GeoLog

Geomorphology

Imaggeo on Mondays: Civita di Bagnoregio – the dying town

Imaggeo on Mondays: Civita di Bagnoregio – the dying town

On top of a steep cliff standing out from the surrounding countryside, lies the small town of Civita di Bagnoregio, one of the most famous villages of Italy. It is often called the dying town, although more recently people have started to refer to it as fighting to live. What this little town is fighting against is the threat of erosion, as its walls are slowly crumbling down.

Located in central Italy, about a 100 km north of Rome, the town of Civita dates back to the Etruscan civilization, about 2500 years ago. It was most likely built on top of a hill for military reasons, since the 200 m of difference in height would provide perfect panoramic views. The city’s major development took place during the Middle Ages, and its well-preserved medieval character is one of the features that makes this city so magnificent nowadays. However, in 1695, a terrible earthquake demolished most of Civita by triggering a major landslide below, and forced people to move to the neighbouring village of Bagnoregio. This was not the only landslide that threatened the city. For centuries, Civita has been fighting against the natural degradation of the cliff, with recurring landslides slowly taking down the edges of the plateau, causing some of the medieval buildings to collapse and plummet into the ravine (Figure 1).

Figure 1. Evolution of the upper urbanised area of Civita di Bagnoregio from historical maps, showing many buildings destroyed by landslides during the past centuries. Credit: Margottini, C. & Di Buduo, G. Landslides (2017).

The geology of the plateau explains why this town is so susceptible to landslides (Figure 2, Delmonaco et al., 2004). The top of the plateau consists of a 20 m thick layer of consolidated rock formed from volcanic ash (ignimbrite), also known as tuff. The tuff was deposited by pyroclastic flows (rapid currents of volcanic debris and hot gas) related to the neighbouring Vulsini volcanic complex. This massive tuff layer overlies a more stratified section of pyroclastic deposits, roughly 70 m in thickness. These quaternary volcanic deposits lie above a bedrock of Plio-Pleistocene clay, which can be found all over the valley. This succession forms a classic setting for landslides. In the fragile clay deposits, slope instability is represented by mud flows and debris flows, while the upper, volcanic part of the plateau suffers from rock-falls, toppling and block-slides as it becomes unstable. Landslides can be dated back to 1373 AD, with 150 landslides documented by scientists who investigated the local geomorphology (Margottini and Di Buduo, 2016).

Figure 2. Geological profile of the study area. Credit: Giuseppe Delmonaco.

It seemed that the fate of Civita de Bagnoregio was to slowly disappear, but the city experienced a major turning point in 2013, when mayor Francesco Bigiotti decided to charge an entrance fee for people who wanted to visit the town. Tourists now pay a few euros to cross to the sloping footbridge towards the town. This proved to be a smart move, since people became more attentive and treated the site with more respect. The money raised by the entrance fee partly goes to preserving Civita’s fragile beauty and since 2015, the dying city received the UNESCO World Heritage status. This recognition of cultural heritage now leads to more investments from the regional government in order to preserve the historical site.

If you have the opportunity to visit the Civita, you will first enjoy a magnificent view on the town and the surrounding valley, before descending into the valley to cross the footbridge that provides the only gateway to the town. After a short climb towards the entrance, you’ll pass through an old arc, immediately bringing you back to medieval times. Then, all there is left to do is wander through the charming, quiet streets, observing the beauty of the classical quiet Italian village. Visit the Geology and Landslides museum, have lunch at one of the many authentic restaurants, or walk all the way to the end of the village, away from the other tourists. From there, a small trail leads into the countryside, where you can enjoy the magnificent views on the sharply eroded, clayey ridges in the surrounding badlands valley.

Previously referred to as the dying town, it now seems that there is some hope left after all for Civita di Bagnoregio. Something that will never change, however, is the interplay between mankind trying to survive in a hostile, but strategic environment of immense beauty, and nature that follows its own course of dismantling and eroding the existing relief.

