GM
Geomorphology

EGU Guest blogger

This guest post was contributed by a scientist, student or a professional in the Earth, planetary or space sciences. The EGU blogs welcome guest contributions, so if you've got a great idea for a post or fancy trying your hand at science communication, please contact the blog editor or the EGU Communications Officer to pitch your idea.

Diving under the scientific iceberg

Diving under the scientific iceberg

written by: Anne Voigtländer, Anna Schoch, Elisa Giaccone, Harry Sanders, Richard Mason, Johannes Buckel

At the EGU General Assembly international researchers from all earth science communities gather and share their most recent endeavors. This year, we, a group of European young geomorphologists, tried a new session format to address challenges we all face in our research, ranging from inaccessible data and methods, unknown initial conditions, up and down scaling in space and time, to unknown processes and land forms. In discussions of conference talks, only the tip of the iceberg of Earth science research can be exploited. The rest of the iceberg, resembling all challenges, ideas and minds (of the audience) usually remains in the shaded, unspoken depth. We explicitly wanted to cater these challenges or ideas and use the crowd of participants to approach or solve them. In the short course SC1.29/GM12.1 “Crowd-solving problems in earth science research”, we wanted to use the synergetic effect of the diverse conference audience as a resource. Our main methodology to access these resources was old-fashioned discussion. We flipped the tables and had problem stating talks for 2 minutes, which is the usual discussion time. Five Early Career Scientists came forward with their challenges and ideas they face in their research and asked the audience for solutions in 40-minute discussion rounds:

How to secure funding for basic, non-societal research?

(Vittoria Vandelli, Università di Modena e Reggio Emilia, Italy)

Perhaps one of the least funded, but historically most productive research areas is basic research, which at the time may appear to have little or no public impact, but often results in ideas and inventions that change history. In a world of ever reducing science budgets, securing funding and finding novel methods of funding research outside of grants, becomes the holy grail. You can write about your work for magazines who in turn cover your travel expenses, sell local stamps to collectors and even involve the curious public for non-mainstream projects. However, in reality, the majority of our basic research relies on grant success, and so the ability to write a strong application (hitting on popular paradigms like ‘climate change’). In that case the challenge is to find and access grants. So why not create an open access database for ECS, to both contribute and utilize for securing grant funding? However, if you have tried and not found success with grants, hobby writing isn’t for you, and the idea of involving the public isn’t feasible, there’s nothing wrong with teaming up and collaborating with an already wealthier researcher!

How to make measurement techniques affordable?

(Anette Eltner, Technische Universität Dresden, Germany)

There are many good reasons to make measurement techniques affordable, such as fostering independent research, having low barrier easy access (financially, politically), increasing the quantity and density of data and thus robustness, greateningr knowledge of and possibilities to improve measurement techniques, and becoming more resilient if devices get swept away in monitoring hazardous processes… However, data quality and reliability need careful consideration, and data processing and analysis need automation to handle increasing data amount. Several examples associated with low cost solutions are already applied in earth science research; foremost are software solutions (e.g. R, QGIS). What we need for the hardware measuring devices is cooperative development of more low cost methods, big data handling and quality assessments. This could be realized in a “maker space” at universities, where scientist from different disciplines can gather to find joint solutions, or platforms and communities, such as GitHub for software. Therefore, the “crowd” and communication in this crowd could be a solution. In an ideal case, low cost methods were associated with a “crowd” supporting the application and development. Additional funding to promote in particular low cost methods should be provided.

Numerical modelling at the edge: why accuracy matters?

(Benjamin Campforts, KU Leuven, Belgium)

Numerical models are transforming our understanding of the world around us, allowing simulations of processes at scales impossible to investigate by any other means. Numerical models are simplifications or idealisations of ‘real’ environments and the accuracy of the model outputs is reliant on how well models represent this reality. Thus, while the possible complexity of numerical models makes them essential and ground-breaking tools for earth science research, they also cause some problems. First of all, how well do we understand these natural processes and how are they incorporated in the model design? And then, which equations and algorithms should we choose, ideally based on in-depth knowledge of natural processes? In this respect, interdisciplinary communication and exchange is required between modelers and field-based scientists in order to parametrize and grasp the physics of the natural processes. Practically we need greater sharing of ideas, open source models and data, to improve accuracy and help to understand errors surrounding model predictions.

How to secure data accessibility as a young researcher?

(Moctar Dembélé, Université de Lausanne, Switzerland)

Depending on where we live, or the topics we work on, data (i.e climatic, atmospheric, hydrological, topographic…) is not available. And when it is available, sometimes it is a challenge to get access to it. To call this challenge might actually be the starting point to overcoming it and allowing ECS to contribute substantially to science. Both, the producers (governmental or private agencies) and potential users (scientists) of the data can help with data access, without personal, national or financial biases. In order to make this happen, we need to clarify why data sharing and accessing is beneficial to both parties. Produced and published (meta)data (where data acquisition is described in a reproducible way) wants more fame, collaboration and citation. Governmental and private data producers could use the same, already existing platforms, scientific peers use to share and access their data. Users, especially ECS, would love to have common platforms to share and access data that could be used to reinterpret and expand data and to identify data gaps

How to overcome the subjective nature of interpreting fluvial archives?

