from asphalt to permafrost blisters

In the course of a conversation with Roger Hobbs, who at the time was Professor of Structural Engineering at Imperial College London, I mentioned my newly found fascination with pavement blisters. Roger had himself worked extensively on the subject of thermal buckling of pipelines and had even published a couple of excellent articles dealing with the upheaval buckling of heavy sheets, so I knew he would be interested in the asphalt blisters. His work on the upheaval of heavy sheets had to some extent been inspired by some problems occurring with the distortions that can arise during the hot rolling of steel sheet and also by the upheaval buckling so often experienced when wood block or laminate floors are not provided with sufficient expansion relief gaps around their edges. It was around this time that fashions in interior decoration were changing in favour of unbonded wood laminate floors over the more traditional carpet. Anyway, in the course of our conversation Roger mentioned the existence of very similar forms of blister called "pingos" known to form in ice at high latitudes.

At the time I had not heard of pingos but assumed they were large versions of the blisters I described above as forming on lake ice sheets. It was some years later that I decided to set as a project for a final year undergraduate project the task of finding out more precisely what are pingos and what are the current explanations for their formation. As shown in the following photograph of a well formed pingo, somewhere in the Mackenzie River delta of Northern Canada, there certainly appeared to be some remarkable similarities in the form of pingos and asphalt blisters. Well yes, they are a little bigger. Typical diameters are in the region of 200 to 400m and the better formed ones have heights that can reach up to 80m. And yes, they are comprised of frozen ground that emerges from the surrounding, ostensibly flat alluvial areas, underlain with permafrost. But the characteristic shape is close to that of the asphalt blister and they have a strong tendency to form domes that are essentially circular in plan.

The similarities are evident when one compares the geometries of the above pingos with those of typical asphalt blisters (see previous blogs), some of which are for convenience reproduced below. 

Furthermore, when we started to delve into the literature relating to pingos we were to find that the currently accepted explanations for their genesis and growth reflect closely those we had found for the emergence of asphalt blisters - albeit with ground water pressure taking the place of gas pressure. And just as for asphalt blisters, it seemed to me there were some pretty compelling factors about the growth of pingos that did not appear to stack-up against the existing hypotheses for their emergence. It has been the problems in having an alternative hypothesis for the emergence of pingos taken seriously by the experts in this area that has to some extent encouraged me to enter blogland. I am hoping therefore to spend the next few postings discussing:

• a little more fully what are pingos:
• the currently accepted hypotheses for pingo growth;
• what are some of my problems with these hypotheses;
• what is my credible alternative hypothesis;
• what has been the reactions of the permafrost community to this alternative hypothesis;
• and, lastly, to explain how the dialogue so far generated over pingo growth has I believe led to some other exciting new theories covering much wider classes of natural phenomena.

This latter aspect will open up a whole raft of fascinating topics ranging from a number of different forms of pavement failure, to the formation of many other periglacial and glacial morphologies, to the movement of ice sheets and glacial ice, to the processes that might be playing and have played a major part in the dynamic evolution of the Earth's crust and by analogy the surface features of many other planets and their satellites within the solar system.

asphalt blisters in other places

The photograph below shows a field of blisters that have formed on a flat roof of a house in central London. Just as for the case of the pavement asphalt blisters conventional wisdom has it that these blisters are the result of the build-up of gas pressure beneath the asphalt sheet. Problems with such an expalnation follow those outlined in the previous blog for pavement asphalt. In contrast, a thermal upheaval buckle explanation is entirely consistent with the geometry of the blisters, again dominated by almost pure circular planforms

The flexural cracks over the upper regions of the blisters at times penetrated through the thickness of the asphalt, again undermining the gas pressure hypothesis for the formation of the blisters.

Scale of the blisters can be measured by the 20p coin having a diameter of 25mm.

alternative explanation for asphalt blisters

For the last few years I been exploring (in it has to be said a rather dilatory manner) the possibility that the upward growth of characteristic blisters in asphalt and other materials might involve a form of two dimensional, thermal buckling. This envisages the working of a thermal ratchet process powered by fluctuations in the solar energy reaching the earth’s surface. For the case of the asphalt pavement blisters the alternations in hot and cold seem to involve timescales of circadian periodicities, or even less, with wavelengths characterising the thermal buckles that are of the order of a few centimetres.

