Seismic Sand

A disk containing a shallow layer of fine sand and covered with rigid transparent plastic is knocked with a rubber mallet. Strange patterns appear when the fine sand is vibrated. When the observer tilts the disk and continues knocking, the sand will slide down like a miniature avalanche. Knocking the disk causes the sand particles to vibrate. The vibration reduces the friction between the sand particles and allows the sand to flow like liquid. The process is similar to liquefaction of sediment during an earthquake. The patterns that appear are the result of complex interactions between the flowing sand and the vibrating air inside, set in motion by the moving walls of the container.