The Volcano.

[Xenor]

There are mountains between LL and Iron Lake, which is why you have to run east or west to get to it rather than straight up. This suggests that the distances we're covering are miles, then you've got the distance from Iron Lake to the volcano. It just seems unlikely that lava flows would travel that far to reach LL. They couldn't travel straight down either, they'd have to pass down Skull Valley or Bloodshore and then curve round to reach LL. This wouldn't happen because there's no terrain that would force them to curve round, they'd just flow straight off the cliffs south of Skull Valley or Bloodshore. I could see Aleport or Wineport getting hit by one however.

[Catapult]

There are mountains between LL and Iron Lake, which is why you have to run east or west to get to it rather than straight up. This suggests that the distances we're covering are miles, then you've got the distance from Iron Lake to the volcano. It just seems unlikely that lava flows would travel that far to reach LL. They couldn't travel straight down either, they'd have to pass down Skull Valley or Bloodshore and then curve round to reach LL. This wouldn't happen because there's no terrain that would force them to curve round, they'd just flow straight off the cliffs south of Skull Valley or Bloodshore. I could see Aleport or Wineport getting hit by one however.

All possibilities. Here's another one:
The volcano may not even erupt in it's current cone. If the volcano is hot-spot related (typical of Hawaii-style volcanos), the earth may have moved over the top of it. If so, the path of least resistance for the lava could be somewhere unsuspected like, say, Bearded Rock for example. Disaster!!!

Although having the existing formation go bang would be so much more dramatic and we must never underestimate the value of a well-designed cinematic...

[Sonic_the_Hedgehog]

All possibilities. Here's another one:
The volcano may not even erupt in it's current cone. If the volcano is hot-spot related (typical of Hawaii-style volcanos), the earth may have moved over the top of it. If so, the path of least resistance for the lava could be somewhere unsuspected like, say, Bearded Rock for example. Disaster!!!

Although having the existing formation go bang would be so much more dramatic and we must never underestimate the value of a well-designed cinematic...

I think the volcano may be hot-spot related considering there aren't any noticeable island arcs, so it's not made by convergence.