Thermokarst failures occur when permafrost—a layer of frozen soil in Earth's polar regions—thaws and becomes unstable, possibly releasing greenhouse gases into the atmosphere.
The main causes resulting in this situation are intense compaction, pressure solution, cementation, filling, carbonatization and recrystallization, but...
The cobbler fancied he beheld all the wealth which the earth had produced in the past century for the use of mankind. Returning home, he buried his money and his happiness at the same time. No more singing.
It helped illustrate pirates the exact way we see them now, that they had missing legs and eyes, sought out buried treasure, and that their ships had the famous Jolly Roger pirate flag at mast.