach the entrance of Mill Cave in Spring Lake Regional Park on Monday, Feb. 4, 2013, near Hastings, Minn.

Brick sifts raccoon teeth and bones from nitrate-rich sand in Mill Cave in Spring Lake Regional Park on Monday, Feb. 4, 2013, near Hastings, Minn. Brick is attempting to determine whether caves like those near Hastings could have been mined for saltpeter by French explorers in the 1700s. Saltpeter was a key component of gunpowder.

A pipistrelle bat, covered in droplets of water, hibernates in Mill Cave in Spring Lake Regional Park on Monday, Feb. 4, 2013, near Hastings, Minn. The caves maintain a relatively warm and stable temperature through the winter, with the bats' narrow range of tolerance.