I hit the opposite of that kind of obstacle. When I was growing up, there was a large undeveloped lot behind our house with a big tree-covered hill. My friends and I used to ride up that hill on our Huffy bikes and come screaming down the side of it. We eventually wore a nice path through the shrubbery which only allowed us to go faster. However, you couldn't see what was at the bottom of the hill until you broke free into the clearing. It had never been a problem before... the runout was nice and smooth.

One day, I was coming down at a speed that in hindsight was much greater than was recommended for the "limited sight distance". As soon as I broke out into the clearing I realised that smack dab in the middle of my runout, someone had placed a very large MOUND OF DIRT... probably from the commercial construction that was going on in the adjoining lot.

I pulled the front end up and both the bike and I went ballistic as we went up the slope of the mound. Everything seemed to be happening in slow motion. It was as if I was suspended in mid-air for a while. Then I was inverted. I kicked away from the bike and launched myself downwards right on top of the mound of dirt. I was then looking up to see the bike tumbling end over end above me and falling STRAIGHT DOWN. I managed to roll away just as the handlebars slammed into the ground where I would have been laying.