The consequences of prolonged volcanic activity are mainly due to its effects on climate change, although there are some more immediate effects. For instance, volcanic ash and clouds are a hindrance to pilots, and in the past 15 years, close to 100 jet aircraft have been damaged as a result of drifting clouds of volcanic ash (Volcanic). These incidents resulted in temporary engine failure and thus endangered the lives of passengers and crew. There are 564 currently active volcanoes. Volcanoes when active can spew out volcanic plumes and ash clouds, and it is the drifting ash clouds which contain fine particles of rock as well as gas which are most hazardous to aircraft. These clouds can be carried hundreds to thousands of miles from the erupting volcano so can be a danger to aircraft worldwide.
It is believed by some people than volcanic eruptions are causing depletion of the ozone layer but their contribution to this damage is at best extremely minimal, according to the Environmental Protection Agency (EPA). They have tracking systems which show that solar transmission decreased significantly between 1980 and 1985, and again between 1990 and 1995 when El Chichon erupted in 1982 and Mt. Pinatubo erupted in 1991. Volcanic eruptions inject hydrogen chloride high into the atmosphere, introducing chloride into the atmosphere, and the chlorine interacts with ozone to break it down.
However, it is known that the major source of chlorine comes from chlorofluorocarbons (EPA). Also, it would take from two to five years for the chlorine from volcanic eruptions to reach the stratosphere where the ozone layer is located, and HCl is solubles so would be scrubbed from the troposphere by the rain. Steam in volcanic plumes would similarly dissolve the HCL before it reached then stratosphere. The eruption of El Chichon did increase stratospheric HCL concentrations by 10 percent but this was gone in roughly a year, and there was no ...