GeoLog

Portugal

Imaggeo on Mondays: A painted forest fire

Imaggeo on Mondays: A painted forest fire

This week’s featured image may appear to be a painted landscape, but the picture is in fact a photo, taken ten years ago by Victoria Arcenegui, an associate professor at Miguel Hernández University in Spain, during a controlled forest fire in northern Portugal.

The blaze is actually hot enough to distort the image, making some of the flames appear as brush strokes, beautifully blurring together the colours of the fire, trees and smoke.

Intense heat such as this influences how light travels to both the human eye and a camera lens. As air warms it expands, while colder air becomes denser. As a result, light travels quicker through thinner warm air but is refracted more in denser cool air. So when there are shifting pockets of cold and hot air, the speed of light through air is constantly changing, creating a shimmering effect.

The prescribed fire in this photo is not only showcasing an interesting phenomenon, but is also providing an important service to the region’s ecosystem. For decades, forest fires were often considered detrimental to the environment, however, researchers say that small natural fires help strengthen ecosystems. For example, by burning old dead vegetation, these fires cycle nutrients back to the soil and clear space for new plants to grow. In addition, some plant rely on fires to spread or activate seeds. Historically, many wildlife management programmes prevented smaller fires from removing vegetation, subsequently creating overgrown forests, which are more susceptible to larger, more destructive fires.

Now, many researchers are studying the effectiveness of prescribed burning, where forests are periodically set on fire in a controlled setting to replicate the ecological impact of natural fires and reduce wildfire risk.

By Olivia Trani, EGU Communications Officer

References

Santín, C. and Doerr, S. H.: Fire effects on soils: the human dimension, Philosophical Transactions of the Royal Society B: Biological Sciences, 371(1696), 20150171, doi:10.1098/rstb.2015.0171, 2016.

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: Small scale processes, large scale landforms

Imaggeo on Mondays: Small scale processes, large scale landforms

This picture was taken in a sea cliff gully landscape at the Portuguese coast. It shows the microrelief which small scale wash and erosional processes produce in these poorly consolidated sediments. These small scale landforms could be interpreted as initial stages of larger scale gully landforms, which can be seen in the back. This highlights the importance of regarding scales and scale linkages in the geosciences.

Description by Jana Eichel, 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/.

Imaggeo on Mondays: A volcanic point of view

Imaggeo on Mondays: A volcanic point of view

It’s not every day that you can peer into a volcano, much less gaze out at the sky from the inside of one. The Algar do Carvão, or “the Cavern of Coal,” is one of the few places on Earth where you can explore the underground reaches of a volcanic site.

The volcanic pit is found on the island of Terceira, part of the Azores archipelago. This collection of islands is an autonomous region of Portugal, located in the Atlantic Ocean about 1800 kilometres west from the Portuguese mainland. The archipelago is an especially volcanic hotspot, situated on the border of three major tectonic plates: the North American, Eurasian and African Plates.

The Algar do Carvão is essentially an ancient lava tube, made up of a volcanic chimney, about 80-90 metres deep, which then opens up into secondary magma chambers. The chimney formed first roughly 3,200 years ago, in the wake of a volcanic eruption. Then a second eruption, occurring in the same spot 1,200 years later, created many of the magma chambers seen today.

A profile of the Algar do Carvão, based on a similar cutaway produced by “Os Montanheiros,” (Credit: Ruben JC Furtado / Wikimedia Commons)

Despite what the cavern’s title suggests, the volcanic site is not a source of coal, but rather named for the walls’ dark black, ‘sooty’ colour. The volcanic pit is actually better known by geologists and cave enthusiasts for its source of silica-rich stalagmites and stalactites, a feature not commonly found in this region. Scientists have hypothesized that the structures’ silicate composition could have come in part from the volcano’s past hydrothermal activity or its population of diatoms, microorganisms which contain silica in their cell walls.

As you can see from the lush flora featured in today’s photo, the Algar do Carvão is teeming with life. Vegetation blankets the mouth of the cone structure and many animal populations thrive in the cavern environment. The volcanic pit is also home to several species found only on the Azores islands, like the troglobian spider Turinyphia cavernicola and the Terceira Island scarab Trechus terceiranus.

References

Daza, D. et al.: Isotopic composition (δ¹⁸ O y δD) of silica speleothems of the Algar do Carvão and Branca Opala volcanic caves (Terceira Island, Azores, Portugal), Estudios Geológicos, 70, 2, 2014.

