This is scientific American's 60 second science. I'm Christopher Intalyata. Got a minute?

In 1982, the ground beneath the Italian port town of Poizawoli near Naples began to swell. In the next two years the town rose

more than six feet. Rocks underground cracked under the strain, sparking tiny earthquakes

and some 40,000 residents were forced to evacuate.

Tiziana Vanorio was one of them.

We were scared, not because of the earthquakes, but because the fear that an eruption was about to come.

But that eruption never came.

And Vanorio, who's now a geophysicist at Stanford University,

wanted to find out how the rock endured the strain.

So she and a postdoctoral student

obtained rock cores from the Campi Flagre,

Caldera, the volcanic area underlying Pozoulli,

taken just before the swelling in 1982. volcanic that sealed off the caldera below.

And the caprocks microstructure

was an intricate network of mineral fibers,

the key, she says, to its strength

and ability to flex under pressure.

The findings are in the journal Science. And that fibrous rock structure?

Vennorio says it looked familiar, very similar to the famous ancient Roman concrete used to build aqueducts and the Coliseum.

And similarly to concrete production, the cap rock probably formed when lime-rich geothermal

fluids percolated upward, mixing with the volcanic ash.

It's probably no accident the Romans ended up with that same chemical recipe.

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