Tuesday 31st July 2018
Due to unforseen circumstances Dr John Davies will not give the talk on the 15th August. Instead Dr Chris simpson will give a talk entitled: "An Overview of San Francisco Geology."
The talk will summarise the last 200M years of geology as it affects the West Coast of the USA, and how this can be seen in the rocks of the San Francisco area today. It will also include some historical aspects of San Francisco, and a trip to the Yosemite National Park.
Saturday 26th May 2018
Evening Meeting Wednesday 16th May 2018 - Post Glacial Environmental Change and Human Adaptation During the Mesolithic in Sussex - Dr. Richard Carter
At the last meeting we had a complete change from geology. Dr. Richard Carter gave us a brief insight to his field of work covering interactions between humans and the environment during the Mesolithic Period.
In order to understand human behaviour at that time it is necessary to understand the environment in which they found themselves. Humans colonised Britain hundreds of thousands of years ago but displacement and recolonisation occurred related to major glaciations and fluctuating ice-sheets with the final (Devensian) Ice-Age ending about 10,500 years ago.
During the early Mesolithic warming temperatures led to the melting of continental glaciers and a rise in sea level. This caused deltas and coastlines to be inundated and low lying land to be flooded. The warmer climate also encouraged a change in vegetation with the development of pre-boreal forests of pine, birch and alder. This was an open landscape. Over time the pre-boreal forest was replaced by boreal type consisting of more deciduous species like hazel, oak and lime with the pines being forced to higher and drier areas. Dense forests with occasional breaks now occurred. By the time of the late Mesolithic temperatures were equivalent to what we experience today and the forests were dense. Throughout this time the changing environment meant changes in the flora and fauna which formed the diet of Mesolithic peoples. This in turn led to the development of new methods and tools for hunting such as the microliths for fixing onto harpoons and spears.
Throughout the Mesolithic the rising sea levels eventually saw the land-bridge which connected Britain to the rest of Europe disappear and Britain became the island it is today.
Dr. Carter also gave a short explanation of modelling hunter-gatherer mobility as this can allow inferences about occupation patterns and types of sites that are used. It may also help to distinguish between long and short term occupation.
This was a fascinating and informative talk.
The next meeting will be held on Wednesday June 20th when member Tony Thorp will give a talk entitled, “ The Geology of Arran”.
Wednesday 9th May 2018
The history of the Montgomery canal was the subject of the last meeting. Andrew Jenkinson commenced the talk with a general history of canal building. Francis Egerton, the third Duke of Bridgewater, built the Bridgewater canal to transport coal from his mines at Worsley to the industrial areas of Manchester. This was the forerunner of all the other canals and is often described as England’s first canal as it was the first to be built which did not follow a natural watercourse, and required the construction of an aqueduct across the river Irwell. It’s success stimulated an intense period of canal building.
In 1791 a grand scheme was developed to build the Llangollen Canal (Ellesmere Canal) to link the River Mersey to the River Severn at Shrewsbury, past Chirk, Ruabon and Wrexham to the Dee at Chester, then continuing to the Mersey at what was to become Ellesmere Port. Branches to the limestone quarries at Llanymynech and the town of Whitchurch were also proposed. Only some of this was realised but the branch to Llanymynech was completed in 1796. It was also suggested that the canal be continued on to Welshpool and then to Newtown.The section from the Frankton junction to Carreghofa, just south of Llanymynech, was built by the Ellesmere Canal scheme.The rest of it was the independent Montgomeryshire Canal which opened from Carreghofa to Garthmyl in 1797, but by then had exhausted its money. The final six miles into Newtown was separately financed under an Act of 1815, and opened in 1819.
The role of the Montgomeryshire canal was mainly the transport of limestone to the many kilns that lined the canal. This allowed the local production of quick lime for agriculture. It was not a commodity that could have been produced at the quarry and then transported as any contact with water would have slaked the lime in a volatile reaction. So the canal would also have been necessary to transport coal and wood for the kilns.
More recently the route in Welshpool was threatened by road building in 1968 which produced a mass “dig” in 1969 when more than 200 volunteers from the Shropshire Union canal Society cleared the channel through the town. Then in 1987 the British waterways Act conferred powers to restore and operate the canal. The canal was renamed the Montgomery Canal. Renovation and operation was taken over by the Canal and River Trust in 2012. The canal continues to be renovated. A lot of the canal is now a SSSI.
