Cumberland Geological Society Presents –
From the Winter Lecture Events Programme:
Starts: 19:30
Location: Tullie House Museum & Art Gallery, Castle Street, Carlisle CA3 8TP
Description: Dr. Dave Millwood: Graphite in Borrowdale
Events are open to members and non-members. This event is free for members and non-members who wish to ‘try out’ the society.
GLACIERS AND CLIMATE CHANGE
Professor Mike Hambrey
A large audience assembled at Braithwaite Institute on November 9th to hear Professor Hambrey (who now lives at Threlkeld) give a comprehensive review of his own glaciological research and the implications for climate change. He outlined some of his field trips to polar regions and displayed photographic and statistical evidence of the depletion of ice from mountain glaciers in different parts of the world and from the great ice caps and ice sheets. Mountain glaciers, especially in the Himalayan chain, contribute greatly through meltwaters to the water supply of large areas of Asia. Significant loss of ice from continental areas leads to rise in sea level, a problem already affecting some low-lying Pacific islands. A special concern in the North Atlantic is the way in which major loss of ice from Greenland cools the ocean and may lead to the disruption of the important Gulf Stream which in turn could adversely affect the climate of NW Europe.
The rate of temperature increase in polar regions is higher than at lower latitudes and his Antarctic field research has revealed how the potential collapse of ice shelves along the Antarctic Peninsula would allow the release of interior ice into the ocean and its subsequent melting.
The deep drilling into the polar ice caps and in particular the extraction of 3000m of ice core from the Vostok site has enabled sampling of trapped air bubbles from the atmosphere going back millions of years. The CO2 levels measured match closely the known temperatures (from other evidence) and indicate how warm periods coincide with high CO2. Such data has shown while the CO2 concentration has not exceeded 300 ppm for most of the last million years, it reached 320 ppm in 1960 and has rapidly risen to 400ppm at present.
Professor Hambrey concluded by warning that rising CO2 together with other greenhouse gases will result in further increase of global temperatures. Present trends, unless checked by radical measures, will lead to a 40C further rise by the end of this century. At this level polar ice caps could not be sustained.
Lecture by Dr. Simon Ferley
Wednesday 12th October 2016
Dr Ferley began from first principles. He considered the properties of soil and the way it’s strength varied with water content, which he demonstrated with samples from his own garden. He then went on to describe the different ways in which slopes fail with some mathematical equations enhanced by some very clear diagrams. It became abundantly clear that water content is crucial to the stability of any slope and that appropriate drainage is essential to prevent failure.
He then discussed measures which could be taken to mitigate naturally occurring failures. These included good maintenance of channels downstream, delaying flow in areas nearer the catchment by tree planting and creating artificial meanders in a stream. He was cautious about flood defences as although they are necessary in some areas, they may exacerbate problems downstream.
Dr. Ferley had some dramatic photographs of rock and soil failures both from this country and abroad, almost all due to inappropriate engineering works rather than natural events.
He finished with a quick resume of the cause of the devastation to the A591 which had been due to excessive rainfall that had, by natural processes, been channeled into a steep, narrow gully.
Susan Beale
Cumberland Geological Society Presents –
From the Winter Lecture Events Programme:
Starts: 19:30
Location: Braithwaite Institute on A66 (GR: NY233241)
Description: Prof. Mike Hambrey: Glaciers and Climate Change, and their relevance to Cumbria
Tristan Pottas, was unable to give this talk but two of his colleagues gave an interesting overview of this exciting new mining project near Whitby. Asher Haynes described the process of exploration and the excitement of discovering a truly vast deposit of polyhalite in North Yorkshire. Polyhalite is an unusual multi-nutrient mineral that is an exceptionally good fertilizer as it is essentially chloride free, does not affect the pH of the groundwater when applied, and needs virtually no processing. However this valuable resource lies 1500m below the National Park with all its tight planning restrictions. Nevertheless the project would bring significant economic benefits to the area by way of employment and would contribute to the national economy. Sirius had been given planning consent after describing these advantages and developing an extraction method which placed most of the infrastructure below ground level. The Company are currently seeking the necessary finance in readiness to commence construction.
David Warburton, completed the evening by describing the characteristics of polyhalite (K 2 MgCa 2 (SO 4 ) 4 2H 2 O) and his recent research Masters degree at University of Leeds where he had attempted to discover how this mineral is formed. This deposit is most unusual in its thickness, averaging 25m, whereas deposits of around a metre are the norm. Polyhalite is a late stage mineral to form in a sequence of evaporates, so how does such a huge volume occur? David attacked the problem from a geochemical perspective, looking at the isotopes of the various elements which all pointed to formation from seawater during Permian time. The study of thin sections by the BGS suggested that polyhalite replaced anhydrite and other minerals, very soon after the original crystals had formed. The results support the formation of polyhalite via seawater concentration processes, though the topic is far from closed and much more research could be completed.
The combination of a more sustainable approach to the extraction of a valuable resource and the attempts to discover its formation and the questions raised made for a fascinating evening. The speakers were both enthusiastic and hopefully will return in due course to update us on their progress.
