The controls of eruption-column dynamics on the injection and mass loading of ash into the atmosphere

Eruption columns inject large masses of volcanic ash rapidly to levels in the atmosphere where commercial aircraft fly. Ascent velocities of volcanic columns are typically 50 to 200 m/s, resulting in rapid injection (on the order of a few minutes) or large concentrations of ash at heights where aircraft fly. The mass loadings of ash in the umbrella region can vary from 2500 mg m^-3 for a 7-km-high column (23 000 ft) to over 20 000 mg m^-3 for a 40-km-high (130 000 ft) column, with a linear variation in between. These concentrations are much higher than those known to cause serious problems to aircraft and engine failure. -Authors