GeoLog

Andes

Imaggeo on Mondays: Sneaking up from above

Imaggeo on Mondays: Sneaking up from above

Take some ice, mix in some rock, snow and maybe a little mud and the result is a rock glacier. Unlike ice glaciers (the ones we are most familiar with), rock glaciers have very little ice at the surface. Looking at today’s featured image, you’d be forgiven for thinking the Morenas Coloradas rock glacier wasn’t a glacier at all. But appearances can be misleading; as Jan Blöthe (a researcher at the University of Bonn) explains in today’s post.

The picture shows the Morenas Coloradas rock glacier, a pivotal example of actively creeping permafrost (ground that remains frozen for periods longer than two consecutive years) in the dry central Andes of Argentina. The rock glacier is located in the “Cordon del Plata” range, some 50 km east of the city of Mendoza.

The rock glacier fills the entire valley and slowly creeps downslope creating impressive lobes and tongues with steep fronts. With more than 4 km length, the Morenas Coloradas is one of the largest rock glaciers of the central Andes.

Taken from a drone, the picture looks straight up the rock glacier into the main amphitheatre-like valley formed by glacial erosion located at ~4500 m.a.s.l. From there, large amounts of loose debris are moved down the valley at speeds on the order of a few meters per year. The creeping process forms tongues of material that override each other, producing the characteristic surface with steps, ridges and furrows.

The central Andes of Argentina are semi-arid, receiving less than 500 mm of precipitation per year, mainly falling as snow during the winter. The region is famous for its wines, which are grow in the dry Andean foreland that is heavily dependent on meltwater from the mountains. How much of this meltwater is actually stored in ice-rich permafrost landforms is unknown.

As opposed to ice glaciers, rock glaciers show a delayed reaction to a changing climate, as large amounts of debris cover the ground ice, isolating it from rising air temperatures. With large areas located above the lower altitudinal limit of mountain permafrost of ~3600 m.a.s.l., the central Andes of Argentina might store significant amounts of water in the subsurface.

Using mainly near-surface geophysics, our research tries to quantify the water storage capacities in the very abundant and impressive rock glaciers of the region. The Morenas Coloradas rock glacier is of special importance in this regard, as first geophysical measurements date back to the 1980s. Since then, active layer thickness has dramatically increased in the lower parts of the rock glacier, indicating that also the ground ice of the permafrost domain of the central Andes is suffering under the currently warming climate.

A final remark: Thanks goes to the entire team of this research project, namely Christian Halla, Estefania Bottegal, Joachim Götz, Lothar Schrott, Dario Trombotto, Floreana Miesen, Lorenz Banzer, Julius Isigkeit, Henning Clemens, and Thorsten Höser.

By Jan Blöthe, University of Bonn, Germany

Imaggeo on Mondays: Late Holocene Fever

Imaggeo on Mondays: Late Holocene Fever

A huge ice fall off the Perito Moreno glacier in the Los Glaciares National Park, southwest Santa Cruz Province, Argentina, was voted one of the three best pictures entered into the EGU’s annual photo contest, by the conference participants at the 2015 General Assembly.

Perito Moreno glacier is one of 48 glaciers feeding into the Southern Patagonia ice field, which combined with the Northern Patagonia ice field, comprise the largest temperate ice mass in the Southern Hemisphere. Like many other mountain glaciers, Perito Moreno, is highly sensitive to climate change. At the surface of a glacier, erosive processes know as ablation, can remove ice from the bulk of the glacial mass. If the ice lost is not replaced in sufficient quantities by rainfall and snow provided by weather systems, the energy balance of the glacier is upset and the glacier starts to shrink. At the glacial surface, the processes of accumulation and ablation, clearly manifest the strict connection between glaciers and climate.

In a recent interview, Bernard Francou, a renowned French glaciologist, explained that glacier depletion in the Andes region has increased dramatically in the second half of the 20th century. In recent decades the glacier recession rates increased at an unprecedented rate when compared to the last the last three centuries. It is estimated that glaciers in this region have lost between 35% and 50% of their area and volume since 1976.

Christian Massari, a hydrology postdoctoral researcher of the Italian National Research Council, says “capturing the precise moment when the large chunk of ice broke off the glacier front was not easy task. It required concentration to patiently wait two hours, on a hot January day, to capture the critical moment.”

You can watch a video of a similar ice fall event, which took place in January 2012, here.

Southern Patagonia Ice Field. Credit: Astronaut photograph ISS038-E-47324 was acquired on February 13, 2014, with a Nikon D3S digital camera using a 65 millimeter lens, and is provided by the ISS Crew Earth Observations Facility and the Earth Science and Remote Sensing Unit, Johnson Space Center. The image was taken by the Expedition 38 crew. It has been cropped and enhanced to improve contrast, and lens artifacts have been removed.

Southern Patagonia Ice Field . Credit: Astronaut photograph ISS038-E-47324 was acquired on February 13, 2014, with a Nikon D3S digital camera using a 65 millimeter lens, and is provided by the ISS Crew Earth Observations Facility and the Earth Science and Remote Sensing Unit, Johnson Space Center. The image was taken by the Expedition 38 crew. It has been cropped and enhanced to improve contrast, and lens artifacts have been removed. (Distributed via Nasa Earth Observatory, Image of the Day ).

