The Geography of Birmingham
People settle in particular places according to the types of natural resources and their availability. Soils and rocks, rivers, plants and animals are directly related to the underlying rock and the soil it produces. Communities prospered or struggled or failed depending on what natural resources there were and what use they were able to make of them. Modern construction methods and urbanisation have made the geology and the geography of Birmingham largely irrelevant to the ordinary citizen - unless, of course, they are gardeners.
The Birmingham Plateau
Birmingham lies in the centre of the Birmingham plateau, an upland area generally higher than 125m above sea level, which lies between the rivers Avon, Severn and Trent. At the northern end of the plateau Cannock Chase is an area of higher ground rising to 250m above sea level; at the southern end of the plateau the Clent-Lickey ridge rises to 320m; while roughly in the middle of the plateau Barr Beacon a few miles north of Birmingham City Centre stands at 215m.
A line drawn through the following towns would roughly encircle the Birmingham Plateau: clockwise from the north - Stafford, Rugeley, Lichfield, Tamworth, Atherstone, Nuneaton, Coventry,Stratford, Redditch, Bromsgrove, Stourbridge, Tettenhall, Penkridge, Stafford. The upper Tame which runs south-east from Wolverhampton cuts the plateau in two from west to east. The River Blythe runs northwards from Shirley to join the River Tame near Shustoke in a wide valley which continues northwards as the Tame flows to its confluence with the River Trent north of Lichfield. The Blythe-Tame valley separates the main part of the plateau from the East Warwickshire plateau. Birmingham lies on the edge of a central lowland part of the Birmingham Plateau.
The plateau is divided into higher plateaus and ridges, low plateaus and river valleys, those locally relevant as follows:
The Sutton Plateau
This low plateau stands west of Sutton Coldfield town. The town centre itself lies just off the plateau in the river valley of Plantsbrook, a tributary of the Tame. The plateau slopes southwards towards the valley of the middle Tame and covers roughly the area between Aldridge and Hamstead in the west and Bassetts Pole to Tyburn in the east. On its western edge a ridge runs from Shire Oak to Queslett where it rises to Barr Beacon. The plateau is made up of Bromsgrove sandstone (formerly known as Keuper sandstone), Wildmoor sandstone (formerly Bunter sandstone) and pebbly sandstone conglomerates which were laid down during the Triassic period.
The West Bromwich-Harborne plateau
This is a low plateau lying south of the River Tame and west of the River Rea; it is similar to the Sutton Plateau (above), being made up of sandstones and pebbly conglomerates.
The Sedgley-Northfield Ridge
This area of higher ground forms part of the main English watershed. Rain that falls to the south of the ridge drains to the Severn via the Bristol Channel to the Atlantic Ocean; rain falling to the north drains to the River Trent and via the Humber to the North Sea. The northern part of the ridge is made up of three sharp folds of Silurian limestone at Sedgley Beacon, Wrens Nest and Dudley Castle Hill; south of this are coal measures which include at Rowley Hill a large intrusion of dolerite, a hard igneous rock. To the south, Northfield lies on Bunter pebble beds, Bunter and Bromsgrove sandstone (formerly known as Keuper sandstone).
The Clent-Lickey Ridge
Parallel to the southern stretch of the Sedgley-Northfield Ridge and separated from it by the valley of the River Rea, is the Clent-Lickey Ridge which also includes part of the main English watershed. The Lickey Hills are made up of Cambrian quartzite which has up-faulted into later carboniferous and Permian rocks.
The Solihull Plateau
Much of southern Birmingham is built on this low plateau which lies south and west of Solihull town centre. This area of Triassic Keuper marl, now known as Mercia mudstone is drained by both the River Cole and the Blythe.
The Mid-Tame, Rea and Upper Cole Valleys
The upper Tame running south-east from Wolverhampton cuts the Birmingham Plateau in two from west to east. Both the middle Tame and the Rea were subject to flooding until the early years of the 20th century when they were deeply culverted. The gently sloping valleys were used to make road, canal and rail links onto the plateau. In the 1970s the M6 motorway was built along the Tame valley and subsequently the M42 as far as Kingsbury. The course of the rivers owe much to the melting of the Pleistocene glaciation and they wend their way largely over Mercia mudstone. Along their courses alluvial deposits have created marshy but fertile land.
The Blythe and Lower Tame Valleys
The wide valley of the River Blythe runs northwards from Shirley to join the River Tame near Shustoke; the Tame then run north to join the River Trent north of Lichfield. This valley separates the main plateau from the East Warwickshire plateau and runs through a wide floodplain of Triassic Mercia mudstone.
William Dargue 18.04.09