Tenerife is part of the Canarian archipelago. These islands are located in the Atlantic Ocean, not very far from the coast of Morocco. There are 7 islands, which are Lanzarote, Fuerteventura, Gran Canaria, Tenerife, La Gomera, La Palma and finally El Hierro. All islands are of volcanic origin and the main hypothesis of formation refers to a magma hot spot leading to the formation of the islands. I have had the chance over time to visit several islands (Lanzarote, Gran Canaria and lastly Tenerife). Of course each island has its own charm and interest, but I must admit that Tenerife has left me with a stronger impression.
The variety of landscapes, type of lavas, volcanic cones, lava fields is really impressive. Also the fact that, even in the national park, one can go roughly as he pleases is to be taken into account (In Lanzarote, for instance, you cannot take a walk on the lava fields in the national park).
So here is my account of a visit made to the Cueva de los Vientos.
Context:
The Cueva de los Vientos is located in the village of Icod de los Vinos, on the west side of the island. It has been proposed as a touristic attraction since only a few years (I think 2009). First there is a quick presentation by the guide of the volcanic origin of the island, and some explanations on how lava tubes form and of the different type of lavas produced by the Teide (A’a and Pahoehoe in this location). Then the tour continues with the visit itself and begins with a short trip by minibus to the cave area.
The guide shows different types of lava on the site and then we proceed with the visit of the cave using an old bridle path to get access to the cave.
Example of Pahoehoe lava – photo by author
The Cueva del Viento itself is a very large structure (the largest of its type in Europe) with a cumulative length of about 17 kilometers. Only 200 meters are open to visit.
The formation of the cave (or caves) dates back to a Pico Viejo eruptive episode about 27.000 years ago.
The visit allows to see many volcanic features related to lava tubes.
photo by author
Hard hats and spelunking type lights are supplied, there is no artificial lighting in the cave.
photo by author
Details from the tube’s ceiling with solidified drops of lava.
photo by author
Inside the tube – note the different heights of the floor showing different periods of the eruption with diminishing lava flowrates. The width of the canal is about 2,5 meters.
photo by author
A side tunnel – there are several lava tubes in this network. Note the texture of the floor, which is quite irregular and shows the lava flow when it cooled down and solidified.
photo by author
Two tubes converge.
photo by author
Here one can very clearly see different phases of the eruption with diminishing lava height.
photo by author
This is a fallen section of ceiling showing a Pahoehoe pattern. This shows the tunnel formation mechanism in which lava cools in surface and continues flowing underneath in the newly formed tunnel. Sometimes the ceiling falls after a time. In that case the event happened after the lava flow stopped in the tunnel. In the area there can be several layers of lava tubes all piled up a bit like tunnels for subway systems.
The visit finishes off with some time in the dark to feel the atmosphere of the cave (in which some specific fauna can be found). The visit finishes by a return to the visitor center by minibus looking at A’a type lava flows.
You can find all the information needed on the website. Some visits are in English, German, French or Spanish, depending on the day of the week.
dfm
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As Inge B. mentioned, please note these posts about the Lanzarote lava tubes by ukviggen:
Recently Nathan took you on a comfortable journey into the Eifel volcanic field. But what is the origin of this intraplate volcanism and where will the journey go?
About 400 million years ago during the Devonian, the Age of Fish, when only plants and insects roamed the land, Laurussia and Gondwana converged into the supercontinent of Pangaea forming the European Variscan Belt. It includes vast mountain ranges stretching from Portugal to Turkey. The Rhenish Massif in central Europe is one of the outcrops of this period, others are the Massif Central in France or the Bohemian Massif in Czech Republic and Poland.
The Rhenish Massif is mainly made of highly folded sedimentary metamorphic rocks, mostly slates, hence the name “Rheinisches Schiefergebirge” or “Rhenish Slate Range”.
Geological map of the Rhenish Massif. Author Jo Weber (Wikimedia Commons)
When the Age of the Mammals dawned and Africa started to collide with Eurasia, a whole lot of volcanic activity started north of the rising Alps. This belt was termed European Cenozoic Volcanic Province by Meyer and Foulger. In the Alpine forelands extensional rift systems developed with the Rhine graben as a prominent feature. Volcanic activity of that period can be found in France (Massif Central), Germany (High Eifel, Westerwald, Vogelsberg, Rhön), The Czech Republic (Eger graben) and Poland (Lower Silesia).