This newly proposed explanation for the growth of blisters suggests that each time the heat input is sufficient to raise the average temperature through the thickness of the asphalt above the critical level required to induce enough compressive stress to power an increment in buckling deformation, there appears to be a small upward growth of the blister. That this upward growth is not fully recovered on subsequent cooling seems to be the result of differential properties of the asphalt when it is hot compared with when it is cold. While the laterally restrained asphalt is hot and under a state of compression any incremental upheaval buckling will be accompanied by high levels of creep deformation - meaning that the asphalt will continue to deform without the addition of further load. But when the temperature drops the asphalt has much higher elasto-visco-plastic stiffness, which means there will be less creep recovery when the compression is removed. The result is that not all the upward growth of the buckle blister will be recovered when the asphalt cools. There is growing evidence to support the idea that a gradually accumulating level of upward buckling deformation will be experienced. Each time the surface temperature is raised to a high enough level, for a time sufficient for the thermal wave to penetrate the thickness of the asphalt, another increment of uplift deformation will be experienced.

In giving talks about the mechanics underlying this process I have sometimes used the simple little model shown below. This consists of a silicon rubber sheet just a few mm thick, cast within a 150mm diameter, relatively stiff, circular jubilee clip around the circumference. A series of parallel black lines are drawn on the surface to enable simple visualisation of any subsequent deformations. To provide a heat source a standard reading lamp is placed a few cm above the disc of silicon and the lamp turned on; the base of this lamp can be seen behind the disc. It normally takes about 20 minutes for the temperature to reach the level required for the compression resulting from the constrained expansion to induce a sudden uplift buckle. Inevitably someone in the audience will witness the moment when the originally flat disc pops-up into the buckle configuration shown in the second photo. I have to say I have yet to witness the moment of the upheaval buckle during a talk.

One of the attractive features for this thermal upheaval buckling providing the explanation of the formation of asphalt blisters is that a heavy sheet when subject to an isotropic in-plane membrane stress (that is the forces developed would be the same in all directions) will have a preferred buckling mode that takes the form of a circular dome, like those shown in my previous blog. The stress required to produce this axisymmetric buckle mode is considerably lower than that required to produce other buckle shapes. This certainly conforms to the observation that most of the uplift blisters take this form. Furthermore, theory predicts that there will be a direct relationship between the amplitude of the buckle and the diameter of the characteristic buckle dome. In other words the thermal buckle hypothesis overcomes all the objections to gas pressure being the cause. And of course the growth would be barely affected by a tiny hole drilled through the thickness of the dome!

blisters on asphalt pavements

A previous blog made reference to blisters forming within ice that had formed on the reservoir in Central park, New York, during the cold snap of February, 2010. What immediately intrigued me was that these ice blisters were very close in form, and also very possibly in their thermo-mechanical origins, to some earlier blisters in asphalt pavements that had caught my attention.

In the course of an unusually hot summer some years ago a number of curious bulges formed within the thin asphalt layer that had only a short time before been laid over the footpaths on Gower Street, just a few metres away from my office at UCL. This practice of applying a thin coating of asphalt appears to have been initiated by the London Borough of Camden (LBC) to overcome the longstanding problems associated with the previously used blocks of paving stones. Hitherto, differential movement between the paving stones on the footpaths tended to develop serious discontinuities between adjacent pavement blocks upon which the unwary pedestrian was liable to trip. As a consequence, local authorities (and certainly not just LBC) whose responsibilities include the maintenance of the footpaths were being faced with expensive compensation claims. Replacing these paving stones with smooth asphalt layers seemed like a good idea. It would remove these discontinuities and consequently reduce the risk of accidents. Well that at least was the idea until the appearance of the upward blisters.

The photograph above show a number of these blisters formed on what had a few weeks previously been an ostensibly flat pavement. Most can be seen to have an effectivelycircular, axisymmetric, geometric form. In some cases these circular blisters have started to overlap, creating little clusters of blisters. In one or two places there can be seen to be nasty scars which represent the remains of LBC's attempts to remove the previous season's crop of blisters. Convinced that these blisters were the result of thermally induced upheaval buckling I included an analysis of their possible development in a short article (written in 1999) discussing the mechanics that would underpin such thermally induced buckling modes in continuous pavements. This was not difficult because it was merely a 2-dimensional version of some earlier work I had been doing to predict the possible occurrence of upheaval buckling of subsea pipelines when hot oil or gas is pumped through them. Incidentally this major problem for oil and gas companies involved with offshore operations is very closely related to the lateral buckling that can occur in railway track when exposed to high summer temperatures. But I will return to some of these closely related problems in later blogs. For the moment let me concentrate on the asphalt pavement blisters.