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 Patagonia landscape dominated by volcanoes

Patagonia Landscape. Credit: Lucien von Gunten (distributed via imaggeo.egu.eu)

Patagonia Landscape. Credit: Lucien von Gunten (distributed via imaggeo.egu.eu)

Imagine a torrent of hot and cold water, laden with rock fragments, ash and other debris hurtling down a river valley: this is a lahar. A by-product of eruptions of tall, steep-sided stratovolcanoes, lahars, are often triggered by the quick melting of snow caps and glaciers atop high volcanic peaks.

The history of the Ibañes River and its valley, in southern Chile, are dominated by their proximity to Hudson volcano (or Cerro Hudson, as it is known locally). Located in the Andean Southern Volcanic Zone, the volcano has an unsettling history of at least 12 eruptions in the last 11,000 years. That equates to a major eruption every 3,800 years or so! The volcano has a circular caldera, home to a small glacier and is neighboured by the larger Huemules glacier.

One of the most significant eruptions occurred in 1991. It is thought to be one of the largest eruptions, by volume, of the 20th Century. At its peak, the eruption produced an ash plume thought to be in excess of 17km high, with ash being deposited as far away as the Falkland Islands. The initial eruptive phase was highly explosive. Known as phreatomagmatic eruption, hot and gas rich magma mixed with ice and water from the glacier on the summit of Mt. Hudson. As the eruption progressed, a period of sustained melting of both the caldera glacier and Huemules glacier began. The result of this was a 12 hour period of persistent lahar generation, with volcanic debris laden torrents racing down the Ibañes valley and its neighbours.

Fast forward to 2009 and the effects of the eruption of 1991 are still visible in the Patagonian Landscape. Lucien von Gunten photographed the inhospitable ‘Bosque Muerto’ (Dead Forest), in the Ibañes valley. The accumulation of the lahar deposits and the ash fall from the eruptive column clogged up the Ibañes river and valley killing a large proportion of the local flora and fauna. The ‘Bosque Muerto’ remains a stark reminder of the devastating effects of the 1991 eruption.

Reference

David J. Kratzmann, Steven N. Carey, Julie Fero, Roberto A. Scasso, Jose-Antonio Naranjo, Simulations of tephra dispersal from the 1991 explosive eruptions of Hudson volcano, Chile, Journal of Volcanology and Geothermal Research, Volume 190, Issues 3–4, 20 February 2010, Pages 337-352

 

If you pre-register for the 2015 General Assembly (Vienna, 12 – 17 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: Paramo Soil

Paramo Soil. (Credit: Martin Mergili,via imaggeo.egu.eu)

Paramo Soil. (Credit: Martin Mergili,via imaggeo.egu.eu)

What lies between 3000m and 4800m above sea level in the mountains of the Andes? A very special place dominated by an exceptional ecosystem: The Páramo. Picture lush grasslands with a unique population of flora and fauna, some of which is found nowhere else on Earth.

Páramos stretch from Ecuador to Venezuela, across the Northern Andes and also occur at high elevation in Costa Rica. The climate here is changeable; dowsing rains can be immediately followed by clear skies and blazing sunshine. Overall, the areas experience low average temperatures and rates of evaporation but moderate amounts of precipitation. It is this changeable climate that means the Páramo is thought to be an evolutionary hot spot, where biodiversity is budding faster than at any other place on Earth.

However, were it not for the traditional Andean clothing the girl is wearing in our Imaggeo on Monday’s image, you wouldn’t immediately know this photograph was taken close to the equator. Martin Mergili visited the Páramos of Ecuador, back in 2007, as a PhD student of the University of Innsbruck (Austria) on a field trip around the South American country. Martin gives a detailed account of how the Páramo soil pictured in the image came to be:

‘Whilst 100 km to the east, in the lowlands of the Amazon rainforest, organic matter is rapidly decomposed and soils may be tens of metres deep due to extensive weathering, the reverse is the case here, 3000 m higher up. In the tropical highlands of the Páramo, the year round moist and cool regime slows decomposition and weathering. The obvious result is a rather peaty soil, rich in organic content, supporting pasture grounds used for herding sheep.’

The Páramos support the local human population by providing the main source of water in the Andean valleys whilst the grasslands provide extensive fodder for grazing cattle or sheep. To provide fresh appetising grasses farmers regularly burn the natural vegetation. To what extent the soil of the Páramos is altered as a result of this practice is not clear, but it might provide an explanation for the presence of the dark grey layer seen in the photograph.’Alternatively’, explains Martin, ‘as the area is influenced by significant volcanic activity, this layer might well be the result of ash falls.’

A further feature of interest is the sequence of undulating layers below the organic soil: still part of the soil, it represents a set of volcanic or sedimentary strata with varying resistance to weathering and erosion, probably influenced by tectonic forces. A metre below the bottom of the image, you would come across unweathered rocks.

Páramo El Ángel in Ecuador with Espeletia plants (Credit: Martin Mergili via http://www.mergili.at/worldimages/)).

Páramo El Ángel in Ecuador with Espeletia plants (Credit: Martin Mergili via http://www.mergili.at/worldimages/)

By Laura Roberts Artal, EGU Communications Officer and Martin Mergili, BOKU University, Vienna

References

Buytaer. W., Sevink. J., De Leeuw. B., Deckers. J.:   Clay mineralogy of the soils in the south Ecuadorian paramo region, Geoderma, 127, 144-129, 2005

Hofstede. R. G.M.: The effects of grazing and burning soil and plant nutrient concentration in Colombian paramo grasslands, Plant and Soil, 173, 1, 111-132, 1995

 

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.

Follow

Get every new post on this blog delivered to your Inbox.

Join other followers: