Friday, 31 October 2014

Between a rock and a hard place - a lecture on Sci Comm

Review of the George de Boer biennial lecture given by Prof. Iain Stewart, Professor of Geoscience Education, University of Plymouth. 
A guest blog By Dr. Lara S. Blythe

Prof Iain Stewart, geoscientist and TV personality, was the guest of honour at the University of Hull on Wednesday 29th October, invited by the Department of Geography, Environment and Earth Sciences in collaboration with their geology society, the Harker Society, to mark the reinstallation of geology as a degree programme after ca. 25 years of absence. Prof. Stewart presented the George de Boer biennial lecture entitled ‘Between a Rock and a Hard Place’ to an audience of well over one hundred people.

Photo by Rebecca Williams
The title, one might think, is not unfamiliar territory to the professional geologist. However, in this case we should think again. Caught between our science and the public, science communication and more specifically, geoscience communication is something that traditionally we scientists have had a bad reputation for. Good then that the Professor of Geoscience Communication at Plymouth University, whose interests are the cultural and social effects of geology, should give us his take on the matter.

Geology, from the perspective of the public, can be likened to an omnipresent invisible subject, which only becomes visible when necessary: at times of crisis. One issue almost immediately brought to the fore was the L’Aquila case in Italy, where a number of senior scientists and officials were sentenced to six years imprisonment for their 'inability to predict the earthquake' that killed 309 people in 2009 (Hall, 2011; Davies, 2013). This case, akin to several aftershocks, has reverberated through the scientific community and highlights the need for a better relationship between geoscience and the public where good communication is paramount.

Even though being a member of the scientific academic community and being in the public domain may seem like a contradiction in terms, the incentives for academics to communicate are clearly present and, in the face of recent developments (e.g. fracking) are increasingly necessary. For me, academia and science represent a true ecological niche whose inhabitants, as Prof. Stewart explained, approach geological events in almost a complete opposite way to the public in order to understand them. Although this niche is seen as typically attracting introverts obsessed with rocks, in short an ‘odd bunch’, these scientists in fact have a responsibility to interpret their research to the public and inform them about the world.

As Prof. Stewart pointed out, why should the public be interested? and how do we get through to a public that may not even be interested? Combined with poor understanding and many misconceptions, science is not popular amongst the public. Why ever not? I hear you ask; because it contains too much erm, science. Too many details and facts that are in essence, boring.  However according to Stewart, and co-author, Ted Nield (2012) people are interested in other people, a point towards which we need to direct out efforts to communicate effectively. Geoscience is both an applied and a visual science, attributes which enable an interesting and ‘audience grabbing’ story to be told out of an otherwise ‘dull’ subject. Take for example, one of Prof. Stewarts Earth Science broadcasts on the BBC – Journeys to the Centre of the Earth, which links Sedimentary, Metamorphic and Igneous rocks through the building stones used by the Egyptians, Greeks and Romans respectively. This series used a visual art to connect history with geology and its applications, and it proved a hit.

Used to fascinate and spark an interest rather than educate, geoscience communication in ‘quiet’ times facilitates the important transfer of information in times of change and crisis. The public know what geoscience is and know where to find out more information for themselves. As the phoenix of geology and geoscience rises from the ashes left behind at former departments country wide, so (geo)science communication must grow into a new world where academics and the public learn to first respect, then trust, and finally communicate successfully. 

Dr. Lara S Blythe. 

The lecture is available here.

Davies, L. 2013. L’Aquila quake: Italian judge explains why he jailed scientists over disaster. The Guardian, World News, 18 Jan.  
Hall, S. S. 2011. Scientists on trial: At fault? Nature, 477, 264-269.
Stuart, I. S. and Nield, T. 2012. Earth Stories: context and narrative in the communication of popular geoscience. Proceedings of the Geologists’ Association, 124, 699-712.

This City Belongs to Everyone

by Chris Skinner

Recently, I was tasked with designing five workshops for our Foundation Science programme to introduce Geography specific material to those students planning on studying it in the future. For one of these workshops I plan on looking at our city, Hull, and its surrounding area, asking how, as Geographers and researchers, we can get involved in understanding and influencing these. I want to demonstrate to my students that whatever your research area you can be invested in your local area.

