GeoLog

“Endless fold”, by Jens Rößiger, was taken in the Pyrenees – its location is approximately 42°19’17.29″N, 3°18’49.02″E. This image is distributed by the European Geosciences Union under a Creative Commons licence.

This fold is part of the metamorphic core of the Pyrenees. The shear zone is almost vertical, producing a small parasitic fold (a smaller fold within a larger one), which looks almost as if it continues into the sky. The metamorphic sediments are about 500 million years old and have been deformed several times, most recently during the alpine orogeny. The alpine orogeny was period of extensive mountain building that occurred towards the end of the Mesozoic as the African and Arabian plates collided with the Eurasian, resulting in the formation of the Alpide belt. While the map below only shows the Mediterranean portion of the Alpide belt, this stretch of mountains extends much further East and includes the Himalayas.

The plate tectonics of the Mediterranean, responsible for the alpine orogeny that spans the region (orange) [Source: Wikimedia Commons].

The fold above lies within the Seira Negra (Black Series) at Cap de Creus, Spain. Much of this region is composed of mylonites (fine-grained rocks that have been through ductile deformation), pegmatites (highly crystalline igneous rocks with crystals >2.5 cm wide) and schists (medium-grade metamorphic rocks, with a large proportion of platy minerals – these are responsible for their sheen). The metamorphic grade of rocks in Cap de Creus decreases from north to south. An overview of the region’s metamorphic geology is given in the map below:

Geology of the Cap de Creus area – Jens’ photo was taken just north of the lighthouse (click to enlarge) [source: Carreras, 2001].

Rocks in Cap de Creus have been subject to a lot of shear stress through faulting and other orogenic processes. These processes have caused high strain in the rocks and extensive deformation. The “endless fold” above is composed of quartzite, with numerous quartz veins running throughout it. The fold is caught up in one of the many classical Variscan shear zones found in the area. Variscan shear zones are so named because they formed during the Variscan orogeny, a mountain building event in the late Palaeozoic, when Eurasia and Gondwana collided to form the supercontinent, Pangea. Relatively young volcanic intrusions (pegmatites) exist within the fold, and some of these have been deformed since, as the mountain range continues to build.

References:

Bons, P.D., Druguetb, E., Hamann I., Carreras, J. and Passchier, C.W. (2004). Apparent boudinage in dykes. Journal of Structural Geology. Vol. 26, pp. 625–636.

Carreras, J. (2001). Zooming on Northern Cap de Creus shear zones. Journal of Structural Geology. Vol 23, pp 1457-1486.

Imaggeo is the online open access geosciences image repository of the European Geosciences Union. Every geoscientist who is an amateur photographer (but also other people) can submit their images to this repository. Being open access, it can be used by scientists for their presentations or publications as well as by the press. If you submit your images to imaggeo, you retain full rights of use, since they are licenced and distributed by EGU under a Creative Commons licence.

“Stolbchaty cape, Kunashir Island”, taken by Dmitry Demezhko. This image is distributed by the European Geosciences Union under a Creative Commons licence.

The Kuril Island Chain is formed by four active volcanoes: Golovnin, Mendeleev, Tyatya and Smirnov. Stolbchaty Cape, where the Okhotsk Sea meets the coast of Kunashir Island, is not far from Mendeleev Volcano – responsible for the many hot springs in the area. These are fed by seawater and heated as the water comes into contact with magma and hot rocks within the mantle.

The picture shows an outcrop of columnar jointed andesite prisms. Andesite is a silica-rich volcanic rock and the columnar jointing results from the rapid cooling of erupted lava. Rapid cooling puts the lava under stress as it contracts and causes it to fracture perpendicular to the cooling surface.

Generally, the top of a lava flow is the coolest part because there is greater heat loss from the surface of the lava flow, but to induce fracturing, the erupting lava must meet an extremely cold surface. Air is insufficient to cause such rapid cooling and the presence of these prismatic columns indicate that the eruption occurred under ice.

Columnar jointing within a caldera-fill ignimbrite in the High Island formation, with some Geologists for scale [Source: CEDD, Hong Kong]

Processes leading to columnar jointing in igneous rocks.

The photographer, Dmitry Demezhko, was not here to look at the jointing though; in fact he is a geophysicist, investigating the thermal field of the Earth. During the last five years he has conducted continuous temperature monitoring in a borehole here with the aim to investigate the origin of temperature variation associated with seismo-tectonic events in the Kuril-Kamchatka region.

