Some days ago, a video called my attention on Facebook, a video of a beautiful explosion of Popocatepetl volcano in Mexico. I ended up in a YouTube channel called Volcano Time-Lapse. This youtuber had dubbed the explosion as the perfect explosion, and for a good reason. At night-time, with not a cloud in the sky, the magnificent white snow-clad Popocatepetl stood in full view of the Tlamacas webcam 4.5 kilometres away, when a brilliant explosion scattered countless particles of light high up into the air, some beyond the webcam’s view, over a kilometre above the crater rim, which then came down like a meteor shower over the upper flanks of the volcano, lighting them up to a distance of up to 2 kilometres from the active crater. The perfect explosion was on May 15. There had been several explosions that day, although not all as photogenic. After learning this, I tried to find more information on Popocatepetl on the MOUNTS Project page, which shows multiple satellite-based data streams, like thermal anomalies or SO2. A rapid increase in sulphur dioxide emissions was apparent since the start of 2023, with a particularly steep rise during February-March, and a peak from 5 May to 8 May, at 4500-5500 tonnes of SO2 per day. How much is this? Not particularly high for Popocatepetl, who is an extremely proficient long-term, sulphur dioxide degasser. But much higher than the 200-500 tonnes per day that were typical in January.
I was curious about this rise, knowing it could mean that something was building up. However, we have had an enormous amount of volcanic unrest towards the end of 2022, and the start of 2023, but very little actual volcanic activity. Cotopaxi, Villarrica, Laguna del Maule, Nevado del Ruiz, Aniakchak, Tanaga, Trident, and Chiles-Cerro Negro have all rumbled but so far not erupted in a substantial manner. This comes to show that volcanic unrest does not often culminate in eruptions, or at least not immediately. But finally, one volcano has provided.
There are four different webcams run by the CENAPRED pointing at Popocatepetl, but that doesn’t help much if the sky is cloudy. Right now, as I write this article, May 22, that happens to be the case. But I believe the volcano is probably erupting behind the clouds. It has been nearly two days of eruption, with a continuous plume of ash pouring into the sky, and lava fountains frequently playing inside the crater. The upper wind has blown eastwards/northeastwards all the time, carrying the ash into Puebla, and protecting Mexico City of this huge, gray inconvenience. People are referring to Puebla as Silent Puebla and discussing the possibilities of selling the ash. There have been some impressive eruption moments, bordering dangerous for the local inhabitants, where lava fountains were continuously showering the uppermost slopes of the volcano in lava bombs. There is a risk for pyroclastic flows if this goes on for an extended period. But for the most part, the eruption has been of a very low intensity. I have watched the webcams several times, but haven’t noticed any instances of the lava bombs flying as far as they did during the perfect explosion of May 15. My guess is that lava is rising up in the crater, and filling it with a lava dome, and in the process is ejecting some ash and lava bombs. But I’m not even sure of this, and much less do I know where will it lead, which makes me all the more curious about it. Will the crater overflow? Will a series of large vulcanian explosions destroy the dome? Could it go full plinian? Or will nothing happen?
The Trans-Mexican Volcanic Belt
I wouldn’t miss an opportunity to talk about the volcanic arc that I personally find one of the most interesting in the world. The Trans-Mexican Volcanic Belt. And it is interesting to consider Popocatepetl in the context of this fascinating volcanic arc.
Like other volcanic arcs, the Trans-Mexican Volcanic Belt is located over a subduction zone. However, unlike most other volcanic arcs, which are more or less parallel to the trench where oceanic crust is subducting, the TMVB is oriented obliquely with respect to the trench. This is probably due to subduction becoming shallow to the southeast, making a small flat slab. Even so, this is a pretty unique shape that does not show up in other flat slab areas of the world. The chain of stratovolcanoes is not particularly long, at 670 km length from Fuego de Colima to Pico de Orizaba, cutting roughly E-W across Mexico, although a few other atypical volcanoes extend the belt a little further both to the east and to the west.
To the east we have the San Martín Tuxtla volcano, which is a shield volcano, constructed of numerous scoria cones, and aa-dominated lava flows, with a composition of alkali basalt and basanite, primitive and alkaline types of magma. It is not unusual for volcanic arcs to have back-arc provinces of basaltic alkaline lavas, and the San Martin Tuxtla volcano is not particularly large either. Although it is a young vigorous shield volcano that has erupted twice historically, in 1664 and 1793-96. In Mexico, the basaltic volcanoes are located outside of the main orogenic area of folding and thrusting of the crust. 3 other major Cenozoic alkaline provinces occur along the eastern coast of Mexico, all outside the main orogen. At least one of them, the Sierra de Tamaulipas province, is still just barely active in the form of the Aldama Volcanic Field. These three provinces are outside the TMVB, to the north.
The western end of the TMVB turns into a graben, the Tepic-Zacoalco Rift. The deepest portion of this rift is 200 km long and 70 km wide, but it continues eastward, slowly fading away into the central section of the TMVB. This rift is part of a wider area of extensional tectonics. It is located at the exact southern end of the Basin and Range Province, and has the mid-ocean ridge of the Gulf of California only 400 km away. The Basin and Range is a vast area of horsts and grabens that extends all the way from Tepic-Zacoalco in the south, to Idaho and Oregon in the north. Two grabens radiate southward from the Tepic-Zacoalco rift towards the Middle America Trench and isolate the area known as the Jalisco Block. Colima volcano fills one of these two grabens.
The Tepic Zacoalco Rift was the site of a rhyolite ignimbrite flare-up 5-3 million years ago. Now it is home to a characteristic style of volcanism. A family of several closely packed, small, central volcanoes occupy the rift. Some of them have alkaline compositions, other subalkaline, and some have both. They are often evolved, most of them have erupted rhyolite and trachyte lavas. The volcanoes are topped with small stratovolcanoes or calderas, while viscous lava flows and domes erupt along the flanks from fissure swarms oriented NW-SE, parallel to the rift. In the map, I refer to them as the rift volcanoes. Ceboruco is one of the rift volcanoes, which made a 3-4 km³ rhyodacite plinian eruption around 990-1020 AD, followed by voluminous andesite-dacite lava flows from fissures across the summit.