Borges, P. A. V., Carlos Crespo, L., Cardoso, P.: Species conservation profile of the cave spider Turinyphia cavernicola (Araneae, Linyphiidae) from Terceira Island, Azores, Portugal, Biodiversity Data Journal 4: e10274, 2016.

Nunes, J.C., J.P. Constância, M.P. Costa, P. Barcelos, P.A.V. Borges & F. Pereira: Route of Azores Islands Volcanic Caves. Associação Os Montanheiros & GESPEA (Ed.). 16, 2011.

Algar do Carvão, Associação Os Montanheiros

Natural Monument of Algar do Carvão, 2011 Regional Secretariat for Agriculture and Environment, Governo dos Açores

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/.

Wildfires in the wake of climate change

Wildfires in the wake of climate change

Last year saw some of the biggest blazes in history, and may be a sign of things to come.

2017 was a record year for wildfires. California and neighboring western states saw the most destructive fire in US history, with an estimated 18 billion dollars worth of damage over the season. In central Portugal, fires caused 115 deaths over the same period. Researchers presenting at a press conference at the European Geosciences Union General Assembly in Vienna, Austria, suggest this may be a sign of things to come.

With climate change, wildfires are expected to be on the rise, as fire-prone regions become hotter and drier. But how did weather and climate contribute to this disastrous season? Strong winds and warm temperatures are thought to be responsible for last year’s fires in California, but it remains unclear how much climate change contributed to these conditions. Etienne Tourigny, of the Barcelona Supercomputing Centre, has been on the case.

“Would this event have been possible with or without climate change?” Tourigny asks. “It’s hard to say. What we can say is that there is a high chance that these kinds of events will be more present and more frequent in the future, especially if we see temperatures increasing as they have”

Central Portugal is already very susceptible to wildfires. It’s hot, it’s dry and it’s forested: a recipe for the perfect storm. The 2017 season was particularly tragic due to an unusual set of circumstances: a tropical cyclone passed as the Portuguese Centro Region was ablaze. The nation hoped that the hurricane would bring rain to put out the fires, but, instead, the storm passed the area by, bringing strong winds and spreading the flames.

200 thousand hectares were burned in two days. Even if this was spread throughout an entire season, it would be a very bad year. Speaking at the conference, António Ferreira, a scientific coordinator at the Research Centre for Natural Resources, Environment and Society in Coimbra, Portugal, puts it frankly: “that’s hell as it was taught in Sunday School.”

The region is also vulnerable to climate change, and an increased risk of wildfires is expected by the end of the century. New strategies are needed to prevent such losses in future. Ferreira emphasised that there is no quick fix and, to reduce the risk, policies, plans, habits and investment have to change.

Even in the high Arctic, fires present a threat. This time, it’s not a direct risk to life or infrastructure, but a threat to the environment. Nikolaos Evangeliou, from Norwegian Institute for Air Research, stated that, even in icy regions, wildfires have the capacity to alter the Earth’s climate and accelerate melting.

Thawing permafrost during the 2017 summer left Greenland’s peatlands vulnerable to wildfires and between 31 July and 21 August about 2300 hectares of peatland were burned. Seven tonnes of black carbon generated by the fires rained down on the ice sheet, making the surface darker and causing it to absorb more heat.

If the ice sheet darkens, it reduces Earth’s ability to deflect solar radiation, allowing more of the sun’s energy to warm the planet. The change in Earth’s reflectivity following last year’s wildfires was small, but it is a warning. With larger fires predicted as the climate warms, we could expect much bigger changes to the Earth’s reflectivity towards the end of the century. Such warming spells further trouble for wildfire-sensitive regions.

By Sara Mynott, EGU 2018 General Assembly Press Assistant

References

Evangeliou et al. Open Fires in Greenland: An Unusual Event and its Impact on the Albedo of the Greenland Ice Sheet. Geophysical Research Abstracts, Vol. 20, EGU2018-12383, 2018, EGU General Assembly 2018.

Leitão et al. Dealing with climate change: how to cope with wildfire threat in a climate transition region. Geophysical Research Abstracts, Vol. 20, EGU2018-16640, 2018, EGU General Assembly 2018.

Tourigny et al. An observational study of the extreme wildfire events of California in 2017: quantifying the relative importance of climate and weather. Geophysical Research Abstracts, Vol. 20, EGU2018-9545-1, 2018, EGU General Assembly 2018.