I recently came across these fabulous videos, and I just have to share it with you guys. I’ll come back with explanations and additional videos after this first short video.
What happens is the small metal ball creates a jet (yes you read that right, a jet) higher than the impact drop of the ball. The ball first creates an impact crater which collapses extremely quickly, and then a significant mass of sand is ejected upwards. Initially, sand is splashed in all directions, much like in the case of a bomb being dropped, and then it just seems to go crazy, diving upwards at twice the impact velocity. When it comes down again, it breaks down due to the lack of elasticity and cohesion. Bear in mind that this is very fine sand here.