IGN: The big question on everyone's mind is why are there so many exploding barrels on this unexplored island?
Amy: All the old wooden powder kegs were left behind by the original Spanish colonists — c'mon, it makes perfect sense! Why they haven't disintegrated after 400 years, why the powder inside is still combustible and ignites from a single bullet hit, and why the Spaniards stacked them up in such convenient places... it's just one of the mysteries of the island, I guess. But mainly there are so many exploding barrels because it's fun to shoot exploding barrels.
"The explosive barrel, frustrating AND hackneyed."
—Comic Book Guy, The Simpsons Game.
This is an exploding barrel. You can tell it explodes because it's red.