How do glacial form?

Answer 1

Glacial erratics aren't exactly formed. They were deposited by glaciers that were moving in that area at one time.

improved= Glacial erratics are exactly formed. Because a glacier is so heavy, the glacier can pluck large rocks as the glacier moves. When the rock is too heavy for the glacier to hold, or the glacier is retreating, it then deposits the rock in a place where it wouldn't usually be found. This is what an erratic is. A large piece of rock in an unusual surrounding.

i hope this helps :)