Glacial erratics are large boulders moved and then left behind by glacial retreat and are dissimilar to the immediate local geology. Glacial till are the muck deposits acquired by glacial scour then deposited upon glacial retreat. read more
The large boulders are called erratics. The basic deposits are called moraines. There are lateral moraines, medial moraines, and terminal moraines. Glaciers plow up "till". The process is still a research issue about how ice and glaciers "pluck" till. It's not quite an obvious as it might seem. read more
Large erratics consisting of slabs of bedrock that have been lifted and transported by glacier ice to subsequently be stranded above thin glacial or fluvioglacial deposits are referred to as glacial floes, rafts (schollen) or erratic megablocks. read more