Imaggeo is the online open access geosciences image repository of the European Geosciences Union. Every geoscientist who is an amateur photographer (but also other people) can submit their images to this repository. Being open access, it can be used by scientists for their presentations or publications as well as by the press. If you submit your images to imaggeo, you retain full rights of use, since they are licenced and distributed by EGU under a Creative Commons licence.

Picture yourself in the Himalaya mountain belt: millions of years of continental uplift have produced a vast kingdom of towering monoliths, and they continue to grow as the Indian plate pushes further north into the heart of Asia. These dramatic, breath-taking and downright enormous geological structures can be simplified into the following tectonic units: the Leugogranites, the Transhimalaya, the Suture Zone, the Tethys Himalaya, the High Himalayan Crystalline Sequence and the Lesser Himalaya.

Himalayan geology, showing exactly where you can find the view below! [modified after O'Brien, 2011]

“Ladakh” by Franziska Wilke. The Indus River feeds the agricultural oasis in Franziska’s photo, a vivid contrast to the surrounding geology! Distributed by the EGU under a Creative Commons licence.

This view is to the south, where the Tethyan Sedimentary Zone overlies the Higher Himalayan Crystalline (HHC). The HHC has been thrust southward onto the Lesser Himalaya through the northward progression of the Indian plate and the resulting stacked sequence forms a barrier to rainfall so that regions to the north are only marginally affected by the monsoon. One such area is the Tso Morari. The Tso Morari Crystallines contain large eclogite bodies (up to a metre across!). Eclogites are very dense bodies of rock that form under pressures far greater than those at the Earth’s crust (over 1.2 Giga Pascales). The eclogites found here contain a mineral assemblage that reflects this: garnet, rutlie, coesite and quartz to name just a few!

Franziska studied Kaghan eclogites, sampled during a former field campaign in Pakistan by her supervisor, Professor  Patrick O’Brien. Since travelling in Pakistan was, and is, quite dangerous these days, she decided to attend the Himalaya-Karakoram-Tibet Workshop in northern India rather than going to Pakistan herself, because she wanted to see the Himalayan eclogites and their relation to their host rocks. Besides having fun sampling rocks, she also enjoyed the breath-taking landscape and the opportunity to take marvellous pictures.

O’Brien, P. (2011) Subduction followed by collision: Alpine and Himalyan examples. Physics of the Earth and Planetary Interiors 127, 277-291.

P. Dèzes (1999). Tectonic and Metamorphic Evolution of the Central Himalayan Domain in Southeast Zanskar (Kashmir, India). PhD Thesis. Institut de Mineralogie et Petrographie, Université de Lausanne. No. 32, ISSN 1015-3578

Imaggeo is the online open access geosciences image repository of the European Geosciences Union. Every geoscientist who is an amateur photographer (but also other people) can submit their images to this repository. Being open access, it can be used by scientists for their presentations or publications as well as by the press. If you submit your images to imaggeo, you retain full rights of use, since they are licenced and distributed by EGU under a Creative Commons licence.

After studying ‘Applied Environmental Sciences’ I decided to go with a friend for six months to New Zealand for the southern hemisphere winter. Leaving as soon as my diploma thesis (on epiphytic lichens) was written, we set off into the distance to work and travel. We chose New Zealand as our dream destination because these two islands have so many different landscapes to offer – and this is how I was able to capture this picture:

“Honeycomb Weathering” by Stefanie Boltersdorf (University of Trier, Germany), taken on the Kaikoura Peninsula, New Zealand. This photo is distributed by the European Geosciences Union under a Creative Commons License.

The photo shows honeycomb weathering on the Kaikoura Peninsula, with extends from the East coast of the South Island. Composed of mudstone and limestone, the terraces were once wave-cut platforms and have since been uplifted and deformed (during the Quaternary). The peninsula extends into the sea and encounters the relatively shallow Chatham Rise, an area of ocean floor to the east of New Zealand that was largely dry during the Cretaceous period, but now lies nearly 1000 metres underwater. This area is also one of the region’s most productive fishing grounds, a consequence of the nutrient-rich water that upwells along the coast. At low tide, the ocean gives way to a rocky floor, which is easily navigable by foot for quite some distance – and from there you can have a better view of the local seals and seabirds. At this spot, a branch of the Southern Alps, the so-called Seaward Kaikoura Range, comes close to the sea.

