I saw this on ABC national news last night. Read Barbara's link, and I can't explain. My first thought was volcanic clay, bentonite, like at Portuguese Bend landslide in Palos Verdes Hills, but then the link said soils were normal and it has been dry.

My best guess is it is deep-seated, in the bedrock. Why now, I can't even guess.

Hey, this site does spell-check now...good.

Chris