During the time of our “transition” we had hoped all volcanoes would have the decency to wait until we are ready, yet alas, the Piton de la Fournaise, the name is French and means “Peak of the Furnace”, couldn´t hold on and let go on 4 February.
Google map showing the location of Reunion. Grab and move.
PITON DE LA FOURNAISE and its geological Setting
The Piton is a very active basaltic shield volcano on the eastern part of French island Réunion (63 km long) in the western Indian Ocean. Many of its earlier eruptions overlapped with those of Piton des Neiges, a shield volcano NW of it. Three calderas with numerous pyroclastic cones formed at about 250,000, 65,000, and less than 5000 years ago by progressive eastward slumping of the volcano. Dolomieu, a 400-m-high lava shield that has grown within the youngest caldera (which is 8 km wide and breached to below sea level on the eastern side), has been the most active part of the Piton in recorded history.
In the context of the Western Indian Ocean, the submarine plateau of the Mascareignes constitutes the area North to the Seychelles with Mauritius, delimiting the trench of the Mascareignes to the West (-4000 to -5000 m), that of Madagascar/Maurice in the South (-4000 with -5000m), and to Rodrigues in the East (-5000 m). On Réunion, the coral reefs are very localised covering part of the Western littoral. The lack of a continental shelf means that the sea quickly becomes deep not far from the coast.
Reunion island is the result of volcanic activity which begun
around five million years ago. Lava erupted from a hot spot in the oceanic crust to form a huge cone rather like a worm cast. It is thought that an island eventually emerged from the sea around three million years ago and gradually, with successive eruptions and much erosion became the island that is still evolving today. Two million years later, the first volcanic mass, the Piton des Neiges, was created. Deep under the ocean the “volcano” forms an immense cone with a base of 200km and a total height of about 7000m. The island, being located above a hot-spot in the Earth’s crust, is slowly, and imperceptibly, moving. It is made up of two distinct volcanoes – the Piton des Neiges (Snow Peak) which is now extinct and the younger and more active Piton de la Fournaise. [reunionisland.fr]
OVPDLF reported that 180 earthquakes at Piton de la Fournaise were recorded from 04.00 to 09.00 on 4 February. A seismic crisis began at 09.10, tremor was recorded at 10.50, and an eruption began at 11.00. Seven hours, this is quite short a time to make preparations. Then observers noted that a fissure had opened on the south flank, triggering an Alert Level 2-2 and the restriction of access by the public to the summit area. The fissure was 500 m long, starting from an area located 100 m outside and to the west of Bory Crater. Activity was concentrated on the southernmost part of the fissure. Lava was ejected from the vent about 10 m high and rapidly flowed SSW towards the Rivals Crater, branched, and spread in an area S and SE of the crater. By late afternoon the farthest-reaching branch had traveled past Cornu Crater. Through the rest of the day, tremor levels decreased to a relatively low level by 18.00 hours,
and from 6 to 10 February small cones had formed over the vents and produced low gas plumes. During that time lava continued to flow from the vents, and another flow traveled further west, while one vent was weakly active with small explosions and small splashes of lava.
5 February, helicopter aerial video from the Daily Motion
From February 10 – 15, the activity of Piton de la Fournaise is characterized by low tremor frequencies with slight changes but generally stable. Visibility was horrible due to bad weather most of the time, and a constant eruption plume did the rest. On the afternoon of the 15th, after some hours of jumps in intensity, the tremor died down. This marked the end of the eruption, even though a glow was still visible, which was probably due to still draining lava tubes.
Therefore, the ban on access to the top of the enclosure and helicopter landing in the volcano area remain in effect until further notice pending the recommendations and findings of volcanologists.
Erik Klemetti says: Even if the eruption didn’t have the longevity of something like Holuhraun in Iceland, it was an impressive event. The lava was able to build a small cone and a fairly impressive lava field during the course of the eruption.
Photographer Hervé Douris (see link below) got some great images of the eruption from an aircraft that show the network of lava flows flowing down the slopes of Piton de la Fournaise, some getting diverted by cones of previous eruptions.
WEBCAMS & NEWS
– http://www.fournaise.info/webcam06.php (super photos and info)
– Le Figaro
SOURCES & FURTHER READING
– IR Photography (photos)
– Iridium-bearing sublimates at a hot-spot volcano (Piton De La Fournaise, Indian Ocean) (paywalled)
– Volcaniclastic sedimentation on the submarine slopes of a basaltic hotspot volcano: Piton de la Fournaise volcano (La Réunion Island, Indian Ocean) (paywalled)
– Le Figaro
Great article, Granyia. Based on what I read and what I saw in the video, I’ll go out on a branch and predict that this will erupt again some day.
Very nice article Granyia
La Réunion island shows some older and eroded vocanoes (to the north of the island) – they gave birth to very impressive scenery (Cirque de Mafate) which are a paradise to hikers.