William Wilberforce House - The Abolitionist was born in Hull
(© Copyright David Hillas and licensed for reuse under this Creative Commons Licence)

I began by hijacking a Departmental staff email discussion to ask "what do you consider to be the most pressing geographical issue facing Hull?", and I found the responses interesting, highlighting how different research specialisms cause people to think of our local area in different ways. So interesting, I wanted to share some of the responses here with you.

Myself,  I would say flooding and the increased pressure caused by rising sea levels. This was shown clearly by the storm surge of December 5th 2013 - the tidal barrier at the mouth of the River Hull had just 40 cm left to spare and the minimum sea level rise predicted by the IPCC to 2100 is 40 cm. Obviously, the city will need to invest in better defences or other solutions. I wrote about this in a previous post.

In mainly short replies, several of the Physical Geographers here agreed in their responses -

"Flooding!" - Professor Lynne Frostick

"Climate/Environmental change, sensu lato." - Dr Jane Bunting

Holding back the tide - Hull's Tidal Barrier
(© Copyright Andy Beecroft and licensed for reuse under this Creative Commons Licence)

Professor Jack Hardisty, however, saw an opportunity to establish the city as the heart of the "Energy Estuary" as the most important issue. Many agencies are working very hard and with great success to create a hub of sustainable energy in the Humber, both in the construction of infrastructure (like the development of the Siemens off-shore turbine factory in Hull), and the generation of power, such as tidal generators.

Professor Jeff Blackford suggested "Economic inequality and lack of social mobility" to be the big issue, and he was supported by many of the Human Geography researchers.

“A combination of its structural economic legacy, urban austerity, and environmental situation” - Professor Andy Jonas

“Flooding and relatedly, the feeling that the place was abandoned and left to rot in the aftermath of the 2007 floods.” - Dr Briony McDonagh

I like this quote from Briony as it highlights how the issue identified by the Physical Geographers, the flooding, is intrinsically linked to those emerging from the Human Geographers. The flooding in 2007 needs to be understood in the physical sense to find out what caused it and how it can be avoided in the future, but also the impacts on people and their perception of the city and its place in the country needs to be understood. I find Hull has a sense of abandonment by the rest of the country that was either started or was reinforced by the bombing during the Blitz (and subsequent lack of reporting) - this same sense emerged post-2007 that the city was ignored in favour of other areas after the flood. Indeed, the major flooding on the 5th December 2013 slipped under the nation's radar somewhat too.

The National Film Theatre on Beverley Road was listed in 2007. It was bombed and burnt out in 1941 and was never repaired - it is one of the last remaining visible bombsites from the Blitz.
(© Copyright Paul Glazzard and licensed for reuse under this Creative Commons Licence)

“The challenge of overcoming Hull’s negative (and inaccurate) imaginative geographies – on the receiving end of too many Hull or Hell jokes…” - Dr Suzanne Beech

However, one issue raised by Professor David Atkinson provoked a discussion. Here's his full response -

“The effects of the city of culture award before, during and after 2017

Hull as an under-bounded city (and current wrangles to fix this)

The elusive nature of place and ‘Hullness’”

A different resonance - Whereas the rest of the country had iconic red phone boxes, Hull's were white (although the tourist office still sold red phone box souvenirs)
(Image by RM21, from en.wikepedia under Creative Commons Licence)

I want to pick up the issue of Hull as an under-bounded city. What does this means? It is down to the way the city boundaries are drawn that exclude some of the sub-urban areas around the city, like Cottingham and Willerby. These areas are more affluent than much of the city and are not included when drawing statistics for the city, or contributing towards Council Tax to run the city's services (which many of the residents in those areas will use). This is a relatively uncommon situation and negatively skews many of the statistical indices for the city and reinforcing its negative reputation in the country. There are plans to rectify this, but as you can imagine it is not popular in those areas that may go from being within the East Riding of Yorkshire region to being with the City of Hull.

Professor David Gibbs also felt this was the major issue and highlighted some of the controversy, suggesting that this would be an interesting topic to look at as part of a workshop.

