“Usually requires more water flow below surface through the limestone to chemically react, change physical properties, displace, and allow for mass flow out of the area.”
Did a google street view. The guy didn’t have a downspout extension at the front of his house, and imagine it was similar in the rear. Dumping 2/3 of his roof water into that side of the house right next to the foundation. And then an earlier poster said they had just had a hard rain.
20 years of water flow, and then one that breaks the camel’s back. In New Jersey with karst terrain it is pretty important to have LONG extensions and perhaps french drains. And at the least - the sinkhole develops away from the house where you might notice it before it collapses.
A lot of sinkholes form from subsurface water flowing through the aquifer.
Imagine if you will, somewhere beneath the surface, there is a water table. It’s where the soil, be it sand, gravel ,limestone, silt,....etc, becomes saturaed with water. The water pressure is such that there actually is flow beneath the surface. If you dug a hole down, exposed the water table, and threw in some gravel to see it, you would actually see something like a stream flowing at the bottom of the hole.
Underground, it isn’t so much a pipe or open conduit, but rather a media like sand, characterized by how water may flow through it or its permeability.
Different compounds in solid chemistry and different shapes and sizes have different permeabilities. This assumes the chemistry remains fairly steady.
In these Karst areas, there likely are some chemical reactions going on, like salt being eaten away r limestone being broken down, becoming less strong, then the subsurface water is able to break it up and move it in solution or physically as smaller pieces.
When there are subterranean caverns, they might grow or tie together with other dynamics.
In this particular case, it probably wasn’t the rainfall at his house causing it, but it might be a rainfall a county away, flowing in subsurface conduits, and his area happens to erode more than others beneath the surface.
Of course, there also is the chance he was playing with an Ouija board and he suffered the consequences most dramatically, or was buried on an abandoned burial ground....sort of like Poltergeist and they can still hear him.....