We estimate initial velocity needed to eject blocks to the observed 2- to 4-km ranges by iteratively calculating the points of trajectories. Drag coefficient influences the range of the blocks. For ballistics of 25 cm and larger that landed within 3.5 km of the vent, drag coefficients variously between 0.06 and 1.5 for spheres and cubes yield calculated vent velocities of 155-840 m/s; smaller and more distal clasts yield values improbably as much as several times higher. But ballistics larger than 10 cm apparently traveled much of their trajectories in a range of very high Reynolds numbers (4x10^5, to 1x10^7), where drag on smooth spheres can be as low as 0.06. Thus if drag coefficients are low (despite previous opinion), fairly small ballistic clasts can achieve fairly long range even with moderate (subsonic) ejection velocities.
Many impact craters point not southeast directly away from the vent but more nearly south. This map-view southward deviation is typically 20 to 40 degrees, the maximum 67 degrees. A pitched baseball or hit tennis ball curves in the direction of applied spin. Thus many projectiles apparently acquired spin about near-vertical axes as they were violently ejected from the vent.
Waitt, R.B., Mastin, L.G., and T.P. Miller, 1995, Ballistic showers during Crater Peak (Mt. Spurr) eruptions, summer 1992: U.S. Geological Survey Bulletin 2139, p.89-106.
