Le Kaiserstuhl, un ancien volcan situé dans la plaine du Rhin, est connu pour ses roches volcaniques très particulières et extrêmement rares : les carbonatites. © cityfoto24, Adobe Stock

Discovering a very special volcano, the Kaiserstuhl

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[EN VIDÉO] Geology of volcanic systems – an invitation to travel
Interviews dating back to 2009 with Georges Boudon, a physicist at IPGP, and members of the team that studies how volcanoes work, from magma generation to eruptions. The vocation of IPGP films is to open the doors of laboratories and accompany scientists in the world of geosciences. This film is part of a series of 14 short films that are an invitation to travel from the cosmos to the center of the Earth. Design and production: Medi@terre, IPGP – 2009

Auvergne is not the only region that has a relief marked by relatively recent volcanic constructions. If you are passing through Alsace, take a detour to the other side of the German border. Between Colmar and Freiburg, right in the middle of this long depression known as the rhine ditchit is the Kaiserstuhl, in other words: the “Emperor’s Throne”.

Located in the southwest of Baden-Württemberg, in Germany, a few kilometers from the border, this mountain range is also linked to a volcanic history, dating back 16 to 18 million years.

A volcano in the Rhine plain.

Contrary to the chain of puys, the Kaiserstuhl appears to be a The study of volcanoes is volcanology or volcanology. Volcanic activity is one of…” data-image=”https://cdn.futura-sciences.com/buildsv6/images/midioriginal/d/c/f/dcfcbbf72e_125167_volcan-arenal-costa-rica. jpg” data- url=”https://news.google.com/planete/definitions/volcanologie-volcano-3537/” data-more=”Read more”>volcano lonely However, this is not really the case if we look at the region on a larger scale. This volcanic edifice is in fact part of the great province eruptive of central Europe, which has some other volcanoes, including the Eifel, located much further north.

The volcano is certainly not very impressive. Largely eroded during the last Origin of the Quaternary glaciations
The…” data-image=”https://cdn.futura-sciences.com/buildsv6/images/midioriginal/c/9/0/c9095f93f2_50015412_map-pleistocene-glaciation-north-arizona-university-dr.jpg” data-url=”https://news.google.com/planet/definitions/climatology-ice-period-1068/” data-more=”Read more”>ice Age, rises today to a maximum height of 557 meters and forms an ellipse of 16 x 12 km. As we walk along the slopes of the massif, certain rocks remind us, however, that we are indeed on an ancient volcano. It is these rocks that make the Kaiserstuhl a very special volcano that has long been an enigma for scientists.

Very rare volcanic rocks

if most volcanic rocks issued by the Kaiserstuhl is said alkaline due to its composition rich in alkaline components (soldier, potash) and low silica is a component of many minerals. It is thus found in certain whole foods, in bones and cartilage, for example. Bonded to other atoms (aluminum, magnesium, calcium, etc.), the…” data-image=”https://cdn.futura-sciences.com/buildsv6/images/midioriginal/0/2/9 /029e94324a_93543_silice .jpg” data-url=”https://news.google.com/planete/definitions/geologie-silice-15955/” data-more=”Read more”>silica (40 to 56% SiOtwo), some rocks found practically do not contain silica (only 0.28 to 5.07%). These last, called carbonatites, really mark the uniqueness of this volcano. In fact, they are composed of 95% of calcitea very rare composition for volcanic rocks that are often marked by silica dominance.

As a reminder, calcite is the mineral often found at the base of limestone and the marbles, with the difference that the calcite is then of sedimentary origin in the first case, and metamorphic in the second. Finding calcite of igneous origin is extremely rare and has long posed a problem for geologists studying the Kaiserstuhl site. Previously, the Kaiserstuhl carbonatites were further described as marbles resulting from a contact metamorphismthat is to say, formed by “cooking” of It is therefore composed of particles that have been dragged by the agents of erosion, and which are deposited in successive strata…” data-image=”https:/ /cdn .futura-sciences .com/buildsv6/images/midioriginal/2/6/1/261f67921e_47250_def-sediment-eutrophisationethypoxia-flickr.jpg” data-url=”https://news.google.com/planete/definitions/ paleontology-sediment-1045/ ” data-more=”Read more”>sediment limestone in contact with magma formation
It forms at high temperature and under high pressure…” data-image=”https://cdn.futura-sciences.com/buildsv6/images/midioriginal/6/1/2/612232a1f7_50034213_gabbro-piotr-sosnowski-wikipedia. jpg” data-url=”https://news.google.com/planete/definitions/structure-terre-magma-461/” data-more=”Read more”>magma hot.

