The Great Crack: Photos and information wanted.

[MarkD]

"Slumps aren't the same as landslides."

Apparently some sources define a slump as a type of a landslide:

"Landslide is a general term used for a variety of landscape processes including slumps, rockfalls, avalanches, debris flows, mudflows, and lahars. "

http://geologycafe.com/landslide/types.html

But perhaps underwater the definitions differ.