GEOLOGY

The area's underlying rock is the reddish-brown clay now called Mercian Mudstone. It is several hundred feet thick, an impervious material which holds water on the surface and mixes readily with it to create a soft sticky mud.

Across the clay plain ice sheets of the most recent glaciation advanced, pushing before and beneath great masses of earth and broken stone. In lakes pent by mile-high ice barriers, gales blew the water into mighty waves, which pounded the rocks into smooth gravel.

As the ice melted this drift material was left in thick deposits upon the clay; torrents of melt-water washed it out of the valleys and scoured them into gorges. 12,000 years of wind and rain have rounded the valley sides, creating today's landscape; only the inter-fluvial ridges are flat-topped and drift-covered, slopes are gentle and valleys silt-filled with mere trickles in their bottoms.

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