SINKHOLE EDITION

I am so scared of sinkholes, why aren't more people eaten by them? What about all of the cats and dogs and mice and bugs they must take into their jaws?
Do they literally just appear or is there a warning?

Look at this one in St Alban's, a street along from my mate's house.

http://www.bbc.co.uk/news/uk-england-beds-bucks-herts-34410423

I am SO FREAKED OUT RIGHT NOW.