At the risk of starting another fight, I want to say that a number of visually different phenomena are associated to what I would call a "split rock". For example, here is a solitary "wedge" inside a wide split:And here is a slab of rock, propped up:I showed several other visually different examples recently here. (The first example there is pretty visually similar with this last example here.) Because of these differences, I find the "explanation" offered by past historic literature unsatisfying. The literature does not tell me what these visually different features mean and sweeps all variety under a common rug of "random donations by passers-by". As I have said, hypotheses which suppress details are certainly not the first choice. And how wide does the split need to be before it no longer counts as a split? I think most would agree that split rocks probably connected to spirits that lived inside the rock. That is consistent with the literature and with the observations. (Personally, I think a gap like the one in the last picture is something different - something a person could walk through.) But the idea that the only relation possible is to donate to that spirit is, I feel, simplistic. I think welcoming the spirit would be different from repudiating and protecting oneself from the spirit. I think the relation between a person and a rock spirit could be quite complex and that this would manifest itself in observables today.
I think there is a difference between this and that:Isn't it obvious that some of the spirits would be "good guys" and some would be "bad guys" and that the ceremony would differ, depending on which was present?
Here is a fact: split wedged rocks are most common at the water's edge. Why would this be?