By Elenora van Rijsingen, Ecole Normale Supérieure, Department of Geosciences, France

How extreme events impact Earth’s surface: reports from the 6th EGU Galileo conference

How extreme events impact Earth’s surface: reports from the 6th EGU Galileo conference

Throughout the year, EGU hosts a number of meetings, workshops, and conferences for the geoscience community. While the EGU’s annual General Assembly brings more than 15,000 scientists together under one roof, the EGU Galileo Conferences allows a smaller number of scientists to discuss and debate issues at the forefront of their discipline. In this blog post, the organisers of the 6th Galileo Conference “Perturbations of earth surface dynamics caused by extreme events” reflect on a week of insightful presentations and discussions on rare and catastrophic events.

“How do extreme events perturb Earth surface dynamics?” This question kept us busy during the entire week of the 6th EGU Galileo Conference “Perturbations of earth surface dynamics caused by extreme events”, which took place in Nepal from 13-19 October 2019. As organisers, we had aimed for a slightly unusual conference venue. We kept the nice hotels to a minimum of two nights and took the participants out to the Bhote Kosi for some camping for the remainder of the week to foster discussions and idea exchange.

The Bhote Kosi valley, about four hours’ drive north east of Nepal’s capital city Kathmandu, was heavily impacted by the April 2015 Gorkha earthquake and a subsequent glacier lake outburst flood event in 2016. This valley still today carries the signs of these earlier events in the form of large landslides, unstable slopes, and reworked river beds. As such, the valley serves as an ideal natural laboratory to better understand and quantify how the Earth’s surface responds to such perturbations. The Bhote Kosi had been a basecamp for a number of us studying natural hazards during the multiple field campaigns organised after the Gorkha earthquake, and this conference was a great opportunity to share what we have learned over the past years while directly illustrating the conference topics.

This conference brought together scientists studying a range of rare/extreme events and their broader impacts on Earth surface processes, biogeochemical cycles and human systems. Credit: Monique Fort

What seemed easy in the early days of planning did not come without inevitable doubts as the conference came closer. How do we make sure we have enough tents for everyone, how do we deal with the frequent power cuts, how do we make sure to cater enough local beer to thirsty geoscientists, and what if everyone contracted food poisoning? Fortunately, 60 participants, including ten Nepali colleagues and many early career scientists, blindly followed us without much afterthought and we were off for a busy and promising week.

The talks and posters covered most extreme event triggers: from earthquakes to volcanic eruptions and from wildfires to storms and tsunamis. These presentations provided food for thought for the geomorphologist, the geochemist, and the seismologist alike. Nepal, with the aftermath of the Gorkha earthquake, was well represented in these presentations, but many other parts of the world were covered as well.

Overall, this conference demonstrated the role of extreme events as geomorphic actors, able to shape landscapes and affect biogeochemical cycles. This conference also highlighted the large range of possible geomorphic responses, both in terms of magnitude and spatial extent, suggesting that the question of how these extreme events should be defined (are they large or are they rare events?) should ultimately be left to the investigators. It is however clear that in terms of geomorphic impact, an extreme event should lead to an observable perturbation above a, to-be defined, background variability, and be followed by a recovery period that leads to an old or new steady-state. As such, extreme events are not created equal and future research is needed to understand why such a range of responses are encountered.

Conference attendees had the opportunity to discuss questions and topics at the forefront of their field, from ethics in science to international cooperation. (Credit: Monique Fort) 

Time for discussion also allowed us to debate on the morality of post-disaster scientific work. We concluded that basic research questions related to these events need to be pursued and frequently require immediate mobilisation of scientific equipment and personal. However, this discussion also highlighted the need for clear and transparent international coordination so as to not interfere with relief efforts and avoid being perceived as greedy ambulance-chasing scientists. This important discussion was backed by input from a large Nepali delegation, providing an insight into how they had perceived these questions directly after the recent earthquake. Further discussions focused on the commonalities of different extreme events and the possibility to define a common framework that would allow us to compare the geomorphic impact of an earthquake to that of a storm or a wildfire.

