Professor John Burland is one of those people who don’t give lectures, and who just stand at the front of a lecture theatre conversationally telling you things, and inviting your comments. It’s a brilliant mode of delivery, and is totally absorbing, particularly when coupled with an enthralling subject. Those of us who’d been to Prof Burland’s earlier talk a couple of years ago knew what to expect, and had been delighted at the opportunity for hearing him again. A lot of the earlier information had to be repeated of course, but this time we had a different, much more optimistic, ending.

The tower is built on soft sand and silt in an area where the water table is very close to the surface, so that seasonal fluctuations affect the foundations considerably. Any building of any size on such substrate must sink into it over time: the problem with the tower is that it hasn’t sunk evenly, and has tilted ever more dangerously over the 700 years of its history. Prof Burland described the detective work that went into the drawing up of historical graphs of the tilt, and how terrifying those graphs are to the people entrusted with saving the tower. The twentieth century part of the graphs come from direct measurement.

The graphs show a steady increase in tilt, mostly in September every year, but with several lurches. Those lurches all coincide with someone doing something in or around the foundations, either in an attempt to stabilise the tower, or to expose the base of the tower that had sunk below ground level. The most recent lurch had in fact been the result of work by Prof Burland’s team, an event he refers to as "black September".

Once they had the graphs, they could try computer modelling for the "best fit" and so deduce the detailed mechanics of the soil immediately beneath the tower – and the best fit showed that it would fall over at a tilt of five-and-a-half degrees. The tilt at the time of the previous talk was five-and-a-half degrees plus a few arc-seconds (I didn’t take notes, so can’t give the exact figure. Suffice it to say that the tower was in an extremely critical state).

However, Prof Burland and his team had succeeded in stopping the tilt increasing by the unpopular measure of putting huge lead weights on the "uphill" side. That idea had come from the observation (from the precise twentieth century measurements on the tower) that, rather than sinking all round with a little bit more on the southern side, the tower was actually rising slightly on the northern side. The weights were ugly though, and could only be a temporary holding measure.

A more permanent solution would be the extraction of some soil from under the northern side of the tower so that it would settle back. The difficulty was how to do that without toppling it over, given that it was already beyond the point where the models predicted it would fall.

At the end of the previous talk, Prof Burland had outlined his soil extraction idea, but had not had the opportunity to try it out. In the latest talk, he described the development and testing of narrow-bore tubular drills that could be inserted into the ground without major disturbance, and how a series of them could extract precise amounts of soil from precise localities. Now he has actually installed 40 drills, and for the last year has been steering the tower by remote control. "Like learning to ride a bicycle by fax" was how he described it. The result has been an alteration in the tilt that will be continued until the angle is a safe five degrees. The effects of the extraction can now be exactly predicted, so that at one point the team shifted the tilt slightly eastwards "just to show that we could".

The angle of five degrees was selected as being the safest they could make it without the change in tilt becoming noticeable. Once the tower has reached that angle, expected in February 2001, the team can then look at more permanent measures of stabilisation that involve isolating the ground beneath the tower from the seasonal fluctuations in the water table.

I can’t hope to get across how exciting this talk was. Here was someone who had been through the most tense of experiences, had had the courage to put a revolutionary idea into practice when the result could have been disastrous, and had actually succeeded in bringing the Leaning Tower back from the brink – and he was standing in front of us telling us about it in a conversational and modest way. Absolutely brilliant.

For a detailed history of the Tower of Pisa, the various attempts to stop it falling, and the current techniques being used to straighten it just enough to make it safe, see http://www.pbs.org/wgbh/nova/pisa

Pictures are available

We woke up to a very untypical Winter Weekend Morning - it was raining, not just a little bit of drizzle but real rain, lots of big fat raindrops. We retreated into the underground car park of the hotel for the first briefing of the morning; the only dry one that we were to get.

Sue introduced the Geology of the area and gave an overview of what we hoped to see during the day. Our first stop was the top of Peak Hill (SY 110872) to look East over Sidmouth and, from the other side of the car park, West beyond Exmouth. The key point of interest was to be the dissected topography influenced by the River Sid, which in its turn influenced the development of the town of Sidmouth. Unfortunately falling rain and persistent mist obscured detail. Later on in the weekend we returned. This time we were able to see some of the large scale structures and appreciate the contrast between the low-lying, undulating landscape following the sediments around Sidmouth and the higher ground to the West beyond Exmouth, the high tors of Dartmoor.

