Turning a love for caves into a conservation cause
John Ackerman of Spring Valley, Minn. discovered 40 miles of underground caverns. Now he is working to protect the caves and have them studied. CBS News' Michelle Miller reports.
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John Ackerman of Spring Valley, Minn. discovered 40 miles of underground caverns. Now he is working to protect the caves and have them studied. CBS News' Michelle Miller reports.