South of the Tepic-Zacoalco Rift, we can find a few volcanic fields, consisting of cinder cones, lava domes, and monogenetic shield volcanoes. These fields are minor, but it is not their size that is interesting but their chemistry. Some of the lavas in this area have a strongly potassic composition, occasionally phonotephrite composition according to the TAS diagram. According to the minerals they contain, some of these lavas can be classified as minettes, and one of the fields in the ultrapotassic belt, the Mascota Volcanic Field, which is active, is thought to have erupted the youngest minettes in the world. I don’t know what the exact definition of a minette is. Alkaline magmas can have rare mineral compositions, so a plethora of terms has been created to describe all these types, minette being one of them. Potassic alkaline magmas often happen in volcanic arcs or related areas, like, for example, in Italy, usually in places where the setting is unconventional, as opposed to sodic alkaline magmas that are more common in back-arcs or intraplate areas. The ultrapotassic volcanic fields of México are at the very western end of the Middle America Trench, and comprise an area of minor volcanism ahead of the more intense volcanism in the Tepic-Zacoalco Rift. This unusual setting is probably the source of its rare chemistry.
I have described the volcanoes near the E and W ends of the TMVB. But the proper arc is the 670-km section that extends from Colima to Orizaba. In this area, there are 3 types of volcanoes.
First, the rhyolite volcanoes, which are found in slightly back-arc positions. These volcanoes erupt rhyolite in the form of extensive lava flows and plinian eruptions from circumferential fissures, a bit like Laguna del Maule does as I have talked about in some of my articles. Two of the rhyolite volcanoes, Acoculco and Los Azufres, have massive uplift domes cut by normal faults, probably overlying shallow granitic plutons. Another, Los Humeros, collapsed 160,000 years ago producing a 230 km³ ignimbrite. A second collapse of Los Humeros generated a 37 km³ ignimbrite 70,000 years ago. A trapdoor resurgent dome pushed upwards the floor of the second caldera to the level of the rim. During the Holocene, Los Humeros has been extremely active and turned to more mafic compositions. Circumferential fissure eruptions from every side of the caldera have issued flows of trachyte, trachyandesite, and basaltic trachyandesite, inundating vast tracts of land with rugged black lava.
Second, we have the Mexican shield fields. A Mexican shield is a type of monogenetic volcano, typically several hundred meters tall, and several kilometres wide. A Mexican shield is enormous. They mostly consist of many piled up lava flows erupted from a cinder cone during a very long-lasting eruption, maybe a decades-long eruption, of mainly basaltic-andesite or andesite composition, although more rarely dacite or basalt. Mexican shields happen alongside smaller cinder cones and andesitic-dacitic lava domes making up volcanic fields. Most Mexican shields are found in México, as the name correctly implies, most Mexican shields elsewhere are probably found in the Cascades. The largest concentration of such volcanoes is in the Michoacan-Guanajuato Volcanic Field, which has nearly 400 monogenetic shields, plus a much greater number of cinder cones, lava domes, and maars, including the historical Paricutín and Jorullo, entirely covering an area of 220 by 160 kilometres in volcanic material, the largest volcanic system of its kind. The Chichinautzin volcanic field immediately south of Mexico City is not so large, but is much younger, and the shields are more concentrated.
And third, we have the stratovolcanoes. Popocatepetl, Pico de Orizaba, Fuego de Colima, and a few others, are classical stratovolcanoes that make tall edifices, with steep upper cones around a central crater, formed in a combination of lava flows, lava domes, pyroclastic flows, tephra layers, debris avalanches, lahars, and reworked volcaniclastic material. Most Mexican stratovolcanoes are on the large side of stratovolcanoes in terms of volume. The stratovolcanoes erupt mainly andesite and low-silica dacite. They are arranged in seven groups or complexes, most of them elongated north-south. Activity started in the north and gradually moved southward. The presently active stratovolcanoes are the southern end of these north-south complexes.
Arc volcanism in Mexico has been on and off over time. An earlier episode happened around 22-11 Ma, and formed an arc of very similar shape and location to the one that exists today, only a little smaller. The volcanoes extended E-W from the east side of Michoacán Guanajuato volcanic field to the area of Pico de Orizaba. Lavas erupted were predominantly andesites and low-silica dacites. This was followed by a hiatus in andesitic volcanism, where basaltic volcanic fields formed lava flows, or calderas produced rhyolitic ignimbrites. Arc volcanism only resumed very recently. The Michoacan Guanajuato volcanic field started to form 3 million years ago, but about two-thirds of the volume have erupted within the last 1 million years. The complexes of stratovolcanoes seem to have become active at some point between 3 to 1 million years ago. Activity in both the stratovolcanoes and Mexican shield fields migrated southward, presumably due to the steepening of the subduction, and rollback of the flat-slab, while rhyolite systems developed in the back-arc.
The Valley of Mexico
Intense volcanic activity during the Miocene and the Quaternary has almost completely concealed any basement rocks across an enormous area of the Trans-Mexican Belt. The volcanoes have altered the topography, obstructed former valleys, and led to the formation of a series of basins, filled with volcaniclastic material. Two important endorrheic basins, ringed by volcanoes, are the Oriental Basin, surrounded by Los-Humeros, Pico de Orizaba, and other volcanoes, and the Valley of Mexico Basin.
The Valley of Mexico is surrounded by volcanoes on all sides. North lie old eroded Miocene volcanic edifices, and younger Plio-Quaternary Mexican shields and cinder cones. To the west, you find a chain of several eroded stratovolcanoes, known as Sierra de las Cruces, formed over a steepening subduction, with ages ranging from 2.87 at the north to 0.39 Ma at the south. In the south stands the active Chichinautzin Volcanic Field. The cinder cones and monogenetic shield volcanoes of Chichinautzin stand taller than any skyscraper, over 1000 meters above Mexico City, and probably much higher from the bottom of volcaniclastic-filled basin, whose existence we probably owe to the very Chichinautzin Volcanic Field who forms a mighty lava dam, 20 kilometres wide and 1-2 kilometres tall, blocking drainage to the south. Some of the cones and craters of this volcanic field extend into present-day Mexico City.
A lava flow in the Chichinautzin volcanic field, around 20 AD, destroyed the city state of Cuicuilco, that at the time dominated the basin. At the time, the basin was occupied by a large lake known as Lake Texcoco. The volcanoes of Chichinautzin formed islands and peninsulas in the lake, and Cuicuilco was on the southern shore. After Cuicuilco, other city states emerged in this important cradle of civilization. This includes Teotihuacan, the largest populated center in the pre-Columbian Americas. The Aztec-capital of Tenochtitlan was also constructed here, on artificial islands within Lake Texcoco. And presently, the Valley of Mexico is home to over 20 million people.
