Lake Ice depths

I drilled 3 holes about 100 meters apart. I started at Skater’s Cabin. Ice depths; 8″, 6″, 12″. Each of these holes had a noticeable ‘air-pocket’ that whooshed as I punctured it., about 2″ above the bottomost layer. The ice was easy to drill which is not typical. There is a list of precautions for traveling on lake ice, you should review them.