There is a hidden (or may be not so hidden) importance of the results and here are some comments:

Commenter Theo has this to say:

Any theories on the pattern? I say that dropping the large amount of fluid in at once caused it to vaporize at a varying rate, resulting in the fluid taking energy away from the lead in pulses. Since it evaporates top-to-bottom, chunks on top are built on from their undersides, and as the fluid pulses away, the chunks bob up and down in the molten lead beneath it accordingly, making the surface of the fully cooled lead disk ridged across the lateral plane.

Commenter serpbot makes an astute opbservation in my opinion:

That looks amazing, looks like the surfae of another planet.

Exactly what I was thinking!  This looks like the surface of a planet.  Imagine a time in a planet’s formation when it is super hot and liquid condenses.