surname, attested from late 12c., probably meaning bald head; cf. Wyclif Stye up, ballard, where Coverdale translates Come vp here thou balde heade [2 Kg.2:23-24, where God kills 42 children for making fun of Elijah's lack of hair.]
A slump is a form of mass wasting that occurs when a coherent mass of loosely consolidated materials or rock layers moves a short distance down a slope. Movement is characterized by sliding along a concave-upward or planar surface. Comments.
The term 'slump' is also used to refer to the material that breaks off in a slumping slide. (images - click to enlarge - above left, diagram of slumping; below right, slump features; bottom right, cross-section of a Toreva block.)