24 September 2018
I’m finally, finally back from a long summer of work travel, which I was lucky enough to cap off with my first Cities On Volcanoes 10 conference in Naples, Italy. The conference was great (more on that later), and after my post-conference field trip (also more on that later), I spent an extra weekend in Naples. There’s so much to see in the city – so much gelato to eat – but one thing I learned was that if you want to sample the local geology, you could do worse than visit a church.
I’m not particularly religious at this point in my life, but I find that I can still appreciate the craft that went into creating churches even if I don’t agree that it was the best way to spend all of that money. Italy in particular is full of fabulous examples of the stonemason’s art, and one was just around the corner from my bed-and-breakfast.
Beth Bartel and I took to calling this the “spiky church”, but it’s actually the Chiesa del Gesù Nuovo, a 15th-century palazzo built for Roberto Sanseverino, the Prince of Salerno. It was confiscated from his family and sold to the Jesuits in the 1580s, then passed to the Fransicans when the Jesuits were expelled from Naples in 1767, and back to the Jesuits in 1821. (Whew!) Now it’s dedicated to St. Joseph Moscati, a doctor and biochemistry teacher who worked there and died in 1927. (He is actually still there, since his body is preserved in an ossuary below one of the altars. Italians have a different attitude toward death when it comes to saints…)
But while the inside of the church is stunning, the stones caught my eye particularly. Italian churches are full of Italian marble, in all colors and configurations, and it’s pretty stunning. Also, visually overwhelming!
But for me, the real star of the show was hidden off to the side, in the hallway leading to Saint Moscati’s old quarters. Fiamme!
Fiamme, appropriately enough, is the Italian word for “flames”, and it’s used to describe lenses of flattened material in volcaniclastic rocks that have undergone compaction and/or welding. In the case of this church, though I don’t know the originating formation, it’s pretty clear that these little dark babies used to be pumice fragments. There’s a neat mechanical contrast just to the right of Beth’s hand, where a small lithic block is undeformed, but the pumices flanking it have been flattened into little glassy streaks. The pumice just wasn’t strong enough to stand up to the compaction, whereas the lithic block was unaffected.
A little Google searching turned up a likely candidate for the rock: Piperno, a ubiquitous building stone in the historical center of Naples. Quarried from Campi Flegrei, its origins have been debated, but the prevailing theories call it either a welded ash fall or ash flow tuff. Regardless of its formation, it was much in demand during the period when the Aragonese ruled Naples, and as a result the interior and exterior of Gesù Nuovo are made of piperno. The style of the outside of the church is sometimes called “diamond rustication” (bugnato in Italian), where the faces of the stones are shaped into low pyramids rather than smooth, flat surfaces. It’s visually intimidating, but it doesn’t serve any defensive purpose (in fact, it would have made it easier to climb!)
There are two other famous Neapolitan building stones – the piperno, the Neapolitan Yellow Tuff, and the Campanian Ignimbrite. All associated with explosive eruptions, which are one of the major concerns associated with having such a large population living near the active Campi Flegrei Caldera and Vesuvius Volcano. Those were big themes of the meeting, but I’ll save them for another post.
For more on piperno:
- Morra et al. 2010: Urban geology: Relationships between geological setting and architectural heritage of the Neapolitan area, Journal of the Virtual Explorer 36 DOI: 10.3809/jvirtex.2010.00261
- Calcaterra et al. 2005, Piperno from Campi Flegrei: A relevant stone in the historical and monumental heritage of Naples (Italy), Environmental Geology 47(3):341-352 DOI: 10.1007/s00254-004-1156-3