Crater formation on a three dimensional granular heap

We present an experimental investigation of crater formation on a three dimensional granular heap due to the impact of particles having a high initial energy. The granular medium used is composed of macroscopic lead beads of diameter 2 mm. The particles are dropped from a height of up to 5 m above the heap. Experimental results show that impacting particles must have a minimum energy to create a crater on top of the heap. The depth of the crater created first increases linearly for a given range of initial energies of particles and then tends to saturate for higher energies. We give qualitative explanations for the experimental results.