Monte Roccamonfina – A relatively unknown Italian volcano with an obscure history

A repost from 2013, written by Henrik

Fig 1. “Roccamonfina di notte”, the medieval town of Roccamonfina at night (Enzo Merlino)

Fig 1. “Roccamonfina di notte”, the medieval town of Roccamonfina at night (Enzo Merlino)

Located some 60 km NNW of Naples in the Campanian province of Caserta lies the medieval town of Roccamonfina, cradling the slopes of an old stratovolcano, considered extinct since its last eruption was at least 50,000 years ago. Roccamonfina is famous for its cuisine based on chestnuts and funghi porcini; Penny Buns or Boletus Edulis.

The volcano itself is massive. With a basal area 17.6 km in diameter, twice the size that of Vesuvius/Monte Somma, the main cone was originally more than 1800 m high before it was destroyed about half a million years ago. Today the mountain is truncated by a caldera measuring some 5 by 6 km in which the current summit cones has grown to an altitude of 1005 m. The last eruptive period is thought to have ended 50,000 years ago, and the volcano is thought to be extinct, a view that may be supported by exploration of its geothermal potential which found a very low temperature of 35°C at 886 m. Apart from this, it would seem that everything else is highly disputed and not very much known except that it is considered to be “a typical alkali-potassic volcano” (Capuano, Continisio & Gasparini; 1992)

Fig 2. The twin thrachyandesitic domes that form the current peak of the Roccamonfino Volcano with the town of Roccamonfina at their base. (itineraiparlli.org)

Fig 2. The twin thrachyandesitic domes that form the current peak of the Roccamonfino Volcano with the town of Roccamonfina at their base. (itineraiparlli.org)

To give a brief summary, the age of the Roccamonfina volcano is variously given as between 1.5 million years (Watts, 1987) and 590 thousand years (Gianetti, 2001). The causes of the caldera collapse given by Watts is that there was a series of St Helens-type eruptions and flank collapses that led to its formation. Gianetti directly disputes this as caldera collapses due to sector sliding “are improbable as tested by the absence of rock-slide avalanche deposits” and considers the most likely cause to be incremental collapses “through repetitive draining of the magma chamber(s) resulting from a succession of moderate-sized volcanic events”. De Rita and Giordano (1996) puts the volcano’s age as 630 – 50 kA and dismiss both the above theories on stratigraphical evidence. Instead they propose that “Geomorphological and structural observations, together with geophysical evidence, suggest that collapse of the volcano summit occurred as a mechanical re-adjustment to the high rate of the Garigliano graben extension during a climax of the regional tectonism at around 400 ka bp”. Going back to Tedesco (“Main Lines of the History of the Roccamonfina Volcano”, 1965) attributes the caldera collapse to “eruptions of a vast magmatic portion of dubitative thrachyte composition produce a thick sequence of mudflows and pyroclastic flows”.

Fig 3. Aerial photograph of Roccamonfina caldera. (campaniatour.it)

Fig 3. Aerial photograph of Roccamonfina caldera. (campaniatour.it)

Leucite from Roccamonfina. Image copyright by John Betts (http://webmineral.com/)

Leucite from Roccamonfina. Image copyright by John Betts (http://webmineral.com/)

Fig 5. Roccamonfina chestnut forest, a most relaxing environment for someone writing their doctoral thesis on the Roccamonfina Volcano. (Alessandro Santulli)

Fig 5. Roccamonfina chestnut forest, a most relaxing environment for someone writing their doctoral thesis on the Roccamonfina Volcano. (Alessandro Santulli)

Great! We have a volcano at least four times the size of Vesuvius with a 5 x 6 km caldera (Tedesco gives 5 x 7 km) and four different scientific papers proposing four different causes for its formation of which two are irreconcilable with each other and the other two. At least Gianetti and Tedesco agree that the caldera collapse could be due to a large eruption or a series of large eruptions.

