]]]] Volcanic Introduction of Chlorine into the Stratosphere [[[[[ (1/14/1990) [Excerpt from article on volcanoes in Douglas M. Considine, editor, Van Nostrand's Scientific Encyclopedia, 7th Edition (New York: Van Nostrand Reinhold, 1989), p. 2973:1] [Kindly uploaded by Freeman 10602PANC] ``Volcanic Introduction of Chlorine into the Stratosphere. Some researchers (Johnston, 1980) now suspect that considerably more hydrogen chloride (HCl) is injected into the stratosphere by certain volcanic eruptions than previously estimated. In fact, this could amount to as much as 17-36% of the worldwide production of industrial production of chlorine in fluorocarbons -- as of 1975 prior to severe reductions is such production brought about by concern with degradation of the protective ozone layer in the stratosphere. Under normal conditions, hydrogen chloride emanating from anthropogenic sources is not a threat to the ozone layer simply because the HCl is soluble in water and thus is removed in rain prior to reaching the stratosphere. Large volcanic eruptions inject HCl directly into the stratosphere forcefully and in significant quantities and thus bypass the absorptive effects of the lower atmosphere. It has been estimated that eruptions of this nature occur at least once per year. As pointed out by Johnston, the moderately to highly silicic magmas of volcanoes along the continental and island arcs, because of their high chlorine content, extreme explosivity, and frequent eruptions are likely to have the greatest atmospheric impact. These observations suggest that the impact of anthropogenic production of chlorine in fluorocarbons should once again be reviewed against the backdrop of disturbance of the ozone layer that may arise from natural, volcanic causes. Researchers have observed, for example, that the Augustine Volcano (Alaska), which erupted in 1976, may have injected 289 x 10E9 kilograms (289,000,000,000 kg) of HCl into the stratosphere. This quantity is about 570 times the 1975 world industrial production of chlorine and fluorocarbons.'' (Johnston, 1980) refers to Johnston, D.A. ``Volcanic Contributions of Chlorine to the Stratosphere: More Significant to Ozone than Previously Estimated?'', Science 209:491-493 (1980). Thanks to AtE subscriber J.W. of Tempe, Ariz., for drawing attention to this reference (mentioned in the October 1989 AtE, p. 3:2, bottom). How many active volcanoes are there in the world? Three references at hand give three answers: 500, 600 and 850. The important point is that active volcanoes are not rare. * * *
Return to the ground floor of this tower
Return to the Main Courtyard
Return to Fort Freedom's home page