(Wolfgang Schwanghart, Universität Potsdam, Germany)

Interpretations of archives and subsequent parametrizations for (numerical) models rely on subjects as well as the very individual and special outcrop site. A first step could be to have the experience based tacit knowledge of a subject be translated into explicit knowledge, in order to make it accessible and comparable for other subjects (deduction). Combining the interpretations of several (interdisciplinary) subjects might provide a more objective, rigor and robust perspective. If enough parameters and proxies exist, we could also turn to statistics (induction). And if that is no option, we might try abduction, like Sherlock Holmes, where iterations of field/archive and model/statistics can, at least subjectively, make data collection more transparent, sharpen the interpretation and define further research questions.

We need to talk!

A synthesis solution to the question and the above stated challenges is: Communication. Obviously you can’t solve the challenges in 40 minutes, but the concept to spend more time for discussions on a conference to tackle the problems every scientists faces in this way or another worked. All five groups with roughly ten participants. Each came into conversation, exchanged experiences, analysed new aspects and developed ideas. We received very positive feedback from all participants and were encouraged to organize a similar event again – so maybe next year we can crowed-solve what the submerged part of an iceberg is called, anyway?

The organization of this session was financially supported by the British Society for Geomorphologie and the Arbeitskreis für Geomorphologie.

 

 

 

 

 

 

 

 

 

written by: Anne Voigtländer, Anna Schoch, Elisa Giaccone, Harry Sanders, Richard Mason, Johannes Buckel
Contact: geomorph-problems@geographie.uni-bonn.de

EGU – realm and maze?

– written by Micha Dietze, Annegret Larsen (both GM Early Career Representatives), and Anouk Beniest (EGU TS Early Career Representative)

An interview with the Susanne Buiter, the current chair of the EGU Programme Committee

Susanne Buiter is senior scientist and team leader at the Solid Earth Geology Team at the Geological Survey of Norway. She is also the chair of the EGU Programme Committee. This means that she leads the coordination of the scientific programme of the annual General Assembly. She assists the Division Presidents and Programme Group chairs when they build the session programme of their divisions, helps find a place for new initiatives and tries to solve issues that may arise. This also includes short courses, townhall and splinter meetings, great debates, events on arts and other events. The programme group also initiates discussions on how to include interdisciplinary or transdisciplinary science and how to accommodate the growth of the General Assembly.

Susanne, you are perfect example of a scientist bridging scientific work with scientific management. What brought you to this and how do you manage keeping the balance?

Susanne Buiter senior scientist and team leader at the Solid Earth Geology Team at the Geological Survey of Norway.

I would not call it perfect! And I find it not so easy to keep a balance. I am very fortunate that my employer, the Geological Survey of Norway, recognises the importance of organisations like EGU for the geoscience community in Europe. That means that I can partly use working hours for EGU activities and that is a great help. For me, EGU fulfils an important task in bringing people together for networking, starting new projects, discuss new ideas and I would like to contribute to making that possible. I guess one thing led to the other, but what is important for me is that all activities are truly fun and rewarding.

It seems you have filled almost all the different possible jobs within the EGU: giving talks, discussing posters, judging presentations, convening sessions, coordinating ECS activities like short courses, acting as Programme Group member and leader, serving as TS Division President, and now working as Programme

Committee Chair. Could you describe what the main goals of the EGU are for you, and what brought you to become such an active member of the EGU community?

I see the role of EGU as serving the geoscience community through enabling networking, discussions and information sharing. Our General Assembly is very important for this and also our journals. I love the outreach and education that EGU does, through the GIFT programme and attempts to interact with politics and funding agencies. By the way, the short courses are for and by all participants, including the ECS, but not only!

Could you shed some light on the structure of this big ship called EGU in a few sentences?

What characterises EGU is that the union is by the community and for the community. EGU has a small office in Munich that oversees the day-to-day operations and coordinates our media activities (www.egu.eu). They are also EGUs long-term memory. We have 22 divisions from Atmosphere Sciences AS to Tectonics and Structural Geology TS. The division presidents are usually also chair of their associated Programme Group, with the same abbreviations AS, BG, CL etc that you see in our programme at the General Assembly in Vienna. They schedule their parts of the conference programme. For this, programme group chairs rely on the work of conveners (you!) to propose and organise sessions. Division presidents are also member of EGU’s council, together with EGU’s executives. Here decisions are taken on budgets, committee work, new executive editors of journals etc. EGU has among others committees for awards, education, outreach, publications and topical events (https://www.egu.eu/structure/committees/). Copernicus is hired by EGU for organisation of the General Assembly and publication of the 17 journals (https://www.egu.eu/publications/open-access-journals/). All EGU journals are open access. Sorry, that was rather more than a few sentences…

How flexible – in your experience – is the EGU administration and organization on a scale of 1-10?

A 9! I would have like to say a 10, but improvements are always possible. The EGU office, executives, divisions and committees put a lot of effort in coordinating all activities. We actually rely on flexibility as EGU is bottom-up. This is also how new initiatives find a place. For example, EGU2018 will have a cartoonist-in-residence and a poet-in-residence, a new activity I am very excited about and that was proposed by participants.

Regarding the ECS, which role do you feel should they play at EGU level? What is running very well and what would you like to change? Where do you think are fields where you see opportunities to become more active?

About half of participants to our General Assembly identify as ECS according to the survey from 2017 and abstract submission statistics for 2018. So they should play an important role! Not only in the General Assembly, but also in our committees. The ECS representatives are important for their feedback to council, making the ECS opinions heard, and starting new activities, such as the networking reception, many short courses, and the ECS lounge. What I would like to change? More ECS session conveners please! I would really like to encourage ECS to submit session proposals during our call-for-sessions in Summer. And please consider to submit your abstract with oral preference, so conveners can schedule ECS talks.

