Then Master Toph replied with "Your worst nightmares!" and started moving the ground to make him trip.

[His Toph impression sounds more or less just like his Sync impression. And even knowing Asch can't see it, he's totally acting this out with his arms, too. It's as much a distraction for Asch as it is for Ion, at this point.]

It wasn't long until she managed to trap him, leaving nothing but his head sticking out of the ground yelling "Let me go!" I don't think he had any idea what he was up against when he started trying to fight back. She had to come back a few hours later to let him out, otherwise he might still be there now.