It's chaotic, injects energy and breaks things down into components. When you made a magic item with 1,000 angry warrior souls you might end up with a problem. Or made with the power of a falling star, the volcano might become the least of your worries
I'm surprised the thing actually sank, since the lava is three times denser than water and also quite viscous. I figured it would just flop onto the surface and then burst into a cloud of steam.