An extensive series of ancient tunnels and quarries under Rome are threatening parts of the city that has been built atop them.

Many years ago, Rome’s earliest architects discovered that tuff, or rock made of consolidated volcanic ash, was a perfect building material. It was strong, yet easily carved into blocks. The soil beneath Rome was layered atop this tuff, so ancient Romans began to mine the rock, creating an intricate system of tunnels and quarries beneath the city.

Throughout the years, the tunnels have been used for a variety of purposes, from catacombs to mushroom farms to – during World War II – bomb shelters.

Despite the fact that the first Romans wisely kept the tunnels narrow in order to support of the ground above, the tunnels have deteriorated over time.

Giuseppina Kysar Mattietti of George Mason University says that part of this deterioration is due to the fact that the rock begins to weather and break down the moment it’s exposed to air. The other factor is human error, if you will. Subsequent generations of Romans continued mining the quarries for building materials, increasing the width beyond what could adequately support the structures being built above.

The result? The streets of Rome, and portions of some of its buildings have been collapsing into the ancient quarries at an alarming rate: 44 incidents in 2011, 77 in 2012, and 83 so far in 2013.

City officials have engaged Kysar Mattietti and a team of geoscientists from Center for Speleoarchaeological Research (Sotterranei di Roma) to map the tunnels, pinpointing areas that are at high risk of collapse. They hope this will be a more effective solution to the problem than the one Roman citizens have employed in the past: plugging tunnels with plastic bags of cement.

The research team uses laser 3D scanning to identify hidden weaknesses in the tunnels. When they’re sure a tunnel is safe to enter, they do so via a manhole and map it by hand.

“There might be cracks, so they will be showing as veins almost, or openings, so we map the openings and map any kind of detachment,” said Kysar Mattietti.

She revealed that in some areas, collapses have left very little ground between the surface and the tunnel: “It’s interesting, because at times when you are down there, you can hear people on top.”

Once the mapping is complete, Roman officials will decide how to proceed and what kind of intervention is necessary to prevent future collapses of buildings and streets.

Image via Wikimedia Commons