GeoLog

Chile

Imaggeo on Mondays: Dust devil sighting in the Atacama Desert

Imaggeo on Mondays: Dust devil sighting in the Atacama Desert

Dust devils are like miniature tornadoes, they form when a pocket of hot air near the surface moves fast upward and meets cooler air above it. As the air rapidly rises, the column of hot air is stretched vertically, thereby moving mass closer to the axis of rotation, which causes intensification of the spinning effect by conservation of angular momentum. In the Atacama Desert [in Chile] they are really common, and the desert is a perfect “lab” to observe and study their formation!

Description by Rita Nogherotto, 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: Cordillera de la Sal

Imaggeo on Mondays: Cordillera de la Sal

The photograph shows the Valle de la Luna, part of the amazing Cordillera de la Sal mountain range in northern Chile. Rising only 200 metres above the basin of the Salar de Atacama salt flat, the ridges of the Cordillera de la Sal represent a strongly folded sequence of clastic sediments and evapourites (salt can be seen in the left portion of the image), with interspersed volcanic material.

This formation evolved when the depression between the Cordillera Domeyko mountain range and the main Andean mountain ranges, filled by an ancient salt flat, was squeezed together over the last 10-15 million years, leaving behind the folded belt of hills seen today. Sand brought along from adjacent areas by the winds was caught between the ridges of the Cordillera de la Sal, accumulating to form the impressive dune shown in the foreground of the image.

Under normal conditions, the perfectly shaped Licancabur Volcano, forming the border between Chile and Argentina, would appear in the background of this sunset scene. However, the image was taken during the Invierno Boliviano (Bolivian winter), when humid air from the eastern side of the Andes travels west across the Andean Plateau, Altiplano. The air masses journey all the way to the otherwise extremely arid Atacama Desert, bringing clouds, rain and occasionally even hail.

I have been to this area three times: first for vacation, then two times for excursions with students, most recently in February this year. Interestingly, the weather was as to be expected for the Atacama Desert only one time. For the two other times, the weather was looking like this photograph, so it is hard for me to believe that the Atacama would be as arid as people always say. However, indeed, the pieces of geological and geomorphological evidence, such as the folded layers of the Cordillera de la Sal, clearly indicate its extreme aridity, prevailing for tens of millions of years!

By Martin Mergili, University of Vienna

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: Chilean relics of Earth’s past

Imaggeo on Mondays: Chilean relics of Earth’s past

As Earth’s environment changes, it leaves behind clues used by scientists to paint portraits of the past: scorched timber, water-weathered shores, hardened lava flows. Chile’s Conguillío National Park is teeming with these kind of geologic artifacts; some are only a few years old while others have existed for more than 30 million years. The photographer Anita Di Chiara, a researcher at Lancaster University in the UK, describes how she analyses ancient magnetic field records to learn about Earth’s changing crust.

Llaima Volcano, within the Conguillío National Park in Chile, is in the background of this image with its typical double-hump shape. The lake is called Lago Verde and the trunks sticking out are likely remnants from one of the many seasonal fires that have left their mark on this area (the last one was in 2015).

The lake sits on pyroclastic deposits that erupted from the Llaima Volcano. On these deposits, on the side of the lake, you can even track the geologic record of seasonal lake level changes, as the layers shown here mark the old (higher) level of the lake during heavy winter rains.

The lake also overlaps the Liquiñe-Ofqui Fault, which runs about 1000 kilometers along the North Patagonian Andes. The fault has been responsible for both volcanic and seismic activity in the region since the Oligocene (around 30 million years ago).

I was there as field assistant for Catalina Hernandez Moreno, a geoscientist at Italy’s National Institute of Geophysics and Volcanology, studying ancient magnetic field records imprinted on rocks. We examined the rocks’ magnetised minerals (aligned like a compass needle to the north pole) as a way to measure how fragmented blocks of the Earth’s crust have rotated over time along the fault.

From this fieldwork we were able to examine palaeomagnetic rotation patterns from 98 Oligocene-Pleistocene volcanic sites. Even more, we concluded that the lava flows from the Llaima Volcano’s 1958 eruption would be a suitable site for studying the evolution of the South Atlantic Anomaly, an area within the South Atlantic Ocean where the Earth’s magnetic field is mysteriously weaker than expected.

