GeoLog

Drumlins

Imaggeo on Mondays: Concord at midnight

Imaggeo on Mondays: Concord at midnight

The high peaks of the Alps are always awe inspiring, but this midnight shot, captured by Alessandro Lechmann, a PhD student at the Institute of Geological Sciences at the University of Bern, further enhance their fragile beauty. With a warming climate threatening snow availability to even the highest peaks, it has never been more important to appreciate the importance of the glaciers which drape the mountain slopes.

This photograph shows a view from the Jungfraujoch (a saddle in the Bernese Alps, connecting the two four-thousander peaks Jungfrau and Mönch, at an elevation of 3,466 metres above sea level) towards the south-east down the Jungfraufirn (an arm of the Great Altesch Glacier).

Originating amidst three of the most famous mountains of the Swiss Alps (Eiger, Mönch and Jungfrau), this glacier flows southwards towards the Concordiaplatz, where it merges with the Ewigschneefäld and the Great Aletschfirn into the Great Aletsch Glacier. Even today, despite reports of receding glaciers in the Alps, it forms the largest and longest Alpine glacier.

In the countries surrounding the Alps, glacial landforms dominate the landscape. From drumlins, moraines (accumulations of glacial debris) and overdeepenings in the foreland to U-shaped valleys (Lauterbrunnen is a marvellous example) and cirques in mountainous regions. Although retreating at rates not seen previously, these glaciers carved the face of central Europe during the last glacial-interglacial cycles.

The building of the railway to the Jungfraujoch research station started in 1896 and was completed in 1912; an impressive feat considering the limited technology before the First World War. Perched precariously 3500 m above sea level, the research station (known for its prominent sphinx observatory), has contributed significantly   to the understanding of the atmospheric sciences, glaciology and cosmic ray physics.

The ridge which the Jungfraujoch is built on, marks the northern margin of the exposed crystalline core of the Alpine orogeny. Interestingly, this mountain ridge, in addition to being a geological boundary, is also a major watershed. Rain that falls north, flows via the Aare into the Rhine, which eventually discharges into the North Sea. Precipitation on the southern flank and melt water from the Jungfraufirn, on the other hand, joins the Rhone in the Valais valley, that ends up in the Mediterranean Sea. This highlights the importance of Alpine glaciers as a water stores which continue to provide water throughout the year.

By Alessandro Lechmann PhD student at the Institute of Geological Sciences at the University of Bern

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: 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