Surviving in 7-15's lava/pink stuff

I found something rather neat while fooling around in the Cotton Alley levels. As you can see in this video, you can safely jump into the pink lava in 7-15 with no repercussions, given you do it just right

What I've learned about this so far is:
- Only seems to affect that particular spot (aim for the middle beam of light)
- Death occurs after 0.5 - 2 seconds, time frame seems to vary (the lava probably sinks and rises with minimal movement, only killing you at its highest point)
- Very small movements are ok, but moving from that particular spot results in death
- You can safely jump out of the lava
- You can also jump in place without dying, but you will randomly die if you spend too long in there

I'm unsure as to what could be causing the problem but I'm guessing that there's a solid block just under the surface that I'm landing on or something. Either way, I thought it was interesting and should be brought up :)