Ok, so I decided to make a timelapse of a volcano erupting while I slept last night, here's the results:
It also continued on looking pretty much the exact same for another 900~ish frames, but I cut that out since there was so little change. Video is done at 5fps, each frame taken at 20second intervals. The lava chunk was placed at highest vanilla layer possible (I do not have CC installed), and inspecting the volcano later showed that it actually placed blocks above that layer.
Also, I can't wait for Inheritance to come out!