Finally, this conference allowed us to lay the foundation blocks for future international coordination efforts. While the exact contours remain to be defined, all participants emphasised the need to prioritise research questions and resources in the case of rapid response efforts. These efforts require clear coordination with affected countries and funding bodies, but for instance also encourage scientific actors to agree on common publication strategies upfront.

Conference participants tour the Bhote Kosi valley to learn more about how extreme events can shape landscapes. (Credit: Monique Fort) 

In the middle of this busy schedule, a day of field excursion provided a welcome change. From small to large, the Bhote Kosi has it all: boulders, landslides, debris flows etc… Driving up the valley all the way to the Nepal-China border provides a humbling experience of how these idyllic landscapes can be turned into deadly traps in the blink of an eye. With closer scrutiny it becomes obvious that the whole landscape has been shaped by a myriad of these catastrophic events, directly questioning the notion of extremes.

After six days of presentations, posters, and late night discussions, it was time to close this intense, yet educational week. In the end there weren’t too many power cuts, no one got sick, most of us managed to shower with hot water and only a few reported spiders in their tents. In line with the local Nepali customs, the end of the conference was celebrated by inspired dancing until late at night when the first shuttles back to the airport started to take people back to Kathmandu.

By Maarten Lupker, ETH Zürich, Switzerland

60 scientists from all over the world came together for the opportunity to debate and discuss issues related to rare/extreme events and how they impact Earth system dynamics. Credit: Monique Fort

Acknowledgments

This conference was jointly organised with the Nepal Geological Society (NGS), without which this week would have never existed. While many people were involved, we would like to extend special thanks to Basanta Raj Adhikari and Ananta Prasad Gajurel from Tribhuvan University as well as the former president of NGS, Kabi Raj Paudyal and the present one Ram Prasad Ghimire. Bhairab Sitaula also provided invaluable help in all logistical aspects of this conference.

The conference was also co-sponsored by the US National Science Foundation, which provided overseas travel grants. Support from DiGOS & GFZ Potsdam were also greatly appreciated.

The organiser team: Christoff Andermann, Kristen Cook, Sean Gallen, Maarten Lupker, Christian Mohr, Ananta P. Gajurel, Katherine Schide, Lena Märki

Geosciences Column: Taking a Breath of the Wild – are geoscientists more effective than non-geoscientists in determining whether video game world landscapes are realistic?

Geosciences Column: Taking a Breath of the Wild – are geoscientists more effective than non-geoscientists in determining whether video game world landscapes are realistic?

For years, geoscientists have been both fascinated and perplexed by the beautiful (yet often inaccurate) landscapes present in several video games. But are people with a geoscientific education better at telling ‘fake’ natural features from real ones? Rolf Hut, an assistant professor at Delft University of Technology in the Netherlands, and his colleagues sought to answer this question in a new study published in EGU’s open access journal Geoscience Communication

“Oh wow, that is a gorgeous volcano… which could never exist in the real world.” As a hydrologist I’m not an expert on volcanoes compared to some other EGU members I know. Yet, while walking through the fictional world of Hyrule in Nintendo’s latest installment of The Legend of Zelda game series: Breath of the Wild my emotions tend to constantly switch between excitement at the beauty of the landscape and puzzlement at the geoscientific… wrongness of it.

“That mountain could never generate enough runoff to feed a waterfall this big.”

“Ice capped mountains in the background of a sweltering dessert looks amazing. But it only takes me five minutes to get up that mountain, so there could never be snow there…” 

I know: it is just a game. First and foremost game designers had to make this game interesting to play and it wouldn’t have been much fun if you had to walk up a mountain for three days, (Edmund Hillary style) only to find a single piece of in-game equipment . So they condensed the game world. They made decisions that might hurt the sensitivities of geoscientists, but which ultimately made the game more enjoyable (and beautiful) for the majority of those people  whose wallets Nintendo is targeting. 

This whole process got me wondering: if I hadn’t been trained as a geoscientist, would I have had the same “this cannot exist in the real world” feelings that I now have? Would non-geoscientists interpret this fake world as something that potentially could exist? Given how many people play video games, versus how many are trained as geoscientists, this is an important research question. If people do ‘learn’ from games like The Legend of Zelda: Breath of the Wild, they might get a wrong impression of how the (geoscientific) world works.

