So how did earth know where to put the ramp?

[The Borgified Corpse]

I'll tell you what's really weird: in that episode where Carter takes the female cadet through the wormhole, they switch positions left-to-right between walking into the SGC's gate and exiting on the alien world (i.e., Carter starts on on the girl's right and ends up on her left side).

Explain that one.

If they flipped sides, I'm guessing it has something to do with a mirror universe.

 

[Nick Ryder]

Someone asked about why it wouldn't scoop dirt out - it kinda did in one episode where the gate was under attack or something and the gate was partially buried. So when they embarked from Earth, they waited for the event horizon to scoop out as much dirt as it could so they could still exit it, even though they were buried a bit . So its been shown to do that. Dirt and rocks won't stop it, but a large stone in the center is enough to basically stop the event horizon from fully materializing.