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Imaggeo on Mondays: Mola de Lord

Imaggeo on Mondays: Mola de Lord

From the easterly Atlantic waters of the Bay of Biscay to the Catalan wild coast (Costa Brava) in the west, the Spanish Pyrenees stretch 430 km across the north of the country. At the foothills of the Catalan Pyrenees you’ll find the Pre-Pyrenees. Despite not reaching the soaring heights of the peaks of the Pyrenees, they nonetheless offer important insights into the geology of the range and stunning panoramas, such as the one featured as today’s Imaggeo on Mondays image. In today’s post, Sarah Weick, a researcher at the Georg August University in Göttingen, explains why the foothills of the mountain belt are a structural geologist’s playground.

The picture was taken from the top of the flat-topped mountain ‘Mola de Lord’, with a beautiful view over the turquoise-blue water of the river Cardener and growth folds, characterised by a significant increase in throw with depth, caused by their syn-sedimentary development The over 1000 m-high mountain belongs to Vall de Lord, close to the Sant Llorenc Growth Structure, formed of folded sedimentary rocks of marine and continental origin that developed from Eocene to Oligocene and display local angular unconformities (where horizontally parallel sedimentary rocks are deposited atop previously tilted layers). Moreover, it is excellently preserved as a structure in the footwall of the Pyrenees and helps to understand how sedimentary deposits are reorganized during the development of a syn-sedimentary growth structure and how they may distribute between the foreland basin and the mountain belt. Outcrops on the mountain top are of conglomeratic composition with clasts and fossilized nummulites – lense-shaped single-celled sea creatures with shells that lived from Paleocene to Oligocene.

As a geologist, Mola de Lord is not the only remarkable location in Catalonia. On a greater scale, the table mountain belongs to the Spanish Pyrenees. There, hikers can experience parts of untouched nature, and witness the mountain’s geological past: from eroded carbonate karsts with unique shapes to the Ebro basin.

The Pyrenees are located in southwest Europe on the border between France and Spain. The Upper Cretaceous to Miocene collision and subduction of the Iberian microplate under the European plate initiated the orogeny, which went through two main phases. The tectonic changes during the Alpine Orogeny that started 66 Ma ago and some earlier Jurassic activity, caused a compressive regime and thus produced a lot of pressure that caused folding on different scales and the continuing orogenic growth. Deformation occurred also after the collision. The orogenic basement can be described by inherited folded formations over a granitic basement.

 By Sarah Weick, researcher at the Georg August University in Göttingen.

 

Imaggeo is the EGU’s online open access geosciences image repository. All geoscientists (and others) can submit their photographs and videos to this repository and, since it is open access, these images can be used for free by scientists for their presentations or publications, by educators and the general public, and some images can even be used freely for commercial purposes. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. Submit your photos at http://imaggeo.egu.eu/upload/.

Imaggeo on Mondays: Dragon Blood Tree

Imaggeo on Mondays: Dragon Blood Tree

On a small and isolated island in the Indian Ocean you’ll find an endemic population of Dragon Blood Trees (Dracaena cinnabari). Burly, with an interesting umbrella-shaped fractal canopy, these unique trees are a sight to behold.

To see them for yourself, you’ll have to travel to the little known Socotra archipelago. Off the coast of Somalia, but belonging to Yemen, the group of islands boast an impressive assortment of endemic plant life, making them know as the ‘Galapagos of the Middle East’.

Crucial to the uniqueness of the flora and fauna of the archipelago is Socotra’s geographical position and how it came to be there. The African plate extends out from the Horn of Africa, east of the Guardafui graben, in what is known as the Socotra Platform. Here you’ll find four islands, of which Socotra is the largest, as well as two scars of former islands which have been eroded away by wave action.

At in excess of 240 kilometres east of the Horn of Africa and 380 kilometres south of the Arabian Peninsula there is no getting away from the remoteness of the archipelago. Testament to this is the presence of seven endemic bird species on the island.

