Have you ever found yourself in unfamiliar territory? Been picked up, carried, and dropped somewhere far away from your origin?
Well, then you might say you felt like an erratic, or maybe that’s not something normal people say.
Erratics are glacially transported boulders made of one rock type that may be different from the local rock type.
If the rock type of the erratic is unique enough to pinpoint the origin, you can draw a line between the origin and the erratic location.
This line tells us the direction in which the glacier was flowing. Here’s a map:
Not all boulders are erratics, some boulders might be transported by other processes, such as rock avalanches or iceberg rafting.