Granular materials are complicated beasts. When packed, forces between grains create a network (above) that shifts as force is applied. And, while grains can stick and resist that force, push a little further and they may slip and avalanche. A new study of this stick-slip behavior monitors disks similar to those above by listening for changes leading up to the slip. Researchers found that vibrations inside a granular material changed measurably before the grains slipped. The scientists hope this will one day allow for monitoring of landslide and avalanche-prone areas. While the changes are not enough to definitively predict when a slide will occur, they may provide valuable estimates of when one is likely. (Research credit: T. Brzinski and K. Daniels; image credit: OIST, source; via J. Ouellette)