Curiosity sparked, we set out to test this. And I say ‘we’ because this type of research requires the expertise of a statistician: Casper Albers, an expert of games for geoscience: Chris Skinner, an expert on science communication: Sam Illingworth, and finally someone who has spent more hours in the fictional world of Hyrule (where the The Legend of Zelda: Breath of the Wild is set) than is in any way reasonable: me. 

We picked screenshots from across Hyrule with geoscientifically interesting features such as volcanoes, glaciers, etc. Through a reverse image search (on Google) we then looked for real world photos with matching features. We wanted to ask both geoscientists and those without a geoscientific education to rate those pictures on “how likely they think that the features in the picture can exist in the real world?”. We wanted people to focus on the geo-features, and yet we assumed that normal photos would likely be instantly recognisable compared to the rendered images from the game world; so in order to account for this we applied an artistic ‘van Gogh’ filter to all images.

Two images used in the survey. Panels (a) and (b) are original and (c) and (d) are processed through the “van Gogh” filter. The left two images are from the video game The Legend of Zelda: Breath of the Wild and the right two images are from the real world. The bottom two figures were presented in the survey with the question “Knowing that this picture has gone through a “van Gogh”-filter, how likely do you think it is that the features depicted in the artistic renderings could exist in the real world?”. A 10-point scale was used, where 1 = completely unlikely to 10 = completely likely. (Credit: Rolf Hut et al. 2019)

We distributed our survey among geoscientists and non-geoscientists through social media channels and at the EGU General Assembly 2018. We found two very interesting results. Firstly, it (luckily) transpires that geoscientists are better than non-geoscientists at recognising what is a ‘fake’ landscape from a game; the difference between geoscientists and non-geoscientists is statistically significant. However, the effect is very small and both groups are fairly good in recognising which landscapes are and which aren’t from the game. 

What this research therefore highlights is that everyone, including myself, can continue to explore the beautiful countryside of Hyrule, without fearing that we will pick up erroneous knowledge about geoscience. 

Of course we have to be careful with interpreting our results: it is only a first study into this new field of science and we encourage anyone to build on our work by studying different games, different screenshots and people across more dimensions than only geoscientists versus non-geoscientist. Our paper is available for free via the open access EGU journal Geoscience Communication, and any questions can be directed to the corresponding author: me. Although please allow some time before I answer: chances are I am not continuously looking at my inbox because I’m spending my time wandering through the beautiful, but recognisably fake, plains, mountains and volcanoes of Hyrule.

By dr. ir. Rolf Hut, researcher at Delft University of Technology, the Netherlands

[This article is cross-posted on Rolf Hut’s personal site]

Imaggeo on Mondays: A walk at the glacier

Imaggeo on Mondays: A walk at the glacier

In 2012 I had the opportunity to help lead a teaching excursion to the Norwegian archipelago Svalbard. On this trip, geography students from the Ruhr-University of Bochum in Germany had the chance to learn more about the nature of this fascinating island.

In addition to Svalbard’s climatology and the wildlife, the region’s glaciology and geomorphology were the main topics we focused on. For example, we walked to the glacier ice, measured the glacier drainage flow and assigned various glacial debris accumulations (also known as moraines) to their genesis. Furthermore, PhD students from the local university showed us field experiments on how the region’s permafrost melts and wet soils slide downhill (also known as solifluction). We could see the giant glacier tongues with ice fronts at the sea level on a boat trip to the old coal mining town of Longyearbyen. The debris cover and the incredibly large medial moraine (debris that collects when two glaciers merge together) of the pictured glacier particularly impressed us.

We were astonished when the two polar bears came into sight after a short moment. Of course, we had secretly hoped to see polar bears on this excursion, but when it actually happened, not only the glaciers and the whole landscape seemed bigger, but also the wild nature of Svalbard got much more impressive. For me, my colleague André and my students this experience will be unforgettable.

By A. Martina Grudzielanek, Ruhr-University of Bochum, Germany

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/.