Boulder

In geology, a boulder (or rarely bowlder)[1] is a rock fragment with size greater than 25.6 cm (10.1 in) in diameter.

Erratics are boulders picked up by ice sheets during their advance, and deposited when they melt.

[3] These boulders are called "erratic" because they typically are of a different rock type than the bedrock on which they are deposited.

Some noted rock formations involve giant boulders exposed by erosion, such as the Devil's Marbles in Australia's Northern Territory, the Horeke basalts in New Zealand, where an entire valley contains only boulders, and The Baths on the island of Virgin Gorda in the British Virgin Islands.

Boulder-sized clasts are found in some sedimentary rocks, such as coarse conglomerate and boulder clay.