By Anita Di Chiara, a research technician at the Lancaster Environment Centre in the UK 

References

Hernandez-Moreno, C., Speranza, F., & Di Chiara, A.: Understanding kinematics of intra-arc transcurrent deformation: Paleomagnetic evidence from the Liquiñe-Ofqui fault zone (Chile, 38-41°S), Tectonics, https://doi.org/10.1002/2014TC003622, 2014.

Hernandez-Moreno, C., Speranza, F., & Di Chiara, A.: Paleomagnetic rotation pattern of the southern Chile fore-arc sliver (38°S-42°S): A new tool to evaluate plate locking along subduction zones. Journal of Geophysical Research: Solid Earth, 121(2), https://doi.org/10.1002/2015JB012382, 2016.

Di Chiara, A., Moncinhatto, T., Hernandez Moreno, C., Pavón-Carrasco, F. J., & Trindade, R. I. F.: Paleomagnetic study of an historical lava flow from the Llaima volcano, Chile. Journal of South American Earth Sciences, 77, https://doi.org/10.1016/j.jsames.2017.04.014, 2017.

 

Imaggeo is the EGU’s online open access geosciences image repository. All geoscientists (and others) can submittheir 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: The unique bogs of Patagonia

Imaggeo on Mondays: The unique bogs of Patagonia

Patagonia, the region in southernmost tip of South America, is as diverse as it is vast. Divided by the Andes, the arid steppes, grasslands and deserts of Argentina give way to the temperate rainforests, fjords and glaciers of Chile. Also on the Chilean side are rolling hills and valleys of marshy topography: Patagonia’s bogs. Today, Klaus-Holger Knorr, a researcher at the University of Münster’s Institute for Landscape Ecology, tells us about what makes these peatlands so unique.

This picture shows an ombrotrophic, oceanic bog at the Seno Skyring Fjord, Patagonia, Chile. It is a view from the inner part of the peatland south toward the shore of the Fjord, in the background Isla Escapada and the Gran Campo ice field. Ombrotrophic bogs are peatlands (accumulations of more or less decomposed plant material which collect in a water-saturated environment) receiving their water and nutrients solely from the atmosphere, i.e. by rain, wet and dry deposition.

Similar to their Northern counterparts in Canada, Northern US, Fennoscandia or Siberia, these southern Patagonian peatlands  formed after the last deglaciation and accumulated huge amounts of carbon as peat.

Peatlands cover only about 3 % of the global land surface but store about a third of the soil carbon pool. Peat is formed primarily as there is excess rainfall, peat soils are water logged, oxygen gets depleted, and decomposition is limited. Pristine, undisturbed peatlands can store as much as 10-50 g carbon per square meter and year.

What makes the peatlands in Patagonia  particularly interesting  is their pristine, undisturbed conditions and extremely low input of nutrients from the atmosphere, compared to the high input into sites in densely settled or industrial regions. This allows studies of peatland functioning under natural conditions and absence of anthropogenic impacts.

Moreover, peatlands in Patagonia harbor a specific kind of vegetation, including cushion forming plants such as Astelia pumila and Donatia fascicularis. These cushion forming plants have a very low above ground biomass but an extremely large rooting system, reaching down to a depth of >2 m in case of A. pumila. As these roots act as conduits for oxygen to sustain viability of the roots in the water logged peat, they have been shown to aerate large parts even of the saturated zone, thereby impeding high methane production and emission. Oxygen supply by these roots is even hypothesized to stimulate peat decomposition and thereby lead to particularly decomposed peat under cushion plant cover.

Another plant species only occurring in peatlands of Southern Patagonia, a small conifer named Lepidothamnus fonkii, has developed a particular strategy to overcome nutrient deficiency: it has formed a close association with bacteria being able fix atmospheric nitrogen to fulfill the demand of nitrogen for growth. While such nitrogen fixation is well known for legumes and some tree species, it has rarely been found for conifers.

A further important factor for peatlands in Patagonia, leading to the term “oceanic bogs”, is the fact that these peatlands in close vicinity to the seashore receive high inputs of sea salts from sea spray, modifying availability of associated elements such as Sodium, Calcium, Magnesium, Sulphur and others.

By Klaus-Holger Knorr, researcher at the University of Münster’s Institute for Landscape Ecology

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/.