There are Sink Holes, and then there are GIANT Sink Holes!
Sink Holes seem to be becoming the norm. They have been appearing all over the planet, usually appearing after a period of heavy rain.
The latest to appear in New Zealand was the result of a torrential downpour, at an area known for it's geothermal activity.
However, geologists didn't expect one of this size, above a dormant volcano.