Why do sinkholes keep opening up in Rome?

Why do sinkholes keep opening up in Rome?
A policeman walks by a chasm which opened in a road in Rome in 2018, swallowing seven cars. Photo: AFP
After another sinkhole opened up in Rome - this time in front of the iconic Pantheon - on Monday, we look at why this happens so often in the city and which neighbourhoods are most at risk.

A two-metre-deep sinkhole opened up outside the Pantheon on Monday, the latest of many chasms suddenly appearing in the centre of the Italian capital over the years.

No one was hurt in the incident, as the normally packed square in front of the monument was empty due to the coronavirus lockdown.

Around 40 of the travertine marble cobblestones, called sanpietrini, gave way when the hole appeared on the Piazza della Rotonda, between the fountain and the Pantheon itself.

“The area, fortunately closed, could have become a really dangerous trap for Romans and the thousands of tourists who on a beautiful day in the middle of spring, in a “normal” period, would have filled it,” the La Stampa newspaper wrote.

Why does this keep happening?

There has been a renewed focus on the phenomenon of sinkholes opening up in Rome after an apartment building was evacuated when the pavement caved in on a road near the Colosseum in January.

Sinkholes (known as voragine) and subsidence are a major problem in central Rome – and they seem to be becoming more common.

There has been a rise in the number of chasms suddenly opening up on the capital's streets in recent years, according to the Italian Institute for Environmental Protection and Research (ISPRA).

VIDEO: Watch the moment one of Rome's monster sinkholes opens

 

There were 100 such incidents in Rome in 2019, though 2018 saw a record 175 sinkholes appear in the city.

By comparison, there were some 20 sinkholes recorded in Naples in 2019.

For most of the past century, Rome recorded an average of 30 sinkholes or other collapses per year, but since 2008 the annual figure seems to have been consistently more than triple that figure.

In recent years, some of the worst incidents have included massive sinkholes that opened up within seconds and were large enough to swallow cars.

Some of the worst-affected areas are the oldest parts of the city.

 
“The most sensitive area is eastern Rome, where materials were quarried in ancient times,” geologist Stefania Nisio, who is working on a project to map Rome's sinkholes, told Adnkronos.
 
The districts most at risk are Appio Latino, Tuscolano, Prenestino, Tiburtino and Quadraro, he said.
 
 
“The main cause of a sinkhole in the city is the presence of an underground cavity,” he explained. “We have many examples of this, especially in Lazio, not only in Rome but also in Viterbo and Rieti.”
 
These are usually man-made tunnels, quarries, or catacombs.

And part of the problem is simply Rome's geology: founded above a floodplain, much of the modern city rests on soft, sandy soil that is easily eroded by water or the vibrations of thousands of cars and scooters traversing the streets daily.

The phenomenon is exacerbated by unusually heavy rains and chronically neglected infrastructure.

In 2018, the city announced a multi-million-euro plan to fix its streets, but progress remains slow.


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