Ice Spikes Explained

Why do spikes form on ice cubes? Without them the world would be vastly different.
Awesome Jingle by Accent:
Thanks to Prof. Stephen Morris from UofT:

Filmed in part by Martin Marek in Olomouc, Czech Republic

Time lapse of a growing ice spike by Lesley Hill, Russ Sampson and Edward Lozowski, with technical help by Kenny Lozowski.

Ice spike image by Dan and Lynn Wolaver:

Concerned ice spike video by rocknut420:

Earth footage courtesy of NASA:

Ice vase image by PgunnG:

Second ice vase image by A K Haart: