Gravestones are full of information. So much so, that they are proving a vital source of information for geologists when it comes to providing details that other rocks don’t.
One such project is turning its attention to gravestones to monitor the effect that acid rain has on rocks across the globe, and how this effect has changed with time.
“Gravestones provide us with a nice model for measuring the effects of acid rain as most of them have dates inscribed, so we have a good idea of when the stone would have been installed,” says Gary Lewis, director of education and outreach for the Geological Society of America (GSA) and one of the project leaders of the Gravestone Project.
The Gravestone Project started in 2009 and has a range of dates collected, over 100-200 years worth, which means that changes will easily be noted during that time. With the data collecting phase now over, the project is aiming to determine if there are any significant changes to the rate of weathering marble headstones over time and how they might coincide with human and atmospheric changes.
Recruiting volunteers from different countries they then head into cemeteries and measure the width of a headstone at five points at its top and sides with the use of calipers. Headstones that have lead letters are also measured to see how much the stone has worn away from the lettering.
“We’ve had over 1600 gravestones measured in more than 930 graveyards,” says Lewis. “The bulk of these are in North America, but we’ve had some across Europe, Australia and other countries.”
With the data, Lewis is interested in finding out whether or not an increase in pollution since the Industrial Revolution and increased rain in various areas has accelerated the rates of weathering, in addition to how the rate of weathering has changed since the arrival of the Industrial Revolution.
So far the team has noticed that bigger cities produce an increased weathering rate, which doesn’t seem a major discovery particularly as nitrogen oxides and sulfur dioxide – acid rain causing pollutants – are released over higher populated areas.
“One feature that is intriguing is that stones seems to weather in one of two ways: they weather more at the top, or more at the bottom,” says Lewis. “We are looking at the geographical spread of those two types to see if that gives us some information that we can map at a larger scale.”
Lewis is unsure whether the results produced will make people think more about the effects of acid rain pollutants, but is hopeful that the data will offer a greater understanding on how gravestones can be used to understand what has been happening over the centuries.