Along the east side of the Mexico Basin lies Sierra Nevada, a series of north-south stratovolcanoes, with the main volcanoes being Tlaloc, Iztaccihuatl and Popocatepetl. Sierra Nevada means snow-clad range, which alludes to the volcanic lovers Iztaccihuatl and Popocatepetl, the second and third highest mountains in México, that are often covered in ice and snow due to their enormous height. The oldest volcano in the Sierra Nevada range is Tlaloc, which started to grow 1.8 million years ago, and was still in full activity by 0.9 Ma. Tlaloc is an edifice with shallow slopes and modified by erosion. The youngest eruptions from this volcano were rhyolitic plinian eruptions that happened only 44,000-21,000 years ago. Iztaccihuatl started to grow at 1.1 Ma. The northern lower portion formed first. The name Iztaccihuatl means white woman in Nahuatl, because it resembles a woman lying on its back, and is often covered in snow. Various parts of the woman, head, chest, knees, feet, are different volcanic peaks formed of viscous lava flows and domes. The highest peak still preserves the summit crater. The feet formed around 440,000 years ago, and the rest of the peaks are probably younger since they seem better preserved. One of the latest eruptions happened 80,000 years ago from the northern flank and formed a massive dacite coulee, up to a few hundred meters in thickness.
Popocatepetl, or El Popo as the Mexicans often refer to it, is the southernmost and youngest volcano of Sierra Nevada. Unlike Itzaccihuatl’s stratovolcano chain, Popo comprises a relatively simple cone crowned by a singular crater. Both mountains reach an enormous size and are partly joined together. Popocatepetl stands at 5426 meters above sea level, and Itzaccihuatl at 5230. The height above the pre-eruptive basement of both volcanoes is probably around 3500-4000 meters, which is very large considering that only a handful of subaerial volcanoes in the world are over 4000 meters tall. This is more than the height above the present-day surrounding basins, because they are filled with several hundred meters or so of ash, debris avalanches, reworked volcanic material, and lava flows.
The northern flank of Popocatepetl is dissected by deep valleys to a substantial elevation of more than 4000 meters above sea level. So the volcano is not particularly young. The northern flank is similarly eroded as the feet of Iztaccihuatl. So I think the main construction of Popo and the southern part of Itza, the head, chest, knees, and feet, was probably simultaneous. But I haven’t seen any ages of the oldest lavas of Popo’s cone. It probably reached an elevation similar to that of today early on, but was later destroyed and reconstructed cyclically during a series of landslides.
In the last 30,000 years, Popocatepetl has produced five VEI 5 plinian eruptions. These eruptions are the best studied of the volcano. Rare plinian eruptions are more impactful and are preserved over a wide area as layers of tephra, so they are more easy to study that the more minor, more typical eruptions.
The first plinian event happened 27,800 cal BP (calibrated years before the present, with present meaning 1950). This event is very interesting. Part of the volcano collapsed in a debris avalanche of at least 10 km3 which reached as far as 72 km downslope from the volcano, destroying everything in its path, something that would have catastrophic consequences if it were to repeat. Following the avalanche, a massive plinian eruption ensued, presumably triggered by decompression, which erupted 1.9 km³ DRE (dense rock equivalent). This is the most evolved plinian eruption of Popo, with 64.8 wt% SiO2 whole rock composition, while the other plinian events range in between 60.6-62.7 wt% SiO2. Popocatepetl does not change much in composition, so this difference is significant. It is probably some of the most evolved magma erupted by the volcano overall.
After this lateral collapse, Popo grew back. Now there is little sign of the collapse scarp and the top forms a symmetrical cone. The upper 1 kilometre of the volcano is very steep, like a huge cinder cone some 4-5 kilometres wide, and it has probably grown from proximal pyroclastic ejecta, from vulcanian explosions and lava fountains. The most typical eruption style probably consists of lava domes/ponds that fill up the summit crater, and blow up in vulcanian explosions showering the upper cone in lava bombs. Or at times, activity probably grows into continuous fountains that feed small clastogenic flows. In fact, much of the upper cone seems to be made of steeply dipping layers of welded spatter, which may have been small fountain-fed flows. The present eruption of Popocatepetl briefly behaved this way, producing continuous fountains over the rim.
The second most typical activity of Popocatepetl probably consists of lava flows. The next 1-2 km of elevation below the upper cone are covered in voluminous lava flows that reach almost 20 km away from the crater. Many of these lava flows probably issued from the summit of Popocatepetl when lava rose in the crater and overflowed. But close to the crater they are all buried in thick ejecta, so this may not have happened in a while. A few of the lava flows have clearly issued from flank vents along a NE-SW rift system.
Edit: After publishing the article, I have estimated the volumes of the two major flank eruptions: the Ecatzingo and Nealticán lava flows. I used elevation contours to get an estimate of each lava flow’s volume, which turned out to be identical at 3.6 km³. Both eruptions were long lived, particularly the Ecatzingo lava flow, piling up numerous small tongues of lava, and each fissure erupted 3.6 cubic kilometres. Nealticán is the youngest-looking lava flow of Popocatepetl, younger than Ecatzingo and the flows from the summit.
The rarest eruptions are the five full-blown plinian eruptions, even though most of the research is dedicated to them. Following the 27,800 BP eruption, the next plinian eruption did not happen until 17,000 cal BP. Authors have referred to this later eruption as the Tutti-Frutti Pumice, or as the Pumice With Andesite. This eruption is the largest and most complex of Popocatepetl. It erupted 2.9 km³ DRE. Eruption started with many thin layers distributed all around Popo, probably resulting from vulcanian to subplinian explosions. It then evolved into a fully plinian eruption where the plume was carried northwest and dropped 10-15 cm of ash across present-day Mexico City. This eruption is the most primitive composition of the plinian events, ranging in 60.5-61.4 wt% SiO2, the magma in the plinian phase was more evolved and came from a shallower reservoir than in the preceding explosions. The primitive character is best seen in the glass composition. Magma is a mix of solid, liquid, and gas. The whole rock composition refers to the solid+liquid composition, while the glass in a volcanic rock represents the part that was molten upon eruption and solidified quickly without forming crystals. So the glass composition is the composition of the molten portion of the magma upon eruption. The glass of the Tutti-Frutti Pumice has 62-63 wt% SiO2, while the other eruptions have 65.5-69.1 wt% SiO2 glasses. So the magma should have been more fluid.
