Table 3. Comparison of Propagation Timescales teq Based on Scaling the Experimental Results of Lacerda [1987] and the Numerical Results of Ogden et al. [2008], With Jet Collapse Timescales tcoll for the Systems of This Studya


System	Pr(0)/Pa	teq,s	tcoll,s

Laboratory nitrogen jet	100	0.15 x 10-3	0.2
vulcanian	100	1	65
Mount St. Helens	100	54	84
Mount St. Helens	150	78	93
Mount St. Helens	250	80	104

aIf teq <= tcoll, we estimate a Mach disk shock has time to form at its equilibrium location.