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Imaggeo on Mondays: Lava highway in Kanaga Island

Imaggeo on Mondays: Lava highway in Kanaga Island

On a rare sunny day, Mattia Pistone (a researcher at the Smithsonian Institution in Washington DC) was able to capture this spectacular shot of Kanaga, a stratovolcano in the remote Western Aleutians, which is usually veiled by thick cloud.

The Western Aleutians form a chain of 14 large and 55 small volcanic islands, belonging to one of the most extended volcanic archipelagos on Earth (1900 km), stretching from Alaska across the northern Pacific towards the shores of Russia.

As part of a team of researchers, Mattia spent three grueling weeks in the isolated region. Being one of the most extended volcanic arc systems on Earth, the Aleutians can shed light on one of the most fundamental questions in the Earth sciences: how do continents form?

The Earth’s landmasses are made of continental crust, which is thought to be largely andesitic in composition. That could mean it is dominated by a silicon-rich rock, of magmatic origin, which is fine grained and usually light to dark grey in colour. However, basaltic magmas derived from the Earth’s upper mantle and erupted at active volcanoes contribute to chemistry of the continental crust. The fact that continental crust bears the chemical hallmarks of both suggests that the formation of new continents must somehow be linked to motion of magma and its chemistry.

Establishing the link between magma generation, transport, emplacement, and eruption can therefore significantly improve our understanding of crust-forming processes associated with plate tectonics, and, particularly, help determining the architecture and composition of the continental crust. The Alaska-Aleutian archipelago is a natural laboratory which offers a variable range of volcanic rocks. The islands present a perfect opportunity for scientists to try and understand the origin of continents.

By collecting samples of volcanic ash erupted at Kanaga and other volcanoes of the Aleutian arc, Mattia and his colleagues are currently investigating the origin of this volcanic ash. Understanding its chemistry allow the team to get a clearer idea of the conditions that were present while the magma was forming and ascending, for example, how much water and iron were present.

The team were based on the Maritime Maid research vessel, and hoped from island to island collecting samples and taking measurements of volcanic activity as part of a large research consortium called GeoPRISMS, funded by the National Science Foundation. The field work was supported by a Bell 407 helicopter and its crew.

Today’s featured image shows an andesitic lava flow erupted in 1906. The volcanic deposits were explored during the field geological mission by Mattia and the team. Kanaga last erupted in 1994. Ash from that eruption was found in the nearby island of Adak. Even at present, there is a highly active system of fumaroles at the summit of the volcano.

If you pre-register for the 2017 General Assembly (Vienna, 22 – 28 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/.

Imaggeo on Mondays: A Bubbling Cauldron

Imaggeo on Mondays: A Bubbling Cauldron

Despite being a natural hazard which requires careful management, there is no doubt that there is something awe inspiring about volcanic eruptions. To see an erupting volcano up close, even fly through the plume, is the thing of dreams. That’s exactly what Jamie  Farquharson, a researcher at Université de Strasbourg (France) managed to do during the eruption of the Icelandic volcano Bárðarbunga. Read about his incredible experience in today’s Imaggeo on Monday’s post.

The picture shows the Holuhraun eruption and was taken by my wife, Hannah Derbyshire. It was taken from a light aircraft on the 11th of November of 2014, when the eruption was still in full swing, looking down into the roiling fissure. Lava was occasionally hurled tens of metres into the air in spectacular curtains of molten rock, with more exiting the fissure in steady rivers to cover the surrounding landscape.

Iceland is part of the mid-Atlantic ridge: the convergent boundary of the Eurasian and North American continental plates and one of the only places where a mid-ocean ridge rears above the surface of the sea. It’s situation means that it is geologically dynamic, boasting hundreds of volcanoes of which around thirty volcanic systems are currently active. Holuhraun is located in east-central Iceland to the north of the Vatnajökull ice cap, sitting in the saddle between the Bárðarbunga and Askja fissure systems which run NE-SW across the Icelandic highlands.

Monitored seismic activity in the vicinity of Bárðarbunga volcano had been increasing more-or-less steadily between 2007 and 2014. In mid-August 2014, swarms of earthquakes were detected migrating northwards from Bárðarbunga, interpreted as a dyke intruding to the east and north of the source. Under the ice, eruptions were detected from the 23rd of August, finally culminating in a sustained fissure eruption which continued from late-August 2014 to late-February of the next year.

My wife and I were lucky enough to have booked a trip to Iceland a month or so before the eruption commenced and, unlike its (in)famous Icelandic compatriot Eyjafjallajökull, prevailing wind conditions and the surprising lack of significant amounts of ash from Holuhraun meant that air traffic was largely unaffected.

At the time the photo was taken, the flowfield consisted of around 1000 million cubic metres of lava, covering over 75 square kilometres. After the eruption died down in February 2015, the flowfield was estimated to cover an expanse of 85 square kilometres, with the overall volume of lava exceeding 1400 million cubic metres, making it the largest effusive eruption in Iceland for over two hundred years (the 1783 eruption of Laki spewed out an estimated 14 thousand million cubic metres of lava).

Numerous “breakouts” could be observed on the margins of the flowfield as the emplacing lava flowfield increased in both size and complexity. Breakouts form when relatively hot lava, insulated by the cooled outer carapace of the flow, inflates this chilled carapace until it fractures and allows the relatively less-viscous (runnier) interior lava to spill through and form a lava delta. Gas-rich, low-viscosity magma often results in the emission of high-porosity (bubbly) lava. My current area of research examines how gases and liquids can travel through volcanic rock, a factor that is greatly influenced by the evolution of porosity during and after lava emplacement.