It is true that we know of very few examples of volcanic carbonatites in other parts of the world, barely a hundred. The volcano Oldoinyo Lengai in TanzaniaIt is currently the only active volcano that emits this type of washalthough the composition of its carbonatites is not exactly the same as that of the Kaiserstuhl.

Where does this singularity come from?

The origin of carbonatites is still debated. Two hypotheses collide. The first advances the fact that carbonate magmas form directly in the The mantle, although solid, is animated by convection currents that…” data-image=”https://cdn.futura-sciences.com/buildsv6 / images/ midioriginal/7/4/6/7466fb8049_50004180_terre-270907.jpg” data-url=”https://news.google.com/planete/definitions/structure-terre-manteau-terrestre-2495/” data-more = “Read more”>earth’s mantlein the same way as “classical” silicate magmas, that is, by partial fusion Ultrabasic and granular in nature, it is essentially composed of olivines and pyroxenes, as well as spinels (picotites, chromites), garnets, plagioclases, amphiboles and phlogopites. The…” data-image=”https://cdn.futura-sciences.com/buildsv6/images/midioriginal/7/a/7/7a798143f4_45467_def-peridotite-brewbooks-flickr.jpg” data-url=”https ://news.google.com/planete/definitions/structure-earth-peridotite-1572/” data-more=”Read more”>peridotites. The difference is that the mantle was previously enriched with COtwo and in Symbol: Ca
Atomic number: 20
Electrons per energy level: 2, 8, 8, 2
Atomic mass: 40,078 u
Most stable isotopes: stable 40Ca with 20 neutrons (96.941%), 42Ca…” data-image=”https://cdn.futura-sciences.com/buildsv6/images/midioriginal/e/b/f/ebf2092c20_50154349_calcium . jpg” data-url=”https://news.google.com/sciences/definitions/chemistry-calcium-5069/” data-more=”Read more”>calcium after intense fluid circulation, and with a very low degree of fusion: that is, only a few minerals of the mantle will melt, to form a magma with a very specific composition that, when cooled on the surface, will give carbonatites.

The second hypothesis suggests that the carbonate magma comes from the fractional crystallization from a magma source rich in COtwo and calcium, inside magma chambers and volcanoes
Coming from the Earth’s mantle through one or more conduits, the accumulated molten rock can…” data-image=”https://cdn.futura-sciences.com/buildsv6/images/midioriginal/d/d/9/ dd921d8236_45733_def -semhur-volcano-magmatic-chamber-wikimediacommons.jpg” data-url=”https://news.google.com/planet/definitions/structure-earth-magmatic-chamber-451/” data-more=”Read more “>magma chamber. In fact, it is common to observe this differentiation process during the rise of the magma: it separates into two liquids magma of different composition that will follow different paths in the continental crust forming, as its name indicates, the continents. It is essentially from…” data-image=”https://cdn.futura-sciences.com/buildsv6/images/midioriginal/7/d/1/7d1ca441ac_44707_def-epaisseur-croute-terrestre-usgs.jpg” data- url=”https://news.google.com/planete/definitions/structure-terre-terrestrial-crust-2491/” data-more=”Read more”>Cortex. The two hypotheses are not, however, incompatible.

The visit to the Kaiserstuhl is an opportunity for a beautiful walk in the vineyards presented in Description of the terrace
A full-fledged architectural element of a building, the terrace is always found outside of buildings, whether on the ground floor (as in most…” data-image=”https: //cdn.futura-sciences .com/buildsv6/images/midioriginal/9/e/3/9e38056ed3_50037627_terrasse-zigazou76-flickr-cc-by-20.jpg” data-url=”https://news.google.com/house/definitions/terrace- house-10934 /” data-more=”Read more”>terrace on the slopes of the ancient volcano.

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