What is most important for ECS to know about the EGU structure?

Know your ECS representative. At the General Assembly, come to the ECS forum on Thursday at lunch time and the ECS corner at the icebreaker. Connect with scientists in your division(s) by attending the division meeting.

From your perspective, what can we do to motivate more ECS to actively shape “their” EGU?

It is building on what you already do: share information on EGU, the divisions, that we are bottom-up and therefore rely on suggestions by community members. Encourage ECS to suggest sessions, volunteer as committee member when there are vacancies (these are advertised on www.egu.eu and through social media), and organise activities at, before and after the General Assembly. Encourage ECS to use the conference in Vienna to network with all participants, not only through ECS channels, and find new opportunities that way. My observation is that many experienced scientists love to discuss with ECS and perhaps even start new collaborations.

Which ways and approaches do you see to better connect ECS within and between Programme Groups?

I find especially connections *between* Programme Groups very interesting, not only for ECS. EGU is growing to a size that it has become more difficult to find time to look outside your own bubble. We have been investigating ways to make our programme more interdisciplinary (https://meetingorganizer.copernicus.org/EGU2018/sessionprogramme/IE) and perhaps in the future also transdisciplinary, to try to create new approaches. That said, I am happy to see at the ice-breaker and networking reception that many ECS identify with more than one division! It is important to cross borders, that is where a lot of exciting research happens.

The mentoring programme is a rather new feature for many divisions. Could you give some feedback on how it went last year? Will it be a permanent item during the EGU General Assembly?

We organised the mentoring programme in 2017 as a pilot, which we on purpose kept somewhat low profile to generate feedback and develop our tools. We see the programme as a networking opportunity for both first-time and experienced attendees. Feedback was very positive, so we are rolling out in full this year. We offer matching, two meeting opportunities at the General Assembly and some guidance (https://www.egu.eu/outreach/mentoring/).

The EGU General Assembly can be overwhelming at first. What would you advice young (and not so young) researchers to do to have a successful meeting?

Attend short course SC2.1 on how to navigate the EGU (Monday at 08:30), read the first-timer’s guide to the General Assembly (https://blogs.egu.eu/geolog/2017/11/29/a-first-timers-guide-to-the-2018-general-assembly/), and make sure you are on the mailing list for your division ECS representatives if they have one. Some divisions have an ECS evening event, do attend! Consider taking part in the mentoring programme of course. And prepare a personal programme before heading to Vienna. Not to follow it in detail, but at least to know where to go for talks, PICO, short courses, posters, and events. I would definitely use the General Assembly to talk to other participants, this is a great chance to expand your network.

Time and space are precious during the EGU General Assembly. There are over 10.000 contributions, many aiming at a talk, but ending up as posters, the session rooms are often overcrowded, the lunch break brings a rush and long queues. Is there any way the Union Council considers to improve certain bottle necks or are we already at the maximum of optimizing some of the conference logistics?

In 2017, we had ca. 17,400 presentations and 14,500 participants. We rented a new hall on the forecourt of the conference centre, which we will also have in 2018. This increased the conference space, taking pressure off the rooms and surely reduced queues. Copernicus and EGU work continuously on optimising the scheduling. We also started a broader discussion on future formats of the General Assembly. I would like to take this opportunity to encourage trying a PICO presentation or convening a PICO session. I have run some poster-only sessions the last years, which have been great fun as we had so much better time for discussions.

Many ECS approach their representatives because they are worried or disappointed to see their initiatives for scientific session proposals not succeeding. Instead they find year after year the same names behind established and crowded sessions. Do you have any advice how to deal with this or do you think this is not really an issue?

I am aware that this may unfortunately play for some sessions, but overall I think we cater well to new initiatives. My advice to Programme Group chairs is to encourage ECS conveners for new sessions and also to include ECS as part of long-running sessions that should rotate, and renew, conveners each year. Our General Assembly offers place for sessions on the basics and fields that require long-term developments, and at the same time also on new, emerging topics. Sometimes these sessions on upcoming topics may be small in number of submissions, but large in attendance. The best I can say to anyone is to discuss concerns or feedback regarding convening with the division president and the ECS division representative.

With the growing amount of members and participants (almost) every year, how do you see the EGU’s future both as a community and as one of the most important events?

EGU is an important voice of the Earth and space science community in Europe. I think the union should continue to do what it is good at: providing a platform for networking, discussions on new and old fun topics, and information sharing. I would like EGU to stay flexible and cater to new formats in its journals and at its General Assembly, the latter also in light of discussions on CO2 costs of meetings.

Thank you Susanne!

Could I emphasize again that EGU is bottom-up and depends on input from our communities? So please contact your ECS representative, the division president or me (programme.committee@egu.eu) with ideas and feedback!

Some more information online here:

www.egu.eu

https://meetings.copernicus.org/egu2018/information/programme_committee

https://www.egu.eu/gm/home/

https://www.egu.eu/gm/ecs/

http://www.geodynamics.no/buiter/

– written by Micha Dietze, Annegret Larsen (both GM Early Career Representatives), and Anouk Beniest (EGU TS Early Career Representative)

 

A geomorphologist’s winter refuge

– written by Michael Dietze, GFZ Potsdam –

The Sävor River, northern Sweden, under late winter conditions. The frozen river has been sensed by ADCP and seismometers to constrain flow properties and bedload transport dynamics (credit: Michael Dietze).