The ductile and tough shale and slate bedrock of the Rhenish Massif presumably was incompatible with extensional rifting. Instead the region acted as a hinge between shear rifting along the Upper Rhine Graben and extensional rifting at the Lower Rhine Basin (Illies et al. 1981).
The Eifel volcanic field is situated west of the Rhine river near Koblenz in the center of the Rhenish Massif. Fluvial deposits prove that this area was uplifted up to 300 m since the Pliocene epoch 5 million years ago and that the uplift had accelerated during the last 800,000 years with maximal elevation around the Eifel volcanic field. Since then the Rhine river and its tributaries were forced to cut deep valleys through the Rhenish Massif, flowing past Hunsrück and Taunus, Eifel and Westerwald, Ardennes and Süder Uplands.
The most recent volcanic activity in the West and East Eifel volcanic fields coincides with this uplift which amounts to 0.35 mm per year on average. The dome building may be a combination of widespread uplift of the so-called Rhenish Shield due to horizontal deformation from Alpine orogeny (Illies et al., 1979 and 1981; Meyer and Stets, 2002) and more locally by uplift due to the Eifel mantle plume (Schmincke, 2007).
To study the deep structures of the Eifel region the Eifel Plume project temporarily deployed a large network of seismic stations in 1997. A shear wave velocity model suggested a 100 km wide low-velocity structure extending down at least 400 km into the upper mantle which could indicate an area of increased temperature and partial melting. It remains debated whether this anomaly caused the Eifel volcanism. Other volcanic areas of the European Cenozoic Volcanic Province lack clear evidence of deep mantle plumes and the spacial distribution and timing of eruptive phases is not consistent with movement of the European plate over a fixed hot spot.
Alternative models could be a magma source derived from previous Alpine subduction or local decompression melting from passive rifting caused by tectonic deformation of the crust. Notably, the Mohorovičić discontinuity (Moho) is only 30 km deep below the Eifel while under the Alps it goes down to about 50 km which could give rise to some mantle turbulence and convection.
South-North section of the Moho beneath Europe between 6 and 9° longitude. Depth is highly exaggerated (Image by chryphia). Data from www.seismo.helsinki.fi/mohomap/
There is an overwhelming amount of literature about the recent quaternary activity of the 300+ volcanoes in the Eifel, sadly most of it paywalled or even without online access, because published in books or exotic German journals. So the following is taken from secondary literature. The eruptive history was e.g. summarized by Schmincke in Mantle Plumes (2007), Schmitt et al. (2010) (see Fig. 1 here for a map of geological map of the East Eifel volcanic field) and is nicely illustrated in this German blog post.
In summary, there seem to have been at least four main eruptive phases:
700,000 to 450,000 years before present: the main bulk of monogenetic volcanoes, small cinder cones and short lava flows erupted in the West Eifel and late some in the East Eifel. Their lava contained leucite (potassium rich) basalts, poor in SiO2, indicating an upper mantle source.
The West Eifel then fell dormant for several hundred thousand years.
430,000 to 360,000 years before present: In the East Eifel the Rieden complex (“Riedener Kessel”) west of the Laacher See had its most productive episode sputtering out several cubic km of lava in larger cinder cones and kilometer long phonolithic lava flows out of a 4 km diameter caldera system.
215,000 to 190,000 years before present: In the East Eifel the Wehr volcano (“Wehrer Kessel”, a 2 km diameter depression) west of the Laacher See and many large scoria cones in the Neuwieder tectonic basin erupted several cubic km of dense rock equivalent. The lava was highly differentiated phonolitic and rich in SiO2, indicating that country rock had been partially melted. During this time the first Maars were blasted out of the West Eifel volcanic field.
100,000 to 10,000 years before present: the West Eifel field was peppered with Maars still erupting the original lava, the last one to be the Ulmener Maar. Simultaneously, a new kind of lava, basanites, poor in potassium, hence leucite free, presumably from the asthenosphere, created large cinder cones and lava flows sometimes right next to the Maars (e.g. Meerfelder Maar next to the Mosenberg).