So what do we know about the Roccamonfina volcano? Here I am trying to reconcile all these various and conflicting statements to piece together a credible, but by no means definitive or accurate account:

Some 1.5 million years ago, volcanic activity began in the Roccamonfina area. 600,000 years ago, this activity had built a 1800 m high stratovolcano composed mainly of leucitic lavas and tuffs with several monogenetic cones on its flanks, some of which were composed of thrachytic lavas.

Then followed two main periods of large eruptions that formed four nested calderas; the first between 546 and 474 kA and the second between 403 and 374 kA. The main cone collapsed to form the central caldera around 496 +/- 50 kA. The collapse of the main cone was accompanied by a ring fracture concentric with and outside the main caldera. This would, to my mind at least, indicate that the main caldera was formed by a large eruption, at least VEI 6+, that was not accompanied by the emission of ignimbrites and that, for reasons at present unknown, the evidence for this has not been found and could be “lost”.

After the collapse of the main caldera, a lake formed in the NW part which has left lacustine deposits inside the caldera. Following this, two large thrachyandesitic domes were extruded around, probably during a second period of activity 385 – 285 kA. This was accompanied by a trachytic ashflow that filled the caldera, the radial valleys and spread out into the surrounding plains. Again, evidence of a very large eruption that seems to have gone missing from the records.

As to the final period of activity that ended about 50,000 years ago, I have been unable to trace any evidence for it except the statement. It would seem that the Roccamonfina Volcano is understudied which perhaps is not surprising considering its extinct status. That said, is there a young geology student out there looking for a study object for her or his doctoral thesis? The setting of Roccamonfina and its cuisine would make this task a most agreeable one!

One last tidbit. In a study published in 2004 of the underlying crust using shear wave velocities obtained from seismic events recorded in 1988–2004 at Roccamonfina station of the INGV-RSNC network, Nunziata & Gerecitano have built the following model: The Roccamonfina edifice stands upon a 5 km thick sedimentary zone (i.e. one rich in silicic rocks, minerals and water). Below this they have found a high velocity zone that corresponds to a body of solidified magma. The corresponding layer of sedimentary rock underlying the surrounding Appenines is 10 km thick. Below the layer of solidified magma, Nunziata & Gerecitano found evidence for a low velocity layer with an average thickness of 10 km which can be associated with the presence of partial melting and they interpret as magmatic reservoir. Such low velocity layer was also found below the surrounding Apennines but with a reduced thickness of 2–3 km. This layer extends to the Campanian Plain and to the Neapolitan volcanic area, from Campi Flegrei to Somma-Vesuvius.

It would thus seem that the Roccamonfina volcano has depleted some 5 km of the sedimentary layer during its lifetime and the only logical conclusion would seem to be that the process responsible is absorption and remobilisation as magma which then has erupted. If you want to, you could imagine it as some kind of a magmatic blowtorch burning its way through the sedimentary layer. Furthermore, it would seem that the zone of partial melting is also much thicker than elsewhere but that no new energy has been added to this for a very long time. In a private conversation with Carl, he speculated that it could have something to do with isostatic rebound after the glaciation of the Alps and Appenines and that as long as they were glaciated and thus depressed, there existed a fold that allowed magma access to the Roccamonfina area. As there is evidence of a physical link between them, the zone of partial melting, and that the first eruptions of Campi Flegrei are thought to have occurred some 40 kA before present but after the last eruptions at Roccamonfina, it is entirely possible that isostatic rebound has shifted the volcanism from Roccamonfina to the Naples area.

HENRIK

41 thoughts on “Monte Roccamonfina – A relatively unknown Italian volcano with an obscure history

    • Mamma’s back!
      Wife and I love that part of Italy. she’s been there, I haven’t but just her stories are something special. Like the Idea of the doctoral thesis..

    • Indeed….

      Am I wrong, or does this look like a prelude to something far more interesting?

      Etna did the same sort of stuff back in 2015, from the Voragine… On-off strombolian eruptions beginning in late August, it picked up just a wee bit in the last days of November…

      And then.. all hell broke loose. Voragine went full-on berserk and threw 4 incredibly energetic paroxysmal events in less than three days.