Why Swedish, Finnish and German geomorphologists meet in the boreal zone to drill holes into icy rivers and frozen ground.

There are many ways to counter the lazy days between Christmas and the EGU meeting. One of the more promising ones is this: think of doing collaborative field work in February, in northern Sweden, on and around a frozen river. This is what Lina Polvi, Lovisa Lind (both Umeå University), Eliisa Lotsari (University of Eastern Finland), Jens Turowski and Michael Dietze (both GFZ Germany) decided to do. They met in Umeå, northern Sweden, at 64° North – just when the thermometer had recovered from its chilling excursion down to -25° C back to a cozy -12° C – to investigate how much and how fast water flows under an ice-covered high-latitude stream, and by which mechanism and how much sand and gravel are transported in these northern rivers during the cold period of the year.

Lina drilling a hole through half a meter of river ice to sense the stream properties (credit: Eliisa Lotsari).

We all know that bedload transport is a key process in rivers, affecting nutrient transport, habitat availability and hazard potential of streams. Yet, currently, in northern regions, scientists are virtually blind-folded for almost half a year when thick ice cover precludes the view to the hydrodynamic processes in channels, and traditional survey and monitoring methods are unavailable. So, how do you measure flow velocity and bedload transport when your research object is hidden below half a meter of compact ice? Well, at least the hydraulics are quite easy: flow velocity can be measured with an acoustic doppler current profiler (ADCP), a device that can measure bed topography and flow velocity in three dimensions in the entire water column. In the summer the ADCP can be towed across the stream on a small raft, but in winter in a frozen river, it needs to be lowered into holes drilled through the ice. And even in the 21st century, a few days before women’s day, the staff at the fishing shop that rented out the motorized ice auger felt the need to carefully and skeptically explain to the women that an ice auger is a “very powerful and dangerous thing”. The three female scientists politely expressed their gratefulness for the concern, pointed out their prior experience, and hired the machine anyway.

Letting the sensors doing their work. Lovisa, Jens and Lina observing an ADPC measuring hydraulic conditions under ice (credit: Eliisa Lotsari).

Packed with the auger, ADCP, geophones and seismometers, a scary ice saw, red spray paint, a GoPro camera, time-lapse cameras, and plenty of duct tape, all five river scientists trudged through the meter deep snow with snowshoes along the bank of the Sävar River until they found a reach with ice thick enough to walk on. How do you recognize that it is thick enough? Well, you may be less careful, but our heroes used a well-known and long-established Swedish testing device with a mass of 400 kg: the moose. Seeing moose tracks in the snow on top of the river ice is always a good sign that it is safe to walk on. Before the first measurement could be made, around 20 holes with a diameter of 20 cm needed to be drilled through 50 to 80 cm thick ice. This was shared fun and with the last ice layer collapse, as the dark brown river water seeped up to the surface, the site was ready for the ADCP surveys, water sampling and underwater videos with the GoPro camera.

Letting the sensors doing their work. Lovisa, Jens and Lina observing an ADPC measuring hydraulic conditions under ice (credit: Eliisa Lotsari).scary ice saw, red spray paint, a GoPro camera, time-lapse cameras, and plenty of duct tape, all five river scientists trudged through the meter deep snow with snowshoes along the bank of the Sävar River until they found a reach with ice thick enough to walk on. How do you recognize that it is thick enough? Well, you may be less careful, but our heroes used a well-known and long-established Swedish testing device with a mass of 400 kg: the moose. Seeing moose tracks in the snow on top of the river ice is always a good sign that it is safe to walk on. Before the first measurement could be made, around 20 holes with a diameter of 20 cm needed to be drilled through 50 to 80 cm thick ice. This was shared fun and with the last ice layer collapse, as the dark brown river water seeped up to the surface, the site was ready for the ADCP surveys, water sampling and underwater videos with the GoPro camera.

Installation of a seismic station to sense hydraulic and sediment transport dynamics of the Sävar River by Micha (credit: Eliisa Lotsari).

Meanwhile, Micha left the slippery ground to explore the bank and terrace landforms around the measurement site. He scouted for suitable locations to deploy geophones and seismometers. Geophysical instruments designed for earthquake analysis in a study about fluvial geomorphology? Indeed, seismic sensors are ideal for gathering information about hydraulic dynamics and sediment transport where other systems would simply fail. The instruments are sensitive enough to record the impacts of the smallest rain drops, and they deliver precise estimates of the seismic wave field emitted by the turbulence of the water and pebbles being dragged over the river bed. And crucially, they do not need to placed within the river, but can monitor everything comfortably from the bank. Three geophones were installed along a line perpendicular to the river, and one broadband seismometer some 30 m upstream. The instruments need to be installed in a hole in the ground, half a meter deep. Luckily, the ground was not frozen throughout, as suspected, and the loose sand beneath a surface layer of only 10 cm of frozen soil was easy to remove. The charcoal brought to defrost the ground was put to good use in a barbecue at lunch time. The sensors were leveled in the holes, oriented to North, connected to the data loggers and the station was ready to record 1000 samples per second for the next month, until the batteries need to be exchanged by Lina and Lovisa.

