Sonar survey confirms mastodon carving at 9,000-year-old Lake Michigan’s ‘Underwater Stonehenge’
High-resolution imaging shows a human-made mile-long boulder array 12 m under Grand Traverse Bay, predating Stonehenge by 4,000 years.
Sonar survey confirms mastodon carving at 9,000-year-old Lake Michigan’s ‘Underwater Stonehenge’.(photo credit: Mark Holley)