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Geomorphology

Imaggeo on Mondays: Drumlins Clew Bay

Imaggeo on Mondays: Drumlins Clew Bay

During ice ages landscapes are sculpted by the power of advancing glaciers. From rock scratches, to changing mountains and the formation of corries, cirques and aretes, through to the formation of valleys and fjords, the effects of past glaciations are evident across the northern hemisphere landscape.

Perhaps not so familiar, drumlin fields are also vestiges of the erosive power of ancient ice sheets. Glacial deposits tend to be angular and poorly sorted, meaning they come in lots of different sizes and shapes. The extreme of this are glacial erratics. Drumlins are are elongated hills made up of glacial deposits and they represent bedforms produced below rapidly moving ice. Our Imaggeo on Monday’s image this week is of Clew Bay in western Ireland and shows the streamlining of drumlins into an extensive drumlin field of glacial sediment. The drumlins here formed during the rapid thinning of the fast moving central parts of the western sector of the British-Irish Ice Sheet, in a process known as deglacial downdraw – probably between 18,000 and 16,000 years ago. The ice was streaming through bays in western Ireland both during and at the end of the Last Glacial Maximum (also known as LGM). This was the time in which the ice sheets covered most of northern America, Europe and Asia. In Clew Bay the ice was a minimum of 800m thick and flowing out into a series of tidewater glaciers situated along the length of Ireland’s western shelf.

By Prof. Peter Coxon, Head of Geography, School of Natural Sciences, Trinity College Dublin & Laura Roberts

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

Communicate your Science Video Competition finalists: time to get voting!

For the second year in a row we’re running the EGU Communicate Your Science Video Competition – the aim being for young scientists to communicate their research in a short, sweet and public-friendly video. Our judges have now selected 3 fantastic finalists from the excellent entries we received this year and it’s time to find the best geoscience communication clip!

The shortlisted videos will be open to a public vote from now until midnight on 16 Apri; – just ‘like’ the video on YouTube to give it your seal of approval. The video with the most likes when voting closes will be awarded a free registration to the EGU General Assembly 2016.

The finalists are shown below, but you can also catch them in this finalist playlist and even take a seat in GeoCinema – the home of geoscience films at the General Assembly – to see the shortlist and select your favourite.

Please note that only positive votes will be taken into account.

The finalists:

Inside Himalayan Lakes by Zakaria Ghazoui. Like this video to vote for it!

 

Glacial Mystery by Guillaume Jouvet. Like this video to vote for it!

 

Floods by Chiara Arrighi. Like this video to vote for it!

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The winning entry will be announced during the lunch break on the last day of the General Assembly (Friday 17 April).

Imaggeo on Mondays: Retreating Glacier

Credit: Przemyslaw Wachniew (distributed via imaggeo.egu.eu)

Credit: Przemyslaw Wachniew (distributed via imaggeo.egu.eu)

The Svalbard archipelago is considered to be one of the best places to study the geological history of the Earth because its rocks represent every geological period. This image shows a view from the peak of Fugleberget (569 m a. s. l.; 77º 00’ N, 15º 30’ E) on the south-western coast of the island of Spitsbergen. Glaciation of this geologically diverse area gave rise to a variety of geomorphic features. The most prominent of them, depicted in the picture, is the Hornsund Fjord that cuts through metamorphic and sedimentary rocks ranging from the Proterozoic (up to 2.5 billion years old!) to the Cretaceous Age (older than 66 million years). A spectacular example of glacial erosion can be seen on both sides of the fjord in the cliffs formed of Paleozoic carbonate rocks. Nowadays, this landscape is changing because glaciers are retreating in response to the rapid warming of the Arctic. Patterns of glacial retreat can be recognized at the margin of the Hans Glacier, which descends to the fjord below. Floating parts of the glacier are unstable as they readily break up, form crevasses, and eventually calve in to the fjord, as recorded in the photograph. The 1.5 km long calving front is retreating faster than the grounded parts of the glacier. As glaciers move, they can leave behind large amounts of dirt and rocks, known as moraines. Reduction in the thickness of Hans Glacier, is reflected by the height of the lateral moraine, which can be seen above the ice edge as an elongated ridge with an irregular surface. Retreating glaciers expose new areas of land and water, which affects fluxes of energy and matter in the arctic environment.

By Przemyslaw Wachniew, AGH University of Science and Technology in Kraków .

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: A Patagonia landscape dominated by volcanoes

Patagonia Landscape. Credit: Lucien von Gunten (distributed via imaggeo.egu.eu)

Patagonia Landscape. Credit: Lucien von Gunten (distributed via imaggeo.egu.eu)

Imagine a torrent of hot and cold water, laden with rock fragments, ash and other debris hurtling down a river valley: this is a lahar. A by-product of eruptions of tall, steep-sided stratovolcanoes, lahars, are often triggered by the quick melting of snow caps and glaciers atop high volcanic peaks.

The history of the Ibañes River and its valley, in southern Chile, are dominated by their proximity to Hudson volcano (or Cerro Hudson, as it is known locally). Located in the Andean Southern Volcanic Zone, the volcano has an unsettling history of at least 12 eruptions in the last 11,000 years. That equates to a major eruption every 3,800 years or so! The volcano has a circular caldera, home to a small glacier and is neighboured by the larger Huemules glacier.

One of the most significant eruptions occurred in 1991. It is thought to be one of the largest eruptions, by volume, of the 20th Century. At its peak, the eruption produced an ash plume thought to be in excess of 17km high, with ash being deposited as far away as the Falkland Islands. The initial eruptive phase was highly explosive. Known as phreatomagmatic eruption, hot and gas rich magma mixed with ice and water from the glacier on the summit of Mt. Hudson. As the eruption progressed, a period of sustained melting of both the caldera glacier and Huemules glacier began. The result of this was a 12 hour period of persistent lahar generation, with volcanic debris laden torrents racing down the Ibañes valley and its neighbours.

Fast forward to 2009 and the effects of the eruption of 1991 are still visible in the Patagonian Landscape. Lucien von Gunten photographed the inhospitable ‘Bosque Muerto’ (Dead Forest), in the Ibañes valley. The accumulation of the lahar deposits and the ash fall from the eruptive column clogged up the Ibañes river and valley killing a large proportion of the local flora and fauna. The ‘Bosque Muerto’ remains a stark reminder of the devastating effects of the 1991 eruption.

Reference

David J. Kratzmann, Steven N. Carey, Julie Fero, Roberto A. Scasso, Jose-Antonio Naranjo, Simulations of tephra dispersal from the 1991 explosive eruptions of Hudson volcano, Chile, Journal of Volcanology and Geothermal Research, Volume 190, Issues 3–4, 20 February 2010, Pages 337-352

 

If you pre-register for the 2015 General Assembly (Vienna, 12 – 17 April), you can take part in our annual photo competition! From 1 February up until 1 March, every participant pre-registered for the General Assembly can submit up three original photos and one moving image related to the Earth, planetary, and space sciences in competition for free registration to next year’s General Assembly!  These can include fantastic field photos, a stunning shot of your favourite thin section, what you’ve captured out on holiday or under the electron microscope – if it’s geoscientific, it fits the bill. Find out more about how to take part at http://imaggeo.egu.eu/photo-contest/information/.

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