Moggy Hollow Natural Area is a 14-acre preserve in Far Hills, New Jersey, important for its role in the end of the last ice age. It preserves the outlet where Glacial Lake Passaic drained toward the Raritan River after the Wisconsin Glacier had blocked lower northern gaps and helped form the lake. At Moggy Hollow, a hard basalt ledge created a spillway 331 feet above sea level, and the escaping water carved a deep ravine through softer rock. Even as the glacier retreated, this remained the lake’s main outlet for a time until other routes opened. The site became a National Natural Landmark in January 1970.

Far Hills, New Jersey · USA