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Imaggeo on Mondays: Sunset on the Giant’s Causeway

Imaggeo on Mondays: Sunset on the Giant’s Causeway

Pictured here is the Giant’s Causeway – a region of basalt columns, created 50-60 million years ago during the Paleogene. The typical polygonal form of the bedrocks, a product of active volcanic processes from the past, is well underlined by the sunset’s light; that’s why I took the photo in the late evening. The separate cracks are extended by weathering over time and are filled eluvium, geological debris from the erosion.

After the lava cooled, approximately 40,000 columns have since been polished by sea wave action. I decided to show the slow action of the sea with a long exposure, because it’s a continuous process, not obvious at first to an untrained person, but nevertheless very important now. I think in one photo we can find a deep history of Earth’s development, which palaeogeographers are still trying to understand.

by Osip Kokin, Lomonosov Moscow State University, Russia

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 licenceSubmit your photos at http://imaggeo.egu.eu/upload/.

Imaggeo on Mondays: Giants Causeway

Imaggeo on Mondays: Giants Causeway

Since its discovery back in the late 1600s the origin of the spectacular polygonal columns of the Giants Causeway, located on a headland along the northern coast of Ireland, has been heavily debated. Early theories for its origin ranged from being sculpted by men with picks and chisels, to the action of giants, through to the force of nature. It wasn’t until 1771 that Demarest, a Frenchman, suggested that the origin of the world-famous headland was indeed volcanic.

“The myth goes that the Irish giant Finn MacCool once constructed a land bridge from Northern Ireland to Scotland in order to meet a rival giant,“ explains Bernhard Aichner, author of this week’s featured imaggeo image. “It is said that he used basaltic rocks from the surrounding cliffs to construct the bridge. Finn´s rival later destroyed most of the causeway, but the remnants still can be seen today as basalt columns descending into the sea.“

We now know that the hexagonal columns along the rugged Irish coastline formed some sixty million years ago, during a time when the ancestors to modern plant species started to emerge and the Earth was going through a period of warming. At the time, Antrim (a modern-day county of Ireland), was subjected to an intense period of volcanic activity as a result of the opening of the Atlantic Ocean.

The Giants Causeway is only a small part of a vast network of lava flows which extended over the Antrim landscape; much of which, through the passage of time, has been eroded away. There were three distinct periods of volcanic activity which resulted in a thick succession of lava flows which has been subdivided into the Lower, Middle and Upper Basalts.

The lavas of the Giants Causeway belong to the Middle Basalts and comprise over 40,000 vertical columns. Recently, a new model was proposed for the formation of the striking polygonal pattern formed by the columns. They formed within a lava flow, which contracted and fractured while cooling very slowly. If the loss of heat is steady, then the pattern formed is uniform, but if areas cool faster than others, the fractures develop unevenly, meaning the columns form in a variety of sizes and shapes: expect anything from pentagons to heptagons if you get a chance to visit the Causeway!

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: The most powerful waterfall in Europe

On the menu this Monday is the opportunity to indulge in some incredible Icelandic geology. Take a look at a tremendous waterfall and the beautiful basalt it cuts through…

Iceland is famous for its striking landscapes, from fiery volcanoes and fields of basalt to violent geysers and pools of the most fantastic blue. One of the country’s many geological gems is Dettifoss waterfall – a 100-metre-high mass of white, tumbling water within Vatnajökull National Park.

With about 200 cubic metres of water falling each second, Dettifoss is widely reported to be the most powerful waterfall in Europe. It certainly looks the part.

Dettifoss waterfall, Iceland (Credit: Neil Davies, via imaggeo.egu.eu)

Dettifoss waterfall, Iceland (Credit: Neil Davies, via imaggeo.egu.eu)

Dettifoss is fed by melt from the Vatna Glacier (Vatnajökull), and the spring spike in meltwater means the fall’s flow can reach some 1500 cubic metres per second. By putting your hand to the rocks beside the fall you can feel the thundering torrents as the basalt vibrates beneath your fingertips.

The Jökulsá river snakes through the park’s volcanic canyons, which are constantly being cut by the erosive force of the fall. Dettifoss isn’t the only great feature in this photo though: the canyon walls are layered with lava flows that – even at a glance – reveal when they were deposited. The relatively smooth deposit at the base of the wall and the thinner skin of smooth basalt in the middle are the product of interglacial eruptions. The two rough, blocky-looking layers are columnar basalt deposits – a feature that forms when lava meets ice and cools so rapidly that it fractures into long, hexagonal columns.

Dettifoss up close. (Credit: Roger McLassus)

Dettifoss up close. (Credit: Roger McLassus)

For many geoscientists, Iceland is the top spot on the geological destination list. If you went to Iceland, where would you go? Been before? Tell the tale. We’d love to hear from you.

By Sara Mynott, EGU Communications Officer

Reference:

Bamlett, M., and Potter, J. F.: Icelandic geology: an explanatory excursion guide based on a 1986 Field Meeting. Proceedings of the Geologists’ Association 99.3, 221-248, 1988.

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.