When in the mirror in Book 2, Rand notice a bunch on very narrow cloud lines. To me these air the marks left behind by jets. But this makes no sense because everything but grohlm are supposed to be dead. whats going on here?

 

Second, I think that Lanfear brought those grohlm. They seemed to pop-up in times way too convenient for her.

 

-Rin

I always took those to be an artifact of that particular world.  It seems to be marked by the passing of great events.  Heck the mere fact that Hurin can follow the passage of the horn and fain supports this.  There are also lines burned into the ground too, where nothing seems to grow, and the char is old as to have no smell if I remember correctly.

 

Now the grolm I am unsure about.  It could be possible that Lanfear brought them with her.  Either that or she can some how call and control them.