Final answer:
Erratics are large boulders deposited by glacial ice. They are found far from their original source and serve as evidence of past glaciation.
Step-by-step explanation:
An erratic is a large boulder deposited by glacial ice. Glaciers transport rocks and boulders as they move, and when the ice melts, these rocks are left behind in different locations. Erratics can be found far from their original source, and their presence is evidence of past glaciation.
For example, in northern Europe, the presence of erratics suggests that the region used to be covered by enormous glaciers. These boulders can vary in size and can be found in different types of sediment, such as gravel and sand. They often stand out in the landscape due to their size and composition.