Fun with Pb: Logic Problem

Pb (Lead)
Melting point 327.46 °C
Boiling point 1749 °C
Density 11.34  g/cm^3
Density of magma ~3.33 g/cm^3
Temp of Magma 700C - 1600C

If I dropped a 50 kg lead weight into the mouth of an active volcano like Mt. Kilauea. It would rapidly turn into a liquid and sink. It is not sinking, the Pb is equalizing to its density. It will continue to displace other molecules until it is surrounded by molecules of similar density.