Thanks for your replies and reassurance that things will probably settle and seal. It seems most other stuff I don't want to seal, like drainage trenches, eventually plugs up and other piles of clay I have dug and just left sit seem to compact over the years with all the rain we get here. That jelly hole does feel very unstable though it is located a couple feet away from the rim of the pond. The top soil will get saturated real soon so it's good to know things will probably settle down.

I have been reading about how springs can sometimes suck water away. There is a lot of springs in this area as there is a square mile of 800 - 1000 ft high mountain behind the pond, which is where the springs and seepage is coming from. As the water is clearly originating from a land mass above the pond I am hoping these springs will be the contributing kind and not the siphoning type. In the winter there has always been some seepage and flow into a shallow drainage trench that is about 50 feet away from and below what is now the lower edge of the pond. There is similar seepage all along the base of the mountain, though I have never noticed a spring where the jelly hole is now located.