On a green hillside outside Rome, something strange is happening. Cracks in the ground begin to emit steam, and animals drop dead owing to asphyxiation. Deep beneath the ground, meanwhile, an earthquake starts to rumble. Is this great city doomed, then, to a terrible fate?
Some 12 miles southeast of Rome, a semicircular formation of hills stretches for nine miles across the Italian landscape. Known as the Alban Hills – or Colli Albani – they have been the site of human settlements all the way back to prehistoric times.
Beginning in the 9th century BC, villages started to spring up in the area, including Alba Longa – home to Romulus and Remus, the legendary founders of Rome. Then, as ancient Rome grew in power, the area became a popular retreat for citizens looking to escape the city.
Today, scientists understand that the hills are a volcanic range that was created hundreds of thousands of years ago during the Pleistocene era. When a series of eruptions hit the area between 560,000 and 350,000 years ago, they left behind a distinctive landscape that would later form part of the backdrop to the city of Rome.
Italy is, in fact, famous for its volcanic activity. Located where the tectonic plates of Africa and Eurasia meet, it’s home to more than ten explosive hotspots. However, while volcanoes such as Vesuvius and Etna are known for their deadly past eruptions, scientists have long assumed that Colli Albani poses little risk.
Indeed, until recently researchers had been unable to prove that Colli Albani had ever erupted at any point during human history. Naturally, then, they thought that the volcano was long extinct. However, recent observations have revealed that this may not be the case.
In the 1990s strange events started to happen around Rome. Beginning in 1991 and lasting for three years, a series of earthquakes shook the ancient city. Then scientists noticed something really odd: the surrounding hills were slowly becoming taller.
Moreover, in September 1999, 29 cows were found dead on the hillsides of Colli Albani. On closer investigation, moreover, it was discovered that carbon dioxide had leaked from the ground and asphyxiated the animals. Then two years later, eight sheep died in the same circumstances.
These strange occurrences were enough to indicate to experts that perhaps Colli Albani wasn’t extinct after all. So, do the volcanic hills outside Rome pose a real danger? Well, in July 2016 a team of scientists from Italy’s National Institute of Geophysics and Volcanology published a study of the region.
In order to gain a clearer picture about Colli Albani, volcanologist Fabrizio Marra and his colleagues collected samples there dating from the past 365,000 years. The team then shipped them almost 5,000 miles to Brian Jicha at the University of Wisconsin in Madison.
Jicha, a geochronologist, studied the materials to determine exactly when Colli Albani had erupted in the past. In particular, by analyzing the rate at which isotopes in the samples decayed, he was able to place the periods of activity at relatively constant intervals.
In fact, Jicha concluded that over the past 100,000 years Colli Albani has erupted approximately every 31,000 years. However, there was one slight issue with this estimate. If true, it meant that the volcano was overdue an eruption by some 5,000 years.
So, should the residents of Rome be panicking? Well, somewhat frighteningly, it isn’t just Jicha’s dates which suggest that something is amiss. According to Marra, there are other factors which imply that an eruption could be on the horizon. Foremost among them is the swelling of the surrounding hills.
Indeed, Marra believes that the area around Colli Albani has risen by more than 160 feet in 200,000 years. Apparently, the change is the result of underground magma making its way towards the surface of the Earth. “It’s pretty clear that this is not a system that you can call inactive,” Columbia University geologist Alberto Malinverno told Scientific American in 2016.
In addition, scientists believe that the earthquakes in Italy during the 1990s were linked to activity under Colli Albani – as were the cracks emitting poisonous gas. It seems that a bubble of magma which had previously been sealed by layers of rock had become so pressurized that it was threatening to break through.
So, just how destructive could such an eruption be? According to some, it could wreak deadly havoc on Rome. Indeed, much as with Mount Vesuvius, which annihilated Pompeii in 79 AD, it’s thought that Colli Albani has the potential to smother the capital city in thick ash and cause rocks to rain down from the sky.
Nonetheless, with the center of Rome located a relatively safe 19 miles from the volcano, many parts would escape severe damage – provided the wind was blowing in the right direction. But for residents of the suburbs, which stretch out to the shadow of Colli Albani, the prospects would be bleak.
Thankfully, Manna and his colleagues see no reason to panic just yet. “It is important to say that there is no sign at the moment that such an eruption could happen soon,” he said. “For at least 1,000 to 2,000 years, such an event is very unlikely.”
Some scientists have in fact cast doubt on the idea that the eruption will happen at all. For example, geologist Guido Giordano believes that old magma cooling below the surface could be to blame. He believes that in certain circumstances this could cause the carbon dioxide emissions and ground shifts that have been observed.
Yet whatever is happening at Colli Albani, everyone seems to be in agreement that the volcano – dormant or not – needs to be closely observed. Hopefully, then, with the right approach, Italy can avoid a repeat of the disaster that hit Pompeii almost 2,000 years ago, claiming thousands of lives.