ORWELL Geology professor Helen Mango from Castleton State College leads another of her popular geology hikes at the Mount Independence State Historic Site Sunday, August 17, at 2 p.m. to explore the 18th century fort sites past. Mango will show you everything from the oldest rocks in the Potsdam Formation to chert outcroppings to the newer rocks of the Great Meadows Formation. The rocks were the foundation for the vast Revolutionary War fortification, Mount Independence, built in 1776 and 1777, and the chert in particular was used by Native Americans for thousands of years to make tools. Wear sturdy shoes and dress for the weather. The Mount Independence State Historic Site is one of the best-preserved Revolutionary War sites in America. It is located nearly the end of Mount Independence Road, six miles west of the intersections of Vermont Routes 22A and 73 near Orwell village; carefully follow the signs.