GeoLog

ash

Imaggeo on Mondays: The ash cloud of Eyjafjallajökull approaches

Imaggeo on Mondays: The ash cloud of Eyjafjallajökull approaches

This photo depicts the famous ash cloud of the Icelandic volcano Eyjafjallajökull, which disrupted air traffic in Europe and over the North Atlantic Ocean for several days in spring 2010. The picture was taken during the initial phase of the eruption south of the town of Kirjubæjarklaustur, at the end of a long field work day. Visibility inside the ash cloud was within only a few metres.

The eruption was preceded by years of seismic unrest and repeated magma intrusions. A first effusive fissure opened outside the ice shield of the volcano at the end of March 2010, followed by an explosive eruption in the main crater of the volcano in April 2010.

Iceland was well prepared for the eruption – the rest of the world obviously was not. The region around Eyjafjallajökull is sparsely populated, residents were prepared days before the eruption and the evacuation went smoothly. However, the grain size of the ejected volcanic ash was fine enough so that the unfavourable and unusual wind direction during these days transported the ash all the way to Europe and led to air space closures almost all over the continent.

By Martin Hensch, Nordic Volcanological Center, University of Iceland (now at Geological Survey of Baden-Württemberg, Germany)

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: Snow and ash in Iceland

Imaggeo on Mondays: Snow and ash in Iceland

Featuring today on the blog is the land of ice and fire: Iceland. That title was never better suited to (and exemplified), than it is in this photograph taken by Daniel Garcia Castellanos in June 2013. Snow capped peaks are also sprinkled by a light dusting of volcanic ash. Dive into this post to find out the source of the ash and more detail about the striking peak.

The picture is dominated by a snowed mountain in Southern Iceland, captured in June 2013, three years after the Eyjafjallajökull eruption. When Eyjafjallajokull erupted, it sent ash kilometers high into the atmosphere disrupting the air traffic in most Europe for weeks.

“This striking Icelandic landscape also inspired Tolkien’s fantasy in The Lord of the Rings,” explains Daniel, a researcher at the  Instituto de Ciencias de la Tierra Jaume Almera, in Barcelona.

Eyjafjallajokull is located in the Eastern Volcanic Zone in southern Iceland and the area photographed is among the youngest (less than 0.7 yr in age) and most active areas of Iceland, right on the contact where the Eurasian and the North American tectonic plates meet.The black rock seen in the image is tephra – fragments of rock that are produced when magma or or rock is explosively ejected (USGS) – from the neighboring Torfajökull rhyolitic stratovolcanic system, know for its cone shaped volcanoes built from layer upon layer of lava rich in silica and consequently very viscous. The light-green colour consists of the ubiquitous Icelandic moss.

In the image, the remnants of winter white snow are dotted with fine grey ashes from the Eyjafjallajökull 2010 eruption (about 30 km to the south of this image). Years after the Eyjafjallajökull eruption, the volcano still burns hot and its lighter ashes are still blown over southern Iceland providing this magical colors over the entire region.

Daniel’s adventures in Iceland didn’t stop at simply photographing stunning volcanic landscapes. He also had the privilege to see the inside of one of the volcanoes in the Eastern Volcanic Zone close up. Watch his descent into the Thrihnukagigur volcanic conduit over on his blog, Retos Terrícolas.

Imaggeo on Mondays: Hot and cold – how ash influences glacial landscapes

This week’s Imaggeo on Mondays is brought to you by Joanna Nield, a lecturer in physical geography at the University of Southampton. Nield explains how volcanic eruptions can impact glaciers and how ash fall can both accelerate and slow down glacial melt…

“Fjallsjökull after the 2011 Grímsvötn eruption” by Joanna Nield, distributed by the EGU under a Creative Commons licence.

“Fjallsjökull after the 2011 Grímsvötn eruption” by Joanna Nield, distributed by the EGU under a Creative Commons licence.

This photo was taken at Fjallsjökull, Iceland in July 2011, shortly after the eruption of Grímsvötn volcano (21 – 30 May 2011).  The Grímsvötn volcanic eruption partially covered many of the surrounding glaciers in a spatially variable layer of tephra ash.

Fjallsjökull (and Hrútárjökull, the smaller lobe on the left of this photo) were south-east of the volcano, exposing them to the dominant wind moving the ash plume and the subsequent ash fall.  We were lucky enough to use terrestrial laser scanning to study the impact on nearby Svínafellsjökull soon after the eruption with funding from the Royal Society – our daily surface measurements showed that shortly after an eruption, ice melt rates could be reduced by as much as 59% compared to clean ice model predictions.

When ash covers an ice surface, it changes the rate that snow and ice is lost from the glacier (the ablation rate).  Dark coloured ash will reduce the albedo (reflectiveness) of the surface, causing it to absorb more heat. This causes an increase in melt rates for thin debris layers, but thick layers of ash insulate the ice and reduce melt.  On top of this, complex feedbacks between debris cover, meltwater and surface shape redistribute ash and change surface roughness – which also influences ablation rates.  It is important to understand these ash-ice interactions as well as feedbacks between the surface and atmosphere to better quantify the impact of volcanic eruptions in glaciated landscapes.

By Joanna Nield, University of Southampton

References:

Nield, J.M., Chiverrell, R.C., Darby, S.E., Leyland, J., Vircavs, L.H., Jacobs, B.:  Complex spatial feedbacks of tephra redistribution, ice melt and surface roughness modulate ablation on tephra covered glaciers. Earth Surface Processes and Landforms, 38: 95-102, 2013

Nield, J.M., King, J., Wiggs, G.F.S., Leyland, J., Bryant, R.G., Chiverrell, R.C., Darby, S.E., Eckardt, F.D., Thomas, D.S.G., Vircavs, L.H., Washington, R.: Estimating aerodynamic roughness over complex surface terrain.  Journal of Geophysical Research – Atmospheres, 2013

The EGU’s open access geoscience image repository has a new and improved home at http://imaggeo.egu.eu! We’ve redesigned the website to give the database a more modern, image-based layout and have implemented a fully responsive page design. This means the new website adapts to the visitor’s screen size and looks good whether you’re using a smartphone, tablet or laptop.

Photos uploaded to Imaggeo are licensed under Creative Commons, meaning they can be used by scientists, the public, and even the press, provided the original author is credited. Further, you can now choose how you would like to licence your work. Users can also connect to Imaggeo through their social media accounts too! Find out more about the relaunch on the EGU website.