So how did the strange looking Dragon Blood Tress and other flora and fauna come to populate Socotra and its neighbours?

It is thought that until 43 million years ago, the Socotra archipelago remained largely submerged. Although there were some brief emergence events during the Jurassic/Cretaceous and Cretaceous/Tertiary, given the area was re-submerged after this time, they are considered of little importance.

Subsequently, Socotra Island continued to grow due to uplift. Despite changing sea depths, there are indications that land species could migrate over from mainland African and Arabia via land bridges and stepping stones. With ‘cousin’ species present in Somalia and Arabia, it’s likely the Dragon Blood Trees originated there in the distant past.

From 16,000 years ago onwards, the isolation of the archipelago grew due to a combination of further flooding of low-lying areas, the formation of large basins (namely the Guardafui and Brothers basin) and increasing distance from the mainland. Since then, the species on Socotra and its neighbouring islands have had time to evolve and adapt to their surroundings, become different, albeit sometimes closely related, to their continental counterparts.

It was only around the third century BC that Socotra started to emerge from its isolation after attracting the attention of the young Alexander the Great during one of his war campaigns. The island then became known in the Hellenic World and all the Mediterranean for being one of the main sources of incense, myrrh and dragon’s blood powder resin.

As Socotra commercial importance gradually faded away in the centuries to follow, Dragon’s Blood resin remained one of the main exports of the island. The resin was considered a precious ingredient of dyes, lacquers and varnishes, and the legend has it that Antonio Stradivari – the famous seventeenth century luthier from Cremona – used Socotra’s red resin to varnish his violins.

yemen

The landscape of the Socotra archipelago. Credit: Annalisa Molini via Flickr.

One thing is for sure, as Annalisa Molini’s (Assistant Professor at the Institute Center for Water and Environment, in Abu Dhabi), photographs attest to: Socotra island and it’s Dragon Blood Trees are stunning.

However, the remoteness of the Socotra archipelago and the current armed conflict in Yemen threaten to put at risk the island’s important and unique natural heritage; one that no doubt, should be protected and preserved.

References

M. Culek: Geological and morphological evolution of the Socotra Archipelago (Yemen) from the biogeographical view, Journal of Landscape Ecology, 6, 3, 84–108, DOI: 10.2478/jlecol-2014-0005, 2014

Brown, B.A. Mies, Vegetation Ecology of Socotra, Springer Netherlands, Dordrecht, 2012. doi:10.1007/978-94-007-4141-6.

Imaggeo is the EGU’s online open access geosciences image repository. All geoscientists (and others) can submit their photographs and videos to this repository and, since it is open access, these images can be used for free by scientists for their presentations or publications, by educators and the general public, and some images can even be used freely for commercial purposes. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. Submit your photos at http://imaggeo.egu.eu/upload/.

Imaggeo on Mondays: Strombolian eruption

Imaggeo on Mondays: Strombolian eruption

Jonas Kuhn, a researcher at Heidelberg University , took the photograph during a field campaign at Stromboli volcano in Italy. The objective of this campaign was to gather data from different gaseous compounds of the volcanic plume. Via emission fluxes of volcanic gases (e.g. SO2, CO2, halogen compounds…) or the ratio of emitted gases, one can retrieve information about the interior of the volcano and magma dynamics. Volcanic gas measurements can therefore contribute to better understanding volcanoes and in predict volcanic activity.

There are several ways in which scientists can gather information about volcanic processes from plume gas measurements. Let’s start by taking a look at sulphur dioxide, as it is emitted by volcanoes in large amounts. A relatively novel measurement instrument, the SO2 Camera, is able to record 2D SO2 distributions with a high time resolution. This means that SO2 emission fluxes can be determined and linked to other volcanological data sets as e.g. seismic data or simply to the occurrence of explosions. The high resolution SO2 emission fluxe data can give insight into the footprints of volcanic processes like the bursting of gas bubbles in the magma. So depending on e.g. the viscosity of the magma one would expect different frequencies in the emission flux of different volcanoes.

