Anyone here willing to calculate the amount of energy involved? Assume 8 x 8 x 8" five lbs ice rock burrowing to depth of 24" in uncompacted soil.
I'm thinking it it was a denser piece of ice and accelerated faster than you'd expect of a Pt 121 free falling lav bomb. Maybe it was partially melted and shaped by aerodynamic forces on the way down. I know such forces tend to favor a sphere but I've seen lava bombs (ejecta which undergoes final cooling while in the air) shaped almost like pointy end missles.