Newsletter - December 2014
The full, illustrated newsletter is available as a pdf for download.
Text extracts are given below.
North West Geologist Number 19 will be arriving shortly (unless you have your newsletter by snail mail in which case you will be looking at it now!!) and we are now planning Issue No 20. Articles on a geological theme are welcomed. These could be articles about a holiday to a classic geology area, or a report of a field excursion, a review of a book with a geological theme, even just a few good images with a bit of explanatory text.
This is an opportunity to have your work published, so go for it!
A Building Stones Guide to Central Manchester
This guide, originally written by Morven Simpson and Fred Broadhurst, has been extensively revised in 2014. Four lavishly illustrated, circular walks are supported by fold-out maps inside the covers.
Many changes have taken place in central Manchester, most recently major refurbishment of the Cathedral, where a new floor has been installed, using two varieties of Carboniferous Limestone from Baycliff, near Ulverston. Small squares of the previous floor, crinoidal limestone from Derbyshire, are being sold in the Cathedral shop.
The Central Library has also undergone major refurbishment, opening up most of the building to public access. The building was opened by King George V and Queen Mary in 1934, on the same day as they opened the Mersey tunnel (Kingsway) and the East Lancashire Road (A580). All three projects provided employment during the Depression. The Central Library has been the focus of celebrations of England's oldest public lending library, established in Manchester 150 years ago.
Manchester Cenotaph, designed, like that in Whitehall, by Edwin Lutyens, has been relocated. It is now 'reunited' with the Civic Centre, having been separated from it by the Metrolink tram system, which is currently undergoing expansion.
Copies of the guide are available from Manchester Geological Association. The cost is £4.50 for members of the MGA - it will be higher at other outlets so buy your copy at the next meetings! Or buy several and use them as Christmas presents for friends and family!
Field Trip to Formby Point
OUGS/MGA joint trip to Formby Point looking at Coastal Processes and Prehistoric Footprints on the beach
21 September 2014
Leaders: AM: Steve Suggitt (Edge Hill University) Coastal Processes and PM: Alison Burns (Manchester University) Prehistoric Footprints
On a warm and sunny September day, 25 OUGS and/or MGA members met in the National Trust car park at Formby Point in Merseyside. We were pleased to see that the red squirrels have returned to this reserve after being almost wiped out by a virus several years ago. Formby Point is aptly named because it juts out into the Irish Sea between two estuaries - the Mersey (Liverpool) to the south and the Ribble (Preston) to the north. As this is one of my local beauty spots, I was particularly interested in finding out more about it.
Steve Suggitt gave us a general introduction to the local geology. At Formby, the beach is backed by sand dunes which have been there for about 2000 years. At Formby Point the dunes are being eroded by winter storms with as much as 30 metres being eroded in one year (2013-14 winter). Thus the appearance of the dunes changes from year to year, something I had previously noticed. The eroded sand is transported by longshore currents south towards Crosby and north towards Southport.
Steve then took us via the sand dunes path and onto the beach. Here we walked south, towards Liverpool, stopping at various points along the foreshore. At several locations, old Christmas trees have been used to make a fence along the dunes, to provide some protection from wind erosion. For a similar reason the dunes have been stabilised by plantingmarram grass which send out rhizomes beneath the surface. Unfortunately human visitors tend to trample over the dunes often destroying the marram grass and allowing sand to be blown inland. We noticed wide gaps in the dunes caused by 'blow-outs' - strong onshore winds had blown the sand away at weak points. These gaps act as wind channels.
In several places the dunes have been eroded by the sea causing landslips which have exposed cross-sections of the dunes. Here bedding and cross-stratification could be seen. We also found a number of brown boulders strewn out along the foreshore. At first I thought they could be erratics but on closer inspection they were too soft and smelled of tobacco! Steve explained that the boulders were actually 'nicotine waste' dumped in the dunes by a Liverpool cigarette factory to fill gaps left by the removal of sand for industrial use. Now dune erosion is uncovering them near to the appropriately named Nicotine Sand Path.
Nearby we noticed a narrow (few cms thick) soil horizon running across a dune. This was approximately 100 years old and showed that the dunes had been stabilised for some time before the land was inundated again by sand dunes. Further along, the remains of the Old Lifeboat Station building from the 1700s is gradually emerging, as the sand dunes are eroded. On our return walk along the beach we noticed interesting ripple marks indicating two different current directions and also rip-up clasts (mud balls) being formed.
After lunch back at the NT car park in the pinewoods, we were met Alison Burns, an archaeologist researching the prehistoric footprints on Formby beach. Alison gave us a short talk on life and environment during the period. The evidence suggests that the prints were formed between 5400 BC and 2300 BC.
Sea level was lower at that time and the area around Formby would have been a salt marsh, providing a lush coastal environment for Stone Age man and many animals. Alison described how the prints were originally preserved when sand was blown into the cavities left by the prints, filling the hardened impression. More mud then flowed into the reed beds from freshwater streams sealing and burying the prints.
The ancient footprints of red deer, roe deer, aurochs and birds as well as humans have been found in the muddy clay-like beds between the sand beds on the beach at low tide. We were able to identify prints of red deer and humans but most of us remain to be convinced of the bird prints, which could easily be confused with modern prints. All prints are transient as they are easily eroded by the tides and modern day activities Towards the end of the afternoon Alison asked if we would help with her PhD project. We were divided into teams and requested to make footprints in the sand whilst walking, jogging and running. The resulting measurements were then recorded for later analysis. I'm not sure what the visitors to Formby beach made of this activity but it was great fun. I hope it helps Alison with her PhD.
This was an interesting and varied day, much enjoyed by all participants. As the trip was oversubscribed, we hope to run it again in the future. Many thanks to our leaders who had to compete with displays, including the Red Arrows, from a nearby air show.
Jane Schollick and Heather Rogers
Geo Web Watch
Most of us have access to the web either via our own computer or using our local library. There are many geo-themed websites out there and so your Editor thought it might be useful to highlight some of these each quarter. If you have any favourite sites which you use, please let me know and I'll be pleased to include them next time.
This month I thought I would turn to a site called Mineralogy Database. The Mineralogy Database contains 4,714 individual mineral species descriptions with links and a comprehensive image library.
Each mineral has a page linked to tables devoted to crystallography, crystal structures, X-Ray powder diffraction, chemical composition, physical and optical properties, Dana's New classification, Strunz classification, mineral specimen images, and alphabetical listings of mineral species. There also are extensive links to other external sources of mineral data and information.
An example of the information is given below:
General Calcite Information
|Composition:||Molecular Weight = 100.09 gm|
| ||Calcium||40.04% Ca||56.03% CaO|
| ||Carbon||12.00% C||43.97% CO2|
| ||Oxygen||47.96% O|
| || ||______|| ______|
| || ||100.00%||100.00% = TOTAL OXIDE|
|Environment:||Found in sedimentary, igneous, and metamorphic rocks.|
|IMA Status:||Valid Species (Pre-IMA) 1845|
|Locality:||Common world wide|
|Name Origin:||From the Latin, calx, meaning lime|
|Synonym:||Glendonite - pseudomorph|
Manganocalcite - variety
Parakutnohorite - intermediate composition between calcite and rhodochrosite