Krakatoa: The Great Volcanic Eruption

36,000 Lives And 3,000 Miles Wide: Inside The Horrifying Devastation Of The 1883 Krakatoa Eruption

In 1883, the volcano Krakatoa exploded, injecting dust 32 km up into the atmosphere. Fallout from this explosion continued for 15 months. If one assumes that the settling velocity of the particles was constant and neglects slip correction, what was the minimum particle size present? Assume that the particles are rock spheres with a density of 2700 kg/m^3.