Flying through the turbulent plume one is aware of a strong smell of fireworks or a just-struck match: a testament to the emission of huge volumes of sulphur dioxide from the fissure. Indeed, the Icelandic Met Office have since estimated that 11 million tons of SO2 were emitted over the course of the six-month eruption, along with almost 7 million tons of CO2 and vast quantities of other gases such as HCl. These gases hydrate and oxidise in the atmosphere to form acids, in turn leading to acid rain. The environmental impact of Holuhraun as a gas-rich point source is an area of active research.

By Jamie Farquharson, PhD researcher at Université de Strasbourg (France)

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/.

Volcanic darkness marked the dawn of the Dark Ages

Volcanic darkness marked the dawn of the Dark Ages

The dawn of the Dark Ages coincided with a volcanic double event – two large eruptions in quick succession. Combined, they had a stronger impact on the Earth’s climate than any other volcanic event – or sequence of events – in the last 1200 years. Historical reports reveal that a mysterious dust cloud dimmed the sun’s rays between in 536 and 537 CE, a time followed by global societal decline. Now, we know the cause.

By combining state-or-the-art ice core measurements with historical records and a climate model, researchers from GEOMAR Helmholtz Centre for Ocean Research, Germany, and a host of international organisations showed that the eruptions were responsible for a rapid climatic downturn. The findings, published in Climatic Change, were presented at the EGU General Assembly in April 2016.

Explosive volcanic eruptions typically emit large volumes of ash and gas high into the atmosphere. The way this ash spreads depends both on how high up it’s propelled and the prevailing weather conditions. When it reaches the stratosphere, it has the capacity to spread far and wide over the Earth, meaning the eruption will have much more than a local impact.

Individually, these events were strong, but not that strong. Their combined force was what made their affect of the earth’s climate so significant. They occurred closely in time and were both in the Northern hemisphere.

Volcanic emissions reflect light back into space. Consequently, less light and, importantly, less heat reaches the surface, causing the Earth to cool. Diminishing sunlight following the eruptions resulted in a 2 °C drop in temperature, poor crop yields and population starvation. The drop in temperature led to a 3-5 year decline in Scandinavian agricultural productivity – a serious problem.

This double event had a major impact on agriculture in the northern hemisphere – particularly over Scandinavia. It’s likely that societies could withstand one bad summer, but several would have been a problem.

An ash covered plant via Wikimedia Commons.

An ash covered plant via Wikimedia Commons.

There’s agricultural evidence to support the theory too. Pollen records read from sediment cores can be used to work out when agricultural crops covered the land and when the land was ruled by nature. Scandinavian cores suggest there was a shift from agricultural crops to forest around the time of the eruption. There is some scepticism regarding the cause of this shift, but the implication is that when food decreases, so does the population, This means there’s no need to farm as much land, nor enough people to do so. In the absence of agriculture, nature takes over and trees once again cover the land.

By Sara Mynott, EGU Press Assistant and PhD candidate at the University of Exeter.

Sara is a science writer and marine science PhD candidate from the University of Exeter. She’s investigating the impact of climate change on predator-prey relationships in the ocean, and was one of our Press Assistants this year’s General Assembly.

Imaggeo on Mondays: Mount Etna

Imaggeo on Mondays: Mount Etna

In this week’s Imaggeo on Monday’s image an almost Martian looking landscape, with ombre coloured soils, gives way to gently rolling hills, covered in luscious woods and vegetation. Were it not for the trees in the distance, you would be forgiven for thinking this image had been captured by a Mars rover. In truth, it is an entirely more earthly landscape: welcome to the slopes of Mt. Etna! Keep on reading as Alicia Mourgán, a researcher at the University of València, gives an overview of the origin of the richly fertile soils and climate of Europe’s tallest active volcano.

Mount Etna is associated with the subduction of the African Plate under the Eurasian Plate. A number of theories have been proposed to explain Etna’s location and eruptive history: rifting processes, a hot spot, and the intersection of structural breaks in the crust. Scientists are still debating which best fits their data, and are using a variety of methods to build a better image of the Earth’s crust underneath the volcano.

The soil around the volcano is very rich in minerals, owing to its volcanic origin. It is composed of a number of eruptive materials of different ages, including ash, sand and desintegrated lava (from one or more flows). Volcanic rocks make some of the best soils on Earth: not only are they formed of a wide variety of common elements, these readily separate into their elemental forms.

In the Etna region there are substantial differences in climate, not only compared to the rest of Sicily, but also from one area of the volcano to another. This is due to the fact that the Etna region has semi-circular shape, spread from north to south-west. This characteristic allows for different environments to be formed each with its own microclimate, benefiting from different exposure and changing proximity to the sea. Altitude in the Etna region varies between 450 m and 1100m above sea level. This factor is the main reason for the temperature changes between the day and night and also across seasons.

Compared to the rest of Sicily, Etna is pretty wet too. The highest levels of precipitation are recorded on the east slopes of the volcano. Rain can be practically absent over the summer, but precipitation can also be very high during the autumn/winter period.

By Alicia Morugán, University de València, València, Spain

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/.

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