GeoLog

Natural Hazards

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/.

Geosciences Column: Do roads mean landslides are more likely?

Geosciences Column: Do roads mean landslides are more likely?

Landslides have been in the news frequently over the past 12 months or so. It’s not surprising considering their devastating consequences and potential impact on nearby communities. Data collected by Dave Petley in his Landslide Blog shows that from January to July 2014 alone, there were 222 landslides that caused loss of life, resulting in 1466 deaths.

A recent paper, in the journal Natural Hazards and Earth System Science investigates, what the potential effects of human denudation can have on the occurrence of landslide events. There is no denying that landslide susceptibility has been increased by human activity. Global warming and greater precipitation are key contributing factors to the rise in the number of landslides which occur globally. On a local scale, the building of infrastructure, particularly roads and felling of trees to make way for agriculture are largely to blame for increased numbers of slides and slumps.

Overview of the study area with mean annual precipitation patterns (top panel), and its location in southern Ecuador (lower left panel). Highways Troncal de la Sierra E35 and Transversal Sur E50 extend in the north–south and east–west direction, respectively. The numbers along the street refer to the corresponding geological unit (1: unconsolidated rocks; 2: sedimentary rocks; 3: volcanic rocks; 4: metamorphic rocks; 5: plutonic rocks). The area of the detailed map (lower right panel) will be used as a sample area for the visualization of a predictive map in Fig. 5. Precipitation data are taken from the study of Rollenbeck and Bendix (2001). From Brenning et al., (2015)

Overview of the study area with mean annual precipitation patterns (top panel), and its location in southern Ecuador (lower left panel). Highways Troncal de la Sierra E35 and Transversal Sur E50 extend in the north–south and east–west direction, respectively. The numbers along the street refer to the corresponding geological unit (1: unconsolidated rocks; 2: sedimentary rocks; 3: volcanic rocks; 4: metamorphic rocks; 5: plutonic rocks). Precipitation data are taken from the study of Rollenbeck and Bendix (2001). From Brenning et al., (2015). Click on the image for a larger version.

The research presented in the paper focuses on landslides along mountain roads in Ecuador, where drainage systems and stabilisation of hillsides is often inadequate and is known to increase the likelihood of landslides. This problem is not exclusive to Ecuador and is often linked to poorer infrastructure and engineering in developing countries. In addition, the study area is a tropical mountain ecosystem, which is naturally more sensitive and prone to landslides. The key question here being: are more landslides likely to happen close to a road (in this particular case an interurban highways), or does greater distance from them offer some hazard relief?

The geology, and local climate and vegetation are important factors to also take into consideration when carrying out an assessment of this nature. Highways E35 and E50 run along Southern Ecuador and intersect the Cordillera Real, which creates a strong local climate divide and generates a precipitation gradient along the area studied. Páramo ecosystems are dominant towards the east, whilst tropical dry forests are common in the west. The geology is also variable across the area studied: dipping and jointed metamorphic rocks are dominant, but are in contact with horizontally layered sedimentary units of loose conglomerates and sandstones. Additionally, the hill sides running along the highways are often deforested to make way for coffee, sugar cane and banana crops. When they are not, they are commonly handed over to cattle for grazing.

By mapping, in great detail, all landslide occurrences within a 300m corridor along the highways, the researchers were able to digitise 2185 landslide initiation points! In total, 843 landslides were mapped and classified by recording the type of movement experienced, as well as the material type (soil, debris or rock) and whether the slide was still active, inactive or had been reactivated. The detailed data meant it was possible to statistically model the likelihood of landslides occurring in close proximity to the highway (25m) vs. some distance away (200m). The results showed that susceptibility to landslides increases by one order of magnitude closer to the highway when compared to areas between 150-300 m away from the mountain road. Furthermore, slides close to the highway were found to be more likely to be reactivated than those a greater distance away.

The study found that the local topography, geology and climate conditions had a lesser influence on the likelihood of landslides. However, the influence of stretches of mountain road constructed in the sedimentary units seems to enhance the hazard.

Landslides occurring along the investigated highways. (a) Typical landslides of the wet metamorphic part of the study area in the east. (b) Typical landslides of the semi-arid, conglomeratic part of the study area in the west. (c) Highway destroyed by landsliding. (d) A highway is cleared from a recent landslide occurrence. From Brenning et al., (2015).

