Final answer:
The uppermost part of a landslide where the land has detached and moved is known as the crown. It is the initial failure and detachment point in a landslide, distinct from the scarp, toe, and bench, which refer to different parts of a landslide.
Step-by-step explanation:
The uppermost part of a landslide where the land has detached and moved to the southeast is known as the crown. In a landslide, the crown is the area of initial failure and detachment and serves as an important indicator when analyzing landslide dynamics. It can be identified by a distinct break or crack at the head of the landslide.
The other terms provided in the options mean different parts of a landslide: a scarp is a steep slope or cliff, particularly one formed by faulting; a toe is the lowest part of a landslide, farthest from where the land began to slide; and a bench is a step or ledge that forms on the sliding surface within a landslide. Therefore, the term that correctly fills in the blank in the given question is 'crown'.