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Imaggeo On Mondays: Loch Leven

18 Aug

Over hundreds and thousands of years, glaciers reshape the landscape beneath them. As they creep forward, the combined weight of the glacier and the perpetual forward movement means the ice continuously erodes away the rock below, permanently changing the terrain.

During the last Ice Age much of Scotland and northern Britain were covered by a thick sheet of ice. Where there might have been once a stream, impenetrable masses of ice pushed their way downwards, widening and carving. As the climate warmed, 10 000 years ago, the ice slowly melted away to reveal broad U-shaped valleys.

David Tanner photographed Loch* Leven, which lies at the bottom of a beautiful U-shaped valley carved out by glaciers during the last Ice Age.

“Loch Leven” by David Tanner. This picture shows a view west along Loch Leven and is distributed by the EGU under a Creative Commons licence.

“Loch Leven” by David Tanner. This picture shows a view west along Loch Leven and is distributed by the EGU under a Creative Commons licence.

“The geology of the valley is very complex” describes David, “There are a series of metamorphosed sediments called the Dalradian (the Celtic name of the area is Dál Riata), which were intensely folded and deformed during the Caledonian Orogeny (in the Devonian)”. The aim of David’s work was to unravel the folding history of the rocks, because, as David explains “the deformation history of the Dalradian, compared to the rest of Scotland, is still poorly understood”. Detailed mapping revealed four different folding episodes.

*(the Celtic word for lake).

Imaggeo is the EGU’s open access geosciences image repository. Photos uploaded to Imaggeo can be used by scientists, the press and the public provided the original author is credited. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. You can submit your photos here.

 

Imaggeo on Mondays: Fossil dunes

11 Aug

Desert winds continually rework the sands on their surface, shifting grains up the stoss side of a dune to pile the sand higher… until the pile gets too steep and collapses under its own weight. This slipping of material along the front of the dune, allows it to move forward and migrate. The movement of the sand grains up and over the crest of the dunes is recorded in the internal structure of the dunes. Relatively thin layers of sediment which are seen to be at an angle with the dominant layering in the unit are known as cross-bedding and are the hallmark of a migrating dune.

Cross-bedding can be generated by water or wind, all you need is a current that will transport sand over sediments. Large scale cross-bedding helps identify ancient dunes, as it is most often associated with flow travelling in a single direction resulting in the forward movement of dunes.

Dunes can form in a number of environments: in river channels, on beaches and of course deserts too. Regardless of where they form, to continue to migrate forward they require a constant supply of sand. If that supply dies down and eventually stops the dunes stop travelling. In time, the layers of grains weld together to form lithified rocks which preserve the ancient structure of the dunes.

The picture shows a section of fossil dunes with the typical cross bedding internal structure that allows visual identification of this aeolian feature.

Fossil Dune

“Fossil dune” by Jorge Mataix-Solera. This picture was taken during a research trip near Haifa, Israel, in 2008 and is distributed by the EGU under a Creative Commons licence.

 

We are grateful to João Trabucho for helping us improve an earlier version of this blog post.

Imaggeo is the EGU’s open access geosciences image repository. Photos uploaded to Imaggeo can be used by scientists, the press and the public provided the original author is credited. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. You can submit your photos here.

 

Imaggeo on Mondays: Beneath a star-studded sky

4 Aug

Marco Matteucci captured this image of the night sky on the slopes of Mount Rosa, the second tallest peak in Alps. Mount Rosa straddles the border between southern Switzerland and Italy the pink mountain’s name comes from the Franco-Provençal word rouése, meaning glacier. Much off the Swiss side of the mountain is enveloped in the ice of Gorner Glacier, the second largest glacier in the Alps. On the Italian side, lies Belvedere Glacier, which is fed by the snow that falls on Mount Rosa.

Mount Rosa ridge, Valle d'Aosta, Italy. (Credit: Marco Matteucci via imaggeo.egu.eu)

Mount Rosa ridge, Valle d’Aosta, Italy. (Credit: Marco Matteucci via imaggeo.egu.eu)

Wish you could capture images like this yourself? You can! Take a look at this brief guide to space photography for some hints and tips. 

Imaggeo is the EGU’s open access geosciences image repository. Photos uploaded to Imaggeo can be used by scientists, the press and the public provided the original author is credited. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. You can submit your photos here.

Imaggeo on Mondays: Spectacular splatter – the marvels of a mud volcano

28 Jul

Mud volcanoes, unlike many others, do not extrude lava. Instead, they release glutinous bubbling brown slurry of mineral-rich water and sediment. They range in size from several kilometres across, to less than a metre – the little ones are known as mud pots, reflecting their diminutive nature. The world’s largest, though, is Lusi: a mud volcano in East Java that released an astonishing 180,000 cubic metres of fluid each day during the peak of its 2006 eruption. It’s likely to continue erupting for another 26 years!

Much of the gas that bubbles up through these muddy pools is methane, though the exact mix of gasses varies from site to site and is tied to other geological activity in the region, with those close to igneous volcanoes often releasing less methane than those associated with clathrate deposits. Small bubbles of gas can coalesce to form a much larger one, which, on reaching the surface, bursts and sends flecks of clayey fluid asunder, just as they do here:

The sediment-rich spatter from a bubbling mud volcano. (Credit: Tobias Heckmann via imaggeo.egu.eu)

The sediment-rich spatter from a bubbling mud volcano. (Credit: Tobias Heckmann via imaggeo.egu.eu)

By Sara Mynott, EGU Communications Officer

Imaggeo is the EGU’s open access geosciences image repository. Photos uploaded to Imaggeo can be used by scientists, the press and the public provided the original author is credited. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. You can submit your photos here.

 

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