“In our group, a lot of work was done on further developing such camera systems. In volcanology this technique has only been applied for the past decade,” explains Jonas.

Another innovative device for fast optical in situ measurement of SO2 andCO2, as well as chemical in situ measurements of halogen compounds in the plume was also tested during the field trip. By using the ratios of other gases to SO2 and the known SO2 flux (from the SO2 camera measurement), fluxes of the other gases can be estimated. Different gases have different solubilities in magma, so they are released from the magma at different pressures.  Ratios of gas abundances in the volcanic plume can therefore contain information on, for instance, changes in the magma level (it’s not uncommon for magma to be ‘invisible’ in the interior of the volcano). The magma level can also be a crucial indicator of volcanic activity.

“What made this field campaign special was that relatively new and young volcanic measurement techniques were tested and used,” outlines Jonas, who goes on to point out ““many of them are still in the development stages. The volcanic gas measurement field is very exciting at this time. Interesting insights have been gained in the last decades and there is still a lot of ideas and new technologies coming up.”

By Jonas Khun,  Researcher at Heidelberg University and Laura Roberts Artal, EGU Communications Officer

Imaggeo is the EGU’s online open access geosciences image repository. All geoscientists (and others) can submit their photographs and videos to this repository and, since it is open access, these images can be used for free by scientists for their presentations or publications, by educators and the general public, and some images can even be used freely for commercial purposes. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. Submit your photos at http://imaggeo.egu.eu/upload/.

Imaggeo on Mondays: The place where water runs through rocks

Imaggeo on Mondays: The place where water runs through rocks

Antelope Canyon, located in Arizona, USA, was formed by erosion of the Navajo Sandstone, primarily due to flash flooding and secondarily due to other sub-aerial processes (think of physical weathering processes such as freeze-thaw weathering exfoliation and salt crystallisation). Rainwater runs into the extensive basin above the slot canyon sections, picking up speed and sand as it rushes into the narrow passageways. Over time the passageways are eroded away, making the corridors deeper and smoothing hard edges in such a way as to form characteristic ‘flowing’ shapes in the rock.

The Navajo Sandstone was deposited in an aeolian (wind-blown) environment composed of large sand dunes: imagine a sea of sand, or an erg, as it is known scientifically, not dissimilar to the present Sarah desert landscape. The exact age of the Navajo Sandstone is controversial, with dated ages ranging from Triassic to early Jurassic, spanning a time period between 250 million years ago to approximately 175 million years ago. The difficulty in determining the exact age of the unit lies in its lack of age diagnostic fossils. The Navajo Sandstone is not alone in this quandary, dating is a common problem in aeolian sediments.

“The picture was taken during a three week Southwest USA road trip in summer 2012. One of the highlights was the visit to Antelope slot canyon, which is located on Navajo land east of Page, Arizona. The Navajo name for Upper Antelope Canyon is Tsé bighánílíní, which means the place where water runs through rocks,” explains Frederik Tack, an atmospheric scientist from the Belgian Institute for Space Aeronomy and author of today’s Imaggeo on Monday’s photograph.

The erosive processes which form the canyon are still ongoing. There is an elevated risk of flash floods, meaning the canyon can only be visited as part of guide tours.

“The canyon was actually quite crowded which made taking this picture challenging, especially as I wanted to capture the peace and solitude of the landscape,” describes Tack.

The effort was worth it: Waved rocks of Antelope slot canyon was one of the EGU’s 2015 Photo Contest finalists!

Imaggeo is the EGU’s online open access geosciences image repository. All geoscientists (and others) can submit their photographs and videos to this repository and, since it is open access, these images can be used for free by scientists for their presentations or publications, by educators and the general public, and some images can even be used freely for commercial purposes. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. Submit your photos at http://imaggeo.egu.eu/upload/.

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