Name That Trauma:: Adam O. on a Burning Rock

I’ve given up trying to figure this movie out, but I heard about your website on Fun For All Ages Podcast and searched and still came up short, so I thought I’d write. I believe this movie was seen by me around 1983-1984. I don't know when it was filmed, but it was in color. Here is all I can remember. There is some kind of big rock in the middle of a town or area that if you touch it you will catch fire for some reason, I remember someone getting pushed into it and they burst into flame, I also remember someone making a path in the sand and oil flowing toward the rock, I assume to ignite it. Then the other part I recall, and this may not even be from the same movie, but I believe it was, there is a cave and after going in it a bit, there is some kind of time warp or portal that was green I believe, like a spinning effect, there were two men in there, and they were fighting. One loses an arm, and the other falls into the time portal, spinning away neverTo be seen again. The reason I…