Each group needs:

• 1 plastic container, ~2 ft² x 2-5 inches high
• enough sand to fill the entire container, to at least 1.5 inches
• 4 different-sized, spherical-shaped rocks of equal density
• 12-inch ruler
• meter or yard stick
• 1 sheet of blank paper (or, use the reverse side of the worksheet if it is copied single sided)
• How Big is That Crater? Worksheet