Something like that actually happened to me several years ago. My lil CJ5 was kicking arse all over this offroad park - at the time, it was a free for all so you could go anywhere without worry of a trail system. Then I came to a lower region full of alkali-rich soil. Odd stuff, like you said, it had an outer layer of crust, but underneath was soft disgusting goo. In an instant, my Jeep lowered over a foot. There was no digging it out so luckily someone else was able to strap it out. That gunk was stuck in my frame for years until I finally did a frame off rebuild! Funny tho, you could pat on what seemed to be hard ground but it would jiggle... I called it an earth boob! After I associated it with boob it was tough to leave. LOL![]()