The seismic sensor network forms a triangle that allows for not only constraining water flow and sediment transport, but also locating seismic point sources, such as cracking in the ice. This latter functionality will become especially interesting when, in late spring, the frozen surface of the river cracks open and potentially an ice jam forms while a flood rushes through the valley. The combined information on timing and location of single events allows detailed insight to the anatomy of this seasonal singularity.  Furthermore, the seismic survey allows inferring the seismic signature of such ice break-up events, along with precursor activity like small cracks that compensate the increasing tension within the ice cover.

Spectrogram of two days of seismic recording. River turbulence is visible around the 10 Hz band (continuous yellow band), the activity period in early morning of 7 March presumably represents an ice break-up event 100 m downstream the installation, and the high frequency activity is caused by wind, interacting with the trees (credit: Michael Dietze).

The field team (Jens, Micha, Lovisa, Lina and Eliisa, from left) enjoying a winter barbecue after successful installation (credit: Eliisa Lotsari).

After two chilly days in the field most of the work is done, the seismic network is ready to operate, the ADCP data is already processed and the team is improvising to enjoy a winter barbecue, chatting about when to meet again to recover the equipment, bring together the data output and share ideas for the follow-up project.

Interested in more high latitude fluvial dynamics, bedload transport and environmental seismology? Approach the team members at the upcoming EGU meeting in Vienna or see the individual web pages:

Lina, Lovisa, Eliisa, Jens and Micha

 

– written by Michael Dietze, GFZ Potsdam –

Do glaciers really do all the work? Perhaps not.

Kerry Leith from the Engineering Geology Department at the ETH Zürich set up a post on their latest publication and the backstory behind it. As they announced on their own website (www.stressdriven.com) review comments ranged from “mediocre or poor” to “[…] provocative, potentially revolutionary (if correct) analysis”. It surely contains interesting thoughts.


written by Kerry Leith (ETH Zürich), edited by Sabine Kraushaar (University of Vienna) –

Illustration of modeled prehistoric river channels and projected hillslopes for the end of significant interglacials at Marine Isotope Stages 13 – 3. The photo is taken looking north from the village of Graechen in the Matter Valley, Switzerland.

The great debate


At the turn of last century two of Europe’s pre-eminent Earth scientists were embroiled in a long-running debate regarding the processes involved in shaping the European Alps. Albert Heim (1849 – 1937) was a Swiss geologist who served as a professor of technical and general geology at ETH Zurich (1872 – 1875), before moving to a professorship at the nearby University of Zurich (1875 – 1911), and Albrecht Penck (1858 – 1945) was a German geologist and geographer who, after a short stint teaching at the University of Munich, became a professor at the University of Vienna in 1885, before moving to Berlin as professor of geography in 1906. While Heim may be regarded as a more traditional geologist, publishing on topics ranging from the mechanics of mountain building, to landslide dynamics, and phenomena associated with glaciation, Penck was very much interested in the manner in which surface processes (e.g. rivers, glaciers, and landslides) shape the landscape. Penck spent much time studying the geomorphology (a term he is attributed to coining in 1894) of glaciations, and outlined four major Pleistocene ice ages based on sediments distributed on the broad planes surrounding the European Alps.

Albert Heim (left) with Albrecht Penck (right) (in Brockmann et al. 1952).

Though I don’t pretend to be a historian, the relationship between Heim and Penck seems to have been a complex one. In ‘Albert Heim: Leben und Forschung’, Brockmann et al. (1952) describe a great friendship between the two scientists, while their writings relating to the origin of the Alpine landscape (a topic which must have been close to each of their hearts) are quite combative. In Heim’s 1885 ‘Handbuch der Gletscherkunde’, he discusses the relative roles of glacial and fluvial erosion in the formation of large Alpine valleys:

The only question is which of the two agents, ice or water, applies the greatest erosional strength to the mountain, or in other words which has the higher efficiency? The decision is not difficult: compared to the effects of water:

a) The ice consumes a larger proportion of it’s energy to overcome its internal deformation, to flow. The water very little.

b) The effect of ice is spread across a large wide area. The river is focused on a narrow path.

c) The ice spends energy crushing fine particles, sanding, and polishing the rocks for which a high pressure is required; the river works at a larger scale, it is to some extent a coarser file, a rougher grindstone, it doesn’t polish or scratch, but works by impacting debris,

d) The presence of ice means that external mechanical, and in a narrower sense chemical weathering agents are excluded from the erosion process, it must do everything itself; the flowing water employs the help of many weathering agents.

He goes on to say:

Glaciers may have produced some morphologies inconsistent with erosion by fast rivers, but in the overall formation of the mountain landscape the effect of glaciers lags far behind. Glaciation therefore likely causes a relative stillstand in valley formation.

This view contains no hypotheses, it is not based on deductions, it is rather a result of direct and observable facts. I consider these to be binding.’*
(*emphasis is mine)

These observations, and perhaps more importantly clear deductions based on what many would say are ‘modern’ principals of energy and geomorphic work are strong arguments for a fluvial (river driven) origin for major Alpine valleys. Contrary to Heim’s statement, however, none of these observations would pass the bar of scientific ‘fact’ today, as (amazingly) systematic studies testing the efficiency of one process against the other are lacking in the literature.

Perhaps that’s because the opinions of the younger Penck were very firmly planted on the other side of the fence. In 1905 Penck published a paper in the Journal of Geology entitled ‘Glacial Features in the Surface of the Alps‘, in which he concludes:

‘The actual surface features of the Alps do not at all correspond to those of a water-worn mountain range. Their conformation is mostly due to ice-action, which becomes most visible where the old glaciation ceased.’