A few months after preparing the little piece analysing the pavement blisters as a form of thermal upheaval buckling, I decided to include it in a talk I was giving at the University of Hong Kong. Unexpectedly, since this is not a topic for which one would expect a great deal of excitement, this aspect of the talk attracted quite a lot of fairly animated discussion. What I had not realised is that a week or so before the talk the asphalt “wear layer” covering the steel plate for the newly completed Chiang Mai suspension bridge had developed similar but apparently somewhat larger blisters. Again, not a subject that one would have thought to be worthy of a great deal of animation, except for the fact that Queen Elizabeth II was due to open the bridge a week or so later. It was though in the course of this discussion I came to realise that what I thought would have been a fairly widely recognised explanation for the origin of pavement blisters was not the one to which pavements engineers had come to subscribe.

Conventional wisdom seems to have formed the view that these blisters within thin asphalt layers are the result of gas pressure building up beneath the aphalt sheet. Not altogether a mad idea given that many upward bulges in asphalt pavements are so often the relief of the pressures caused by the growth of roots of trees or other plants. There were certainly no tree roots on the Chiang Mai bridge deck and I am confident there were none beneath the pavements on Gower Street. But the gas pressure variant of this model seems plausible. There are at least two schools of thought as to the origins of the gas pressure. When the black asphalt surface is subject to radiant energy from the sun it and the underlying soil can experience very high temperatures. In these circumstances some of the moisture in the underlying soil might be expected to absorb sufficient energy to allow it to evaporate to form steam. If totally restrained this phase change would be accompanied by the development of high gas pressures. So what better way to relieve these high pressures than to induce an upward bulging in the form of blisters in the asphalt layer? A variant of this gas pressure explanation of the blisters is that the gas release is the result of the evaporation of certain volatile materials within the asphalt mix itself. This source of gas pressure would certainly be much more credible in situations such as the Chiang Mai bridge deck where it is unlikely that much moisture would exist between the steel top plate of the box girder and the asphalt wear layer.

However, there are a few problems with the gas theory expalanations. Blisters will form in those areas where the bond between the asphalt and the underlying material is relatively weak. Areas of low bond strength will most likely have fairly random shapes. That being the case the plan shapes of the upward deformation of the asphalt if formed through gas pressure would reflect the probable irregularity of the weakened areas of bond. Laws of probability would therefore suggest a circular planform to be the exception rather than the rule. And yet the plan shapes of the blisters as shown in the above typical photograph, and incidentally many more taken from asphalt pavements around the world, have a very robust tendancy to form with almost perfectly circular planforms. A related problem is that the actual extent of the weakened bond areas would be most unlikely to be the same at different locations over the asphalt surface. In these circumstances a gas relief explanation would be expected to produce plan areas of the blisters that reflect this irregularity in size. Again, this does not seem to be the case. Blisters of a given amplitude of uplift at different locations over the asphalt surface have a remarkably consistent lateral extent. Furthermore, in a gas pressure relief model the lateral dimensions of the blisters would be unlikely to change very much as the amplitude of the upward bulge increases. Again, this does not conform with observations that show the diameters of the circular bulges increasing as their heights increase.

But if all this is too abstract to convince you that the origins of the blisters might be something other than the relief of gas pressure there is a much more compelling piece of evidence that might help. Blisters tend to grow incrementally over hot periods measured in days to weeks. Growth rates depend upon both the temperature ranges and the numbers of cycles of heating and cooling experienced. By selecting two embryonic blisters of around the same degree of growth a tiny hole was drilled into one but not the other. The hole penetrated into the void beneath the asphalt blister but was small enough to be barely visible. Over the next week or so the blister with the hole was found to grow at the same rate as the one without a hole!

Here are a few more examples of blisters both old and new taken after rain to show even more clearly their form and extent.

I wonder if you have observed such blisters and where? Would be interested in your evidence and views.

more evidence of thermal ratchetting in lake ice

Pictured in the top picture are the remains of what had a few days earlier been some of the ice rings discussed in an earlier blog. The sharp edges of the discrete portions of the ice-ring debris have all but melted away and the relic rings are barely discernible from the surrounding ice. That the ice sheet has experienced repeated cycles of warming and cooling is evident from the interesting star shaped feature at the background of this picture. The radial cracking from what had been a small circular hole is typical of the tensile crack patterns associated with the hoop tensile stress concentrations experienced around a hole when a sheet undergoes cooling. With the cracks filling with water and partially turning to ice these radial cracks would not be closed during the subsequent warming phase. Having undergone repeated cycles of cooling and warming these radial cracks have grown to become characteristic features of the ice sheet. Another example is shown in the lower picture.

