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Geosciences Column: How erupting African volcanoes impact the Amazon’s atmosphere

Geosciences Column: How erupting African volcanoes impact the Amazon’s atmosphere

When volcanoes erupt, they can release into the atmosphere a number of different gases initially stored in their magma, such as carbon dioxide, hydrogen sulfide, and sulfur dioxide. These kinds of gases can have a big influence on Earth’s atmosphere, even at distances hundreds to thousands of kilometres away.

A team of researchers have found evidence that sulfur emissions from volcanic eruptions in Africa can be observed as far as South America, even creating an impact on the Amazon rainforest’s atmosphere. The results of their study were published last year in the EGU journal Atmospheric Chemistry and Physics.

Amazon Tall Tower Observatory based in the Amazon rainforest of Brazil (Credit: Jsaturno via Wikimedia Commons)

In September 2014, the Amazon rainforest’s atmosphere experienced an unusually sharp spike in the concentration of sulfate aerosols. During this period, the Amazon Tall Tower Observatory (ATTO) based in Brazil reported levels of sulfate never recorded before in the Amazon Basin.

Sulfate aerosols are particles that take form naturally from sulfur dioxide compounds in the atmosphere. When sulfate aerosols spread throughout the atmosphere, the particles often get in the way of the sun’s rays, reflecting the sunlight’s energy back to space. These aerosols can also help clouds take shape. Through these processes, the particles can create a cooling effect on Earth’s climate. Sulfate aerosols can also facilitate chemical reactions that degrade Earth’s ozone layer.

Fossil fuel and biomass burning have been known cause an increase in atmospheric sulfate, but researchers involved in the study found that neither human activity increased the level of sulfate in the atmosphere significantly. Instead, they examined whether a volcanic eruption could be responsible.

Scientists have suggested for some time that sulfur emissions in the Amazon could come from African volcanoes, but until now they’ve lacked proof to properly justify this idea.

Edited Landsat 8 image of the volcanoes Nyamuragira and Nyiragongo in Congo near the city of Goma. (Credit: Stuart Rankin via flickr, NASA Earth Observatory images by Jesse Allen, using Landsat data from the U.S. Geological Survey.

However, in this study the research team involved caught volcanic pair in the act. By analysing satellite images and aerosol measurements, the researchers found evidence that in 2014, emissions from the neighboring Nyiragongo-Nyamuragira volcano complex in the Democratic Republic of the Congo, central Africa, increased the level of sulfate particles in the Amazon rainforest’s atmosphere.

Satellite observations revealed that volcanoes experienced two explosive events in September 2014, releasing sulfur emissions into the atmosphere. During that year, the volcanic complex was reportedly subject to frequent eruptive events, sending on average 14,400 tonnes of sulfur dioxide into the atmosphere a day during such occasions. This amount of gas would weigh more than London’s supertall Shard skyscraper.

Map of SO2 plumes with VCD > 2.5 × 1014 molecules cm−2 color-coded by date of observation. The 15-day forward trajectories started at 4 km (above mean sea level, a.m.s.l.) at four locations within the plume detected on 13 September 2014 (light blue) are indicated by black lines with markers at 24 h intervals. (Credit: Jorge Saturno et al.)

The images further show that these emissions were transported across the South Atlantic Ocean to South America. The sulfate particles created from the emissions were then eventually picked up by an airborne atmospheric survey campaign and the ATTO in the Amazon.

The researchers of the study suggest that these observations indicate that African volcanoes can have an effect on the Amazon Basin’s atmosphere, though more research is needed to understand the full extent of this impact.

By Olivia Trani, EGU Communications Officer

References and further reading

Volcanic gases can be harmful to health, vegetation and infrastructure. Volcano Hazards Program. USGS.

Aerosols and Incoming Sunlight (Direct Effects). NASA Earth Observatory

Saturno, J., Ditas, F., Penning de Vries, M., Holanda, B. A., Pöhlker, M. L., Carbone, S., Walter, D., Bobrowski, N., Brito, J., Chi, X., Gutmann, A., Hrabe de Angelis, I., Machado, L. A. T., Moran-Zuloaga, D., Rüdiger, J., Schneider, J., Schulz, C., Wang, Q., Wendisch, M., Artaxo, P., Wagner, T., Pöschl, U., Andreae, M. O. and Pöhlker, C.: African volcanic emissions influencing atmospheric aerosols over the Amazon rain forest, Atmospheric Chemistry and Physics, 18(14), 10391–10405, doi:10.5194/acp-18-10391-2018, 2018.