In the East Eifel only the Laacher See erupted 12,900 years ago, without doubt the most powerful eruption of all time in the Eifel probably equalling the total output of the West Eifel volcanic field. The Laacher See erupted more than 6 cubic km of magma within days, with an at least 25 km high eruptive column spreading tephra from Italy to Sweden. The magma is thought to have differentiated over several thousand, possibly tens of thousands of years, showing zonation from mafic to evolved phonolite and carbonatite. Pyroclastic flows temporarily built a dam in the Rhine river which eventually broke unleashing torrential floods, illustrated here (in German). Finally the emptied magma chamber collapsed leaving this recreational lake.
The “Loch Lochy” of Germany, the Laacher See. Image by USEBlackbird (Wikimedia Commons)
So the Eifel volcanism occurred in tens to hundred thousand years periods intermitted by hundred thousand years of dormancy. There was a general trend of eruptions starting in the NW progressing to the SE. Eruptions became increasingly voluminous and explosive with time and there was a shift of lava from an upper mantle source to partially melted crust.
Today the Eifel volcanism is dormant. As already featured in Nathan´s post abundant CO2 emission is a sign that the Eifel volcanic field is not extinct. But also seismically the region is active. Earthquakes during the past 36 years are almost exclusively confined to the upper 15 km. There is no indication of magmatic origin so far. The highest earthquake density is east of the Laacher See and west of the Neuwieder basin along the Ochtendunger fault zone on a NW to SE axis, aligned to the general tectonic setting in the Rhenish Massif.
Recent earthquakes (Sep 2012 to Jan 2013, green, enlarged) and earthquakes dating back 36 years recorded by the seismic station Bensberg, University of Cologne. Image by chryphia.
And here a 3D plot:
Since 1975 up until January 2013 over 1180 local earthquakes were reported by the seismic station Bensberg (University of Cologne) with some increased frequency in the last years.
Earthquake data from the seismic station Bensberg from 1975 to 2013 (between 5.21 and 5.472° lat and 7.25 and 7.65° lon, as in 3D plot). Image by chryphia
Helium and other noble gases that are found in high concentrations around the Laacher See are indicators of the volcanic origin of the Mofettas. Helium isotope 4 (4He) is naturally formed in earth´s crust. Another rare Helium isotope, Helium 3 (3He), is produced by fission and bombardement with high-energy cosmic rays, so what we find on earth was created before our solar system formed. In the atmosphere it escapes into space. Looking at the 3He to 4He ratio in volcanic gases relative to the ratio in earth´s atmosphere (Ra) gives a clue about the source of the magma. If it´s of deep origin, it still should contain relatively high 3He. The 3He/4He ratio measured from Mofettas from the Laacher See is 5.5 Ra, indicating an upper mantle source, but it is less than measured at mid oceanic ridges (8 Ra), thus there is mixing with 4He from the crust.
So there we are today. Was this the end of it for the next 100,000 years? As long as the Brubbel squirts and the earth rumbles occasionally we can´t be sure of it. Maybe the ants will tell us one day.
Tufa Outcrops, Mono Lake. Image from Wikimedia Commons.
We had 2 weeks in California; after a weekend in San Francisco and some chillaxin’ by the pool in Sacramento; we took the roadtrip of a lifetime. (many thanks Val x) We visited Lake Tahoe, Mono Lake, Yosemite, Mariposa and drove back to Sacramento via Route 49; the gold rush route…
Trees were more my thing in those days, I armed myself with Stuart and Sawyer’s Trees and Shrubs of California; (ISBN 0520221095) bought for $8 in a second hand bookstore in Berkeley and managed to tick off a fair few… Including this baby:
The Grizzly Giant, species: Sequoiadendron giganteum. From Wikimedia commons.
Statistics: 63.7m high (somewhat truncated by a lightning strike, I guess…) Circumference at ground level: 29.5m, Diameter at 1.5 m from the ground: 7.8m, Estimated bole volume: 963m^3 and old enough to have lived through the action described below!!!
It wasn’t much of a mishap, more of an oversight… We were visiting because my girlfriend (at the time) had seen a picture; something like the one above, and had fallen in love with the desolate beauty of the place. So we went and looked around; we saw the tufa rock formed by accretion of materials at hydro thermal vents and exposed when Los Angeles began tapping Mono Lake’s tributaries; the lake itself is highly saline/ alkaline. We saw Black Point, formed under a much deeper Mono Lake 13,000 years ago; now a flattened cone of basaltic debris. We had a good long look at Negit Island; built by several eruptive episodes between 1600 and 270 years ago. We goggled at Paoha Island created by a magmatic intrusion under the lake between 1720 and 1850; it has an exposed section of rhyolite and 7 (count em’) dacite cinder cones! There was a seismic swarm in 1980 including EQs of up to 6mag (estimated, richter scale) and another in the nearby White Mountain fault in 1986.
Mono Lake is not the whole story; to the south there are a series of domes, coulees, flows and craters stretching all the way to the Inyo Craters; many of these were formed in a series of violent eruptions ~600 years ago. When I say violent I mean phreatomagmatic explosions followed by the opening of a 6km multi- vent fissure, pyroclastic flows affecting the Mono Lake area and then (geologically shortly afterwards) a virtual repeat 40 kms south at the Inyo Craters, followed by coulee and dome building!!! The remaining features are thought to have arisen in the last 2000 years. Mammoth Mountain and the Long Valley Caldera are nearby… Quite a piece of volcanic real estate, I think you’ll agree:
The Big Picture… Approx 50kms top to bottom. Wikimedia commons again.
“Comparison of risk from pyroclastic density current hazards to critical infrastructure in Mammoth Lakes, California, USA, from a new Inyo craters rhyolite dike eruption versus a dacitic dome eruption on Mammoth Mountain” Kaye et al (2009)
“THE GEOCHEMISTRY OF THE INYO VOLCANIC CHAIN: MULTIPLE MAGMA SYSTEMS IN THE LONG VALLEY REGION, EASTERN CALIFORNIA” Daniel E. Sampson and Kenneth L. Cameron (1987)
Send your urgent and much needed donations for those poor unfortunate endotheworlders who were not wiped out (they must be devastated) to schteve’sschwissbanking.ch
Please spare a thought and a dime for those not raptured up to heaven in the recent non- apocalypse; give generously, it’s nearly christmas after all…
Since this didn’t happen everywhere all at once…
I intend to set up a refuge high in the hills of La Gomera with a nice piece of (terraced) land and a look out tower; we’ll charge post 2012ers top- whack to come and contemplate… Me n’ Lizzie will be there most of the year looking after the goats and generally taking care of the place (and going for long walks and jaunts to El Hierro and stuff.) So once again Volcanocafers please dig deep for this very worthy cause…
Somewhere like this, Pico del Teide is in the distance…
But seriously, and since we are still here; a genuine appeal (and some of my highlights):
This rather special place was started by Carl and Ursula after a group Volcanoholics decided they wanted their own place with their own rules… Those that wanted to go multidisciniplary, collaborative and friendly came here and (boy!) the discussion was, and still is, far ranging… The Welcome page and blog rules are here:
The average post rate is ~ one every 3 days, (that includes before and after Carl statistics…) some volcanoblogs manage more, but usually these are brief updates. What we get here are crafted pieces, made by amateurs in their spare time…
The hit rate is around ~150 visits per hour; this doesn’t include dragon visits…
I won’t lie to you; a blogpost can be quite a bit of work, depending on your skills… Carl once mentioned that he could write a 1200 word opera review in 20 minutes, and Geolurking seems to be able to get something revolutionary on tectonics done in only slightly more time…
Birgit deserves her own paragraph; she can research, compile, edit, post and get an intelligent layman up to speed on a particular subject in less time than it takes a crocodile to swallow an unwary victim!!!
Me? I’m at the other end of the scale; maybe 20 hours work on Teneguia Technicalities and Context, but that did include editing with wordpress which was a first for me… Don’t let me scare you, I can be quite ambitious…
I am asking everyone to keep the posts coming; think of it as an extended comment and you will do fine…
This one’s for our resident geologist… The little engine that could x
Visits to volcanoes “a la Ukviggen” are always popular; (Mount Snowdon anyone? The narrow gauge, rack and pinion railway is the only one of it’s kind in the UK.) as are summaries of your favorites; (Karenz on Sakurajima is a very good example.) and memories of eruptions that were special to you; (Bobbi’s piece on Redoubt is a classic, and don’t forget Newby’s uncle on Erebus.)
Ascending eruption cloud from Redoubt Volcano as viewed to the west from the Kenai Peninsula April 21, 1990 (R. Clucas)
For the more ambitious how about an original piece of research? (Irpsit wrote a fascinating series about a big hole!!!) Controversial stuff is great, got an alternate theory? (Peter Cobbold on El Hierro is excellent.) What about something inter- disciplinary? (Diana Barnes on Scheeps helping to revive volcanic badlands is wonderful!) Technicalities more your bag? (Wagabond on marine seimic sounding; great insights.) Plotters, hows about “beefing up” a special plot? (Plotting for Beginners 2 may get done one day, but feel free to jump in!!!)
One of Birgit’s awesome SEM images of material from El Hierro…
If none of these inspire how about something outrageously off topic for the Scheeepy Dalek?
Nothing is like the smell of a Motorcade in Depresneyville in the morning. Remember that when people shoot at you, they just wish to greet you welcome to Ukraine.
So please, go and do yr research, track down the info on yr chosen subject and write something up… Include the standard Volcanocafe disclaimer and a reasonable list of references; and you’re done…
Posts are best submitted as plain text word documents; attached to an email. Pictures should be separately/ individually attached; most formats are fine but please no psd, crw or nef (they are too big and probably not supported by WP either; they need to be converted first). Jpg, gif, png, tiff are commonly supported formats and will do well.
However; when I asked Sissel about this, she said: “Just send it, I will edit what is neccessary!” (another inspirational blogger; remember The Little Prince?)
Have you ever made a comment that you (later) wished you’d saved for a guestpost? Then we want to hear from you; (give us as much detail as possible: approx dates, subject, etc. and we will go digging) dragons can search all 70,000 comments and extract that moment of inspiration…
My top tip (I know it’s environmentally unfriendly) is to print out the papers that you are really interested in; the references for yr article; that kinda thing…
Posts and comments are the lifeblood of the blog, there are (almost) no stupid questions or statements.
So there you have it, no more excuses for not handing in your homework!!!
A quick re-cap: Sakura-jima is a post-caldera cone of the Aira caldera. She emerged roughly 13,000 years ago on the southern rim of the caldera, building an island which was eventually connected to the Osumi Peninsula during the eruption of 1914. She is located near the junction of several tectonic plates, whose movement drives eruptive activity.
Sakurajima’s lavas have tended to be andesite – dacite. But she has produced effusive lava flows.
Lava rocks along Nagisa Lava Trail on Sakurajima, Jakub Hałun, 2012, Wiki Commons.
In 1914, lava’s filled the strait between the island and the mainland. The 1914 eruption started as explosive with an eruption column and pyroclastic flow. Effusive lavas were produced later after a large earthquake. During the later stages of the eruption the centre of the Aira Caldera sank which seems to indicate that lava is sourced from a common reservoir. Other effusive eruptions occurred in 1471 (believed to be her largest recent eruption), 1779 and 1946.
Kagoshima covered in ash. NYPL Picture Collection — Illustrated London News, 1914, Wiki Commons
A study by Goto, H Ishibashi, T Yanagi looked at the temperatures of her dacite lavas. The temperatures appear to be a consistent (850°C) with few magmatic inclusions in the lavas. The lavas contain phenocrysts of plagioclase, clinopyroxene, orthopyroxene and magnetite. These show a bimodal distribution of plagioclase phenocryst compositions. This implies a) injection of basalt magma into the resident magma chamber; and, b) the magmas are well mixed before eruption.
Yanagi et al (1991) had found that the lava flows became more mafic with time from an initial dacite composition. They proposed a two chamber system with a plagioclase pyroxene plug separating an upper dacite chamber from a lower basalt chamber.
Nagel et al researched this further looking at 12,000 years of eruptive history. They discovered that there was a cycle of mafic and more felsic lavas prior to the 1471 eruption. After the 1471 eruption the mafic content of lava has increased to 55% of the dacite lava showing magma mixing. They propose a shallow dacite magma chamber which is repeatedly flushed with mafic magma from a deeper chamber.
Since 1914 Sakura-jima has been relatively quiet; eruptive activity has been mainly ash, lava bombs and gasses, which may or may not be accompanied by earthquake activity.
