Concepcion volcano is a 1,600 m tall stratovolcano that shares the Island of Ometepe with Maderas. The island sits in Lake Nicaragua, the largest lake in Nicaragua. It is both the tallest and most active volcano in the country, last erupting in 2014. The current series of eruptions are ongoing.
Its base above water is around 14 km in diameter. The volcano erupts basalt to andesitic dacite lava, tephra and pyroclastic materials. It upper slope is barren and was mostly built between 1883 and 1977. The cone occupies and almost completely buries what may or may not be a small caldera from its first eruptive cycle. http://link.springer.com/article/10.1007%2Fs00445-002-0256-8#page-1
The volcano has been very active, erupting over 25 times since 1883. Most of the eruptions were VEI 1-2 in severity. Eruptions are mostly explosive in nature. There are active fumaroles on the crater.
The Island of Ometepe is some 276 km2 in area, measuring 31 km by 5 – 10 km wide. The volcanoes occupy the ends of the island. There are nearly 30,000 people living on the island full time. Primary industry is livestock, agriculture and tourism. The island sits some 100 km SSE of Nicaragua’s capital of Managua and its 2.22 million people.
Nicaragua hosts some 19 volcanoes, six of which erupted over the last century. The volcanoes are part of the Central American Volcanic Arc or Belt.
The volcano grew within what is called the Nicaraguan Depression, which is a graben that extends some 800 km through El Salvador, Nicaragua, Costa Rica and into the Caribbean Sea. It is home to almost all of Nicaragua’s volcanic activity.
The graben contains the two large lakes, Lake Managua and Lake Nicaragua. Concepcion grew through Lake Nicaragua and sits on the thick sediment below the lake. It is referred to as having “feet of clay” as its base is built on lake sediments, clays and other strata. As such, it is structurally weak and the entire edifice is spreading outward from its center due to the force of gravity. This spreading also influences the evolution and behavior of its relatively shallow magma chamber.
Eruption styles range from full Plinian to sub-Plinian and most recently Strombolian. There are lava, domes, pyroclastic flows and tephra observed from historic eruptions.
Concepcion had two fairly large historic eruptions. The oldest was a VEI 5 some 19,000 years ago. That eruption produced some 5.2 km3 of material. It is referred to as the Upper Ometepe Tephra.
A more recent large eruption around 861 BC produced 0.1 km3 of material, about one tenth that Mount St. Helens did in 1980. That eruption is classified as a VEI 4. http://www.bgs.ac.uk/vogripa/searchVOGRIPA.cfc?method=detail&id=2502
Frequent eruptions since 1883 have all been in the VEI 1 – 2 range. They have grown the height of the cone and kept the upper half of the mountain barren of vegetation. They have also produced a lot of tephra deposited downwind. Prevailing winds are typically east to west.
Current activity has been explosive in nature, with over 2,400 explosions since the current round of activity started in 2014. Smithsonian GVP reports 117 explosions between 30 June – 7 July 2015.
The four known sequences of eruptions begin with a mostly basaltic series of eruptions. Over time as the magma cools and crystallizes, eruptions become increasingly explosive in nature until a new large injection of magma occurs and the cycle repeats. Early cycle eruptions are typically heavily basaltic and emit from the base of the volcano.
At the end of the first known cycle of eruptions, the VEI 5 eruption some 19,000 years took place. This may have left a small caldera which was refilled by later eruptions. The first eruptive phase started with low alumina basalt that evolved into dacitic magmas. The last three cycles have been fairly recent, over the last 2,500 years and are characterized starting with high alumina basalts and evolve to silicic andesites. Residence time of magma during the last three cycles appears to have decreased as magma has not had time to evolve from basaltic to dacite. Concepcion is thought to be near the end of its current eruptive cycle.
The other interesting thing about Concepcion’s eruptions is the slumping action of the volcano on its clay base. This is thought by some scientists to have modified the shape of the shallow magma chamber, thus triggering eruptions and shaping the nature of those eruptions.
The cone itself is riddled with fault lines and scarps. It is also capable of producing significant lahars due to the loose tephra that is produced on a regular basis. These lahars are caused by rainfall rather than melting of ice and snow.
To date, no cone collapse has been observed throughout its history which is somewhat odd considering its shape and height. The Borgia and Van Wyk paper suggests that due to the spreading of the edifice on soft underlying strata, forces that would make the cone collapse are relaxed and dissipated before they can come into play and tear the cone apart.