  1. Damon’s Rule Of Volcanic Quiescence: If it looks like a volcano, it can erupt. 50K years is nothing. I know it’s apples/oranges, but there are plenty of Hawaiian volcanoes that have erupted after well over 200K years, admittedly not via the previous conduits.

    • The volcanic field south of Mobile Alabama is effectively dead… buried under 15 km of sediment, but it too will probably be back sometime during the next Wilson Cycle.

    • My local area has a caldera that, could’ve rivaled Crater Lake,
      but for a slightly different path. No one knew it existed until the
      Late 1990’s Here is a bit about it by the fellow who mapped it:
      http://www.bakercityherald.com/csp/mediapool/sites/BakerCityHerald/Outdoors/story.csp?cid=4119784&sid=874&fid=151
      I agree that you never,ever want to say a volcano is “extinct”..
      Tower Mountain refers to the Lookout Tower on the mountain
      -that lookout has lived a charmed life. I know personally two
      fires that came close to getting it…

    • Reminds me of this story….

      A group of tourists are hiking in some place volcanic. Their guide tells them “This volcano, the big one in front of us erupts every 30 years, very predictably. Last time it did, was 15 years ago. So we’re as safe as we can be now…”

      One of the hikers said “Yeah you know that. Everybody living in the valley know that. Even we know that… BUT DOES THE VOLCANO KNOW THAT?”

      resounding BOOOMMMM…..

    • I think Bárdarbunga heard you 😉

      The public drumplots and tremor graphs around Bárdarbunga have not been updating for about a month. Does anyone know if the stations are broken or if it’s just the actual updating of the public plots that’s not working? If the stations are really down, I guess the precision of quake detection will be a bit worse than usual. Small events would have poor locations or not be detected at all.

      • I should have known what will happen. 😀

        Yea, all the stations near Bardy are actually down, VON, DYN and KIS. The closest one working is probably DJK.

        The problem is the detection of smaller events, yes, but a bigger problem is locating depth, since the closest station is quite far and that makes the depth error bigger. That is why we saw quite better depth detection at Bardarbunga when the KIS station was introduced.

        A similar, but less problematic situation is at Katla.

        • Agreed, the depth detection will suffer the most. This is quite obvious from the geometry of the problem. A change in depth that is small compared to the distance to the measuring station will not change the arrival time significantly. If all stations are far away, there just isn’t enough information to accurately determine the depth.

  2. Wednesday
    01.03.2017 09:45:02 64.671 -17.423 0.1 km 3.5 99.0 6.0 km NE of Bárðarbunga

    Wednesday
    01.03.2017 09:38:11 64.664 -17.377 0.1 km 3.0 99.0 7.6 km ENE of Bárðarbunga
    Wednesday
    01.03.2017 09:21:28 64.664 -17.389 1.5 km 3.5 99.0 7.1 km ENE of Bárðarbunga
    Wednesday
    01.03.2017 09:13:14 64.671 -17.422 0.1 km 3.4 99.0 6.1 km NE of Bárðarbunga

      • They are a bit “under-fed” with infornation regarding data, but since the magnitudes and signals are strong, they will eventually nail it. Except for the depth, which has a very likely error range of up to 5km or more.

        Tho an additional temporary monitoring network will be deployed around Askja, Herdubreid and Bardarbunga (in a collaboration project between the IMO and Univ. of Cambridge), in addition to the existing network which will be fixed when the conditiond allow for access.

        I hope they are able to make some velocity models out of the data from the dense network, atleast for Bardarbunga and Herdubreid, since Askja was already done.

    • All I really remember is going to play baseball at a recreational complex inside what I know know was a large scoria cone. The restrooms there were closed at the time due to noxious gases (not toilet related) and they had portable units set up nearby for the users. It wasn’t until I started hanging out here that I realized what the geology of the recreational complex is… and that the gas problem there was likely H2S or SO2.