Still in the rain we moved off into East Budleigh (SY 066849). We travelled along the high street to see the Cob and Cobble cottages typical of an East Devon village before reaching the church, the focus of our attention. The Cob is a mixture of mud and straw and the Cobble is the stone base, which gives the cottages structure. The Church of All Saints originates from the Saxon time, when, as a small church, it served a large village (including Salterton until the 19^th Century) of agricultural workers, fishermen, seamen and merchants who were involved in legitimate trade exporting wool to the continent. There was also trade of a less legitimate ilk. Smuggling was rife along the coastline at this time and was organised by - or at least condoned by - some of the local vicars of the time. One of the most well known of these is Ambrose Stapleton (1794 - 1852) he was vicar for 58 years from the age of 25. There is speculation that smuggling tunnels, used by him and his associates, emerge at the vicarage. There were other well-known families, the most famous of which are the Raleighs who lived at Hayes Barton. Walter Raleigh was born in 1552 (or 1554 depending on your sources) and was tutored by the vicar at All Saints Church. There is a memorial to Walter Raleigh in the Church which was defaced, when was beheaded, by the shield being cut off.

The Church itself remains an interesting building even after being rebuilt by Bishop Lacey around 1920. It contains some excellent examples of 16^th Century Tudor oak carved pew ends, there are some fascinating images too numerous to describe but worthy of further investigation. There is in particular a 'Green man' whose symbolism is a source of much discussion. All you can do is go and have a look for yourselves it is well worth a visit.

So what of the stones, after all this is also a geological visit. Outside the church there are splendid examples of local stones and the use that they serve as building stones. The colour is predominantly earthy red, tending to be poorly sorted with evidence of algal mats. Outside the church there is some otter sandstone and inside some bee stone. This was our chance to get used to the look of the rock to see if we would be able to recognise it in the succession at source. The journey to our next stop was a welcome respite from the rain!!

Or next stop was Madeira walk in Exmouth (SY 002803). We were to look at the cliff behind the walkway; there were some other people around, walking their dogs - I am not sure what they thought of us standing, wet and bedraggled looking at the cliffs. The overall impression of the cliffs was again an earthy red colour with some interesting features. We saw poorly sorted angular clasts, some quartz and some slaty looking material all in a red sandstone matrix. There were some fine horizons but still predominantly course material. There was some discussion about the environment of deposition, probably aeolian. This horizon was the lowest bit of the Permian that we were to see, later on in the weekend we would be looking for other bits of the succession. We finished this visit back in the real world by observing, with the other people of Exmouth, 2 minutes silence at 11.00 on the 11^th day of the 11^th Month. It was quite moving to be standing there in silence in the rain.

Our next stop was back along the beach to Rodney Point (SY019798) where we saw huge red cliffs (5m high) with several sets of truncated cross bedding. Inspite of the wind blowing off the sea it was still spectacular; look at the website to see a picture of a waterfall going backwards. We saw evidence of low angle structures steepening and then cut off. There were mud flasers and fine clay drapes across ripple surfaces; an excellent area for discussion of way-up structures and their recognition in the field. It was a fascinating site and again well worth a further visit, but do check the tides. I am sure that we would have spent much longer there had the wind and the rain not made the area quite so inhospitable. An excellent morning's geology but lunch in warm dry cars was a welcome interlude.

Suitably refreshed we set of in the rain again to our next exposure, the ominously named Dark Lane at Budleigh Salterton.This proved to be an impressive sunken lane cut down some 5m. by the passage of cart wheels over some hundreds of years.

A good exposure of Triassic Otter Sandstone was seen composed mainly of red poorly sorted sands with low angle cross-bedding on a scale of a few metres or less. Some areas showed planar bedding and lenses of coarser material and clay. A few isolated pebbles up to 30 to 40 mm were seen, and some showed the polished and faceted surfaces typical of ventifacts, ie. stones shaped by the action of windblown sand. Some discussion ensued as to the possible environment of deposition of the sands, aeolian or fluvial? The poor sorting, mainly small scale of the cross-bedding and the presence of material coarser than 5mm. argued against an aeolian origin, but the presence of ventifacts suggested erosion surfaces exposed to wind action in a desert environment. The general picture emerging was that of distal portions of alluvial fans with in-persistent flow from high ground. A more detailed investigation at this location might find both aeolian and fluvial deposits present.

