Cork That Volcano

THE PRIMARY CAUSE OF THE HOLE IN THE EARTH'S protective ozone layer is a group of man-made chemicals called chlorofluorocarbons (CFCs), used in refrigerators, air conditioners and plastic foams. The chlorine released when these compounds decompose attacks ozone, letting dangerous ultraviolet light from the sun shine through.

But a report in Nature suggests that nature can help the process along. Ozone depletion was expected to be reasonably mild in 1991; instead, it was severe. That year also saw major eruptions by Mount Hudson in Chile and Mount Pinatubo in the Philippines. Volcanoes release enormous amounts of dust. Dust, along with ice crystals, provides surfaces where ozone-destruction chemistry works most efficiently. Unfortunately, while the industrial world is phasing out CFCs before the turn of the century, other compounds are also ozone destroyers -- and volcano control is somewhat farther off.