This submission was reminiscent of the intro scene to Indiana Jones. He snatches the idol, and the all sorts of nasty traps start cascading during Indy's mad dash for the exit. I really liked the setup and the sled event, but when the volcano erruption is thrown in, I grew skeptical. Some reasoning for this would make the whole setup that much better.
Apparently volcanos are capable of forming very speedy conditions, enough for this mountain biker to set a land speed record. If I DM this encounter I'd probably add seat belts to those sleds.