GeoLog

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Imaggeo on Mondays: A dramatic avalanche from Annapurna South

Imaggeo on Mondays: A dramatic avalanche from Annapurna South

The Annapurna massif is located in an imposing 55 km long collection of peaks in the Himalayas, which behave as a single structural block. Composed of one peak (Annapurna I Main) in excess of 8000 m, a further thirteen peaks over 7000 m and sixteen more of over 6000 m, the massif forms a striking structure within the Himalayas. Annapurna South (pictured in today’s featured image), the 101st tallest peak in the world, towers 7219 m above sea level.

Glaciers in High Mountain Asia, a region that includes the Himalayas, contain the largest volume of ice outside the polar regions. The water trapped, as ice, in the glaciers of the Himalayas is an important source of drinking water, water for irrigation and water for hydropower generation throughout the region. As the Earth’s climate changes and negatively affects glaciers world-wide, scientists are working hard to understand what increased glacier melting means for the communities which depend on them.

Emily Hill is one such scientist. Her and a team of colleagues spent 2 weeks at Annapurna Base Camp in Nepal conducting measurements on the debris covered South Annapurna Glacier.

“We frequently heard avalanches but often they were over too quick to capture on camera. Fortunately, this was one of the largest and the camera was at the ready. These avalanches are an important source of mass for the glacier below,” reminisces Emily.

Glaciers accumulate ice throughout the winter months, as snow adds to the glacial column during the cold months. In addition, avalanches deliver additional snow throughout the year.

“I’m not too sure of the scale of the avalanche, it could probably have been a couple of 100 m across. The avalanche occurred early afternoon when the solar radiation was highest and increased melt is likely to have caused the failure,” describes Emily.

Avalanches in the region are not only an important source of mass accumulation for many of the glaciers, they also pose a hazard not only to climbers of these mountains but also further down along the tourist trail up to Annapurna Base Camp, where there is an avalanche risk section of the route.

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: Landslide on the Cantabrian coastline

Shimmering blue seas, rocky outcrops and lush green hills sides; this idyllic landscape is punctuated by a stark reminder that geohazards are all around us. Irene Pérez Cáceres, a PhD student at the University of Granada (Spain) explains the geomorphology behind this small scale landslide on the Asturian coastline.

Landslide on the Cantabrian Sea. Credit: Irene Pérez Cáceres (distributed via imaggeo.egu.eu)

Landslide on the Cantabrian Sea. Credit: Irene Pérez Cáceres (distributed via imaggeo.egu.eu)

This picture was taken in May 2011 in the coast of Llanes (Asturias, Spain). I was living in Oviedo (Asturias, Spain) doing my Master in the structural geology of the Axial Zone of the Pyrenees. Thus, geomorphology and geohazards are not my specialty or area of expertise. However, the landslides are well known and studied in this region, and people from Asturias call them Argayos.

This argayo is situated in Niembru Mountain, over the San Antolín beach, constantly affected by waves and swell of tides of the Cantabrian Sea, and continuous rain typical in the region. It was defined as a rotational landslide with two fracture surfaces, possibly conjugated in wedge shape. It is approximately 50 meters high and 60 meters width at its base. The slide volume is calculated at 45000 m3. It is carved in quartzite altered by the water rain infiltration through crevices in the surface. The initial displacement was between 10 and 15 meters in the scar. Experts say this landslide is still active, moving and evolving continuously. It is an imminent risk for the swimmers, but it is very difficult to control it, due to the size and the slope, and the technical requirements to stabilize the rock. On the other side of this mountain, further landslides are evident, as a result of the building of a road.

These natural geomorphological processes are very common in the north of Spain, mainly in riverbeds, as well in other nearby beaches. The main causes are the abundant (and sometimes heavy) rainfall, the typically clay rich soils, steep slopes, building works that destabilize the slopes, and the absence of vegetation in some areas. They vary in in size and volume, and can sometimes have important material consequences and can pose a significant risk for the local inhabitants. The annual economic cost for repairing the damage caused by these processes is estimated to be 66 million of euros in this region.

Studies carried out in the Department of Geology of the University of Oviedo (Mª José Domínguez and her group), indicate that 70% of the landslides in Asturias happen when it rains over 200 mm during over a period of a minimum of three days. Research has also been carried out to try and predict when landslides might happen, examining numerous landslides over the last 20 years approximately. It seems that one conditioning factor is the exact location of new buildings, being that ancient constructions used to be in secure zones, probably because people observed more minutely to the nature, but the new ones are more vulnerable.

