Predicate 
crumble:
Roleset crumble.01 Verbnet Class: 1 "cause to be in little pieces":
Roles:
Arg0:causer of crumbling
Arg1:thing crumbling
Examples:
| ergative (-) | 
|---|
person: ns
tense: past
aspect: ns
voice: active
form: full
| The market crumbled.
 
 | 
| Arg1: | The market | 
| REL: | crumbled | 
| agentive (-) | 
|---|
person: ns
tense: past
aspect: ns
voice: active
form: full
| John crumbled the cookie.
 
 | 
| Arg0: | John | 
| REL: | crumbled | 
| Arg1: | the cookie | 
It's possible this verb will take higher args (EXT, start point, end
point) but I rather doubt it.