The three remainder plinian eruptions happened at 3700 BC, 300 BC, and 800 AD, and had DRE volumes of 2 km³, 1.2 km³, and 0.5 km³ respectively. There is a trend of the plinian eruptions becoming increasingly frequent and increasingly small. This could be seen as a sign of escalating activity at Popocatepetl during the past 30,000 years. The last plinian eruption inundated some human settlements of the time in lahars, which are probably the greatest hazard of Popocatepetl’s plinian eruptions, since lahars could potentially reach into major cities like Puebla, or even Mexico City itself.
Probably shortly after the 300 BC plinian eruption, the Nealticán lava flow erupted from the NE flank. This lava flow is enormous. With 4.2 km³, the Nealticán lava flow involved a larger volume of magma than any of the plinian events. The eruption was long-lived and probably lasted a few or several years. One interesting thing about the flow is that the early lavas have 61-63 wt% SiO2 while the later lavas have 63-64 wt% SiO2, so that the eruption changed from andesite to dacite. This is a little counter-intuitive, since the dacite, more evolved, should have come out first. Dacite would pond in the upper part of the storage under Popocatepetl and be the first to erupt. My speculation is that the magma came from a storage somewhere else, possibly under the immediately adjacent Iztaccihuatl volcano, that erupts viscous dacitic lavas from many vents over a broad area. Popocatepetl may have drawn magma from a shallower storage than its own, under Iztaccihuatl, from the bottom up, erupting the least evolved magma first, and gradually changing towards more evolved dacites. I’m thinking of a similar relation as that of Hualca Hualca-Sabancaya, in Peru. Hualca Hualca has the magma, but Sabancaya does the erupting. Here, Iztaccihuatl would be playing a similar role as Hualca Hualca, and Popo would be playing Sabancaya.
Additionally, Popocatepetl has erupted several times historically. Not much is known about the older eruptions. Popo was dormant from 1804 to 1919. There was some minor activity in 1919-1927, including explosions and the growth of a small lava dome. From there the volcano was dormant until 1994, when it awoke with intense fumarolic activity and explosions. Since 1994, the smoking mountain has been in near continuous eruption. Lava fills up the crater, vulcanian explosions blow up the lava and deepen the crater. This repeats again and again.
The biggest development in the eruption might well be the present episode. As of now, the volcano has had sustained plumes of ash and lava fountains for 3 days in a row. I suspect the crater might be filling up with lava. A rising magma column. As far as I know, this kind of activity has not been described in this volcano before, so it is hard to know what to expect. I can see the possibility of almost anything happening, as well as nothing in particular happening. Even a plinian eruption is possible if my Iztaccihuatl speculation is correct, since vast amounts of dacitic-andesitic magma could very well start flowing into Popocatepetl. Although the most likely option based on what we know about the volcano is that some powerful vulcanian explosions will blow the lava away, or maybe that bigger lava fountains will form and shower the upper cone in spatter, with a small risk of pyroclastic flows from collapsing spatter and ejecta. Only time will tell.
To follow the eruption, the following links are most useful, which include webcams and seismograms:
I will watch with curiosity how this volcanic situation evolves, which I think could teach a lot about how this volcano works. A volcano that we don’t know much about other than the big five plinian eruptions.
Alvarez, G. M., C, M., Fucugauchi, J. U., & Uchiumi, S. (1991). Southward migration of volcanic activity in the Sierra de Las Cruces, basin of Mexico? – A preliminary K- Ar dating and palaeomagnetic study. Geofisica Internacional, 30(2), 61–70. https://doi.org/10.22201/igeof.00167169p.19184.108.40.2064
Hasenaka, T. (1994). Size, distribution, and magma output rate for shield volcanoes of the Michoacán-Guanajuato volcanic field, Central Mexico. Journal of Volcanology and Geothermal Research, 63(1–2), 13–31. https://doi.org/10.1016/0377-0273(94)90016-7
Israel Ramírez-Uribehttps://doi.org/10.1130/B36173.1Claus Siebe Magdalena Oryaëlle Chevrel Dolors Ferres Sergio Salinas; The late Holocene Nealtican lava-flow field, Popocatépetl volcano, central Mexico: Emplacement dynamics and future hazards. GSA Bulletin 2022;; 134 (11-12): 2745–2766. doi:
Macías, J. L., Arce, J., García-Tenorio, F., Layer, P. G., Rueda, H. N. R., Reyes-Agustín, G., López-Pizaña, F., & Avellán, D. R. (2012). Geology and geochronology of Tlaloc, Telapón, Iztaccíhuatl, and Popocatépetl volcanoes, Sierra Nevada, central Mexico. In Geological Society of America eBooks (pp. 163–193). https://doi.org/10.1130/2012.0025(08
Siebe, C., Salinas, S., Arana-Salinas, L., Macías, J. L., Gardner, J. V., & Bonasia, R. (2017). The ~ 23,500 y 14 C BP White Pumice Plinian eruption and associated debris avalanche and Tochimilco lava flow of Popocatépetl volcano, México. Journal of Volcanology and Geothermal Research, 333–334, 66–95. https://doi.org/10.1016/j.jvolgeores.2017.01.011
Sosa-Ceballos, G., Gardner, J. V., & Lassiter, J. C. (2014). Intermittent mixing processes occurring before Plinian eruptions of Popocatepetl volcano, Mexico: insights from textural–compositional variations in plagioclase and Sr–Nd–Pb isotopes. Contributions to Mineralogy and Petrology, 167(2). https://doi.org/10.1007/s00410-014-0966-x
Sosa-Ceballos, G., Gardner, J. V., Siebe, C., & Macías, J. L. (2012). A caldera-forming eruption ~14,10014Cyr BP at Popocatépetl volcano, México: Insights from eruption dynamics and magma mixing. Journal of Volcanology and Geothermal Research, 213–214, 27–40. https://doi.org/10.1016/j.jvolgeores.2011.11.001
78 thoughts on “Popocatepetl and the Trans-Mexican Volcanic Belt”
Thank you, Héctor! El Popo has certainly been garnering some recent interest. Are you allowed to publish a link to the video that inspired your article?
Yes! Here is the video:
Maybe a slight possibility that the recent fountains were from basalt getting to the surface from deeper down. At least, there seems to be some plausibility from the colour of the ash.