To conclude, detailed geological and geomorphological studies are always recommended to carry out before constructions. Thereby it is possible to minimise this common geohazard in Asturias.

By Irene Pérez Cáceres, PhD Student, Granada University.

 

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/.

GeoTalk: Matthew Agius on how online communication can help identify earthquake impact

In this edition of GeoTalk, we’re talking to Matthew Agius, a seismologist from the University of Malta and the Young Scientist Representative for the EGU’s Seismology Division. Matthew gave an enlightening talk during the EGU General Assembly on how communication on online platforms such as Facebook can help scientists assess the effect of earthquakes. Here he shares his findings and what wonders online data can reveal…

Before we get going, can you tell us a little about you’re area of research and what got you interested in using online communications to complement our understanding of earthquakes and their impact?

My area of research is the study of tectonic structures and dynamics using different seismic techniques. The regions I have studied the most are Tibet and the Central Mediterranean. During my student days many friends wondered about my research and I felt that there was a need to reach out for the public in order to eliminate misconceptions on how the Earth works, in particular about the seismic activity close to home – Malta. This led to the creation of a website with daily updates on the seismic activity in the Mediterranean. We set up an online questionnaire for people to report earthquake-related shaking. The questionnaire proved to be successful; hundreds of entries have been submitted following a number of earthquakes. This large dataset has valuable information because it gives an insight on the demographics in relation to earthquake hazard of the tiny nation.

How can social network sites such as Facebook and Twitter be used to assess the impact of earthquakes?

Nowadays the general public has access to smart phones connected to the internet, which have become readily available and affordable. This resulted in a rapid use of social websites. People increasingly tend to express themselves in ‘near’ real-time online. Furthermore, smartphones are equipped with various technologies such as a GPS receiver and an accelerometer – the basic set up of a seismic station – and also a camera. Altogether this has the potential to provide an unprecedented level of information about the local experience of an earthquake. Its immediate analysis can also supplement instrument-based estimates of early earthquake location and magnitude.

Out in the field – Matthew Aguis in the Grand Canyon. (Credit: Matthew Aguis)

Out in the field – Matthew Agius in the Grand Canyon. (Credit: Matthew Agius)

What sort of information can you gather from sites like Facebook or Twitter, and what can it tell you?

Users can post comments as well as photographs directly on a page, say a page dedicated to earthquakes. Such post are time stamped and can also have geolocation information. Although the posted information might seem too basic, the collective data from many users can be used to establish the local feeling in ‘real time’. Another way is to have a specific application that analyses the text expressed by social media users. Similar applications have already been considered in a number of regions such as USA and Italy, and have shown very interesting social sentiment expressed during and after an earthquake shake.

How do the earthquake sentiments relate to the geology? Can you see any patterns between what people say and share online and the intensity of the quake in a particular area?

This is a new area of research that is still being investigated. Earthquake intensity, shaking and damage in a local context, are known to vary from one place to another. These variations are primarily due to either the underlying geology, the seismic wave propagation complexities, or a combination of both. So far various mathematical models have been published for famous areas such as San Francisco Bay; soon scientists will have the opportunity to compare their models with information on people’s sentiment gathered in this new way. Such sentiment is expected to relate to the geology, to some extent.

And another shot of Matthew in the field – this time from Mount Etna. (Credit: Matthew Aguis)

And another shot of Matthew in the field – this time from Mount Etna. (Credit: Matthew Agius)

What are the difficulties of dealing with this sort of data, and how do you overcome them?

This type of data compilation is known as crowdsourcing. Although it is has powerful leads, one has to take careful measures on how to interpret the data. For example one must not assume that everyone has a public social profile on the internet where to posts his/her sentiment. One also has to consider that mobile phone coverage is sometimes limited to cities leaving out large, less inhabited areas without a network. Another limitation can be related to the list of specific keywords used during text analysis, a typical keyword could be ‘shake’; users might be using this term in a completely different context instead of when the ground is shaking! I think the best way to overcome such difficulties is to combine this data with current seismic monitoring systems; upon which an event is verified with the seismic data from across the investigated region.

During your talk you proposed other ideas for data analysis, how can it be used to support civil protection services and inform the public?