Very early in the morning, after sleeping next to the sea and having breakfast in our small van, ‘Berty’, the tide was very low and we took the opportunity to go for a walk. It was on this adventure we found this stunning structure, peppered with small molluscs that were sheltering in the eroded depressions. These depressions are a consequence of honeycomb weathering – a process initiated when salt meets porous rock. Sea spray delivers salt to the rocks, which, after the water has evaporated, is deposited in the pore spaces. Over time, the salt crystals push the minerals apart and weaken the rock. Small pockets collect seawater and erode into ever-larger depressions, eventually creating this marvellous honeycomb structure.

Although I have been dealing with epiphytic lichens during my diploma thesis, I remained true to them, even after my trip. After my return, and inspired by my trip to the highly lichen-rich New Zealand, I started my PhD thesis – investigating a method of quantitatively and qualitatively assessing nitrogen deposition in lichens, with the help of stable isotopes.

By Stefanie Boltersdorf, with Geo-facts from Sara Mynott

Imaggeo is the online open access geosciences image repository of the European Geosciences Union. Every geoscientist who is an amateur photographer (but also other people) can submit their images to this repository. Being open access, it can be used by scientists for their presentations or publications as well as by the press. If you submit your images to imaggeo, you retain full rights of use, since they are licenced and distributed by EGU under a Creative Commons licence.

 This week’s Imaggeo on Mondays is brought to you by the photographer himself, Antonio Jordán (Univerity of Sevilla, Spain), who describes the impact of forest fires on soil properties.

“Soil water repellency” by Antonio Jordán, distributed by the European Geosciences Union under a Creative Commons licence.

This photo was taken while planning some field experiments: in the image, several water drops are resting on a surface soil layer without infiltrating. This process is known as water repellency. Water repellency is a property of soils which, until recently, has not received much attention despite its geomorphological consequences (limiting water infiltration in soils, increasing runoff rates and enhancing the risk of soil erosion). Vegetation, including tree species such as pines or eucalyptus, or shrubs, such as heather, fungi and other soil microorganisms are the main sources of hydrophobic organic substances in soils. Climate, soil texture and structure may also modulate the degree of hydrophobicity.

Forest fires are a major cause of soil water repellency. During the combustion of litter and soil organic matter, some organic substances from the soil volatilise and escape as part of the smoke. However, another part can be displaced in depth and condense following a hot-to-cold gradient. These organic substances form hydrophobic coatings on the surface of soil particles and aggregates. So, when the soil reaches temperatures between 200ºC and 250ºC, water repellency can be increased or induced. If temperature peaks are higher, combustion and volatilization are more intense, and hydrophobic substances may be completely lost or destroyed.

Therefore, soil scientists use soil water repellency as an index of fire severity. A simple way to determine the degree of water repellency is to measure the time required for infiltration of water drops. The development of a water-repellent soil layer, as seen here, together with the loss of vegetation cover that protects soil may trigger soil erosion processes in sensitive areas just to get the first storms of the wet season.

I took this photograph a few days after a forest fire very close to Montellano (Sevilla, SW Spain). The region is characterised by a dense pine forest, shallow soils and steep slopes. The fire affected between 70 and 80ha, quickly climbing the northern slope of the mountain reaching the top, and progressing down the southern slope within a matter of hours.

By Antonio Jordán, University of Sevilla

Imaggeo is the online open access geosciences image repository of the European Geosciences Union. Every geoscientist who is an amateur photographer (but also other people) can submit their images to this repository. Being open access, it can be used by scientists for their presentations or publications as well as by the press. If you submit your images to imaggeo, you retain full rights of use, since they are licenced and distributed by EGU under a Creative Commons licence.

If you are pre-registered for the 2013 General Assembly (Vienna, 7—12 April), you can now submit photos and moving images to our annual competition! Winners receive a free registration to next year’s General Assembly.

The fourth annual EGU photo competition is now open! Up until 26 March, every pre-registered participant of the General Assembly can submit up to two photos on any broad theme related to the Earth, planetary, and space sciences. Short-listed photos will be exhibited at the conference and the winner will be voted for by General Assembly participants.

In addition, we will also be running a competition for the best moving image, for which we invite you to submit unedited films/footage no longer than 3 minutes in duration.

If you submit your images to the competition, they will also be included in the EGU’s open access photo database, Imaggeo. You retain full rights of use since photos submitted to the database are licensed and distributed by the EGU under a Creative Commons license. This means that Imaggeo content can be used by scientists for their presentations or publications, by the press for news articles, and others or education, blogs — you name it! — as long as they are attributed to the photographer.

You will need to register on Imaggeo so that the organisers can appropriately process your photos. For more information, please check the photo competition page on Imaggeo. Previous winning photographs can be seen on the 2010, 2011 and 2012 winners’ pages.