It’s quite unusual for an article nominatively discussing ‘glacial features’ to make such a bold statement against an alternative origin (this should require a study (or more) of itself), and is almost certainly an attack on the opinions of Heim and others by the new Berlin professor. Penned largely as an opinion piece in (what is now at least) one of the most influential geological journals, the article constantly alludes to what must have been a vibrant argument at the time, rallying around the personal observations of glacial features by Penck and his colleagues during his time in Vienna.

Paris and Grenoble at war


Around the time of Heim’s retirement, the debate was reignited in the ‘Battle of the Alps‘ between two former students of the great Parisian geographer Paul Vidal de La Blache (as reported in a 2001 article by N. Broc). Emmanuel de Martonne (1873-1955) was a ‘cold’, ‘distant’, and ‘gruff’ provincial bourgeoisie, who first married de La Blache’s daughter, before replacing him as the Head of Geography at the University of Paris in 1909. From a simple background, Raoul Blanchard (1877-1965) was slightly younger than de Martonne, and the complete opposite in character. Charismatic, fearless, and adored by students, on completion of his PhD in Paris Blanchard was appointed to the University of Grenoble in 1905, and rapidly gained a devoted group of disciples. There started a battle that would span two world wars, and settle in what seems to have been an exhausted truce around 1945. As in the conflict between Penck and Heim, the younger, charismatic (Grenoble) geographer seeking to make a name for himself favored a glacial origin for the Alpine landscape, while the elder (Parisian) statesman correlated features observed in the field with the operation of fluvial processes. Here, it’s important to know that de Martonne worked under Penck in Vienna from 1895 – 1899, and in Broc’s (2001) article, he openly wonders if the position taken by de Martonne is ‘..the influence of certain German and Austrian geographers reacting against their predecessors?‘.

de Martonne (left) favoured a fluvial origin and assumed the Head of Department role in Paris. Vidal de la Blache (center), the former Head of Department who had previously worked under Penck, and supervised the PhD’s of both men. And Blanchard (right) the glacial proponent from Grenoble.

In the colorful debate, Blanchard, commenting on one of his first student’s publications stated:

this young geomorphologist (Blache, 1914) ‘victoriously refuted the theories’ of E. de Martonne on evolution of alpine valleys ‘Demonstrating that stepped tiers on Belledonne’s flanks were glacial erosion levels’, he asserted that ‘none could belong to an ancient Pliocene valley bottom (that is to say, anterior to glaciations)‘. And Blanchchard, who was never modest in triumph, concluded: ‘So this boy of twenty years has seen more than the head of French physical geography!’ (referring to de Martonne, who at the time was 20 years his senior).

The first world war interrupted proceedings, and one can assume the discussion immediately faded to the background. In 1926 André Cholley’s thesis emerged from Paris as a direct challenge to the school of Grenoble. In this, the 40 year old geographer (who Blanchard irreverently terms a ‘young man‘) identified more than six levels of erosion between 350 and 1400 m a.s.l., attributing them wholly to the effects of interglacial fluvial incision (this is essentially our “new” result). Blanchard, in commentary to a latter work championing repeated cycles of glacial erosion by his student (Blache, 1931), pondered ‘Can we suspect the existence of old erosional surfaces? No trace … ‘ and in reference to Cholley’s thesis ‘to negate the hypotheses ventured: even before demonstrating inanity, we feel that they are useless.’. Of course the suggestion of remnant valley floors did not occur entirely in isolation, and workers such as Gygax (1934) and Machatschek and Staub (1927) came to similar conclusions in other regions of the Swiss Alps. However, to my knowledge, only Gerber (1959) perpetuated the idea beyond the second world war.

A lingering haze


Jump forward more than half a century, and our manuscript proposing a strong fluvial overprint on extremely old glacial landforms in the Swiss Alps was described a reviewer as ‘a significant departure from conventional wisdom‘, while another commented

… it strains credulity to think that delicate features such as fluvial knickpoints* could survive being overridden by ice with little to no modification‘.

*nb. ‘knickpoints’ are essentially smoothed waterfalls for geomorphologists

There has not yet been a study to quantify the degree of erosion of an alpine landscape through a single glacial cycle (at least in the last half-million years), and without going into too much detail, the paradigm that erosion during ice ages is the key driver of topographic change in the Alps is now so ingrained in the scientific literature that our proposition of what is essentially a very old idea was regarded by one reviewer as a ‘provocative, potentially revolutionary (if correct) analysis‘.

Recently, a number of studies have made significant steps to clear the haze. Korup et al. (2007) reasoned that deep gorges close to main trunk valleys in the Alps had to be older than the current glacial, while in a 2015 article, Matt Fox, myself, and a co-authors used erosion rate estimates to demonstrate that fluvial gorge formation in a catchment on the southern side of the Alps outpaced glacial erosion at the same location for the last ~400 kyr. However, without good reason to attribute a large amount of erosion to one glacial cycle, and little to others, the paradigm of a primarily glacial origin continues to dominate scientific literature.