Similar thermal ratchet cracking can be observed in sheets of asphalt pavement, and related morphologies and mechanism have been described for the development of periglacial features at high latitudes and altitudes and especially in regions of permafrost. But I will return to some of these possibly analogous forms of behaviour in later blogs.

others too have observed ice rings

It would appear that similar ice ring formations have been observed in the past. A web search revealed the even more extensive patterns of ice circles were observed to have developed on Lake Ontario during the winter of 2007. Whether the two possible mechanisms based upon observations of ice-rings on the Central Park Reservoir, suggested in previous blogs, would apply to those observed on Lake Ontario is not known. The pictures posted were insufficiently clear to be able to say whether their origins might be similar. Whatever might be the explanation for their initiation and development these curious circles of ice represent a fascinating natural phenomenon that would seem to warrant further more detailed investigation.

If you would like to see the pictures of the ice rings on lake Ontario go to:

http://www.wkbw.com/younews/14298812.html

which was posted by DUSTY41 24th January 2008. Or for a reproduction see ice-rings

references to thermal blister buckling

Apologies, I forgot to provide the references used in the previous blog. I regret they all seem to have emerged from a single author, but he does seem to be the only one recognising that similar processes might be occurring in areas other than the development of ice rings.

References:

These were the ones used in my previous blog:

(1) Croll, J. G. A. A new hypothesis for the development of blisters in asphalt pavements, Int. J of Pavement Engineering, 9(1), February, 2008, 59-67.
(2) Croll, J.G. A. The role of thermal ratchetting in pavement failures, J. of Transport, Proc ICE., 162(3), August, 2009, 127-140.
(3) Croll, J. G. A. An Alternative Model for “Pingo” Formation in Permafrost Regions, paper presented at 21st Int. Congress of Theoretical and Applied Mechanics, ICTAM-04, Warsaw, 15-21 Aug., 2004.
(4) Croll, J. G. A. Mechanics of thermal ratchet uplift buckling in periglacial morphologies, Proceedings of the SEMC Conference, Cape Town, September, 2007.

and these might be of related interest:

(5) Croll, J. G. A. From asphalt to the Arctic: new insights into thermo-mechanical ratcheting processes, Proc 3rd European Conference on Computational Mechanics Solids, Structures, Lisbon, Portugal, 5-8 June, 2006.
(6) Croll, J. G. A. Dynamics of patterned ground evolution, Ninth Int. Conference on Permafrost, Fairbanks, Alaska, 30 June – 3 July, 2008.

It is noticeable that apart from conference papers most of the above publications appear in engineering or mechanics journals. One wonders why the material dealing with permafrost and periglacial processes has not been able to see the light of day in the more specialist journals in these fields?

musings on the origins of ice rings

Having been overwhelmed with responses to my earlier observations of ice rings on New York's Central Park reservoir and being unable to bear the suspense of awaiting for all your theories as to how they might have formed, I feel compelled to advance some of my own hypotheses. Certain of the ideas expressed below are related to views I have been trying to encourage as to the thermo-mechanical origins of much wider classes of periglacial morphologies. And it has partly been some of the frustration of not having been able to find a satisfactory outlet for these views, or being able to have them taken seriously by the experts in these fields, that has encouraged this blog. But more about some of these wider musings in a later blog.

As was shown in the 2 photographs posted on the previous blog, there appear to be two distinct types of ice-ring. Each would seem to be the result of distinct thermal-mechanical processes responsible for their development.

Type 1 ice-ring (are shown in the lower of the above 2 pictures): It was interesting that most of this class of ice-ring had formed in zones of lake ice that were within a 50m distance of the footpath following the reservoir edge. Perhaps of significance, this zone was also about the maximum distance over which it is possible for someone to lob a snow ball or some other object onto the ice sheet. In other pictures not shown here a series of almost spherical balls of ice could be seen to be resting on the surface of the ice sheet. Most were observed to be sitting in locally depressed areas of the sheet ice. Other ice balls were observed to be in more advanced depressions where the balls and the supporting ice had all but disappeared. Having a relatively large surface area exposed to fluctuations of solar radiation these balls of snow melted fairly rapidly each time the temperature exceeded 0oC. The latent heat contained within this melt water seemed to concentrate and accelerate the surface melt of the ice sheet in the zone surrounding the surface ball. Eventually the ice balls melted completely leaving circular areas of either very thin or at times fully melted ice. Why these circular depressions would then give rise to the build-up of crushed ice around the periphery of the circular depression to form the distinctive ramparts could have been the result of subsequent cycles of heating and cooling. [Incidentally, I did try a few tests of my own. Unfortunately, the weather had changed the day after I had lobbed my own snow balls onto the ice. Heavy intervening cloud cover meant that my snow balls had not experienced sufficient radiant energy to cause the anticipated melting. Because by the time of my next visit the ice sheet had melted in this area my own little test was never completed!]

