The study of the Irwell Catchment’s Composition
- Bedrock is given to the name of the base rock of the earth formed up to 2500 million years ago.
- Usually below the Superficial Geology however can be exposed on the surface at some outcrop.
- As shown on the map below Manchester and Salford sit on a sandstone strata whilst to the North and East areas fall within the Upper, Middle and Lower Pennine Coal Measures. Creating opportunities for viable mineral extraction through the catchments history.
- For the bedrock Geology we have chosen to compare the upper and lower parts of the area to illustrate the geological diversity within the catchment.
- The diagram above compares the geological structure of Manchester and Salford to that of Rossendale Valley in the north. The two sections are generalised interpretations of the layering, depths and types of rock in each area and their properties/uses.
- In Rossendale the geology mainly comprises Millstone Grit and Shales. Millstone Grit has been extensively quarried for building stone since the Industrial Revolution. More importantly, it was the Haslingden Flag (highlighted in red) that was the principle reason for the growth of quarrying in this area, because of it’s similarly to Granite.
- Haslingden Flag is also of scientific interest to Geologists because of its elongate “birds foot” type delta. Lee Quarry in Rossendale is a Site of Special Scientific Interest because of the Haslingden Flag found there. More information about this incredibly rare rock can be found at valleyofstone.org.uk.
- Layers of Rough Rock within the Grit at Rossendale have also been known to contain marine fossils (see below) evidencing the origins of the River Irwell. The fossils indicate that the area was once covered in shallow seas, only leaving a spring in the hillside where the river was formed.
- In Manchester and Salford there are a variety of sandstones which are more permeable than that of the solid geology in Rossendale. This Sandstone sequence here forms the most important groundwater aquifer in the North West.
- Superficial rock is the youngest formation of geology and covers the majority of the Bedrock below.
- Formed within the last 2 million years.
- The depth of the superficial geology varies greatly due to topography, hydrology and human activity.
Through the ages
- Timeline Below shows the development of the superficial geology within the UK.
- Devension Period also known at the last ice age, falling within the Quaternary glaciation.
- The Post-Glacial period also known as the Holocene period, this created sedimentary deposits as the ice melted forming in river basins and valleys.
- Anthropogenic Period this is humans influence on the planet, in terms of geology this includes mineral extraction, land use, depositing waste material and infilling worked land.
- The anthropogenic (artificial) deposits are also particularly interesting as they show humans modification of the terrain since the Industrial Revolution.
- An example of worked ground in the catchment area would be the Ship Canal, where both superficial deposits and bedrock were excavated to a depth of 8m along the length of the canal.
- In relation to the River Irwell, made ground has occurred in the river valleys where meander loops have been infilled with excavation material from the Ship Canal (see diagram below).
- Over 90 boreholes have been found in this area of the catchment alone which have been wholly or partially backfilled with artificial deposits.
- The planning permission granted in 2006, is a combination of a Greater Manchester and South Lancashire Mineral Extraction Plan.
- The variety of locations demonstrates that due to infrastructure and urbanisation, sites that are economically viable for mineral extraction how reduced significantly since the industrial revolution.
- Surface extraction has is the highest form of active mineral extraction with in the Irwell catchment with a small amount of active underground mineral extraction to the North.
- Coal and Shale extraction has had the largest number of planning permissions granted followed by sandstone, sand and gravel.
- The data suggests due to the lower number of active sites, mineral extraction is not seen as an attractive or economically viable approach compared to historical mineral extraction.
- The Manchester Coalfield, Oldham Coalfield and South Lancashire Coalfield all fall partly within the Irwell Catchment area.
- Manchester Coalfield to the south of the catchment.
- Oldham Coalfield to the East.
- South Lancashire Coalfield to the North.
- These collieries extracted mineral from Lower and Middle Pennine Coal Measures.
Number of Collieries that Fall Completely with the Irwell Catchment 1850 – Present
- The number of collieries represent within the graph show no reference to size or efficiency of the mineral extraction as coal has been extracted from the site since the 1600s records were not kept.
Larger mineral extraction information is available from the Coal Authority.
The Bradford Pit (East Manchester)
- The Bradford Pit located east of Manchester city centre became the epicentre of a community, a lifestyle and an approach to industry.
- Coal had been extracted from the area since 1600s.
- In 1797 the Bradford Pit opened and fuelled the Stuart Street Power Station.
- Demonstrating a holistic approach an underground conveyor belt was constructed to transport the coal underground directly to power station.
- The Bradford pit also supplied the Bradford Ironworks.
- In 1968 Bradford pit closed after subsidence to surrounding buildings led to the pit being economically inviable, regardless of the high quality coal remaining below.
- As the coal industry declined, social uneasy and mass unemployment occurred leading to riots and strikes in the 1980s.
- Post Industrial brownfield sites are currently being developed for the communities that were left in ruin once industry declined.
- ‘All that glitters is coal’ shows the human and environmental cost Manchester paid to give birth to the modern world.
- The rivers of Manchester are shown as poor people utilised as labour in the industrial revolution, belonging to a city of exploitation and disregard.
- The coal heap forms into the historical and present day skyline of Manchester, a city that has developed on the location and natural resources however still doesn’t utilise these aspects.
- The cotton texture, clouds and community show what Manchester is famous for, and underpins the artistic and academic cultural that has developed since the industrial decline.
Useful Links and PDFs
Manchester and Salford 3D Superficial Deposits Model: http://nora.nerc.ac.uk/7513/1/IR07001.pdf
The Geology of the Rossendale Anticline:
Mineral Resource Information in Support of National, Regional and Local Planning: Greater Manchester:
The Geology of Manchester and the South-East Lancashire Coalfield by H.M Stationary Office (1970) Cedric Chivers Ltd: Bath