Imaggeo on Mondays: Double strombolian explosions at Mt. Yasur volcano

Imaggeo on Mondays: Double strombolian explosions at Mt. Yasur volcano

The Yasur volcano located in Vanuatu archipelago is permanently active since its discovery in 1774 by Cpt. James Cook. Its activity consists mainly in moderate regular strombolian explosions within the crater. But sometimes, more powerful explosions throw ash and bombs beyond the crater rim and may represent a hazard for tourists and people living next to the volcano. Otherwise, the Mt Yasur displays regular fireworks, witness from the living Earth.

Description by Jean-Guillaume Feignon, as it first appeared on imaggeo.egu.eu.

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/.

Iceland’s rootless volcanoes

Iceland’s rootless volcanoes

Picture a volcano, like the one you learned about in primary school. Can you see it? Is it a big rocky mountain, perhaps with a bubbling pool of lava at the top? Is it perched above a chasm of subterranean molten rock?

I bet you didn’t picture this:

Rootless cones in the Lanbrotshólar district, S Iceland. Created by the 940AD Eldgjá eruption, there are over 4000 rootless cones in this area. Credit: Frances Boreham

You’d be forgiven for mistaking these small volcanoes for a scene from the Lord of the Rings, or maybe a grassy version of the surface of Mars (in fact, these kind of volcanoes do occur on Mars). These, however, are in Iceland and are called rootless cones.

These mini-volcanoes are unusual because they are ‘rootless’ meaning, unlike most volcanoes, they are not fed from the underground. To make them even stranger, they erupted only once and as part of the same event.

This type of volcanism is observed in several places around the world and occurs only in a unique set of circumstances. Despite showing similarities to more traditional volcanoes (like pyroclastic cones), the cones pictured above actually erupted several tens of kilometres from a ‘true’ volcano.

Rootless cones occur when a hot lava flow produced by an eruption travels away from the volcano and meets water. This can be a lake, a river, a glacier or simply a bit of soggy ground. The only criteria are that there needs to be water, and it needs to be trapped. Lava flows are usually at temperatures of over 1000oC and so, when they come into contact with trapped water or ice, its causes a build-up of steam, which can explode violently through the lava forming a rootless cone.

An article, published in the Journal of Volcanology and Geothermal Research in September by volcanologists from the University of Bristol and the University of Iceland, analysed the shape and location of some of these cones to understand more about the environment in which they formed.

These features are found in northeast Iceland in the region around lake Mývatn. The area, 50 km east of the city of Akureyri, is world famous for its beautiful scenery and unusual landscapes.

The volcano responsible for the phenomena is the Þrengslaborgir–Lúdentsborgir crater row which erupted around 2000 years ago. The eruption produced a huge lava flow that covered an area of 220 km2; over 2% of the surface of Iceland. The flow, known as the Younger Laxá Lava, permanently changed the landscape, diverting rivers and damming lakes. After its extrusion from the volcano, the stream of molten rock meandered through different environments including river gorges and wide glacial valleys.

The flow’s diverse 67km journey allowed lead author Frances Boreham and her colleagues, to learn how it interacted with its surroundings. As she explains it, “one of the things that makes the Younger Laxá Lava such a great case study is the range of environments that the lava flowed through.”

Rootless cones do not all look the same and vary greatly in size, from small ‘hornitos’ which are about the size of a small car, to large crater-shaped cones hundreds of metres in size. The scale and complexity of the deposits makes them difficult to study as Boreham explains, “One of the biggest challenges is trying to understand and unpick the different effects of lava and water supply on rootless eruptions. We see a huge variety in rootless cone shapes and sizes, but working out which aspects are controlled by the lava flow and which by the environment and available water is tricky, especially when working on a lava flow that’s approximately 2000 years old!”

From Boreham et al. 2016. “Different types of rootless cone and associated features. a) Scoriaceous rootless cone at Skutustaðir, Mývatn. Cone base is ~100 m diameter. b) Explosion pits (marked with arrows) surrounding a scoriaceous rootless cone near Mývatn. c) Spatter cone at Mý d) Hornito in Aðaldalur, NE Iceland. Map imagery on d ©2017 DigitalGlobe, Google.” Licensed under creative commons.

Despite their beauty, the rootless cones represent a more serious issue. Lava flows are often thought of as quite benign compared to other volcanic hazards like pyroclastic flows. The presence of rootless cones suggests this isn’t always the case. “As far as I know, none of these rootless cones are currently taken into account for lava flow hazard assessments, in Iceland or elsewhere in the world. While not applicable everywhere, wet environments with a history of lava flows, such as Iceland or parts of the Cascades, could be affected and these hazards should be considered in future risk assessments and plans, e.g. by identifying vulnerable property, roads and infrastructure.” said Boreham.

By Keri McNamara, freelance science writer

Keri McNamara is a freelance writer with a PhD in Volcanology from the University of Bristol. She is on twitter @KeriAMcNamara and www.kerimcnamara.com.

