GeoLog

imaggeo on mondays

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: Iceberg viewing in Cape Spear, Newfoundland, Canada

Imaggeo on Mondays: Iceberg viewing in Cape Spear, Newfoundland, Canada

Cape Spear in Newfoundland, Canada is the easternmost location in North America and one of the few places in the world where you can contemplate icebergs from the shore. Every year, about 400 to 800 bergs journey down to this particular point. These 10,000-year-old ice giants drift along the northern shore of Newfoundland with the Labrador Current.

About 90 percent of these icebergs come from western Greenland glaciers, where they break off directly into Baffin Bay. Often these bergs remain in the bay for several years, preserved by the cold arctic waters and circulating along with local currents. Eventually, many icebergs escape through the Davis Strait, drifting down the Labrador Current and passing through Iceberg Alley to reach the Grand Banks of Newfoundland, the region of the North American continental shelf where Cape Spear is situated. This journey from Greenland to the Grand Banks usually takes between two and three years.

Cape Spear is just a few kilometres from Newfoundland’s largest city, St. John’s, and attracts many tourists during spring and early summer months to enjoy the immense icebergs. The chances of seeing them depend greatly on the temperature, wind direction, ocean currents and amount of sea ice during the winter, which protects icebergs from erosion. The icebergs have a great impact on Newfoundland’s identity and economy, bringing tourists and even giving breweries unique ice for beer and liquor production.

On the other hand, the floating ice can be a hazard to oil platforms and cargo boats. Smaller bergs can be especially hazardous since they are harder to detect with marine radar. If deep enough, the icebergs can also damage seabed structures like pipelines and cables. Thus, it is important to keep monitoring the dynamics of icebergs, especially since there will likely be a greater volume of ice breaking from the Greenland glaciers and drifting in the North Atlantic due to climate change.

By Simon Massé, PhD student, Université du Québec à Rimouski, Canada

References

Barber, D.G., Babb, D.G., Ehn, J.K., Chan,W., Matthes, L., Dalman, L. A., et al.: Increasing mobility of high Arctic Sea ice increases marine hazards off the east coast of Newfoundland, Geophysical Research Letters, 45,2370–2379, https://doi.org/10.1002/2017GL076587, 2018.

Diemand, D., Icebergs, Encyclopedia of Ocean Sciences, 3: 1255-1264,  2001.

Iceberg Finder, Icebergs Facts. Newfoundland & Labrador Tourism, 2012.

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 Monday: Mount Elgon, a balance between fertility and destruction

Imaggeo on Monday: Mount Elgon, a balance between fertility and destruction

This colourful cropland patchwork is located on the fertile flanks of Mount Elgon, Uganda at an elevation of 2,400 metres above sea level. The extinct shield volcano, the oldest in East Africa, is mostly covered in clouds and provides an infinite flow of wonderful waterfalls.

Due to the climate at this elevation, the cultivated crops experience more temperate weather conditions compared to crops more typically grown in the tropics. This gives the region a less tropical outlook than what is observed at lower elevations, where the landscape views are dominated by banana trees.

Still the local communities intensely cultivate the land at these higher elevations since the soil is very fertile, a product of the mineral-rich volcanic material that was deposited during eruptions in the past twenty million years. The cultivation is only stopped by the steep cliffs that you can see in the background and the borders of the national park that encompasses Mount Elgon’s volcano top.

The image evokes a feeling of tranquility, but in reality, the environment is very prone to natural hazards, resulting in numerous fatalities within the densely populated communities every year.

Rockfall events in the Ugandan Mount Elgon area, such as this one pictured, have destructive and fatal impacts on local communities. (Credit: Jente Broeckx)

While the local lithology results in fertile fields, the area’s steep slopes and severe tropical thunderstorms make the region vulnerable to landslides. Mount Elgon’s steep cliffs pose a second risk as they can generate rockfalls, with big blocks as large as the houses at the foot of those cliffs. Both landslides and rockfalls often leave a trace of destruction on their path, sweeping away houses and causing fatalities.

Luckily, the view we see here on the north-facing side of Mount Elgon has rather gentle slopes, experiences milder storms and receives relatively low precipitation throughout the year.

My colleagues and I study the area’s susceptibility to landslides and the high risk this poses for its inhabitants, their livelihoods and the infrastructure. The picture was taken during one of our field work campaigns, where I was mapping landslides and landslide-free locations to calibrate the first landslide susceptibility map for the Mount Elgon region. At this year’s EGU General Assembly, I will give an oral presentation on this research.

This environment provides a duality that, on the one hand attracts people with its rich natural resources, but on the other hand poses a risk for their survival. It is one of the many places on earth with a fragile equilibrium between a growing human pressure and the forces of nature.

By Jente Broeckx, a PhD researcher at KU Leuven, Belgium

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: The Crossroads of Flood and Drought

Imaggeo on Mondays: The Crossroads of Flood and Drought

This picture was taken on the way back from collecting field measurements at the Lordsburg Playa in southwestern New Mexico, USA. The setting sun highlights the contrast between the dry, cracked soil and the standing water from antecedent rainfall.

A playa is a flat topographic depression in arid or semi-arid regions that contains a large amount of deposited sediment. When the surface of the playa is dry, this deposited sediment is exposed and at risk of being entrained into the atmosphere by wind.

With an extent of approximately 250 square kilometers, Lordsburg Playa is a dust ‘hot spot’ in the southwestern Unites States. Dust events originating from the playa are normally small, but they can contain high dust concentrations and occur frequently during the dry season in spring.

The Lordsburg Playa is of particular interest to the local population, as the interstate highway I-10 crosses over the region. Under windy conditions, dust emissions from the playa can drastically reduce visibility on the highway and cause severe traffic accidents.

In October 2016, I went on a one-week field trip to the playa, installing a temporary measurement site to study local dust emission mechanisms. At that time, parts of the playa were still flooded from summer monsoon precipitation. During the field trip, we observed a local, but strong dust event. The event started in the morning and peaked at around 9:00 am when visibility was reduced to a few meters for a short time. Fortunately, the dust was blown northward during this event and the highway was not affected. Visibility recovered shortly after, but small-scale dust phenomena such as dust plumes and dust devils occurred almost continuously during most of the day.

By Martina Klose, a post-doctoral researcher at the Barcelona Supercomputing Center (BSC) in 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/.