Landslides occurring along the investigated highways. (a) Typical landslides of the wet metamorphic part of the study area in the
east. (b) Typical landslides of the semi-arid, conglomeratic part of the study area in the west. (c) Highway destroyed by landsliding. (d) A
highway is cleared from a recent landslide occurrence. From Brenning et al., (2015).

In future, the model can be used to predict locations where landslides are more likely to occur along the E35 and E50. Recently, engineering works have been carried out along the studied stretch of highways to stabilise the hillsides. The data collected as part of the research presented in the paper will be useful in the future to monitor the efficacy of the improvements. On a larger scale, further studies of this type could be used by local governments when planning new infrastructure and could lead to incorporation of cost-effective mitigation measures in new developments.

 

By Laura Roberts Artal, EGU Communications Officer

Reference:

Brenning, A., Schwinn, M., Ruiz-Páez, A. P., and Muenchow, J.: Landslide susceptibility near highways is increased by 1 order of magnitude in the Andes of southern Ecuador, Loja province, Nat. Hazards Earth Syst. Sci., 15, 45-57, doi:10.5194/nhess-15-45-2015, 2015.

Imaggeo on Mondays: Artists’ Paint Pots

Many artists draw inspiration from nature and it’s not surprising when faced with landscapes which are as beautiful as the one featured in this week’s Imaggeo on Mondays post. Josep Miquel Ubalde Bauló writes about the origin of the colourful mud pots and bobby-socks trees!

Artists' Paintpots in Yellowstone National Park Credit: Josep Miquel Ubalde Bauló (distributed via imaggeo.egu.eu)

Artists’ Paintpots in Yellowstone National Park. Credit: Josep Miquel Ubalde Bauló (distributed via imaggeo.egu.eu)

This picture corresponds to The Artist Paint Pots, found in in Yellowstone, the first National Park of the world. Yellowstone is one of the most geologically dynamic areas on Earth. A huge underlying magma body releases enormous amounts of heat , which feed more than 10000 hydrothermal features (geysers, hot springs, mudpots, fumaroles), approximately half of all those found in the world.

The Artist Paint Pots is a small geothermal area, which was named after the pastel multicoloured mud pots. Much of the water in these mud pots is near boiling (85 ºC), meaning it is is difficult for life to thrive in them . Only some cyanobacteria and algae can live under these extreme conditions, and they are responsible for the beautiful colours in the mud pots.

The mud pots are acidic thermal features with a limited water supply. For their formation they require sulphite-reducing bacteria, which use hydrogen sulphide for energy, giving sulphuric acid as a waste product. The acidic water slowly dissolves the surrounding rocks, forming fine particles of silica and clay. This viscous clay-water mixture creates a muddy area, with the hot mud boiling and gas bubbling at the surface. The paint pots are coloured mud pots, which range from pink to bright red to purple, due to the iron oxides, potassium, and magnesium in the soil. The reason for the colours in the mud pots is a lack of sulphur. When sulphur is present, it reacts with iron oxides forming pyrite, which is grey.

In this area you can observe some groups of standing-dead trees. Whilst some of them burned in the fires of 1988 (during an unusually dry summer), others have been killed by the runoff from nearby thermal features, which flooded the area around the trees. Minerals in the water plugged the base of the trees and killed them, leaving their bases white. Those trees are known as bobby-socks trees.

By Josep Miquel Ubalde Bauló, Soil Scientist, Miguel Torres Winery

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/.

GeoEd: A risky business

In this month’s GeoEd post, Sam Illingworth explores the pitfalls of being a scientist in the public eye. Following the recent acquittal of 6 geoscientists on manslaughter charges after ‘failing’ to predict the 2009 L’Aquila earthquake, is it time we thought about improving how risk is communicated to the wider public?

At the beginning of November of this year, six Italian scientists were acquitted of manslaughter; an appeals court in L’Aquila (a medieval Italian city on the edge of the Aterno river) overturning the 2012 guilty verdicts that were originally cast against the researchers.

In their initial trial, the scientists were convicted of multiple manslaughter charges, by failing to predict the devastating earthquake, which struck at 03:32 CEST on 6 April 2009, and which was responsible for the deaths of 309 people. It has taken the past two years to acquit these six scientists, and the initial ramifications of the convictions were far reaching, with other researchers from across the globe wondering if a precedent had now been set, regarding liability for the conveyance of information.

