Q: I can’t even begin to explain this phenomenon, but it looks pretty cool. This is just a hollow metal fence post at the end of the driveway.
There is nothing hanging above it that could have dripped down, so it was made from the bottom up.
A: Physics may be dreary in high school but it explains much physical beauty outdoors!
In your case, you saw what some scientists call “pipe ice”. It occurs when the top of a pipe is colder than 32 degrees F. while the middle and bottom is warmer than 32 degrees.
Water at the top freezes but water at the bottom expands, leading to a rod of ice extruded from the pipe end. It looks like yours melted a bit at the tip.
This phenomenon is similar to frost flowers, which form when the top of a plant freezes but the bottom stays warm enough to send water up to the frozen area, which is extruded in curly ice formations.