The next talk will be on Wednesday 16th May when Guest speaker Dr. Richard Carter will give a talk entitled: “ Postglacial Environmental Change and Human Adaptation During the Mesolithic in Sussex.”
Sunday 8th April 2018
Evening Meeting Wednesday 14th April 2018- "Creataceous Fossils Araripe Basin Brazil" - Bob Loveridge
Twenty three members attended the last meeting when Bob Loveridge (Visiting Research Fellow University of Portsmouth) entertained us all with a superb talk on the Crato Formation of the Araripe Basin of Brazil. The Araripe Basin is located in a forested cirque in the north central part of the Chapada do Araripe, a large tableland in north-eastern Brazil. The Crato Formation ( Late Aptian in age) is 50-60m thick and is composed of a series of rock types with the basal unit of micro-laminated limestones, the Nova Olinda Member, yielding spectacular fossils which earns the formation its status as a Fossil Konservat Lagerstätte. There is a huge number of fossils all of which are exceptionally preserved and includes insects, arachnids, vertebrates and plants.The Chapada do Araripe is now a UNESCO GeoPark and collecting fossils is illegal without a permit but the area continues to be used for extraction of the limestone for buildings and roads which is leading to it’s destruction.
The fossils are preserved by pyrite/geothite which is thought to be due to pore waters permeating the specimen and envelopment by bacteria which create a covering over the outside of the carcass causing a micro-environment in which mineralisation of tissues can occur i.e. “bacterial sealing”.
The talk was accompanied by superb photographs and SEM pictures of the fossils but also by the escapades that Bob and partners undertook in order to study them.
The next talk will be on Wednesday 25th April when Andrew jenkinson will give a talk entitled: “Rocks along the Cut” - looking at rocks along the Montgomeryshire canal.
Wednesday 21st February 2018
Evening Meeting Wednesday 14th February 2018 - "The Origins of Atoms" - Dr. Geoff Steel.
We all have seen and been taught about the Periodic table of elements but how many understand how these elements came into being. Geoff's talk went a long way in helping in this understanding.
The first lighter elements were formed by Big Bang nucleosynthesis. The Big Bang being the cosmological model that best explains the origin of the universe. During the first second following the Big Bang, a wide range of events were occurring including cosmic inflation, elemental particle formation, the formation of baryonic matter, collisions between elementary particles, decreases in particle energies and temperatures. Between one second and three minutes after the Big Bang temperatures cooled to about 109K at which Big Bang nucleosynthesis could occur. This led to the production of protium (1H), deuterium (2H), tritium (3He), helium (4He), and some Lithium (7Li) but no heavy elements were formed. The heavier elements had to wait until later to be formed by Stellar Nucleosynthesis.
Most stars produce energy by fusing hydrogen to form helium, with the release of energy. The outward flow of energy (thermal pressure) released balances the collapsing force of gravity, and this stabilizes the star's size. As helium increases in the core it reduces the rate of hydrogen fusion which in turn decreases thermal pressure and the star starts to contract. Depending on the initial mass of the star Helium can fuse to form carbon nuclei which leads to the formation of a carbon core via a process known as the Triple Alpha Process. This increases thermal pressure of the core to a point where it will overcome gravity and the size of the star increases giving rise to a red giant. If a star had sufficient mass, though, eventually enough carbon would accumulate so that the temperature and density reach a point where carbon nuclei could be fused into Neon nuclei. This carbon burning core would be surrounded by two outer shells, the innermost burning Helium, and the outermost burning hydrogen. This pattern of the central core collapsing and increasing temperature continues until a further round of fusion occurs and more shells form. How many shells are eventually formed is dependent on the initial mass. Eventually iron (56Fe) will be formed but the average binding energy per nucleon has now reached maximum so there can be no more energy-generating reactions, all reactions are required to be endothermic. The star therefore undergoes gravitational collapse. The star then enters a runaway phase leading to the development of a supernova explosion which in turn can lead to the production of even higher elements via a process involving neutron capture.
Finally Geoff explained that the abundance of lithium, beryllium and boron in the universe is thought to be due to the process of Cosmic Ray Spallation. This refers to the process where interstellar collisions between very energetic cosmic rays and interstellar nuclei causes the heavier nuclei to break up forming smaller nuclei. During the collision there is expulsion of a large number of protons and neutrons from the object hit. Cosmic Ray Spallation not only occurs in deep space but also in the earth's upper atmosphere and crustal surface.
The next meeting will be on March 14th when Bob Loveridge will give a talk entitled: “Cretaceous Fossils of the Araripe Basin, NE Brazil”