GEOLOGY

Detailed explanation-1: -Small ash particles form a dark cloud in the troposphere that shades and cools the area directly below. Most of these particles fall out of the atmosphere within rain a few hours or days after an eruption.

Detailed explanation-2: -During major explosive eruptions huge amounts of volcanic gas, aerosol droplets, and ash are injected into the stratosphere. Injected ash falls rapidly from the stratosphere–most of it is removed within several days to weeks–and has little impact on climate change.

Detailed explanation-3: -The simplistic view of ash behavior in the atmosphere would suggest that very small (> 30 m) ash should stay aloft for days to weeks-the settling rate is between 10-1 to 10-3 m/s if you apply Stokes Law to the settling of the ash.

Detailed explanation-4: -Fine ash particles may remain in the atmosphere for days to weeks and be dispersed by high-altitude winds.

Detailed explanation-5: -The finest dust often gets carried hundreds or even thousands of km downwind. Explosive eruption plumes such as those generated at volcanoes like Mt. St. Helens or Pinatubo can reach high into the atmosphere.