“I agree with [Professor Atkinson], the under-bounded nature of Hull and the debates between Hull and the [East Riding of Yorkshire] would be good and lots of on-line debates to tap into on press websites – see the Hull  [Daily Mail] website for a good deal of lively debate in the comments section!"

This issue was also picked up by Dr Kevin Milburn. Here is his full response -

“For a long time it seems the city’s location has been a handicap (or at least perceived as being such), to which I must also lob in the relatively poor transport connectivity of the city, especially to other cities and towns in the North. It feels like it would almost be quicker to get to, say, Grimsby or York, by unicycle than public transport. Now, however with renewed interest in the opportunities offered by the estuary, most obviously demonstrated by the recent Siemens investment announcement, perhaps Hull’s peripheral location might actually start to be something of a plus point. The city’s isolation/'end of the lineness’ – and supposed subsequent uniqueness – was interestingly used as a positive by the Hull 2017 bid team.

I also agree with the points raised re. Hull’s boundary and the impact this has on where Hull finds itself on national league tables re. schools, poverty, unemployment rates etc. I find it bizarre that somewhere like Romford can be considered, administratively at least, part of London (it doesn’t get more Essex!) and yet Cottingham, for example, is not part of the Hull metropolitan area.”

HS3 - Could a high speed rail link between Manchester-Leeds-Hull improve the city's connectivity?
(Image by mattbuck, from en.wikipedia under Creative Commons Licence)

David Atkinson raised further points that might contribute to the sense that Hull is dislocated from the rest of the country, something picked up above by Kevin - 

"- a lack of central government funds to assist with reconstruction after the war

- the sudden collapse of the fishing industry in the 1970s and 1980s, and the failure of national government to protect Hull's interests (as perceived by the locals)

- the decline of some other, traditional, heavy industries with limited central government assistance in the 1980s-2000s

- the rising sense that other cities and regions could sneer at Hull (reaching its height in the 2003 'Crap Town' accolade)"

I found this exercise really interesting and really insightful, and I look forward to seeing how the people involved above shape their future research in order to investigate the issues they've highlighted. I can't speak for the others, but I am sure it is true, but I love this city, my city, and whilst we're not blind to its issues and problems, we embrace its wonderful character and personality which, honestly, is unlike anywhere else in the world - that's partly why we won, and were so proud to win, the City of Culture status for 2017. Nothing sums it up better than the bid video - This City Belongs to Everyone.

I think my students are going to find the responses useful and I plan on having an enjoyable and lively discussion about them during the workshop.

Friday, 17 October 2014

Remembering a loyal Malawian colleague and contemplating the challenges of mortality for collaborative research in Africa

By Elsbeth Robson

This blog is prompted by the tragic death of my valued colleague and collaborator at the Centre for Social Research of the University of Malawi – James Milner. On 2nd September 2014 James was involved in a road accident while conducting fieldwork in the north of Malawi. He was hospitalised and later died in Mwaiwathu Private Hospital, Blantyre on 7th September 2014. The James I knew and miss was committed to his work, his family and his church.

James’s sudden death is a huge shock and loss to his family, friends and colleagues around the world. He worked as an economist for the Government of Malawi for five years and 19 years as a research fellow at the Centre for Social Research, University of Malawi. He studied as a postgraduate at Williams College in the USA and York University in the UK.

I worked with James on an ESRC-DFID funded project investigating young people’s use of mobile phones in Africa (available here). He joined the project team in 2012 and quickly became a valued colleague for his dedication, loyalty, dependability and thoroughness. We last undertook fieldwork together in January earlier this year when we spent several weeks running a large questionnaire survey with a team of research assistants. It was demanding work involving long days in remote communities, rough roads, heat, occasional malaria and even reluctant respondents at times. Our evenings were spent closely quality checking piles of completed questionnaires and closely monitoring research assistants’ performance. James’ contribution was vital to ensuring everything went smoothly.

