If you throw dynamite into a pool of lava, will it explode or melt? I was playing a table-top rpg with a friend. It was set... well it was pretty weird, so I won't get into it. Suffice it to say the bad guy had a stick of dynamite and we were on a volcano. I hit the dynamite with my slingshot, knocking it into the lava directly behind the villain. My DM said the dynamite melts away. I said it should have blown him up. Needless to say, as a couple nerds (we were, after all, playing a fantasy game and then arguing about the physics of it) we were pretty upset with each other.
What would have happened in this... totally realistic scenario? Would the stick of dynamite exploded? Or simply melt away?
 A: The most likely answer is that the nitroglycerin portion of the dynamite would deflagrate (burn) and the diatomaceous earth would melt. Neither constituent would detonate.  Dynamite needs a shockwave to detonate.
Now, this is not to say that the deflagration of the nitro would be a tame thing.  Bullets are propelled out of guns by deflagration of materials behind said bullets.  It appears as an explosion because it is confined.
The dynamite would burn, most likely very rapidly.  Rapidly enough to make it appear as an explosion?  Probably not, since it is not confined; but I would not try viewing the experiment unprotected from anywhere closer than 30 yards. 
A: Dynamite may be detonated by heat using a fuse and doesn't require another high explosive to detonate unlike TNT for example. It also doesn't require confinement in order to explode.
Dynamite will not melt away and the lava will definitely cause it to explode.
A: Whether an explosive just burns or detonates when it comes in contact with heat is what defines an explosive as a "primary" or "secondary" explosive.  Nitroglycerin and lead azide are examples of primaries.  They would likely detonate if thrown into lava.  Dynamite, being nitroglycerin stabilized by diatomaceous earth or sawdust, is a bit tricky to classify.  TNT and C-4 (RDX) are examples of secondary explosives.  They would likely not detonate if thrown into lava and would just burn, unless they were confined in a metal pipe.