Tectonics of Central America is driven by the subduction of the Cocos Plate under the Caribbean Plate. There is a triple junction in southern Mexico with the North American Plate. There is another triple junction in the south with the South American Plate. Finally, Panama is referred in some locales as a microplate. The Middle America Trench sits offshore to the west. Over geologic time, the Caribbean plate pushed through the gap between North and South America.
The Central American Volcanic Arc / Belt are primarily back arc subduction volcanoes. As with all other complex regions, there is a twist. In the case of Central America, the graben called the Nicaragua depression opened up shortly after a significant ignimbrite outbreak in the region of El Salvador through Nicaragua to Costa Rica. This outbreak took place in the late Miocene some 5 – 15 million years ago and produced significant andesitic and dacitic material.
The area north of Concepcion has multiple calderas with fairly recent (in geologic terms) eruptive histories. One of the referenced papers believes the Chortis block which contains Nicaragua and is bound on the north by the Guayape Fault through Honduras is rotating counterclockwise, which in turn allowed the entry of magmas fueling the ignimbrite outbreak referenced earlier to the surface and opened up the depression containing the lakes, calderas and other volcanic structures.
The paper compared the opening of that depression with the opening of the depression that allowed the Toba magmas to reach the surface.
Concepcion is a case of a volcano that was built on a soft foundation. This has allowed the volcano to operate through several eruptive cycles without the normal sorts of cone collapses, debris flows and caldera forming events we normally see from other stratovolcanoes. When the entire edifice is slowly spreading, the normal structural loads that would catastrophically tear apart a volcano are released incrementally over time.
This slow spreading has also helped drive what is going on in a very shallow magma chamber, only a couple kilometers below the volcano itself.
Would not surprise me if this volcano were to be moderately active for many years to come.
Click to access CarretalAGU.pdf
Click to access 0deec51af968c670c3000000.pdf
Thank you Agimarc, great article again, lots of stuff new to me here. So the volcano is standing on it’s clay base like a donkey on ice with all four sliding in a different direction? This must mean that it becomes broader and the Island bigger over time.
Right idea, but it is a bit more complex, as when you introduce more volcano into the lake from above the lake, it displaces water. Don’t know what the shoreline looks like. At first glance, the island should get bigger as the volcano gets wider and shorter. But if the water level comes up a bit, it could even out.
The thing that worries me about this volcano is that it seems very well behaved. The way Murphy’s law works, is that if you say something won’t happen, it will happen instantly. What happens when it transitions to a new eruptive phase (basalt-heavy) is also unclear. Normally, when you introduce new basalt into a magma chamber full of crystal mush, it is the trigger for large eruptions. Why it doesn’t work that way with Concepcion has me scratching my head. Cheers –
I have made a timelapse from the Sinabung webcam over 3 hrs. The quality of the images is not good but it does show us what the people there have to endure all night long. Click to start, should open in a new tab, I hope it works.
Great article! This is one of the few volcanoes I have actually climbed 🙂 Lovely almost perfectly cone shaped volcano with lots of strongly sulfur-smelling small fumaroles on the way up (and also wild Jocote berries/fruits right after you exit the rain forest 🙂 The ascent was fairly steep with lots of loose gravel, but not that hard. We didn’t quite reach the summit crater rim though.
Omotepe is indeed well worth a detour (and not only for the volcanoes!) if you’re traveling through central america
Thanks, Tom. That is way cool. Cheers –
Preliminary! 16 minutes ago:
M 6.2/6.5 – Redoubt Volcano/Southern Alaska – 124/91 km depth – USGS/EMSC
Something is brewing there…
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Howdy Granyia – This one was strongly felt here in ANC. Initial thump rolled for a while which faked us into thinking it was over until the surface wave hit then it rolled for a long while. This is not under Redoubt. It is south of Iliamna in Cook Inlet and north of Augustine, very deep, though. My Lovely Lady is not happy. No damage or rearranged shelf items that I know of. Went on for a while.
Wouldn’t it be great to live in a country where the furniture rearranges itself every now and then? I always have to haul my sofa with my own bare hands…
Hmm… USGS has it 15 km south of Iliamna and ESMC 21 km NW of Iliamna, both on land. Both points are roughly 80 km away from Augustine and 55 km from Mt. Redoubt. If it weren’t for the the depth I would guess Iliamna is rumbling, but with over 100 km deep it sounds rather purely tectonic… or what do others think?