How crystal rich is the magma at Popocatepetl? It is not extremely viscous, but still dacite or andesite, so perhaps the crystal load is not so high and maybe a crystal poor batch surfaced. In any case lava fountains need some mobility in the magma, if it is viscous enough to make a dome I think it would be too much to make a fountain as opposed to exploding. Popo does do the latter, and quite often, but it was clearly fountaining recently, so something is up.
If it’s basalt, it would be a first for Popocatepetl and probably for any Mexican stratovolcano, so I don’t think that’s very likely. Although some of the stratovolcanoes may have rarely erupted basaltic-andesite, I’m not sure, so it could be basaltic-andesite.
Popocatepetl is high in phenocrysts, I think usually 40-60 vol%. But the glass is not excessively evolved. Volcanoes like Merapi, Augustine, Sheveluch have rhyolitic glass. Instead, the glasses of El Popo are usually dacitic, and sometimes even andesitic. I’m not sure why this is, but it means that Popo is not extremely viscous, and more prone to making lava flows than lava domes.
Interestingly the ash seems to have changed colour from pale grey to black these past days. GeologyHub showed two different containers of gathered ash from Puebla with pale grey the day prior and a very distinct black that day in his recent video on El Popo’s increased activity.
Compositonaly zoned magma system … most polygenetic magma systems are to a degree or more .. the staler systems are just felsic gunk
Popo may have similar viscosity to Sakurajima and shinmoedake volcano its lava flows just looks the same: That means that pancake domes are really simply only ponded blocky lava flows. Mayon seems to have sligthly lower viscosity still like Karangetang does. With the perfect combination of temperatures and Sio2 very difftent magma compositons can assume the same apparence : )
Woud be fun If Popo coud overflow but perhaps it may blow up before that. Is there any signs of rising lava pool in the crater ?
Mayon seems to be variable. Some of the videos I have seen it does look like it has something like a dome, and the lava is pretty slow even on the over 45 degree slopes. But there are a lot of videos from 2018 showing it doing actual liquid lava fountaining, bring orange and everything. Probably a bit like Etna the base mag.a is fluid but can easily cool to become more viscous. Fountain fed flows also tend to become blocky and viscous anyway, as seen at both Cumbre Vieja and Pu’u O’o.
Fuego seems very similar to Mayon, mafic but variable in viscosity. It is kind of strange to think that both do their most powerful eruptions when fluid magma surfaces, the more evolved stuff is effusive… 🙂
Popo is going well right now – worth a look at the webcams
A great Article that Popocatepetl deserves! It is a bit challenging to apply the different volcanic systems of TMVB to the right locations on the map. For me the zonal (west-east) distribution is new. I’m much used to the meridional (north-south) chain of American volcanoes from Alaska to Tierra del Fuego (Peninsula Land of Fire).
The behaviour of Popocatepetl reminds to the eternally and daily active volcanoes of the Americas, Japan, Indonesia or Italy (single case Stromboli). F.e. Sangay, Sabancaya, Reventador, Suwanose-jima. But Popocatepetl does longer breaks and larger eruptions. It is more dangerous than the eternally active volcanoes, but usually relatively “friendly”.
Interesting are the lava flows. When were the last big lava flows? Are they rather a’a or block lava?
Metepetl is a huge blocky flow from Popo, I call them magma glaciers, huge stuff and far more viscous than typical basaltic Aa flows
It seems lime they act a bit like glaciers too, there looks to be a chain of craters above where the lava flowed out, but no deposits to show them being explosive in origin. Perhaps the lava emerges relatively fluid but gets backed up in the flow, which inflates over time. For it to flow out of a crack like that it cant be too sticky, and the other flows seem thin despite the higher silica content. Basalt flows can become blocky looking if inflated and erupted fast, like Holuhraun, although these tend to get pahoehoe breaking out of the flow margins.
Plus, as the magma cools upon erupting, it will significantly increase in crystals, so what might be a sticky but mobile lava just becomes like a dome a few km away. For stratovolcanoes with mafic melt this isnt so much of a thing but volcanoes with andesite or dacite melt probably are increasingly subject to this process.
Is interesting to watch Santiaguito, it was a real dome for a long time but seems it has become increasingly less viscous, and more like a stratovolcano, its last flow was only meters thick although that was over a year ago now so things could be different today.. Santa Maria was a basaltic andesite volcano before, so perhaps after a few more decades to centuries Santiaguito will end up like this too.
Thanks! The youngest lava flow is Nealtican, which I talked about in the article, around 300 BC perhaps.
No lava flows afterwards? So this must be as exceptional for Popocatepetl as Plinian eruptions. The Nealtican flow happened after a Plinian eruption in 300BC. Is this related?
After the last Plinian eruption 800AD no lava flow extruded. It looks like there has to be a huge quantity of new magma in Popocatepetl’s system to create first a Plinian and second a big (tall, broad and long) lava flow.
There are many lava flows on all sides of Popocatepetl that seem to have issued from the summit crater since after the last lateral collapse. It is possible lava flows were more common during the early reconstruction of Popo. There are two major flank eruptions from fissures which formed lava flows. The Ecatzingo eruption in the SW flank at 3.6 km3. And the Nealtican eruption in the NE flank, also 3.6 km3. Ecatzingo overlies some of the flows from the summit in that area, and Nealtican is the youngest-looking. So maybe lava flows have changed from summit overflows to flank fissures as the volcano has grown taller.
Lava flows from Etna the other day.
Nice way to depict the flows
The ash plume from Popocatepetl rapidly changed color several times between 6:51 and 6:58. https://www.youtube.com/watch?v=D9Ywlay65qQ
I think that the color depends on the relative proportions of ash and water vapor in the plume. Ash is dark grey to black, and water vapor is white.
I remember that I saw a lava fountain. Was there a change between ashy and lava plumes/fountains?
This is only kind of volcano related. The mods can feel free to remove it if they deem ot off topic.
Anyhow. Here’s a link to a movie, about movies about the Kraffts of volcano films fame.
Thanks for the link. Hertzog almost always does fascinating documentaries where he looks behind the story..an attempt to shed light on what drives people to do the unusual/extraordinary.
Tokyo has had a 6.1 earthquake today, after a period with some stronger earthquakes near Loyal Islands, PNG and Philippines. Do the quakes indicate a certain development arround the Philippine Sea plate or are they accidentally?
A video of the crater of Popocatepetl. The music is a bit unsettling. But even more surprising to me is the absence of a lava dome inside the crater. I guess all the lava was by explosions and scattered across the broader crater and into the ash plume.
