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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: Velociraptor in the Zagros Mountains

A velociraptor in the Zagros fold and thrust belt. Credit: Stephane Dominguez (distributed via  imaggeo.egu.eu)

A velociraptor in the Zagros fold and thrust belt. Credit: Stephane Dominguez (distributed via imaggeo.egu.eu)

How many times have you turned your head up to the sky and spotted familiar shapes in the clouds? Viewing structures from afar can reveal interesting, common and, sometimes, funny patterns.

Satellite images are often used to map geological terrains. They offer a bird’s eye view of the planet and the opportunity to see broad scale structures, the scale of which would be impossible to grasp from the ground. They can, from time to time, much like when you cloud spot, reveal interesting and unexpected features too!

The image above is a processed LANDSAT 7 Satellite image. Stephane Dominguez, a researcher at the University of Montpellier, acquired the image to study the Zagros Fold and thrust belt: the result of the collision of the Iranian Plate and the Arabian Plate.

Whilst studying the image, Stephane noticed an uncanny resemblance…who knew the Zagros mountain belt hosts a velociraptor? Stephane modified the image, using Photoshop, to obtain the false colours which highlight the dinosaur shape in the image. A little thumbnail of a velociraptor is included too, for comparison!

The surface morphology of the image is dominated by EW trending folds, with partially eroded cores. Darker/black areas correspond to salt diapirs that reached the surface in the fold cores or along reverse faults bounding the folds. We’ve featured the Zagros Mountains in our Imaggeo on Monday’s posts recently; you can find more details on the geology of the region here.

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: Mesopotamia, the ancient land between rivers

Mesopotamia, an area rich in history and considered as the cradle of civilisation, with the first populations establishing themselves in the region some 6000 years ago,lies between two great rivers: the Euphrates and the Tigris. The ancient territory spans areas of modern-day Iraq, Kuwait, the northeastern section of Syria and small sections of southeastern Turkey and southwestern Iran.

The history of Mesopotamia is intrinsically linked to the great rivers which define it. From changes of the river themselves (autogenic), through to non-living environmental factors (known as allogenic) and human activities, the rivers respond to a wide range of processes by changing their courses and forming new waterways.

However, keeping track of the river’s changing paths during their long histories can be tricky. Based on a common assumption made by archaeological studies of the Mesopotamian floodplain, where periods of activity of a river channel are considered to be closely linked to the ages of archaeological settlements, Jaafar H. Jotheri, (a PhD researcher at the University of Durham, UK), was able to study the history of the two rivers.

Most of the identified ancient settlements in the region are thought to have been established near active channels. “Therefore, the existence of settlements in certain areas is a good indication of the probability of the existence of a river close to the site and vice versa,” explains Jaafar. “Not only that, the ages of a settlement can give a suggested age during which a particular river channel was active,” he adds.

Cuneiform script, a style of writing which involved pressing a stylus into soft clay tablets and making indentations representing word-signs, was widely used in ancient Mesopotamia. A number of middle to late Holocene cuneiform tablets make direct reference to rivers. They often record instances in which settlers interacted with the rivers: the digging of new irrigation channels, the annual cleaning of a river or using the river to transport goods from one city to another.

“These texts are useful to determine the locations and period of existence of rivers, particularly when some texts refer to identified sites,” explains Jaafar.

Using this information, Jaafar has been able to identify and map three main courses of the Tigris, during three different time periods. These are, from oldest to the youngest: the Pleistocene course, the Holocene course and the modern course, as are seen in this week’s Imaggeo on Monday’s image.

Sumerian Cuneiform on a clay tablet. From Shuruppak or Abu Salabikh, Iraq, circa 2,500 BCE. British Museum, London. Credit: Gavin.collins, distributed via Wikimedia Commons.

Sumerian Cuneiform on a clay tablet. From Shuruppak or Abu Salabikh, Iraq, circa 2,500 BCE. British Museum, London. Credit: Gavin.collins, distributed via Wikimedia Commons.

No archaeological sites were found associated with the Pleistocene course, compared to the Holocene course, with which many archaeological sites are associated (dated from ~ 4000BC to 1200 AD).

“We have historical texts that suggest that the Holocene Tigris channel was abandoned and relocated to form the new modern course after 1258 AD, in a process known as avulsion” says Jaffar,  “there is also an indication that human activity might have been a trigger for the avulsion,” he adds.

The historical text indicate that farmers broke the banks of the Holocene aged channel of the river Tigris, digging irrigation canals to water low elevation farms.  The newly excavated channel (or canal) became the main waterway.
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: Mountains, rivers and agriculture

This week’s Imaggeo on Mondays image blends a range of geoscience disciplines. The post, by Irene Marzolff, a researcher at Johann Wolfgang Goethe-Universitaet, explores how the mountains, rivers and soils of the High Atlas in Morocco are intrinsically linked to the agriculture of the region.

High Atlas landscape. Credit: Irene Marzolff (distributed via imaggeo.egu.eu)

High Atlas landscape. Credit: Irene Marzolff (distributed via imaggeo.egu.eu)

The image was taken in the southern slopes of the Western High Atlas, north of the city of Taroudannt. The snow of these mountains, which in April is still prevailing on the highest ranges in the background of the photo, is a significant water resource for the region. The high interannual variability of precipitation and its changing patterns associated to climate change present a serious challenge for natural environment and for the sustainable use of water as a resource in agriculture and tourism, the two major economic sectors in the area.

A characteristic open cover of Argan trees (Argania spinosa) can be seen on the lower mountain slopes in the middle distance of the photo: an endemic species with small, oil-rich fruits resembling olives that yield high-quality oil used in medicine, food and cosmetics. The species is a relic of the Tertiary (66 to 2.8 million years ago) but has been under threat from human exploitation for centuries, by excessive grazing, fire-wood cutting, charcoal making and changes to the groundwater table. The area is part of the UNESCO-MAB Biosphere Reserve “Arganeraie” committed to the preservation and sustainable use of the trees.

The river bed in the foreground is formed by fluvial processes typical for this high-mountain region, with highly variable seasonal discharges controlled both by rainfall and snowmelt. It will in the near future drain into the Sidi Abdellah Reservoir that is currently being constructed near Tamaloukt. This reservoir will add to the 10 already existing water storage lakes in the region of Souss Massa Drâa, which is in urgent need of additional water resources: The Souss Valley to the South of the High Atlas is one of Morocco’s most intensely farmed agricultural regions, with agro-industrial production of bananas, vegetables and citrus fruit. Much of this, including 90% of Morocco’s tomato production, is exported to the European market.

By Irene Marzolff, researcher at the Institut fuer Physische Geographie, Johann Wolfgang Goethe-Universitaet, Frankfurt.

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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