But getting back to the first hypothesised origin of the ice rings, each time the temperature increases the surrounding ice would want to expand into the thinned area and the thinned ice within the depression would want to expand outwards. The total relative movement would be constrained and the comparitively high strength of the surrounding thicker ice would cause the outer boundary of the thin central disc of ice to be crushed. Over a number of cycles of heating and cooling this would have the effect of heaping-up the crushed thinned ice around the edges. Since the thin ice layer would crack when subject to tensile stress during cooling the compressive crushing strains would not be recovered after a full cycle of heating and cooling. With many such cycles occurring over the period of a single day it becomes possible to conceive of a mechanism capable of building up the peripheral circular ramparts.

It is possible too that where the local melting had exposed a circular pool of water a further contribution to the build up of the rampart rings might have been wind. Small wind generated ripples would cause the free surface water to splash over the edge of the hole. Some of this splash water would be refrozen and assist in the build-up of the ring ramparts. This process can often be observed at locations where lake ice has experienced crack fractures. Splashing over the edges of the ice on both sides of such cracks induce the build-up of ice ridges. Upon warming these open fractures often reclose leaving a characrteristic double ridge following the line of the previous crack.

On the day following the above observations there was heavy cloud cover and little variation in the sub-zero temperatures. It was interesting to observe over this period a gradual flattening of the ice-ring ramparts and an associated thickening of the ice within the circular regions.

Type 2 ice-ring (are shown in the upper of the above 2 pictures): The ice-rings shown here have quite different forms to those shown in the lower picture. The border rings comprise discrete slabs of thin ice that have clearly fractured from what had earlier been a flat sheet of ice. How they got into these elevated and rotated positions is possibly due to a somewhat different mechanism.

Around the edge of the cluster of ice rings shown in the upper picture can be seen a few smaller embryonic rings for which the ice sheet is still largely intact but has been thrust up to form small diameter domes of ice. One of these is visible at the lower left of the top picture. The top has been partly melted away by the heat of the sun to reveal the cavity beneath. The cause of these ice blisters is likely to be a form of thermal uplift buckling like that recently described as being responsible for the blistering of asphalt pavements(1,2) and at larger scale frozen ground to form features such as seasonal frost mounds, palsas and perennial pingos(3,4). When the ice sheet is heated diurnally the ice being restrained will develop horizontal compressive stresses. For the thin ice at the edge of the Central Park reservoir, it would not take large increases in temperature within the ice to induce a thermal uplift buckle. The diameter of the characteristic dome shape depends inter alia upon the ice thickness and the level of compressive stress reached during the diurnal warming period. That the uplift buckle is not fully recovered during nocturnal cooling would again be the result of the ice cracking under the tensile stresses developed during the restrained shrinkage. It would take just a few cycles of heating and cooling for the ice domes to reach the heights and diameters typical of the ice rings shown in the top picture above. Fracturing of the dome to leave the debris rings shown in the picture would have occurred once the melting of the top portion of the dome had spread far enough that the then open shell of ice would be no longer capable of developing the very efficient load carrying capacity provided by the membrane stresses available for the complete dome. At this stage the open water beneath the dome would again start to ice over, leaving the remains of the ice dome in the form of the debris ice-rings shown in the top picture.

With the ice beneath the relic dome being thinner than the surrounding ice, alternations in solar energy, caused by breaks in the cloud cover, could see the mechanism described above for the development of the type 1 ice ring starting to add to the piling up of ice around the peripheral ring.

Then again, the type 1 ice rings could just be the result of a longer term melting process operating on the discrete edge accumulations characterising the type 2 ice rings.

