I dug out some abyssalite that was separating magma from contaminated water. Now, where the two meet, igneous rock and dirt are spawning infinitely at that spot. See this video:
The magma is not losing any mass, so I don't know where the igneous rock and dirt are coming from. Also, I saved and loaded, and after a few seconds, dirt started infinitely spawning again, but not igneous rock. Good luck!
Let magma meet contaminated water.