An explosive eruption blasts a mix of hot gas, pulverized rock and ash out of the vent at high velocity. This turbulent jet entrains and heats the surrounding air, becoming buoyant enough to rise for kilometres as a convecting eruption column. Once the column stalls near its maximum height it spreads outward as an umbrella cloud, and prevailing winds sweep the fine ash downwind, while heavier particles fall out closer to the vent.
The 1991 eruption of Mount Pinatubo lofted ash more than 35 km into the stratosphere and injected enough sulfur aerosol to cool global average temperatures by roughly 0.5°C for over a year — a reminder that ash plumes are as much an atmospheric hazard as a local one, closing air routes across entire continents.
A 3D eruption column rises above a volcanic vent, spreads into an umbrella cloud, and drifts downwind as ash particles settle out at rates that depend on grain size, wind and eruption intensity.
Higher eruption intensity drives a taller buoyant column that stalls and spreads into an umbrella cloud; downwind advection and grain-size-dependent settling then shape where ash actually falls.
Raise eruption intensity to loft the column higher, adjust wind speed and direction to bend the plume downwind, and switch the grain-size mix to see fine ash travel far while coarse ash falls near the vent.
Fine volcanic ash can stay suspended in the stratosphere for weeks, circling the globe and disrupting jet aircraft engines thousands of kilometres from the source volcano.