Deep under the streets and buildings of Rome is a maze of tunnels and quarries that dates back to the very beginning of this ancient city.
In 2011, there were 44 incidents of streets or portions of structures collapsing into the quarries, a number that rose to 77 in 2012 and 83 to date in 2013.
To predict and prevent such collapses, George Mason University geoscientists Giuseppina Kysar Mattietti and scientists from the Center for Speleoarchaeological Research (Sotterranei di Roma) are mapping high-risk areas of the quarry system.
Volcanism created the land Rome was built upon. These volcanic rocks, or tuff, were a boon to Rome’s earliest architects, who soon learned the tuff was strong and easy to carve into building blocks. Lighter, less compacted volcanic ash was used as a main ingredient in mortar.
I had heard the Romans used volcanic ash in their mortar, but had always wondered why they had started doing that. Well, there you go.
Via NBC News.