The volcano is looking very calm now.
Looks like magma withdrawed in thermal image, looks like a sagged pancake dome wigh perhaps being lost gas and the magma sagged, I seen these drainbacks sag fissures in other Popo pancake domes
Héctor, there is some more to the mechanism:
You decribe (quote) “However, unlike most other volcanic arcs, which are more or less parallel to the trench where oceanic crust is subducting, the TMVB is oriented obliquely with respect to the trench. This is probably due to subduction becoming shallow to the southeast, making a small flat slab.”
The flat slab production might be a only symptom. The underlying mechanism is different rotation and stress:
The Cocos and Rivera plates (Fig. 1) share a divergent margin with the Pacific Plate but have an oblique convergence and anticlokwise rotational component with respect to North America. Related to this transtensional regime, palaeomagnetic studies performed since the 1970s have suggested occurrence of counter-clockwise vertical-axis crustal block rotations in central and southern Mexico that also affected areas within the TMVB.
So this volcanism between the two continents is more than logical.
Thank you for the interesting piece.
As far as I can tell from reading the article’s abstract, the authors were trying to measure whether there was any vertical rotation of blocks due to normal faulting/rifting but found no rotation within the TMVB lavas they analyzed.
Hard to prove, but certainly more than logical with the differences between the movements of the North- and South American Plates.
I am wondering about that strange sort of plateau south of Cuba and Yucatan, like a step in the ocean.
Anyway, if we draw a straight line from Mexico City to Miami and then a little out into the sea and a second parallel line from Caracas to Galápagos and then close them we get a sort of square which is totally volcanic, older and new, with the Antilles being the Eastern border. Possibly the old realm of good old Tethys, American section.
Well, there are some very interesting things about the location of the Trans-Mexican Belt. First that the present volcanic arc is a copy of the 12-22 Ma volcanic arc, which I briefly mentioned, the present distribution of volcanoes is almost identical to then. So it doesn’t arise from some transient slab geometry circumstances, since the same situation must have occurred during the Miocene.
The other is that the TMVB marks the exact southern end of several volcano-tectonic provinces, including the basin and range province, a large system of grabens across western North America. Also is the southern end of the Sierra Madre Occidental silicic large igneous province. It is a continuation of the Miocene Comundú volcanic arc of California, if you match Baja California to the Coast of Mexico by closing up the Gulf of California. And lastly it also marks the southern end of the Eastern Alkaline Province, which is a series of large massifs of trachyte-phonolite calderas, and basanite-alkali basalt shield volcanoes, that starts in the Trans-Pecos volcanic field of Texas and ends in the Sierra de Otontepec/Tantima, next to the TMVB. Most of these volcano-tectonic provinces are interrelated and roughly contemporaneous: the Basin and Range, the Gulf of California, the Comundú Arc, the Sierra Madre Occidental, and the Eastern Alkaline Province.
Very interesting indeed, esp. the setting of a volcanic arc.
How does the oceanic rift of California Bay influence the TMVB? It is part of the “East Pacific Rise”, the divergent plate boundary which pushes the eastern Pacific plates (f.e. Rivera Plate) towards central and southern America. There is a regional complex situation between divergent and convergent plate boundaries.
An obvious consequence is that it cut the former Miocene arc, Comondú-TMVB, in two. This may have allowed the west end of the TMVB to become weird, with the potassic volcanic fields, and the Tepic-Zacoalco rift. The Gulf of California rifted across the former Miocene Comondú arc, and in a way you could consider that the Tepic-Zacoalco Rift is a weak continuation of the Gulf of California into the TMVB, which didn’t manage to fully rift the arc. Some small grabens opened as far east as the longitude of Mexico City. The Gulf of California is thought to have opened 5 million years ago, which coincides with a rhyolite flare-up across Tepic-Zacoalco Rift, which was probably the initial formation of the rift.
Although there is probably more to it.
The plate border line appears to me exceptional, a bit like San Andreas Fault (transform fault). There plates move in opposite direction like cars on road. Something of this may also happen around TMVB. There is subduction from the south, divergence from west. The TMVB must be moving east, while northern Mexico stays stable and the Cocos Plate subducts from southern coast.
This map shows the tectonic plates of Mexico:
Between Californian Bay and TMVB must be some kind of triple junction between a subduction zone and a divergent zone.
Considering the direction of the Pacific Plate, created by slab pull in Japan, Kamchatka, and the Aleutians, it makes sense that extension (the Basin and Range), happens where it does.
One must consider why it would try to pull the west coast off North America instead of just pull the Atlantic apart faster.
One thing to consider would be that when the Rockies formed, their roots jutting down nearly 60 km, this was something like a boat putting down an anchor. It drags in the asthenosphere and makes the continent resist being pulled toward Japan. That would both create tensional forces between the Rockies and the coast, precisely where the Basin and Range is, and partially shield the MAR from the pull, possibly explaining why it is one of the slower spreading ridges out there.
It’s an interesting idea. In that case, not just the Rockies but the whole North American Craton would have dragged down the plate. The lithosphere under the North American Craton is 200 km thick, while that of the Basin and Range is 50-100 km thick.
Although it is also important to consider that rifting tends to follow volcanic arcs. In places like the Marianas or Tonga, the back-arc basins opened up exactly following the volcanic arcs. So volcanic arcs seem to be able to turn into rifts.
One shouldn’t forget terranes. California is one, this is another one:
An analogy: North America as a giant lava boat.
Consider that while plate motion from rift to subduction occurs along a narrow vertical range (a few 10s of km max), the reverse motion of deeper material in the other direction can be spread out over hundreds and even thousands of km (the upper, or even the whole, mantle), and if the volumetric flow rate is the same, but diluted over a much larger cross section to that flow, the flow speed will be much slower.
So, motion of earth material is fast (relatively!) subductionward at and near the surface, but probably starts to slow from the brittle-ductile transition down to the moho, to a near halt there, and then is in very slow reverse from somewhat farther down the rest of the way to the 440km transition, if not clear down to the core.
This is not dissimilar from the flow in a lava channel: fast at the surface away from the channel edges, slowing toward the edges and toward the bottom. Just take the motion of the deeper mantle material as the “zero speed” reference frame, the bottom of the channel, and the situation seems analogous, though the scale (in all four dimensions) much larger.
We’ve all seen small lava boats overtaking larger ones in such channels, due to the larger ones’ deeper keels dragging in the slower lava near the bottom of the channel.