Aerial view of the city of L'Aquila east-centre (Photo Credit: Public Domain, via Wikipedia.org)

Aerial view of the city of L’Aquila east-centre (Photo Credit: Public Domain, via Wikipedia.org)

Sadly, scientists are far from unaccustomed with judicial proceedings, from Galileo vs. the Catholic Church, to more recent examples of scientists being sued by a gym regarding injury rate statistics, or NASA being sued for trespassing on MARS. However, the recent allegations against the L’Aquila six (actually there were seven experts in total; more on this later), calls into question the fundamental belief system of accountability. If a building surveyor were to tell you that the foundations of your house were sound, yet you were later to find evidence of subsidence you would expect compensation from the surveyor. So why not also from the scientists, after all are they not too experts in their own field?

Well, for one thing, finding evidence for subsidence is far more of a precise art than trying to predict earthquakes. On the one hand you are looking for something that already exists, and on the other you are searching for something that may or may not be. In addition to this, surveyors are usually protected by professional indemnity insurance.

Are scientists adequately protected (Photo Credit: Sandstein via Wikimedia Commons)

Are scientists adequately protected (Photo Credit: Sandstein via Wikimedia Commons)

However, in the case of scientists communicating risk, is not being able to accurately predict an earthquake or a volcanic eruption really professional negligence, or is it simply to be expected given the impossibility of fully accurate predictions?

What is potentially worrying to scientists is that the line between professional negligence and unforeseen circumstance would appear to be very blurred indeed. Although, in some instances the distinction is far more clear-cut, for example the behaviour of the seventh member of the panel of experts in the L’Aquila case, Bernardo De Bernardinis. The then deputy director of the Civil Protection agency had, prior to the earthquake, advised locals to “sit back and enjoy a nice glass of Montepulciano” wine. Bernandinis was not acquitted, although his prison sentence was cut, from six to two years.

Although many might view Bernandinis as being guilty of nothing more than pompous over confidence, it is important to remember that as scientists we still have a role to inform the public as to the seriousness of any potential dangers, even if we are not ultimately to be held accountable for our inability to predict them. In other words, failing to predict a natural hazard (or other such incident) should not be seen as professional negligence, but failing to adequately inform the general public of the consequences of any potential threats, probably should be.

Of course, communicating risk goes well beyond natural disasters, and is something that many of us do when we talk about the effects of both current and predicted climate change. In these situations, scientists also regularly put themselves in the firing line, although this time often with regards to the media and pressure groups with an anti-climate change agenda.

One of the most well known examples of this was when a Competitive Enterprise Institute (CEI) analyst made the following, frankly horrific statement, about Penn State University climate researcher Michael Mann:

“Mann could be said to be the Jerry Sandusky of climate science, except that instead of molesting children, he has molested and tortured data in the service of politicized science.”

Dr Michael Mann: fighting the fakers (Photo Credit: Reason4Reason via Wikimedia Commons)

Dr Michael Mann: fighting the fakers (Photo Credit: Reason4Reason via Wikimedia Commons)

Dr Mann has subsequently sued the CEI, but such legal proceedings are both incredibly expensive and time consuming, and often represent a completely alien world to many scientists who are simply just doing their job.

In the US, scientists working for government or federal labs are now offered free legal counsel and support by the organization Protecting Our Employees Who Protect Our Environment (PEER). In addition to this, some scientific professions are now requiring their researchers to have professional indemnity insurance, for example in the UK, legislation was recently introduced that requires all health care scientists to have a professional indemnity arrangement in place, as a condition of their registration with the health & care professions council.

According to Jeff Ruch, the director of PEER, threatening scientists for their science “is a bully strategy,” and “bullies don’t like to be pushed back at.” Whilst the work of PEER and their contemporaries is admirable, is this a position that scientists should ever be finding themselves in? And is there anything that they could be doing to avoid such potential pitfalls?

In some cases, these pitfalls could be avoided by a more careful consideration of how to communicate risk, by explaining to the general public that there are many uncertainties associated with the calculations and predictions that are being made. However, I think that this is something that many scientists are already reasonably adept at, and if scientists are guilty of anything it is sometimes of being overcautious with their predictions, or of waiting to comment until they are absolutely 99.9% sure (with the obligatory 0.1% margin of error).

Media and science communication training can help scientists prepare for how to deliver their research and advice in potentially alien and hostile arenas, but there will always be instances where people have a set agenda to follow at any cost.

There may well be a public perception that scientists failing to predict natural disasters, or underdetermining a certain problem, are like the proverbial bad workmen who blame their tools. However, in trying to communicate risk I think that it might well be a case of “don’t shoot the messenger,” even if it turns out that they have no message to convey.

By Sam Illingworth, Lecturer, Manchester Metropolitan University

 

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