Is there an earthquake spell in the game?
I did forget about that one because it's not available in the Beta (bumped to a higher tier, probably). If I recall it did knockdown with a chance of poison, but there may have been some Earth damage as well. But two spells isn't worth an entire resistance category dedicated to them in my opinion.
On an extended related note. I've noticed a couple of times that one of my party will say something similar to "I've spotted something". However, they don't indicate what that something actually is. And sometimes it's not immediately obvious what is being referred to.
From what I can tell, it's usually a place you can dig.
Yes.