During fieldwork we usually travelled as a team together with a driver and several research assistants in a Toyota Landcruiser and as I always do I regularly reminded everyone to wear a seat belt and encouraged those reluctant to use the seatbelts because they were dusty, difficult to adjust and uncomfortable that it is better to ‘Arrive Alive’. I am a passionate believer in the virtue of seatbelts having been personally in two vehicle accidents (overturned minibus on US fieldtrip; collision in Germany) where seatbelts saved lives and because I might have been orphaned as a child had my mother not been wearing a seatbelt in an accident at high speed on a UK dual carriageway. It is painful for me to know that last month James was not wearing a seatbelt and was flung from the vehicle sustaining injuries, while the front passenger (a visiting researcher from the London School of Hygiene & Tropical Medicine) and the University of Malawi driver who were wearing seatbelts escaped relatively unscathed.

I took this photo in July 2013 during the qualitative fieldwork phase of the mobile phone project. James (wearing glasses, 3rd from left) is standing together with our hardworking team of research assistants during a break from transcription of interviews at the College of Medicine Guesthouse in Blantyre, Malawi.

While mourning the loss of a colleague James’ untimely death prompts wider reflections on the unevenness of the playing field between academics in/of the Global North and those in/of the Global South. It is a stark reality that life expectancy in the Global North (UK average life expectancy is over 80 years) far exceeds life expectancy in the Global South (like expectancy for Malawi is about 55 years). This bare demographic fact has major implications for trying to build and sustain long term North-South academic research collaborations.

It is more than poignant that on the weekend of his death James was expected to be travelling to the UK to present at a DFID-ESRC event in London with a collaborator from Durham University.  Sadly, during the past three decades of my career James is not the first academic collaborator I have worked with in Africa who has died before old age. An academic geographer at University of Malawi, as well as two team members (one a young researcher) in Ghana at University of Cape Coast all died during or shortly after we worked together on collaborative international research projects. None of these died in road accidents I believe but HIV/AIDS is one of the top causes of adult deaths for both Malawi and Ghana along with stroke and heart disease which also kill plenty of people in UK too. I can recall only one colleague in UK I might have collaborated with if he hadn’t died of cancer in his 50s. Other UK colleagues continue to be academically active into their 70s and 80s.

Where the death toll from road accidents in Africa are concerned expatriates are also not immune. I knew two British geographers and long term Africa residents who died tragically in car accidents in Kenya and South Africa. Their contributions to research and teaching which might otherwise have been expected to continue for several decades longer were curtailed.

Mortality on Africa’s roads is shockingly high - Malawi has the 3rd highest rate of deaths from road traffic accidents in the world (here) exacerbated by poorly maintained vehicles and dangerous driving habits.

Are my experiences of the tragic loss of colleagues typical for researchers who work in the Global South and try to build up long term collaborative relationships? I suspect these experiences are not unique and there are similar challenge for those who work in Africa and other poor countries. 

Wednesday, 8 October 2014

Why Japan’s deadly Ontake eruption could not be predicted

Why Japan’s deadly Ontake eruption could not be predicted

By Rebecca Williams, (@volcanologist)

This article was originally published on The Conversation on the 30th September 2014. It is re-posted here in order for the article to be updated as further news about the ongoing activity comes in, and analysis by Japanese volcanologists and the JMA are released. 

Mount Ontake, Japan’s second-highest volcano, erupted killing at least 31 people (as of Oct 27th, the death toll is at 57 and 6 are missing) on September 27. Since then, there has been feverish speculation about why tourists were on an active volcano and why the eruption wasn’t predicted.
Mount Ontake (also known as Ontakesan) is a stratovolcano which last erupted in 1979-80 and 2007 (there was also a possible, unconfirmed eruption in 1991). Before this, there were no recorded historical eruptions at Mount Ontake.
Since the eruption in 1980, Ontake has been monitored by the Japan Meteorological Agency (JMA). It has seismometers around the volcano to record volcanic tremors and instruments to measure any changes around the volcano. This would provide the JMA with signs that there was magma movement underneath the volcano and that perhaps an eruption was imminent. There had been a slight increase in volcanic tremors starting at the beginning of September. Why, then, was this eruption not predicted?

No warnings

Firstly, the ability to predict volcanic eruptions is an ambition that volcanologists are far from realising. Magma movement under a volcano will cause volcanic tremor, make the ground rise and fall and release gases such as sulphur dioxide. If these signs are monitored closely, then it may be possible to forecast that an eruption may be imminent.