Well, there’s a pretty deep keel under the Rockies …
This only works, of course, if the mountain’s roots have to co-move with the mountain rigidly, so they can act as a keel, rather than being swept back like a dangling cape or something. Essentially, the “lava boat” is the crust down to the brittle-ductile transition and the “channel lava” is everything under that. However,
shows a giant cool spot at depth directly under the Himalayas: mountains have cold roots. The brittle-ductile transition should be much deeper amid them than elsewhere. So there is, in fact, a big rigid keel jutting down underneath large mountain ranges into the ductile material below and around them.
Continuous tremor and lava fountains at Popo right now.
While Popocatepetl does “dry” eruptions, Costa Rica has an example for “wet” explosive volcanoes: https://ticotimes.net/2023/05/26/powerful-eruption-rocks-costa-ricas-rincon-de-la-vieja-volcano
Usually it is some kind of phreato-strombolian volcano. This was a larger bang.
I’m curious about the submarine volcanic field northwest of San Martin Tuxtla on the map. What’s it called?
That is the Anegada High. I noticed it in some maps of the TMVB and a global gravity anomaly model. I looked it up and it’s older than I thought, based on stratigraphy the Anegada High volcanic field is thought to be Miocene in age, it’s apparently covered in sediments.
Seems like Popo has been erupting ash continuously for at least five days, with occasional lava fountains and lava bombs. As of this moment it is still erupting though it was busier earlier in the day.
How unusual is that?
Yes, it seems to be endlessly jetting ash and some incandescent fragments of lava, accompanied by constant tremor. It will soon make 8 days of almost continuous tremor (there was only a day or two that had little tremor). I think this activity is very unusual for Popo.
Some photos of Popocatepetl evolution:
I find it interesting that in 1994 the summit of Popocatepetl was a very large, 600-700 meters wide and 500 meters deep, crater. Craters this size are often formed after very large explosive eruptions VEI 4-5. So that crater must have been the legacy of the 800 AD plinian eruption, since no other eruption of large magnitude has taken place since. What is surprising is that this crater had not been affected by almost any filling in the 800-1994 period. There was only a small nested crater at the bottom in 1994. Then, between 1994 and 2001, lava filled up the 800 AD crater to almost overflowing. Since then, Popocatepetl has been making mostly explosions and lava domes/ponds inside a small nested crater. So it calls to attention that the 1994-present eruption is probably the most substantial activity since the 800 AD plinian eruption.
Unless however Popocatepetl’s plinian buildups worked fundamentally changed after 800AD, it stands to reason the volcano is capable of another essentially at any time this many years later. I haven’t though much about Popo as its recent constant activity normally implies that it’s venting and releasing strain instead of pressure-cooking its way to a major event, but maybe that’s not quite accurate? Unless the system wasn’t receiving much new magma 801CE – 1993, couldn’t there be a decent amount of material capable of a bigger bang than we’ve seen from it? I just wonder what would trigger such frequent activity while avoiding triggering the entire system to blow itself out, or how exactly that would work. Also implies it’s possible Popo fundamentally did change after 800CE?
Just sitting here wondering if Popo is going to really Po-pop… (I’ll see myself out)
Thanks for another spectacular piece Hector, you’re seriously en fuego right now.
Maybe the crater needs to fill up with lava for the next plinian eruption to happen. But in this case does it need to go dormant and erupt again to do a plinian eruption, or can it go off right away?
I agree that there could be a lot of built-up magma after a millennium of relative quiescence. And in fact, now that I think of it, that could explain one aspect of Popocatepetl’s eruption. During the start of the eruption in 1994-1998, the volcano degassed 9 million tonnes of sulphur dioxide, more than half the amount of SO2 emitted in the 1991 Pinatubo eruption. At it’s peak in 1996-1998, when it started effusing effusing lava, it was emitting 9,000-13,000 tonnes/day of SO2, which is when most of the degassing happened. All of this gas may have come from built up magma during the previous millennium, that had finally found a way to release some excess gas. So there may be enough magma to produce another plinian eruption, or one of those voluminous flank lava flows.
There is another option for the summit crater: it’s younger than 800 CE, but the result of a large effusive flank eruption. I cite Kilauea 2018 as precedent: no kaboom, but the summit crater got something like 700m deeper.
That would be a good option if there were any lava flows the right age. But the only young looking lava flow (not fully covered in soil, rough surface) is Nealticán. And Nealticán, in terms of stratigraphy, underlies the 800 AD plinian eruption, and shortly postdates the 300 BCE eruption, according to various articles. The last lava flow was shortly after 300 BCE, and the last plinian event in 800 AD, according to the stratigraphy presented by many authors.
Nice read, thanks!
About the Michoacan-Guanajuato Volcanic Field, there is a recent BV article showing how the magma has been repeatedly trying to reach the surface during the last few decades, but keeps getting stuck (for now…) at 8 km depth. https://doi.org/10.1007/s00445-023-01645-0
About the Popo, a paper I love is this reconstruction of its recent (800 years) activity from pre- and post-Columbian sources. It features really cool early drawings of the volcano, with a plume reaching the stars! https://doi.org/10.1007/s00445-016-1010-y
Thanks Jean-Marie Prival!
I remember following one of those Michoacán Guanajuato swarms when it happened. I remember the swarm as being gigantic and of a clear volcano-tectonic distribution in time. I think it was the swarm of 2020, which had 3000 located earthquakes, with >M 3.1, since the seismic monitoring there is nowhere near as sensitive as in the United States or Iceland. There have been two other swarms more recently. One in 23 September 2022 and onwards, with 200 earthquakes M 3.1-4.3. And another very recently, which started this year on 15 March, and by 21 March had produced 80 located earthquakes > M 3.1, not sure if it has continued afterwards, I will check. It’s interesting that these swarms keep striking just north of the Tancítaro volcano. I suspect that Tancítaro represents the centre of the Michoacán Guanajuato volcanic field, or at least of its south-western side, since other akin volcanic fields of monogenetic shields tend to be arranged around similar eroded stratovolcanoes. For example, the Cerro Nevado volcanic field in Argentina, is arranged around the stratovolcano of that same name, and several young Mexican shields and cinder cones are arranged around the Three Sisters in Oregon. So the vigorous seismic activity under Tancítaro volcano, in the largest andesitic volcanic field of the world, is certainly exciting:
Jean-Marie Prival, the links you provided go to a pay PDF download site. So I was unable to download either citation.
