http://pubs.usgs.gov/of/of97-262/of97-262.html
"Ash column generated by the eruption of Mount Pinatubo, a volcano in the Philippines Luzon volcanic arc, on June 12, 1991. The climactic eruption of Mount Pinatubo occurred three days later on June 15, 1991, and was one of the largest eruptions of this century. The climactic event lasted about 9 hours and erupted over a cubic mile of rock material. It injected a 20- million ton sulfur dioxide cloud into the stratosphere to an altitude of more than 20 miles. The climactic Pinatubo cloud was the largest sulfur dioxide cloud ever observed in the stratosphere since the beginning of such observations by satellites in 1978. It caused what is believed to be the largest aerosol disturbance of the stratosphere this century, although smaller than the estimated disturbances from the eruptions of Tambora in 1815 and Krakatau in 1883. Sulfate aerosol formed in the stratosphere from sulfur dioxide in the Pinatubo cloud increased the reflection of radiation ! from the Sun back into space. Consequently, the Earth's surface cooled in the three years following the eruption, by as much as 1.3 degrees ( Fahrenheit scale) at the height of the effect."
It stands to reason that the ash and rock thrown out is going to react with these acids.
Frederick