Safe distance. EPA/Kimimasa Mayama

However, all of these things can also happen without any volcanic eruption. Knowing what these signs mean for an individual volcano relies on data collected during previous eruptive episodes, as each volcano behaves differently. Mount Ontake has only had two known historical eruptions and previous to the 1979 eruption, had not been monitored, so scientists here had no previous data to work with. Volcanic tremors are very common at active volcanoes and often occur without being associated with an eruption.
Secondly, the type of eruption that volcanologists think occurred at Ontake is one that does not cause the signals typically monitored at volcanoes. The images and videos captured by hikers on the volcano show that the ash cloud was mostly white, which can be interpreted to mean that the eruption was mostly steam.
The effects of the pyroclastic density currents, the flows of ash, and gas that flowed over the ground from the summit, suggest that they were low-temperature and low concentration. Both of these point to there being no magma directly involved in the eruption. Instead, it is likely water had seeped into the volcano and was superheated by magma within the volcano and flashed to steam causing what is known as a phreatic eruption. Phreatic eruptions occur without magma movement, hence the lack of precursor signals. The 2007 eruption was also phreatic and also occurred with little warning.

Power of nature

So, if an eruption like the one in Japan could not be predicted, should tourists have been allowed up Mount Ontake? Ontake is a place for religious pilgrimage, as well as a popular destination for hikers and climbers. This is quite common for volcanoes around the world; tourists flock to Kilauea, Hawaii to watch the lava flows, climb volcanoes in the Cascade Range, USA and even ski at volcanoes such as Ruapehu in New Zealand. A phreatic explosion such as the one seen at Ontake on Saturday is possible at all of these places.
There is something compelling about the power of nature, and the beauty of a volcano that draws people to them. Volcanoes are inherently dangerous places and there will always be risks to those who visit them. However, events like that at Ontake are thankfully rare. Laying the blame at the foot of either the hikers, or the authorities that allow tourists to visit active volcanoes would be misplaced.

The events at Ontake were tragic. It’s my opinion that it was a tragedy that could not have been predicted or prevented, given our current level of knowledge. It highlights the need to understand volcanic systems better. My thoughts are with the survivors, and the families of those who didn’t make it.
The Conversation

This article was originally published on The Conversation. Read the original article.

Please post links to updated information in the comments below.


Latest death toll
It seems that this eruption claimed the lives of 57 people, and 6 others are still unaccounted for. Recovery efforts are expected to recommence in the spring.

'Lessons' in disaster preparedness
The events on Mount Ontake in September have already led to calls for better disaster preparedness on Japan's volcanic mountains. Toshitsugu Fujii, the director of the Coordinating Commitee for Prediction of Volcanic Eruptions, stated in a press conference that he believes there is a gap in the understanding of the commonly used volcanic alert signals. He said "a level 1 danger alert refers to what is 'normal' for an active other words, anything could happen inside the crater". He goes on to say that the committee is now looking into the perceptions of these alert levels from those who release them, to those who use them, such as climbers.

Others have issued a call to arms for volcanologists, asking for a national agency for volcanology, rather than research on individual volcanoes being the responsibility of individual university research groups. Shozawa Shin'ichiro states that the only volcanoes in Japan that have manned observatories are "Mount Usu, Mount Unzen, Sakurajima, Mount Aso, and Mount Kusatsu-Shirane" and that "the University of Tokyo, for instance, used to assign instructors and technical associates to its volcano observatories in Kirishima, Izu ƌshima, and elsewhere, but nowadays these facilities are largely unmanned. No researchers were stationed at Mount Ontake, nor are there any on Mount Fuji". Other countries with active volcanoes do have government agencies who are responsible for monitoring active volcanoes, such as the US Geological Survey, who have the Hawaiian Volcano Observatory and the Cascades Volcano Observatory. Currently, in Japan, this responsibility lies with the Japan Meterological Agency (JMA).

