Geomorphologists have found it difficult to determine how to measure weathering rates. Thomas Meierding has studied stone deterioration by assessing: 1. The original state of the stone, 2. How much matter has been removed, 3. How much time has passed since the stone was in its original state. He has studied marble tombstones across the U.S., focusing on small-town cemeteries with unpolluted atmospheres to test for rain variablity. He found direct correlation between sulfur dioxide emissions and high weathering rates (rather than an expected correlation with amount of rain fall). The most rapid deterioration occurred between 1905 and 1960, especially, 1930 to 1960. The research team concluded that acid rain dissolves a thin surface layer of the marble, but sulfur dioxide attacks the interior of the stone and probably causes more extensive damage more quickly. -- AATA