Urban Geology – a mixture of technofossils and landscape psychology

Posted by lcb14 at Oct 06, 2015 09:55 AM |
After a week of field work based within two East Midland cities, Jonathan Hall explains the contemporary Earth Science themes explored within our Urban Geology module…
Urban Geology – a mixture of technofossils and landscape psychology

Investigating an exposure of Triassic Mercia Mudstone and overlying till on Granby Street

The fourth-year Urban Geology module develops the skills needed to analyse the geology, natural (solid and drift) and anthropogenic, of urban settlements. This field-based module uses and combines field and archived geological and topographic data. Identifying and mapping solid and drift geology within an urban area was our objective for the first day. Our introductory exercise involved deducing and mapping the solid bedrock and the overlying superficial deposits within Victoria Park by studying the topography of the playing fields; this involved lying on the ground in order to detect subtle breaks in slopes and larger surface depressions. Afterwards, we walked a transect from University to the River Soar; as we progressed along Welford Road we discussed the nature of the landscape, including the large and curved embankment opposite Morrisons which is believed to represent the remains of an ancient meander and related outer-bank erosion, and the fundamental indicators of alluvium and river terrace deposits alongside Welford Road Stadium.

Examining granite curb stones and discussing provenance on University Road
Examining granite curb stones and discussing provenance on University Road
Man-made geology was the main topic for our second field day. As a group, we initially examined the composition of paving slabs, curb stones and building textiles used on campus and discussed provenance and the associated properties which make these materials suitable for use within an urban and populated environment. Later we studied a transect from University to the City Centre, stopping frequently en-route to examine synthetic artefacts (termed ‘technofossils’), ranging from aluminium cans to vehicles, to gain an appreciation of preservation potential and how each is an example of the Anthropocene concept. We also inspected building facades and monuments, including the Ketton oolitic limestone which forms part of the Haymarket Memorial Clock Tower.

Students mapping Victoria Park using a ground conductivity meter
Students mapping Victoria Park using a ground conductivity meter
The application of electro-magnetic ground conductivity mapping in detecting geological variations, groundwater contaminants or any subsurface feature (e.g. pipes, drains, archaeological structures) related with changes in ground conductivity, was investigated on our third field day. Using a Geonics EM-31 Ground Conductivity Meter, we surveyed a large area within Victoria Park and identified sites concealing potential superficial boundaries or hidden man-made objects. During the afternoon we listened to a guest lecture by Dr Mike Howe, Team Leader of the National Geological Repository, outlining the online resources associated with artificial deposits, including borehole scans detailing made and infilled ground, alongside geochemical, hydrological, landfill and mining records.

Urban Geology group photograph within Park Tunnel, Nottingham
Urban Geology group photograph within Park Tunnel, Nottingham
Our final field day involved a short train journey to Nottingham to explore examples of actual outcrops within urban settings. As a group we investigated the sandstone exposed beneath Nottingham Castle and within Park Tunnel; detailed logging of the pebbly sandstone enabled the identification of sedimentary structures, such as trough cross bedding and imbrication, and facilitated the deduction of dune processes and associated palaeoenvironments. Foreset orientation and attitude were measured digitally, after a demonstration of Midland Valley Fieldmove Clino software. Finally, the petrophysical properties (porosity, permeability, water saturation etc.) of the sandstone were also comprehensively discussed, combined with the proposition of suitability for an aquifer or hydrocarbon reservoir. For the assessment for this module, I will produce a short desk study of an urban area of my choice and use the skills I learnt throughout the module, for example, drawing cross sections using borehole records showing artificial, superficial and solid geology, and creating digital elevation models.

All geologists need to consider how to map effectively within urban areas: this is increasingly important because, as the world population exceeds 7 billion, urbanisation and global development are likely to remain persistent issues. Being able to analyse and understand urban environments, and associated challenges (e.g. landslides, flooding and pollution), in a geological context is a fundamental skill for the present and for our future. This module has been intriguing and enjoyable, and highlights the issues related with urban geology and the Anthropocene concept. The motivation, enthusiasm and friendliness of the lecturers (Jan and Richard) made this fieldwork an invaluable and unique educational experience, enabling me to improve my existing geological field skills by applying them in urban settings and gain new skills.

Jonathan Hall is currently a fourth-year undergraduate in the Geology Department at Leicester.

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