There are 35 disaster prevention councils which have been set up to cover 35 active volcanoes across Japan. A survey conducted after the Mount Ontake eruption showed that half of them have yet to set up evacuation plans, though they are considering this and are also considering asking climbers to submit plans before accessing the mountain. These groups also call out to central government for support to improve their disaster preparedness. "If the central government draws up guidelines, it would facilitate the move (to improve disaster prevention measures)," said an official with the Fukushima Prefectural Government, which serves as the secretariat for the Mount Adatara and two other volcano disaster prevention councils.

At Mount Asama, the council have developed a smart phone platform which it uses to alert climbers to weather and volcanic events, if the climber has signed up to the service. However, only a fraction of the mountain visitors have signed up to the alerts. The council are looking at ways to extend the use of its warning system and the JMA seem to be considering rolling it out at other locations. Noritake Nishide, the Director-General of the JMA said that "portable handheld devices such as smartphones should be instrumental in terms of providing information to individual mountain climbers".

Unprecedented coverage on social media
Much of the news of the eruption, and details about the event, were first to be found on Twitter. Hikers on the volcano were tweeting images and commentary during the eruption and this proved invaluable to understanding the processes that occurred. Sadly, recent pathology reports indicate that half of the victims died whilst taking photos of the eruption. Though, apparently Nikon repaired a camera found on a deceased victim, cleaned it and returned it to the family, after recovering some 200 photos. Some survivors found themselves hounded by journalists for details and photos, whilst they were still trapped on the volcano. It led to a lot of armchair volcanology and criticism of the JMA for not predicting the eruption. More thoughts on this below.

Hindsight bias
The article above was largely written in response to several inflammatory articles suggesting that there was someone to blame for this tragedy, or that 'warning signs were missed'. I will not link to those articles here. These types of articles either fall into the trap of thinking that someone must be to blame, or they have looked at the events with 'hindsight bias'. Jonathon Stone has written an excellent article about hindsight bias that I urge you to read here:

Wednesday, 1 October 2014

Freshwater limestones and the salt budget of the Mediterranean Sea

by Dr Mike Rogerson (@MikeRogerson7)

Freshwater limestones and the salt budget of the Mediterranean Sea have as much to do with each other as a hookah-smoking caterpillar does with a baby capable of turning into a pig. In both cases, the link could not be more simple; they both exist in the same storyline, the former case being my research career and the latter Alice’s Adventures in Wonderland. The caterpillar and the pig/baby are elements slowly manoeuvring Alice towards her showdown with the Queen of Hearts. Whether or not my career will end up with me in court, we are yet to see.

Freshwater limestones and the salt budget of the Mediterranean Sea share a fundamental characteristic - they are both essentially controlled by a single equation; the Froude equation. The Froude number (Froude is pronounced “Frood”, as in “sass that hoopy Ford Prefect, there’s a frood who really knows where his towel is”) tells you whether water flowing through a gap is moving slowly enough that waves can go through the water in the opposite direction to the flow, or not. You’ve probably seen the impact of the “hydraulic jumps” that form because of transitions between these two states – think back to the last time you were gazing at a waterfall. Remember how the water pours over in a sheet? That water has a Froude number that is “super-critical”. The water that seems to be boiling and upwelling downstream of the waterfall is “sub-critical”. The strange “standing wave” that seems to dance at the foot of the waterfall is a “hydraulic jump” between these two states. There is another one just above the waterfall, but you need a bit more practice to notice that.

The waterfall analogy works well for us, because freshwater limestones do in fact make waterfalls. These beautiful sediments form when calcium and carbon in the river water react to form calcite – limestone – to make crusty lumps and sheets on the river bottom. They are beautiful, by the way. Here are a few pictures if you don’t believe me (Images © Mike Rogerson).

The calcite forms inside a community of microorganisms living on the bottom of the river – a biofilm. The way the river water, the biofilm and the calcite interact is one of the wonders of nature, with implications for the global carbon cycle, the evolution of life on our continents, the way we can reduce the impact of metal pollution on our waters and the future of oil production in the south Atlantic. Not even Lewis Carroll tried to convince us to relate such apparently unrelated scenes. The world is a strange and unpredictable place, and anyone that tells you that you can understand it intuitively is not to be trusted. 