The piton de la Fournaise (meaning furnace) is very active. This time it seems the eruption was quite short. On one side of the volcano, up to the shore the land is empty. It is the “Grand Brulé” – great burned space.The volcano is very well monitored and the authorities forbade acess to the volcano a few days before the eruption as the seismic activity was ramping up.
For what it’s worth, it looks as though Bárðarbunga is going to go star-free for what I think is the first time since the current episode started:
I have been watching for that too, although we still have 11 hours or so before it drops off the chart
Indeed, for the first time since august 2014 there is now no stars on the Iceland seismic map on the IMO site.. The seismic part of this event seems to be tapering off markedly – will be interesting to see if the magma will stop flowing after subsedience stops… The activity in the dike seems to be fairly unchanged the last couple of months.
Congrats on the new blog btw and interesting articles! 🙂
I think you misread scale 🙂
Nope, we’re officially starless as of now. In fact, there’s nothing stronger than a 1.7
Do we end with a whimper, or a bang? Or maybe we haven’t ended at all; maybe the caldera floor has just hit rock bottom, but the magma inflow from deep will continue largely unaffected.
Is it only me, or has the Nornahraun vents stopped letting out visible gas/ash? It seems quite dead on the Mila 2 cam right now… I’m sure there is still magma coming up though.
Difficult to be sure but… it does look very quiet. If I squint at it I think I can still see magma glow reflected on walls of vent, but that’s about it.
Thank you Graniya. Very nice reading material.
Just had a confirmed 4.1. First M4 in a while.
Nevermind, hasn’t been too long since the last M4. Lol
Actually, the horizontal GPS measurements look like there might be some slight inflation at Bardarbunga. This is also an indication that the eruption may be ending.
Bravissima, Granyia! 🙂
How about the theories connecting the Reunion hotspot to the Deccan traps? Are they still valid? If that is the case we can expect a lot more coming from Piton…
Thanks Renato! Where did you see that theory? I never came across it when I researched for the article.
Hello Granyia: not really “theories”, rather the usual speculation around hotspots and mantle plumes: (Wikipedia: Réunion Hotspot) https://en.wikipedia.org/wiki/R%C3%A9union_hotspot
Nice article Graniya. It was a good read.
Hello everyone, and thanks for the new blog! Very interesting new article, too!
. . . not to mention wonderful photos.
Smithsonian weekly volcanic activity report 11 – 17 Feb is up. New activity mostly in Kamchatka, Central and South America, Reunion and Indonesia. Cheers –
Subsidence in Bard has stopped and even maybe started to reverse. this scenario was previously postulated by Jon and others to lead to a major caldera event. What is the opinion now among the more experienced in this site? Also, after 6 months of heavy seismic activity, could the ground be so fractured that no mor high energy quakes are needed or even possible when the region is kneeled by tectonics or magma movement? Like floating crushed ice compared to a solid ice sheet! what do you think?
Well, originally I thought that this would be Hawaii-like, with the caldera subsiding and the flank flow ending when the magma ran out. Then I saw that it could be Askja-like, with an eventual collapse of the caldera lid, leading to a violent caldera eruption. The flows have been subsiding at Holuhraun for a while, and the rate of caldera subsidence has concurrently slowed.
In order to have a violent caldera-forming eruption, the roof must entirely collapse, exposing the magma chamber, or it must be blown completely off. Neither of these appear to be happening at the moment. Therefore, I suspect this eruption will simply peter out. Slow inflation actually may signal the end. Grimsvotn, for example, began inflating as soon as its eruption ended.
This isn’t entirely the case.
If a large enough crack is opened, it could potentially depressurize the magma chamber, allowing the pressure to release. Also, there is potential for melt-water from the glacier to enter into the magma chamber through one of these destabilized cracks – henceforth resulting in a phreatic detonation, which may lead to more water, more depressurization, and so forth.
A caldera’s roof collapsing can only occur after the magma has left the chamber – the caldera eruption doesn’t necessarily happen as a result of that happening (Although there is typically a very large ignimbrite that comes as the collapse occurs).
Thanks for explanation! I do not know what is ignimbrite, links to read more?
Last 2 +4 quakes gave very different results on the icecap as judged by the gps readings. Why? The latter was much more shallow giving and was followed by a temporal rise of the gps station…..
Thanks Spica for very informative link. Now I understand more.
Interesting article about Bardarbunga in Bernard’s blog: http://www.earth-of-fire.com/holuhraun-decrease-in-seismicity-and-future-of-the-eruption.html
The SW to NE trending portion of the dyke looks like it is starting to build up some pressure, if one can look at the EQs along its path as an indicator. They’ve been there throughout the episode, but in the last couple of days that line on the IMO map (of EQs) is starting to get thicker.