scarps and vales

• central and southern england has low-lying clay vales, alternating with chalk ridges , with their distinctive steep scarp and gentle slopes
• examples of chalk ridges include the North and South Downs
• limestone hills include the Cotswolds, Chilterns and the Mendips
• the clay vales stretch across Wiltshire and oxfordshire
• the river thames has its source in the cotswolds and flows southeast through the low lying basin into the North sea