No single scientific definition of the term exists, and it has been applied to a variety of rock features that fall into one of four general categories: - A glacial erratic is a boulder that was transported and deposited by glaciers or ice rafts to a resting place on soil, on bedrock, or on other boulders. It usually has a different lithology from the other rocks around it.
Что в итоге?
Not all glacial erratics are balancing rocks; some are firmly seated on the ground. Some balancing erratics have come to be known as rocking stones, also known as logan rocks, logan stones, or logans, because they are so finely balanced that the application of just a small force may cause them to rock or sway.