As tweeted by T-Ray:
http://a.yfrog.com/img877/320/m2fam.jpg
Zooming in on the left lower corner you see a little dark smoke and some tube like structures that you'd expect in a volcanic environment...but that looks a lot like a river running through the middle.
I'm hoping that this is actually the boundary between the grassy wet plains and volcanic biome, both on amerish. I can hope, right?
The spikey rocks all over don't look like a highland kinda place at all, though. They definitely seem volcanic.
Potentially its a river of lava.