Our next location was the sea front at Budleigh Salterton. As we emerged from our cars a strange bright light appeared in the sky, and after some discussion we decided that this must be THE SUN!

After a quick look at the lime kilns and raised beach by the car park we set off along the beach. The beds here are dipping gently to the east, allowing us to work our way down the succession as we traversed west. Our first exposure was in the Otter Sandstone, similar to that seen in Dark Lane but showing a distinctive honeycomb weathering pattern. Some odd vertical cylindrical concretions were seen in some horizons (chert?).

Further to the west the junction with the underlying Budleigh Salterton Pebble Bed was exposed. The top of the bed is marked by a deflation surface consisting of ventifacts with ‘desert varnish’ covered surfaces. Some of these are in the form of the distinctive three edged dreikanter pebbles. In places a bright yellow mineral has been deposited on this surface, tentatively identified as Jarosite and subsequently confirmed as such by Bob Symes. This surface has been taken as the junction between the Bunter and Keuper divisions of the Triassic.

The Pebble Bed consists of a conglomerate of rounded pebbles up to about 100 mm. in a matrix of red sand and silt. Layers and lenses of sand were seen, and in places the conglomerate showed cross bedding and imbrication. The pebbles are mainly purple quartzites, and are thought to have an origin to the south. Fossils have been found in the pebbles indicating an Ordovician or Devonian origin. The large clast size and extreme rounding of the pebbles indicate deposition in a very high energy environment, and flash floods from mountains to the south draining into a desert basin seems consistent.

Walking further westwards we came to a recent cliff fall, and Sue postulated that the base of this fall concealed the underlying Littleham Mudstone.

By now the light was beginning to fade, so it was back to the very comfortable Royal Glen Hotel for swimming, drinking and eating!

As a change from Saturday the sun shone brightly from a clear blue sky nearly all morning as we tramped westwards along the beach from Sidmouth. The first part of the walk, from the Esplanade, took us onto the Millennium Walkway and past on the landward side an up thrown, I suppose that I should say faulted, block of Otter sandstone, on which the local graffiti artists, all except Kilroy, had made their marks. At head height the cliff was composed of a water-lain coarse to extremely coarse sandstone showing truncation of cross bedding etc. and channel fills. Above head height the sediment became-more uniform but not wishing to "do a penguin" I did not look up. Seawards of the Walkway the Chit rocks formed a wave cut platform in the beach, apparently the last stack had fallen about 1870. Two artificial islands or groynes had been built in the bay of hard rock from Scandinavian, the Walkway was also so protected. This was to deflect the waves and keep the sand from being stripped from the bay. The net result was that the cliff eastwards of Sidmouth was experiencing more frequent landslips!

The end of the Walkway boasted a fort and the junction of the Mercian mudstone nee Keuper Marl cliff with Otter Sandstone.

Rock falls were in evidence along these cliffs and so nobody ventured too near the cliffs from here onwards. A line of springs could be seen in the Mercian Mudstone, all contributing to cliff erosion.

Another oddity, at the base of the cliff past the Mercian mudstone cliff were irregular layers of a pasty blue green less competent material within the overall red sandstone deposit. Apparently the cause of this was the reduction of the ferric (red) iron to ferrous iron within the sandstone, due to organic material being bacterially decomposed?

The Cretaceous, in the form of greensand could be seen at the top of the cliff and was found as pebbles in the shingle at the base.

We were walking on a falling tide and the wave cut platform, in the Otter Sandstone provided a number of features for discussion including calcretes (small), desiccation cracking and trace fossils in the form of filled burrows, so shallow water conditions would have existed during the deposition of the sandstone notwithstanding this area of trace fossils no other evidence was found for organic life.

The final stop was in the corner at the farthest west end of the beach where, just above the shingle, the basal Triassic bed was located. A backward looking view from the beach showed the dissected nature of the land surface with the farmland (Keuper Marl) and the Cretaceous greensand (the forested hill crests) being evident in each valley.

That an application has been to have this entire coastal section, to Charmouth in the east, declared a World Heritage Site, and so protected is not surprising. Definitely an extremely interesting length of coastline.