GEOLOGY AND NATURAL VEGETATION

The geology of Church End is simple. Keuper Marl, the red clay of the Midlands, covers the whole area. It is many hundreds of feet thick and impenetrable by water. Overlying the clay in places are patches of drift, two of sand and gravel north-west of the village, and two very small ones northeast of it. Boulder clay and mixed drift lie about Coventry Road and extend south through Yardley, and north of Lea Hall. There is or was a narrow outcrop of soft Arden Sandstone curving about the site of Glebe Farm.

The drift is a legacy of the most recent Ice Age, remnant of masses of transported material deposited by glacial lakes and terminal moraines, broken by ice, smoothed and partially washed away by melt-water torrents as the glaciers dwindled. Immense rivers coursed down former drainage channels, gouging out deep trenches : the larger of these became infilled with silt, becoming wide, flat-floored valleys across which small post-glacial streams meandered and flooded.

Drift survives as a thin capping on interfluvial ridges : the solid material, fragmented rock, is resistant to wear unlike the soft clay. The porosity of drift makes it a storehouse of water, which cannot penetrate the impervious clay beneath and so spreads out across it, appearing as springs at the interface. Sandy material is washed down from the highest levels, leaving stony ridges : these are dry and un-welcoming to heavy afforestation, so that they are relatively clear of trees and firm underfoot.

Valley sides, bare of drift, were in natural conditions very thickly wooded : clay is fertile and its rich topsoil retains water enough for the thirsty oaks. That tree tolerates bush and bramble undergrowth : a natural oak forest, like that which once lay between the village and Coventry Road (and over most of the modern Birmingham area) was a largely impenetrable deciduous jungle. This petered out beside boggy side-streams and at the edges of the Cole flood-plain : there willow and alder and tussocky grasses covered waterlogged silt.

Natural vegetation can be deduced from the known characteristics of the surface rocks : but old names tell a story too. Throughout the Quarter there were marl (clay) pits, brick kilns, tile-houses : there were wood-names like 'ley' = clearing in wood, 'riddings' = land cleared of wood : and there were moors and mores = bogs beside streams and in places where the water-table was higher than a depression in the drift.

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