Dorset Downs

[1] The Dorset Downs are bounded on the north, along the steep scarp face, by the Blackmore Vale, a large clay and limestone valley.

On the east, the Downs were once, thousands of years ago, continuous with Cranborne Chase, but the River Stour now cuts a valley between them,[dubious – discuss][citation needed] which is the location of Blandford Forum and the eastern boundary of the downs.

From the northern scarp face, the hills dip gently southwards before the chalk disappears beneath the Bagshot Beds which form the heathlands of the county, between Dorchester and Wareham.

This southerly strip of the visible chalk (sometimes referred to as the South Dorset Downs or South Dorset Ridgeway) continues westwards behind Weymouth, and rejoins the main body of the downs at their western extremity at Eggardon Hill.

This property of chalk also means there are many seasonal rivers, called winterbournes, that flow depending upon the level of the water table.