"Mylonite exposures in Marathon County reveal highly deformed, very old rocks—around 1.8 billion years old—that stand out as striking geologic features along the glacial trail and make for an educational and visually impressive detour for visitors interested in Earth’s tectonic and glacial past." - Stacey Leasca Stacey Leasca Stacey Leasca is an award-winning journalist and co-founder of Be a Travel Writer, an online course for the next generation of travel journalists. Her photos, videos, and words have appeared in print or online for Travel + Leisure, Time, Los Angeles Times, Glamour, and many more. You'll usually find her in an airport. If you do see her there, please say hello. Travel + Leisure Editorial Guidelines