Updating the state-of-the-art


In two earlier studies, my co-authors and I found that fractures growing in bedrock below Alpine glaciers during a particularly strong shift to glacial conditions (known as the Mid-Pleistocene Transition (MPT), around 780 kyr ago) may have developed in a somewhat explosive manner, literally popping rock off the glacier bed as the massive alpine glaciers thinned (See this post for a video of similar fractures forming in California recently). While glaciers are certainly important conveyors of fractured rock, we suggested the energy for fracturing, and therefore degree of erosion, was derived from elastic stresses in the rock itself. Modelling subsequent glacial cycles indicated the return to glacial conditions then confined and stabilized the deep valleys, preventing erosion during subsequent glacial cycles. The Alps have been through nine major glacial cycles with a period of approximately 100 kyr since the MPT, and although some sedimentary evidence indicates the first cycle likely caused the most erosion, the common assumption that Alpine valleys are the result of cumulative glacial erosion has (at least in the last 70 years) prevented researchers looking further into the fluvial history of the region.

Predicted distribution of various types of fracture beneath an Alpine valley. Here we start with a ‘V’ shaped topography, introduce ice, and manually cut out the center of the valley. Fractures forming in tension and shear are colored yellow and orange, respectively, while active ‘micro-cracking’ is purple, and regions in which we predict explosive fracturing are marked in red under the ice. Note how the area of explosive fracturing increases as we remove ice, and the difference in fracture distribution between model Stages 14 and 32, for which the only difference is the relief of stresses during the intermediate period of deglaciation (Leith et al. 2014a, b).

Our recent study


Spurred on by our previous results, and recent advances in the evaluation of longitudinal river profiles (see Perron and Royden, 2012), we decided to test whether the geomorphology of major tributary valleys in the central Swiss Alps reflected that of a fluvial system. Controversially, we adopted the deductions of Heim, updated with what we now know regarding energetic fracturing in exhuming bedrock, and assumed a strong period of glacial erosion and overdeepening at the MPT, followed by climate cycles in which no erosion occurs at the valley axis during glacial periods. We first searched for attributes of the present-day river channels consistent with that of a normal fluvial system (i.e. a reduction in gradient with increasing catchment area, downstream elevations that approach the present-day Rhone Valley, and a population of similar knickpoints across multiple catchments). The first two observations were reasonably easy to confirm using standard GIS tools (thanks to efficient and open-source QGIS), while the latter required us to undertake a recently developed ‘chi’ analysis that allows us to scale the river morphology by stream power (strong rivers generally erode faster). We found that both the elevation, and upstream location of around 80% of identified knickpoints were consistent with our concept of a fluvial origin, lining up nicely with where they should be expected given the timing of glacial – interglacial transitions derived from MIS curves. As knickpoints erode, they also propagate upstream with time, and the oldest are are now located approximately half-way into each valley; beyond which exists what we term a ‘relict glacial landscape’ that has essentially been uplifted and covered / uncovered by ice with minor erosion over the last 780 kyr. We found that predicted uplift rates are within 15% of present-day measurements, while erosional efficiency for each catchment is reasonably consistent across the region (as expected, given the similar bedrock and rainfall patterns).

This was good news. We then decided to take parameters from the ‘chi’ analysis and run forward models to see if we could reproduce the river profiles with our assumed history. It’s one thing to locate a few (70) steepened sections on an undulating channel profile, it’s something else to reproduce the form of 100 km of combined river channels using the same assumptions. But that’s what we did, reproducing the channel profiles with a mean residual elevation error of just 26.3 m. Given the 400 – 700 m of relief between the Rhone Valley and the uppermost knickpoint in each catchment (this depends on the degree of initial glacial overdeepening), the error is remarkably good. We found our calculated erosion rates are exactly in line with what should be expected for river channels and retreating knickpoints in an alpine setting. The animation below demonstrates two of the larger catchments in our study area developing since MIS 12 and 10, respectively.

Some valleys were initially carved out far below the level of lakes surrounding the Alps, and therefore spent much time filled with sediment (in fact many valleys today remain in this state). However, as if a giant were rising from a bath tub, subsequent tectonic uplift has continually raised the bedrock mountains, while water draining off continually washes sediment out of the valleys, maintaining terrace surfaces that smoothly transition onto to the relatively stable foreland. As evident in our above model of channel evolution, the results allow us to assess the elevation of the channel at any stage since bedrock on the valley floor was exposed. This is a deliberately simple model, and doesn’t include complicating factors such as isostatic rebound (the effect of removing the mass of glaciers from the mountains), landslides entering the channels, movement on tectonic faults, or even the manner in which rivers erode bedrock. However, natural systems are complicated, and constantly changing, making it difficult to define a start point from which to begin studying these phenomena (the end of the last glacial around 18 ka is typically assumed to be a reasonably significant ‘reset’). In fact, no-one really understands any of these effects, and all are topics of rapid advance with popular debate among Earth scientists. Results from our study could allow scientists to stretch the observation window by almost 50x (to 780 ka), while discrepancies between what we model and what we see in the field are useful targets to start looking at the effects of different phenomena on the formation of river valleys.

We demonstrate an example of the insights that may be gained from our channel evolution model by picking three cross-sections where the mountainsides adjacent to the rivers appear relatively stable. Assuming that the rock slopes evolve toward a consistent slope angle determined by long-term rock strength (a concept known as ‘strength equilibrium’), we project the modeled channel elevation at the end of each interglacial from the center of the valley up to the flanks of the mountains. At this time we find modeled incision rates are lowest, and might expect rates of landsliding around the rivers to be similarly low, as relatively long planar slopes separate the retreating landslide front from the active river channel. We find that upper hillslopes consistently project toward our initial (upper) channel profile, while hillslope breaks at our selected cross section locations are reasonably consistently picked up by the projected stable river elevations, suggesting a very old landscape may be preserved at higher elevations, while lower slopes are controlled by retreating waves of landslide formation. The correlation of model results and hillslope profiles at three locations in the study region is summarized in the figure below.

