Interesting.
There's a Six Flags park there and an old naval shipyard and sub dock called Mare Island.
The shipyard closed in the late 90's and then Warner Bros ended up getting some of the property for Hollywood stuffs.
Yeah, Mother Nature
You really may be on to something here.
The shape is definitely unique but why I don;t exactly know yet, though I like your theory.
It would make sense to me that there would be a necropolis underneath to feed their sick habits, and if so then they would make sure it is heavily protected and safeguarded but thats just my speculation.
Keep digging!