Sink holes are very common place in my part of Missouri mostly because of all of the caves, at one time the city used a huge sink hole to dump its garbage and scrap metal..long before anyone even thought about the effect it had on the water supply...old timers use to tell about pushing old cars off the side of the sink hole and watch them disappear..the dump site was closed about 25 years ago, finally got full , a layer of construction waste and dirt was placed on top of it all...I am just waiting for the entire mess to fall in and open the old sink hole again