H
Flow mobility and runout relationships
Runout can be related by simple frictional arguments to height dropped by;      L = H/tan α
Where H/L = the coefficient of friction or Heim coefficient and  α = internal angle of friction, where flow only occurs where angle is > α .
Show that different types have different mobility characteristics as described by relationships between, L-runout H-height dropped, V-volume, and A-area.

Mobility firstly in terms of L as function of H
Rockfalls - ratio in order of (0.6) correspond to tan 30 degrees what we'd expect for small granular flows. Rf's only travel a few hundred m & are limited to talus apron around base of dome.
Pf's - more mobile
Pumice flows - data less well constrained but more mobile (black dots)

Mobility measured as a function Log H/L as a function of V suggest block-and-ash flows from Montserrat (red small flow, blue collapses) & Unzen (white squares) are systematically slightly more mobile than Non-Volcanic avalanches.