Understanding of grain avalanche onset, segregation, and pattern formation is especially relevant to the application to long run-out rock-avalanche systems.Earthquakes often trigger large rock avalanches, which may flow at speeds over 200 km/hr and are highly destructive. Historic flows have destroyed entire towns and killed thousands of people. Modern flows occur at the earth’s surface throughout North America and the world. 

Many of these deposits show unusually long run-out, in which events flow across a flat surface more than ten times the initial vertical drop height. Controlled laboratory experiments to date have generally neither looked for nor produced such long run-out lengths, and existing geological models of flow are ambiguous, untested, and occasionally contradictory.

"Birdseye" view of the avalanching table. Particles enter along the ramp an flow onto an unconfined table. Cameras capture the shape of the flow during and after deposition.

The ramp region and oscillator for the experiment. The oscillating motor can be switched out and replaced with a high-frequency shaker. Flow profiles can be obtained with fast cameras focused on the ramp and flat portions of the apparatus

Particle motion in a sand avalanche. Image of side surface of sand layer in chute and features that are tracked
 

velocity profile of flows over smooth surface (left) and rough surface (right). x = flow depth in particle diameters, y =velocity in arbitrary units. Base of the flow at x=50.Flow over a smooth surface is faster & strongly dependent on the transition region between the slope and the flat run-out, while the flow over a rough surface depends on height.
 

For further information please contact  wlosert@glue.umd.edu or juliof@geol.umd.edu

Send comments to wlosert@glue.umd.edu. Last updated 12/05/2002