What controls the rate of calcite formation at the river bottom is mostly how fast you can get calcium and bicarbonate ions from the river to the bottom, and how fast you can get the protons produced by the mineral formation (Ca2+(aq) + HCO3-(aq) ⇌ CaCO3(s) + H+(aq)) back out into the river. This happens by diffusion, which is a really slow process in water. If you don’t believe me, gently pour a kettle of boiling water into the middle of a completely still, cold bath, leave it for 10 minutes and then try and find it with your hand. You should have no problem.

The distance the diffusion of the ions in the river have to travel is controlled by the still layer that sits at the bottom of all flowing waters. If the water is moving slowly, this still layer is thick. If the water is moving fast, it is thin – but it is there. If the water is moving super-critically, it is very thin indeed – and therein lies the rub. The calcite will form much faster on the top of our waterfall where the flow is super-critical than it will upstream or downstream. This is actually good news for the biofilm; their economy is driven by photosynthesis, which needs light. The light hitting the river bottom is stronger when the water layer is thin, and also when it is super-critical. The bigger the waterfall gets, the happier the biofilm is. The consequence of this is that the waterfall gets higher, the biofilm gets happier, the Froude number gets higher and the waterfall gets higher again. And look how high some of these things get. These whole walls have been built by a biofilm precipitating a mineral from water, exploiting the physics of how water flows. You’ve got to be impressed.
Plitvice Lakes Croatia. Photo by permission from Jack Brauer. Check out his stunning photography here:
If you have super-critical flow of water through a sea-strait, then the amount of water you can push though per second is controlled by the friction on the sea floor. A good example is the shallow and narrow Strait of Gibraltar at the western end of the Mediterranean Sea. You can see the standing wave on the eastern side of the Strait – I hope that is convincing enough that there is a Froude transition happening in there. If you have a region - like the Mediterranean Sea - which is pretty dry, then the total amount of evaporation is a bit bigger than the amount of rainfall. Because you can’t just pour as much water as you like through the Strait of Gibraltar, this means the Mediterranean is a bit saltier than the Atlantic. So long as sea level stays the same, this balance is maintained. If you reduce sea level though, the Gibraltar gap gets smaller, it gets harder to push water though it and salinity in the Mediterranean gets higher. Vice versa if you raise sea level – the Mediterranean steadily gets more and more similar to the Atlantic.
The Strait of Gibralter from above - note the standing wave at the eastern side. © Mike Rogerson
24,000 years ago there was an ice sheet on Britain. Its probably what you call the “ice age”, but really you should call it the “last glacial maximum”. You can tell these glaciers were there though, because we have lovely glaciated valleys in the North of Britain, stunning fjords in the west of Scotland and you can see moraines (which formed at the southern ends of the ice sheet) all over eastern Yorkshire. There were also ice sheets in North America, Scandinavia, Kamchatka, Iceland and other places. And all the water to make these ice sheets came out of the ocean. All that water removed from the ocean was enough to drop sea level by 120 to 130m. For the Strait of Gibraltar, which today is about 245m deep, this means the bottle-neck got an awful lot smaller. The Froude number was even higher than today, and it was even harder to balance the Mediterranean salt budget. 

The fact that water in the Mediterranean was a lot saltier than today during the last glacial maximum is not an obvious consequence of growing ice sheets in Britain and elsewhere. But the consequences of climate change are rarely obvious and intuitive. But what the Froude controls on freshwater limestones and Mediterranean salinity tell us is that features of the natural environment can be predicted by mathematics, even if they are completely impossible to relate without that tool. It probably is no accident that Lewis Carroll was a mathematician – he was used to following internal logic without worrying that it told him things outside his everyday experience. He knew that the world is always more complicated than it seems on the surface.
So the message we should all take home is that if mathematics tells us that raising CO2 in the atmosphere is not a great idea, then we should pay attention. Maths does a much better job of predicting the world than our experience-based guesswork ever can. The mathematics for climate change were worked out in the 1900’s, and the first prediction of climate change was made by an equation – not by a model – in 1908. Look up SvanteArrhenius’ “Worlds in the Making”. It may not seem obvious from your everyday life that climate change must be true, but neither is it obvious that biofilms make waterfalls. Nature works in mysterious ways.
Plitvice Lakes, Croatia. By Donarreiskoffer via Wikimedia Commons