Until now social sentiment with regards to earthquakes has been studied through the use of Twitter or Facebook. But citizens are also making use of other online platforms such as news portals. All this information should ideally be retrieved and analysed in order to understand the earthquake sentiment of an area better. Furthermore, such studies must also be able to gather the sentiment in multiple languages and establish geolocation information from clues in the user’s text. I think it is time to implement a system to be used by civil protection services, whereby immediately after an earthquake has been established, an automatic alert is sent via a dedicated phone app and, at the same time, a web bot crawls the web to ‘read’ and analyse what people are expressing across multiple platforms. A felt map can then be generated in real time. This could be very useful for  civil protection services during a major disaster, helping them to redirect their salvage efforts as civilian phone calls become clogged.

Matthew also mans Seismoblog, a blog dedicated to the young seismologists of the European Geosciences Union – keep up with the latest seismology news and research on Seismoblog here.

Geosciences column: Shelter island – building a barrier to protect the coast

The latest Geosciences Column features recent research into tsunami hazards and explains how island building out to sea can help protect buildings on the shore…

Barrier reefs are well known for holding off the wrath of the ocean and sheltering the serene lagoons that stretch between them and the mainland. Barrier islands possess the same protective power, taking the impact of waves that have built up across the ocean and dissipating their energy before they break on the continent. Now, a team of Spanish and Columbian scientists have shown how this barrier island effect can be harnessed to protect communities from the worst of ocean waves – the tsunami.

Tsunamis are generated when vertical faults beneath the seabed slip, causing a large earthquake (over magnitude 5 on the Richter scale) and displacing a huge volume of water. They pose a greater hazard than earthquakes alone, and in seismically active coastal areas they are a significant concern. One such area is the seismic belt that shadows the coastline between Ecuador and Columbia, where the Nazca Plate subducts beneath the South American.  There have been six major quakes along the belt in the last century, the most recent of which was a magnitude 7.7 quake that resulted in a devastating tsunami and the destruction of an entire island within the Mira River Delta in 1979.

Spot the difference. Top: the island of El Guano prior to the 1979 tsunami; bottom: the same area following the tsunami. (Credit: Otero et al. 2014)

Spot the difference. Top: the island of El Guano prior to the 1979 tsunami; bottom: the same area following the tsunami. (Credit: Otero et al. 2014)

In the Columbian department of Nariño alone, the 1979 tsunami resulted in the loss of over 450 lives and 3080 homes. But the devastation would have been greater if it weren’t for El Guano, a sandy barrier island that was once present just off the country’s Pacific coast. By modelling tsunami as it happened, and how it would unfold if it occurred again today, Luis Otero and his colleagues from the University of Norte, Columbia, and the Environmental Hydraulics Institute IH Cantabria, Spain, showed just how good a barrier the island was – cutting the energy transferred to the island city of Tumaco by up to 60%.

It’s not the first time natural defences have been shown to protect the coast. Indeed, studies of the 2006 Boxing Day tsunami in Indonesia have shown that reefs, mangroves, beaches and dunes all provide the coast some protection by absorbing the tsunami’s initial impact and slowing the speed of the advancing wave.

How flooding would differ if El Guano island was present: (a) shows the current situation and (b) shows what would happen if the island was recreated. The white regions represent the areas that are not flooded and the black line shows the shoreline. (Credit: Otero et al. 2014)

What a difference an island makes: (a) shows the current situation and (b) shows what would happen if the island was present. The white regions represent the areas that are not flooded and the black line shows the shoreline. (adapted from Otero et al. 2014)

Tsunami hazard in this region is both high and likely, and the team show that rebuilding the island would be a worthwhile engineering effort if the government hopes to afford the area the same protection it had in ’79 in the future. Elongating the island would increase its protective potential even further, as would reshaping the it to form three similarly shaped barriers to cut the energy transferred to the Columbian coastline beyond.

Otero’s tsunami model showed such engineering would offer tremendous protection to Tumaco and the other inhabitants of the Mira River Delta in the event of a tsunami – particularly one that occurred at high tide. But because Tumaco is such a sizable coastal city, some unprotected areas would remain.

Currently, the government’s focus is on establishing a swift and effective early warning an evacuation strategy, but a barrier island could provide a big boost to the safety of the local population and the security of local infrastructure.

By Sara Mynott, EGU Communications Officer

Reference:

Otero, L. J., Restrepo, J. C., and Gonzalez, M.: Tsunami hazard assessment in the southern Colombian Pacific basin and a proposal to regenerate a previous barrier island as protection, Nat. Hazards Earth Syst. Sci., 14, 1155-1168, 2014.

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