      • Not completely sure, but I think it was here: 40.852534° – 14.107957°

        As for the gas detection, the USN is really into “gas free engineering” and routinely checks spaces and compartments on a ship that have been closed for extended period or when the conditions of the air may be suspect. It’s highly likely that someone got a sniff of something so they had someone do a gas free check and found it not suitable for use/occupation.

        What would be ultra cool, is if someone did a daily check of the gas levels there and kept a log book of them. This scoria cone is right in the middle of the Campi area… but, I’m sure that research quality tests are done of that particular volcanic system.

  3. Couple of small quakes at Lady H past 24 hours, not on the quake list but has been captured on the Hekluvoktun seismicity graph. No other signs that I can see of anything impending.

    My head says Hekla has changed her pattern but I’m still hoping for some activity this year … fingers crossed! 😀

    • And here we go, 3 of them;

      Thursday
      02.03.2017 07:50:33 63.995 -19.752 0.1 km 0.2 99.0 4.1 km W of Hekla
      Wednesday
      01.03.2017 17:33:35 63.985 -19.702 2.2 km 0.6 99.0 1.8 km WSW of Hekla
      Wednesday
      01.03.2017 17:33:12 63.982 -19.693 5.6 km 0.9 99.0 1.7 km SW of Hekla

      Source: IMO

        • I know of one refugee from Iceland… a Florida girl who got stuck there with her husband when he was assigned to a detachment in Iceland. She is quite happy to not be there. (since she grew up in Florida/Louisiana, it’s understandable. Sun is not readily available there and I’m sure she was suffering from withdrawal.) Here in Florida, the Sun can figuratively pound you into the dirt it’s so strong. Me, well, I’m not really a “sun” person, but I do on occasion go out and sit in it for a few minutes just to wash the sleep off. If you are into Geology, Iceland is the place to be. It’s almost has it all. Except maybe for a subduction zone… but there is probably the remains of one buried somewhere under the Icelandic Crust… which could account for some of the strange geochemistry of some of Hekla’s magma. That’s a much more plausible idea than the notion that part of the Hreppar micro-plate is starting to subduct. (But on a geological time scale, you can’t really rule that out either. Wilson cycles have to start somewhere ya know.)

          • Subduction has to start somewhere, but it doesn’t start at an active spreading ridge! Oceanic crust subducts when it has cooled enough to no longer float on the mantle. That takes more than 100 million year, and at a spreading rate of say 2cm per year, that is 200 million centimeters – you need to be more than 2000 kilometer from a spreading ridge before you can consider subduction. Spreading ridges can be overridden by continental crust, but not by oceanic crust. I.e., no subduction in Iceland.

          • The way I understand Iceland, is that it is a chunk of crust over top of another chunk… which accounts for it’s insane thickness in places. But, that could also be under-plating from the hotspot…

            In support of the strangeness of the area, the Jan Mayen shard is a fragment of continental crust that sheared off of Greenland. Hence the Jan Mayen “microcontinent” moniker. It got where it is from the funky interplay of the hotspot and the spreading ridges as Iceland was being built. But now, it is effectively welded to the Eurasian Plate.

          • Yes, but that subducted a long time before the spreading ridge (and Iceland) formed. It is (or would be) a left-over from the formation of Pangea..

  4. Italy is fascinating, and Sardinia’s distance from the mainland opens questions about its volcanic past, and its relationship to the volcanism of Naples. Further south there appears to be more in the way of mud volcanology, with the appearance of the one on the roundabout at Fiumicino near Rome’s airport, that was said to have been triggered by excavations nearby, and the more recent mud volcanoes to the east of the Apennines, which are said to be linked to buried organic matter, like the one in Sicily and others in the far south of the mainland.

    https://watchers.news/2016/11/05/mud-volcano-santa-vittoria-in-matenano-italy/

    The question around Colli Albani being a potential mud volcano is another factor in the recent tectonic quakes that have shaken Rome in recent months.

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