In the meantime — get shooting!

Last year’s winning photo: Melt Stream by Ian Joughin, distributed by EGU under a Creative Commons licence.

“Kalalau Valley” by Martin Mergili, taken from Kalalau Lookout on the island of Kauai, distributed by the European Geosciences Union under a Creative Commons License.

At over 5 million years old, the island of Kauai is the oldest island in the Hawaiian Achipelago. Hawaii, Maui and Oahu are all younger and lie further to the southeast. This island chronology is no coincidence – the Archipelago formed as a result of intra-plate volcanic activity.

Intra-plate volcanism occurs where an upwelling magma plume or ‘hot spot’ lies beneath a continental plate. In this case, the Pacific Plate has moved over a hot spot in the northwestern direction, so that the younger and more active islands are located in the southeast, and the older islands are further north. As the plate passes further from the hotspot, the crust cools, becoming less buoyant and causing the oldest islands in the chain to sink and form atolls when fully submerged.

Volcanic has ceased on Kauai and now erosive forces are those that shape the island, resulting in deep gullies and canyons cut into the highlands. In the north and northwest of Kauai the roaring waves of the Pacific Ocean hit the island after travelling for thousands of kilometres undisturbed. These waves meet a steep and rugged coastline with swells that can reach 10 m high on the Na Pali Coast. Running water has cut spectacular valleys into these cliffs, forming the Nualolo and Awaawapuhi, and Kalalau (above) Valleys. During the summer, carbonate sands fringe the island – you can just about see them here, but they are washed away by heavy wave action in the winter months.

This view of the Kalalau Valley was captured by Martin Mergili (Geologist from BOKU, University of Natural Resources and Life Sciences, and keen photographer), who explains that he took “this photo on a holiday trip to Hawaii in August 2010 (as far as a geoscientist can spend a “real” holiday in Hawaii). The viewpoint is called Kalalau Lookout, located in the humid highlands of Kauai, close to the misty Alakai Swamps and Mount Waialeale, one of the wettest places on Earth”.

Imaggeo is the online open access geosciences image repository of the European Geosciences Union. Every geoscientist who is an amateur photographer (but also other people) can submit their images to this repository. Being open access, it can be used by scientists for their presentations or publications as well as by the press. If you submit your images to imaggeo, you retain full rights of use, since they are licenced and distributed by EGU under a Creative Commons licence.

“Rainbow in stone” by Marina Manea, distributed by the European Geosciences Union under a Creative Commons licence.

Nothing better characterises the wild US West than endless landscapes of red hoodoos, spires of rock protruding from the bottom of an arid drainage basin or badland. Found mainly in desert and dry, hot areas, hoodoos are distinctive from similarly-shaped formations, such as spires or pinnacles, because their profiles vary in thickness throughout their length. Their distinctive colour bands are the product of erosional patterns differentially affecting layers of harder and softer minerals.

Nowhere in the world are hoodoos as abundant as in the northern section of Bryce Canyon National Park in Utah, USA. There, these formations, also known as goblins or in French as demoiselles coiffées (“ladies with hairdos”), dominate the landscape.

At Bryce Canyon, hoodoos are formed by two continuously operating weathering processes. The first, frost wedging, occurs as a result of Bryce’s over 200 annual freeze/thaw cycles. In the same way potholes are formed on a paved road, water breaks open the rock when it seeps into cracks, freezes, and expands. Secondly, the hoodoos are also sculpted by rainfall, both physically, because it removes debris, and chemically, because its slightly acidic pH dissolves the limestone.

Marina Manea, who works in the Computational Geodynamics department of the Universidad Nacional Autonoma de Mexico, took this early-morning picture from a helicopter whilst on holiday in Utah in August 2010. She explains, “Bryce Canyon has a unique geology, with deposits from the late Cretaceous and early Cenozoic eras. It is not a classical canyon but, rather, a collection of amphitheaters modelled by the erosional force of frost-wedging and the dissolving power of rainwater acting on the colorful limestone rock of the Claron Formation. In this way, the spires, or ‘hoodoos,’ are formed. The rocks forming the hoodoos are limestone (sedimentary rocks) exhibiting beautiful colours (red, orange, or white). The entire geology of the Bryce Canyon is related to the geology of the Grand Staircase region and Black Mountains volcanic complex. It rained just before this picture was taken, which explains the exceptionally vivid colours on display here.”

The area around Bryce Canyon was originally settled by Native Americans and later by Mormon pioneers. The national park was established in 1928 and today around 1.3 million (2011) people annually travel to witness its wild terrain and spectacular sunset colours.