Geosciences Column: Using volcanoes to study carbon emissions’ long-term environmental effect

Geosciences Column: Using volcanoes to study carbon emissions’ long-term environmental effect

In a world where carbon dioxide levels are rapidly rising, how do you study the long-term effect of carbon emissions?

To answer this question, some scientists have turned to Mammoth Mountain, a volcano in California that’s been releasing carbon dioxide for years. Recently, a team of researchers found that this volcanic ecosystem could give clues to how plants respond to elevated levels of carbon dioxide over long periods of time. The scientists suggest that studying carbon-emitting volcanoes could give us a deeper understanding on how climate change will influence terrestrial ecosystems through the decades. The results of their study were published last month in EGU’s open access journal Biogeosciences.

Carbon emissions reached a record high in 2018, as fossil-fuel use contributed roughly 37.1 billion tonnes of carbon dioxide to the atmosphere. Emissions are expected to increase globally if left unabated, and ecologists have been trying to better understand how this trend will impact plant ecology. One popular technique, which involves exposing environments to increased levels of carbon dioxide, has been used since the 1990s to study climate change’s impact.

The method, also known as the Free-Air Carbon dioxide Enrichment (FACE) experiment, has offered valuable insight into this matter, but can only give a short-term perspective. As a result, it’s been more challenging for scientists to study the long-term impact that emissions have on plant communities and ecosystems, according to the new study.

FACE facilities, such as the Nevada Desert FACE Facility, creates 21st century atmospheric conditions in an otherwise natural environment. Credit: National Nuclear Security Administration / Nevada Site Office via Wikimedia Commons

Carbon-emitting volcanoes, on the other hand, are often well-studied systems and have been known to emit carbon dioxide for decades to even centuries. For example, experts have been collecting data on gas emissions from Mammoth Mountain, a lava dome complex in eastern California, for almost twenty years. The volcano releases carbon dioxide at high concentrations through faults and fissures on the mountainside, subsequently leaving its forest environment exposed to the emissions. In short, the volcanic ecosystem essentially acts like a natural FACE experiment site.

“This is where long-term localized emissions from volcanic [carbon dioxide] can play a game-changing role in how to assess the long-term [carbon dioxide] effect on ecosystems,” wrote the authors in their published study. Research with longer study periods would also allow scientists to assess climate change’s effect on long-term ecosystem dynamics, including plant acclimation and species dominance shifts.

Through this exploratory study, the researchers involved sought to better understand whether the long-term ecological response to carbon-emitting volcanoes is actually representative to the ecological impact of increased atmospheric carbon dioxide.

Remotely sensed imagery acquired over Mammoth Mountain, showing (a) maps of soil CO2 flux simulated based on accumulation chamber measurements, shown overlaid on aerial RGB image, (b) above-ground biomass (c) evapotranspiration, and (d) normalized difference vegetation index (NDVI). Credit: K. Cawse-Nicholson et al.

To do so, the scientists analysed characteristics of the forest ecosystem situated on the Mammoth Mountain volcano. With the help of airborne remote-sensing tools, the team measured several ecological variables, including the forest’s canopy greenness, height and nitrogen concentrations, evapotranspiration, and biomass. Additionally they examined the carbon dioxide fluxes within actively degassing areas on Mammoth Mountain.

They used all this data to model the structure, composition, and function of the volcano’s forest, as well as model how the ecosystem changes when exposed to increased carbon emissions. Their results revealed that the carbon dioxide fluxes from Mammoth Mountain’s soil were correlated to many of the ecological variables analysed. Additionally, the researchers discovered that parts of the observed environmental impact of the volcano’s emissions were consistent with outcomes from past FACE experiments.  

Given the results, the study suggests that these kind of volcanic systems could work as natural test environments for long-term climate research. “This methodology can be applied to any site that is exposed to elevated [carbon dioxide],” the researchers wrote. Given that some plant communities have been exposed to volcanic emissions for hundreds of years, this method could help paint a more comprehensive picture of our future environment as Earth’s climate changes.

By Olivia Trani, EGU Communications Officer

References

Cawse-Nicholson, K., Fisher, J. B., Famiglietti, C. A., Braverman, A., Schwandner, F. M., Lewicki, J. L., Townsend, P. A., Schimel, D. S., Pavlick, R., Bormann, K. J., Ferraz, A., Kang, E. L., Ma, P., Bogue, R. R., Youmans, T., and Pieri, D. C.: Ecosystem responses to elevated CO2 using airborne remote sensing at Mammoth Mountain, California, Biogeosciences, 15, 7403-7418, https://doi.org/10.5194/bg-15-7403-2018, 2018.