How long would it take for a volcanic ash cloud to dissipate?

The dissipation of an ash cloud depends on whether the ash made it into the stratosphere. read more

For example, Mt St Helens ash cloud made it from the volcano all the way to New York / New England. The ash cloud from Mt Pinatubo (Philippines), which was blown into the stratosphere, circled the earth, and cooled the earth’s climate for a couple of years. read more

Volcanic ash clouds, if they reach the stratosphere, can last for 3–4 years until they dissipate. If the clouds don’t reach the stratosphere, but are limited to the troposphere, the ash fall dissipates much closer to the volcano, with less ash fall at a greater distance. read more

Met Office forecasters monitor volcanic eruptions as part of their role in the global network of nine Volcanic Ash Advisory Centres. It provides forecasts every six hours giving an 18-hour prediction of where the volcanic ash cloud is and details of the differing concentration levels. read more