Howdy Granyia – Too early to tell. Its depth indicates tectonic. This last round of quakes have mostly been 100 km deep – the ones near Talkeetna NW of ANC and this one. One of the interesting things about this one was considerations of the Katmai – Novarupta eruption a century ago. Katmai is roughly twice the distance from ANC that this quake was. It produced 5 – 7 7+ Richter quakes. I wonder how strongly felt they were here a century ago. Cheers –
Hey, I’ve caught a bird again! On a webcam, that is – this time in Italy, near Napoli with Mt. Vesuvius in the background. Who would try an educated guess… or even knows what it is? First I thought it might be a bird of prey, but the beak is too straight, I think, and too reddish. A brown Seagull? A Skua perhaps? Any idea?
Ah, now we know! They are really good at the AVO!!
“Tuesday, July 28, 2015 8:30 PM AKDT (Wednesday, July 29, 2015 04:30 UTC)
The M6.3 earthquake that occurred this evening at 6:35 PM AKDT near Iliamna Volcano was tectonic in nature and not related to the volcano. According to the Alaska Earthquake Center (AEC), it was located about 9 miles (15 km) SSW of Iliamna, at a depth of 73 miles (117 km). This depth indicates it occurred in the subducting (downgoing) slab, as opposed to in the crust immediately below the volcano.”
Article out of the local fish wrapper on the quake follows. Cheers –
And the magnitude has been updated to a 6.46. Cheers –
Great new post by Erik Klemetti on the Eruptions blog (and follow up comment by Boris Behncke)
Thanks Michael, yes it IS a great post! And if Erik does have a head line like this it must be really, really important!
Yes, Erik is NOT one for baseless scaremongering
Sinabung is ablaze! I don’t know why, I guess the feared dome collapse has taken place, or at least a big chunk of it has come down. I have been watching for half an hour, and it always looked liked this.
I am making another time lapse, maybe that will tell us more.
Here it is. Yes it looks like a dome collapse event, with the debris still burning at the foot of the mountain. Click on it to start timelapse (opens in new tab).
Wow, the Piton de la Fournaise is fairly busy this year, it’s the third eruption I think!
Here are the images of two of the 4 webcams
Good morning/evening all! Here are some details from the Piton de la Fournaise eruption and a webcam image a few minutes ago.
From the Activity Bulletin of Friday, July 31 at 11:30
24 hours after lowering the alert level to 1, the Piton de la Fournaise erupted again on July 31, 2015 at 9:20 local. This eruption was preceded by a seismic crisis of 90 min and 80 min of major deformation. The eruption was confirmed by a hiker and by observation of a plume, recording a flow at the Piton Partage station and an observation by the OVPF from the Pas de Bellecombe. The crack is located in North East Piton Kapor and stretches to the Nez Coupe Ste Rose. Alert level: ongoing Eruption, 2-2.
From the Activity Bulletin of Friday, July 31 at 20:00
The eruption that began this morning at 9:20 local continues tonight. Although the level of tremor has decreased slightly throughout the day, the intensity of the event remains important. A long crack approximately 1 km opened during several hours on a flat topographic zone in the North East of the Enclosure at the Pitons Kapor and Payenké. These cracks produced a dozen fountains that tonight would be more than five. The longest lava flow reached this afternoon the Plain of Osmunds. Recognition and levies on site were able to be conducted with the logistical assistance of SAG (Air Section of Gerndarmerie)
Estimates of flow rates between 28 m3/s (first) and 11m3/s (thereafter) were produced from the gas measurements and are confirmed by satellite image analysis. The plume of volcanic gas reached tonight 3200-3500 m altitude. Alert level: ongoing Eruption.
(Google transl. – http://www.ipgp.fr/fr/ovpf/actualites-ovpf)
The small cinder cones piled up by the fountains are clearly to see, also occasionally some red-hot glow on the webcam (link above)
and some video footage from a local media (imaz press). The lava type is clearly aa.
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and some night video
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Very good, both videos, thanks dfm! The second reminds me of Holuhraun last September! 🙂 It seems that the fumes are not quite as toxic, as lots of people are walking near it in Reunion.
thanks, I found also the lava fountains were impressive.
it’s a bit misleading. Actually the volcano is a huge attraction on the island, I heard of more than 2500 vehicles per day going up the volcano (island population is around 800 k). But the acess is severely restricted, only volcanologit can go nearer.
Reunion was also in the news earlier last week due to part of a 777 found on the beach, reawakening the Malaysian Airlines Flight 370 search from a year and a half ago. Cheers –
Update Gunung Raung: After a decline in activity for the previous two or three days, volcanic tremor as well as visible action rose again to new record hights. Lava fountains could be seen of 300-400m above the caldera rim. (given that the caldera is 500 m deep, that makes the fountains up to 900 m high!). From satellite images it is thought that a new cinder cone has built up on the caldera floor. An airport in northwesterly direction of the volcano closed again yesterday.