boulder
boulder
A detached rock mass larger than a cobble, having a diameter greater than 10 in (25.4 cm) or 8 phi units, or about the size of a volleyball, being somewhat rounded or otherwise distinctively shaped by abrasion in the course of transport; the largest rock fragment recognized by sedimentologists. In Great Britain, the limiting size of 8 in (20.3 cm) has been used.
A general term for any rock that is too heavy to be lifted readily by hand. Also spelled bowlder.