Strange, at least the first one is open access and should be downloadable by anyone. The second is pay-walled, unfortunately, but you can ask the corresponding author by email, in general they are always happy to provide a copy. Or else look for something called “libgen”, it is not legal, but the science publishing business being what it is…
Crazy deep quakes at almost all of the volcanoes that make up the Katmai system, 30-40 km deep ULF earthquakes. It would seem a good bit of magma is on the move, very interesting in seeing where this can go
Interesting in the Chinese curse sense, I’d say — that’s a potential VEI7 progenitor.
It’s possible but I doubt it, another novarupta would be awesome.
A bit Off Topic: Did the asteroid which hit Yucatan (and helped to terminate dinosaurs), cause volcanism on the site of impact? This asteroid was so big that it must had hit a wound into the earth and let magma rise. At the same time the explosion was so hot with sun-like temperatures that it made the earthcrust liquid on its own.
It did not penetrate the litosphere but yes melted alot of crust, that woud have formed alot of impact melt basicaly asteorid made lava. The Chicxulub impact melt sheet was many many kilometers thick, so yes basicaly a shallow magma chamber in the seafloor made by the impact. Its not Impossible to think that this impact melt coud have erupted as pillow lava on the seafloor years after the impact. The crater was full of hydrothermal vents and black smokers for 10 000 s years after the impact.
No extrusive impact melt rocks have been found in the Chicxulub drill cores, but not Impossible To think it coud have erupted as non volcanic pillow lava after the impact
Had it hit a thinner litosphere like at a ridge it woud have made an automatic ” mini flood basalt ” as the shallow astenosphere woud get unroofed
Whatever happened Chixlulub defentivly produced its own magma chamber as drill cores have very nice melt sheets. The Chicxulub melt woud have had a granitic obsidian composition. The impact vapour plume woud reach 20 000 C and the melt left over well over 2000 C and be as fluid as water perhaps, so hotter than Komatites even. Perhaps the cooling formed very nice columnar joints in that or even cooled so slowly it coud have Re – crystalized as granite some of it
Ok, so it was only the impact energy which made something like liquid rock. The temperature was high enough to make rocks and metals evaporate. The asteroid hit a shallow sea with typical maritime sedimentary rock. There was gypsum (calcium linked to sulfur) which became gasiform and changed climate. If there were liquid rocks, they were liquid sedimentary rocks, but not “magmatic” rocks.
I would think if it us remelted then it has become an igneous rock again. Rock types are a bit blurry really, ash is kind of a sedimentary rock as well as igneous, and the hydrothermally altered rock that is found at most volcanoes is metamorphic, only actual liquid or recently cooled magma is completely igneous I guess.
Along that line…
I have been interested in the Tsunamis that followed the impact. There are areas of the ocean that received no Tsunami at all.
It just depends on the directions of the waves.
The sedimentary limestone over the granite that the asteorid hit is a thin layer
The silicate stuff the granite basement rock as well vaporized and melted
The carbonate cover on the granite was destroyed instantly into gas
At 20 000 C everything will turn to gas vapour at the impact site
Research I would nominate for an ignobel award. Four volunteers washed one arm with a particular brand of soap and left the other arm unwashed, before being subjected to the kind of mosquitos that spread yellow fever. It turned out those mosquitos did not like a soap called ‘Native’: the mosquitos went for the unwashed arm. But for the soaps called ‘Dove’ and ‘Simple Truth’, the mosquitos went for the washed arm in preference over the unwashed one. Just so you know..
Name of the soap the mosquitoes hate?
I did say.. it has the name ‘native’. And yes, that is a terrible name for advertising purposes.
During this pause in volcanic discussions, I thought that it might be a good time to bring up an earthquake question that I’ve been wondering about for years. Do any of you earthquake gurus have any idea why there is an almost constant earthquake swarm near the North American / Caribean plate boundary just north of Puerto Rico? I don’t know of any other location with such consistent activity near a plate boundary, although my view of earthquakes is somewhat skewed by the USGS earthquake map, which shows quakes down to magnitude 2.5 near US locations and only down to magnitude 4.5 in all other areas.
I was also interested to know why there seems to be a connection between these quakes near the plate boundary and the larger quakes farther south in Puerto Rico. After the Jan 6 5.8 earthquake and subsequent large quakes, the activity to the north completely disappeared for several weeks and then slowly returned.
Puerto Rico is one of the most seismically active regions in the world.
The island chain is sitting on top of a microplate that’s being subducted at the Puerto Rican trench at somewhat of an oblique angle…hence there is a mismash of faulting of various types and flavors including several active transform faults.
As reflected by the frequent activity, faults typically do not store a lot of energy before releasing (usually in the M2-M4 range), but on occasion, quakes in the 7’s are known to occur.
Here’s an article I dug out of my library that gives a nice layman’s overview.
Thanks, Craig. That was an interesting article. It mentions a planned follow-up, but I couldn’t find any relevant later article that included Rosetta Stones in a Google search.
You also mentioned some times the highest mountain of Mexico which is a volcano: Pico de Orizaba. The last eruption was a VEI2 in 1846. It did both explosive and effusive eruptions, maybe a bit more effusive than Popocatepetl? It lies on the east end of TMVB. How does this situation influence the behaviour of Orizaba?
We got an update on Mount Edgecumbe today. The rate of inflation and location has changed. The rate of inflation has increased.
Interesting paper made this year on the activity: https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2022GL099464
Looking at the insar data in the tweet, it looks like the inflation slowed significantly in the past few months, doesn’t mean the volcano is finished though.
Aniakchak and Trident are more likely to deliver an eruption in the near future. The formerly deep swarm is shallowing at Trident and from the look of it, Aniakchak is doing something similar to Edgecumbe just much faster and much more intense. (Last time we got an update, Aniakchak is rising 20x faster than Edgecumbe)
Interesting year for the Aleutians for sure.
Would an Edgecumbe eruption be similar to Chaiten 2008?
Mount Edecumbe is a basaltic andesite in TAS diagrams, and souch lavas are often quite fluid think Nishimoshima. More viscous than Etna.. but still fairly fluid. Depending on temperatures it can be really fluid like Villaricca to medium high viscosity like Santorinis Nea Kameni
Depending on gas content you can get a plinian eruption too, but edgecumbe wont form any lava domes as magmatic viscosity is too low. But I guess you gets huge tephra rich lava fountains and spiney Aa flows 🙂