Imaggeo is the online open access geosciences image repository of the European Geosciences Union. Every geoscientist who is an amateur photographer (but also other people) can submit their images to this repository. Being open access, it can be used by scientists for their presentations or publications as well as by the press. If you submit your images to imaggeo, you retain full rights of use, since they are licenced and distributed by EGU under a Creative Commons licence.

“Amazonian floodplain” by Jürgen Kesselmeier, distributed by the European Geosciences Union under a Creative Commons licence.

After the Nile, the Amazon River is the second longest river in the world and, by releasing up to 300,000 cubic metres per second into the Atlantic Ocean, accounts for approximately one-fifth of the planet’s total river flow. The river and its tributaries are characterised by extensive annual flooding of over 350,000 square kilometres of forested areas. Floodplain water levels may exceed 9m.

Not all of the Amazon’s tributaries flood simultaneously each year. For example, many branches begin to flood in November and continue to rise until June, whereas the Rio Negro starts rising in February or March.

The freshwater ecosystems of the Amazon floodplain are vital repositories of biodiversity, hosting fish, reptiles, and other aquatic animals normally inhabiting the river’s main water channels but migrating to newly-flooded areas in order to feed and reproduce. The region’s flora also relies on the annual flooding cycle: seeds are dispersed by the water and by fruit-eating animals and fish that thrive in the temporary wetlands.

This view of the flooded forest was captured by Jürgen Kesselmeier, a biogeoscientist at the Max-Planck-Institut für Chemie, Mainz, Germany. He explains, “I took this picture at the end of April 2008 during one of my visits to the Amazonian rainforest, in the Várzea, or ‘floodplain’ region of the Rio Solimoes near Manaus (shortly before this river joins the Rio Negro). This area is known to show a flood pulse of 10-15m, meaning the water level of these river systems fluctuates by 10-15m on a regular basis every year. This picture was shot near the time of maximum flooding and therefore large areas were inundated. It features a magical-looking forest and, to me, offers a glimpse into just why this ecosystem is so special.”

Logging and the clearing of land for cattle ranching change the Amazonian floodplain landscape. Overfishing, the construction of dams and roads, and pollution, from nearby human habitations and gold mining in smaller streams, also threaten the local ecosystem.

Imaggeo is the online open access geosciences image repository of the European Geosciences Union. Every geoscientist who is an amateur photographer (but also other people) can submit their images to this repository. Being open access, it can be used by scientists for their presentations or publications as well as by the press. If you submit your images to imaggeo, you retain full rights of use, since they are licenced and distributed by EGU under a Creative Commons licence.

This week’s Imaggeo on Mondays is brought to you by the photographer herself, Marion Bisiaux (now at Stendhal University, Grenoble, France), who tells us about her exciting field trip to the British Columbia’s Coast Range.

“Combatant Col under a storm” by Marion Bisiaux, distributed by the European Geosciences Union under a Creative Commons licence.

This picture was taken during the Waddington Range Ice Core Project in which I participated during my PhD at the University of Nevada, Reno, US and at the Desert Research Institute, also in Reno. The scene was captured in July 2010, during a month-long field trip at the Combatant Col, the mountain pass below Mount Waddington in British Columbia’s Coast Range that sits at 3000m elevation and contains more than 200m of ice. The aim of the project was to drill an ice core to retrieve information on the past climate of the area. The results were published in 2012 in the Journal of Glaciology and are available online.

The camp (tents only) was located just below the massive north face of Mount Waddington. The weather was rather rough as we had several storms hitting the camp, but the scenery was impressive, with avalanches running on Mount Waddington’s face, crevasses, overhanging seracs, among other phenomena. The photograph shows the high winds on the Mount that stopped the ice-core drilling for a few days and forced drillers to hide in their tents.

Notwithstanding the strong weather and striking scenery, what I remember the most is the human aspect of this scientific expedition. Everyone was very motivated, working very hard to make the drill happen, and united by the same goal: the success of the expedition and the increase of knowledge.

This field trip will be the topic of a book Carnet Glacé (in French), which will tell the story of the expedition.

By Marion Bisiaux, glaciologist and science communication student

Imaggeo is the online open access geosciences image repository of the European Geosciences Union. Every geoscientist who is an amateur photographer (but also other people) can submit their images to this repository. Being open access, it can be used by scientists for their presentations or publications as well as by the press. If you submit your images to imaggeo, you retain full rights of use, since they are licenced and distributed by EGU under a Creative Commons licence.