Projected stable hillslopes from modeled end-of-interglacial channel elevations.

A comparison with glacial erosion models


Of course it’s natural to compare our results with what one reviewer described as the ‘wide body of literature‘ addressing the potential effects of glacial erosion on the Alps. In fact, the hypothesis that glaciers drive erosion in Alpine regions is so broadly accepted that important institutions such as the Swiss National Cooperative for the Disposal of Radioactive Waste (NAGRA) commendably spend significant resources investigating the phenomena (five reports have been commissioned to date NAB 09-23, NAB 10-34, NAB 10-18, NAB 10-33, NAB 12-48), while studies addressing fluvial erosion in this region are almost non-existent (I believe NAGRA, for example, is yet to address this issue). To allay readers concerns, we looked closely at the the predicted distribution of glacial erosion in the same region as described in two recent studies (Sternai et al., 2013, and Heman et al., 2011), comparing this to our own results. The erosion predicted by the two models varies widely, with the model of Herman et al. (2011) predicting around 1000 m more erosion than equivalent locations and time intervals in Sternai et al. (2013). However, when we look at the upper ‘relict glacial’ reaches determined for each catchment in our study region, we see that given the right selection of parameters, both models are likely to be doing a reasonable job at predicting the distribution of erosion in the region. Our fluvial models do a very good job reproducing the river profiles in the ‘fluvial’ section of the landscape. these observations led us to incorporate a figure illustrating the ‘best of both worlds’, with adjusted glacial model results upstream (for the die-hard fans), and our fluvial model results downstream. This analysis can help us better understand where and when the glacial models are working, and (incorporating results from fracture models discussed above) may help better parameterize the calculation of overdeepening in the future.

Upper: Modelled stages of fluvial incision. Lower: A ‘best of both worlds’ compilation of numerical model results for three valleys in our study region. Black lines indicate the present-day profiles of the Rhone valley and three tributaries. S0 (adjusted) and L0 refers to the modelled present-day elevation of the valley axis determined from glacial (Sternai et al. 2013) and fluvial models (Leith et al. 2018). Grey lines represent the downstream projection of the modeled glacial profiles into what we regard as the fluvial portion of the landscape.

Conclusions


Our results show that the European Alps are in the middle of a long transformation, from an early post-glacial landscape back to a more stable sub-aerial system. Our findings provide first insight into long-term (~0.7 My) erosion rates in this region, and strongly suggest that deglaciation leads to a marked increase in sediment production as a result of rapid river incision and increased landslide activity. Insights derived from this study will allow practitioners to better assess the response of alpine landscapes to climatic fluctuations (critical for geohazard evaluation and planning for nuclear waste storage), and may open the door to a wide range of research into long-term mechanical, biological, and chemical systems within similar environments.

Looking north from the village of Eisten in the Saas Valley, the bedrock river channel takes a significant dive downstream at the location of our MIS 3 to present knickpoint (bracketing the Last Glacial Maximum).


References:

Blache, J., 1914. Le bord d’auge glaciaire du Grésivaudan (rive gauche), Recueil des travaux de /’Institut de Géographie alpine, 353-406

Blache, J., 1931. Les massifs de la Chartreuse et du· Vercors

Broc, N., 2001. Ecole de Grenoble contre école de Paris : les Alpes enjeu scientifique. Revue de Géographie Alpine, 95-105.

Brockmann-Jerosch, M., 1952. Albert Heim : Leben und Forschung. Basel : Wepf.

Cholley, A., 1925. Les Préalpes de Savoie (Genevois, Bauges) et leur avant-pays. Étude de géographie régionale

Fox, M., Leith, K., Bodin, T., Balco, G., Shuster, D.L., 2015. Rate of fluvial incision in the Central Alps constrained through joint inversion of detrital 10Be and thermochronometric data. Earth and Planetary Science Letters 411, 27-36.

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Herman, F., Beaud, F., Champagnac, J.-D., Lemieux, J.-M., Sternai, P., 2011. Glacial hydrology and erosion patterns: A mechanism for carving glacial valleys. Earth and Planetary Science Letters 310, 498-508.

Korup, O., Schlunegger, F., 2007. Bedrock landsliding, river incision, and transience of geomorphic hillslope-channel coupling: Evidence from inner gorges in the Swiss Alps. J. Geophys. Res. 112.

Leith, K., Fox, M., Moore, J.R., 2018. Signatures of Late Pleistocene fluvial incision in an Alpine landscape. Earth and Planetary Science Letters 483, 13-28.

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Leith, K., Moore, J.R., Amann, F., Loew, S., 2014b. Sub-glacial extensional fracture development and implications for Alpine valley evolution. J. Geophys. Res. 119, 62-81.

Machatschek, F., Staub, W., 1927. Morphologische Untersuchungen im Wallis. Eclogae Geologicae Helvetiae 20, 335-379.

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Sternai, P., Herman, F., Valla, P.G., Champagnac, J.-D., 2013. Spatial and temporal variations of glacial erosion in the Rhône valley (Swiss Alps): Insights from numerical modeling. Earth and Planetary Science Letters 368, 119-131.

written by Kerry Leith (ETH Zürich), edited by Sabine Kraushaar (University of Vienna) –