Anyway, these were some of my thoughts while wandering around New York during the cold snap in February. Still waiting to hear from anyone who has observed similar features and perhaps given some thought to why they might occur.

ps Shortly after these observations I prepared the paper ice-rings for which it transpired I could not find a suitable publication outlet which would encourage discussion of this curious phenomenon. It was for this reason that the blog was started.

curious ice rings

A recent trip to New York in mid February, 2010, followed the heavy blizzards that saw much of the eastern seaboard experiencing snow falls heavier than anything seen for the previous 10 years. While spared the worst of these blizzards the city of New York saw significant snow falls. Streets had thick coverings of snow, transport systems were seriously disrupted and the lakes and ponds of Central Park had extensive areas of thick surface ice. Central Park reservoir had large areas of ice thick enough that even 2 days later were still capable of supporting large flocks of gulls, but probably not skaters. It was in the vicinity of the edges of these sheets of lake ice that the ice-rings were found to have developed. Picture 1 (this is the first of the pictures above - I have yet to figure out how to format these more effectively) shows the location where these ice-rings were observed. One of these ice-rings can be seen near the left border of the ice sheet close to the eastern edge of the reservoir. Other areas exhibiting clusters of ice-rings are shown in Pictures 2 and 3.Those shown in Picture 2 were at the time of observation typified by central areas in which there was either no ice or ice that was relatively thin compared with the surrounding ice sheet. The circular edge ramparts ranged from 100 to 400mm in diameter and were comprised of heaped small grained particles of crushed ice. These ice-rings contrast with the similar sized edge accumulations of ice-rings shown by those of Picture 3.The ice-rings of Picture 3 can be seen to have ramparts that are composed of discrete areas of broken and rotated sheets of ice. Like the ice-rings type 1 the diameters were in the range of 100 to 400 mm. There appeared to be some evidence that these two distinct forms of ice-ring had been formed by two very different thermal-mechanical processes.
I am wondering if anyone else has observed these ice rings in New York? Or perhaps you have seen them somewhere else? Would be interested to know.
I would also be interested in your ideas as to how they might have formed? I have my own theories but will spare you these at the moment since i am interested to hear your views.

an explanation of blog name

The toheroa is a shell fish found buried beneath the wide open sands of New Zealand's coastal beaches (or should I say Aotearoa's beaches). Because they are such rare delicacies and consequently were for a long while plundered mercilessly, the toheroa was some 60 years ago in serious danger of becoming extinct and accordingly became protected by a law prescribing very limited times of year at which they could be dug-up. They remain protected to this day.

So why as a new blogger have I chosen to call my site after this exquisite antipodean shellfish?

First, one of the enduring memories of childhood on Waitarere, a delightful beach on the west coast of New Zealand some 70 miles North of Wellington, was the annual harvest of toheroa to allow my mother to make her delicious version of toheroa soup.

Second, despite their size, anything from 100 to 200 mm in length, they were devilishly difficult to locate. Typically buried beneath 100 to 200 mm of sand, the only way of locating their position was a small tell-tail depression on the surface. Torn finger nails and bloody fingers were occupational hazards while digging them out as their smaller cousins - the pipi - protected them by getting in the way of the dig.

And third, the toheroa is a gorgeous creation of evolution and as far as I know unique to the shores of New Zealand.

I hope the toheroa will provide a metaphor for one of the aims of this blog - namely, to try and uncover the delights of science (well some restricted areas of science at any rate) and encourage open dialogue of some of the issues that conventional science publishing seems more and more to be thwarting. This was brought home to me when thinking about a suitable outlet for sharing some observations and musings as to the possible causes of some curious ice rings that had formed on the ice sheet covering the Central Park Reservoir in New York, during the recent blizzards that hit the eastern seaboard of the USA. In a later blog I will try to elaborate on these observations and musings. But in a way (if I can be excused for the pun) this was the tip of the iceberg. For some time, to a large extent unsuccessfully, I have been trying to suggest new ways of explaining certain natural and man made morphologies that appear to be incompletely understood. But I don’t know if you ever tried to publish outside of your comfort zone? It is not easy. Like the toheroa many science disciplines have their heads buried in the metaphorical sand, having created protective shells to keep out all interfering outside influences. Like the toheroa their disciples protect themselves with pipi-like protective barriers - often in the form of peer reviews. So I hope too that this blog will encourage open and free discussion of aspects of science and natural phenomena that it is currently difficult to generate. And in the process I hope it will help expose all those aspects of the social/political organisation of science that are currently working against its true development.

So you can see I have set an ambitious agenda for the toheroa blog. More I hope to follow.