The volcano is less than one million years old. Most eruptions are small and Strombolian in character, tossing bombs onto the crater rim. Western Utah is an example of a rift zone. Continental rifting happens as Earth's crust and mantle are pulled apart. It has been continuously active since 1972. But Erebus volcano on Ross Island, Antarctica, is in a continental rift zone. Erebus is an active volcano with a convecting lava lake within a summit crater. Thus, Erebus volcano is the natural and powerful source of additional stratospheric HCl and SO 2, and hence, the cause of the Antarctic ozone depletion, together with man-made chlorofluorocarbons. Mount Erebus (elevation: 12,444 feet, 3,794 m) is on Ross Island in the Ross Sea. Depending on Erebus activity, this corresponds to additional annual stratospheric HCl mass of 1.0–14.3 kilotons (kt) and SO 2 mass of 1.4–19.7 kt. Based on the NCEP/NCAR reanalysis data over the last 35 years and by using the NOAA HYSPLIT trajectory model, we show that Erebus volcano gas emissions (including HCl and SO 2) can reach the Antarctic stratosphere via high-latitude cyclones with the annual average probability P ¯ ann. However, the cause of HCl and H 2SO 4 high concentrations in the Antarctic stratosphere, leading to considerable springtime ozone depletion, is still not clear. PSCs form during polar nights at extremely low temperatures (lower than −78 ☌) mainly on sulfuric acid (H 2SO 4) aerosols, acting as condensation nuclei and formed from sulfur dioxide (SO 2). Hydrogen chloride (HCl) is one of the principal components in these reactions on the surfaces of polar stratospheric clouds (PSCs). Heterogeneous chemical reactions releasing photochemically active molecular chlorine play a key role in Antarctic stratospheric ozone destruction, resulting in the Antarctic ozone hole.
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