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Find
a headstone that is more than 80 years old. Notice that weathering
is evident on these older markers. Rocks, such as marble, cannot
last forever in a weathering environment. A crack in the headstone
allows water to enter. This water freezes in the colder months,
expanding the cracks in the stone (physical erosion). Some grave
markers are made of rocks whose minerals dissolve in water. When
these minerals dissolve there are more pockets for water to enter
and do further damage to the headstone (chemical weathering).
Limestone is paticularly affected by acid rain. Notice that in
areas where the stone has been exposed to lichens and moss, the
weathering effects are more dramatic. .
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