The Northern Chilterns

Landscape and Geology

The Chilterns stretch from the Thames near Goring Gap to Letchworth. This is an range of low chalk hills of over 70 km in length. The deposits in the area were laid down during the Cretaceous Period . The higher ground in the southern part is dominated by Cretaceous chalk deposited about 70 million years ago.

While the area to the north of the Chilterns is dominated by the Gault Clay laid down 100 million year ago and the oldest formation being Lower Greensands formation deposited 120 million years ago. The Gault Clay, was deposited by rivers heavy in silt flowing into the sea. The Greensands are shallow sea deposits, while the Chalk was laid down in deeper ocean conditions. This was a period that the climate as much warmer than now.

The Clay between the higher ground is sandwiched between the Chalk above and the Greensands underneath, but due to erosion and the rock being tilted and been lifted up, forming a dome (anticline). The Dome part being erode the most clearing the chalk and some of the clay. The Greensand to the north then being exposed and eroded. Since the Clay was softer it was eroded more than the harder Greensands and Chalk. The deposition and erosion of the Quaternary glacials and interglacials shaping the land to their present state. The image above shows a simplified diagram of the main stages from top left to bottom right.

Walking in the Chilterns

The area that I will be providing walking routes is the part of the Chilterns between Wilbury Hill between Hitchin and Letchworth and Shappenhoe Clappers between Sundon and Shappenhoe.

This is an area that crosses parts of Hertfordshire and Bedfordshire. The area between Luton and Hitchin gives you an area of varied countryside in an area that is not very demanding of the walker.

There are several high points in this area, that only require a short hike up to the summits, none no higher than 200m, the higher hills, between Letchworth and Shappenhoe are Wilbury Hill, Deacon Hill, Barton Hill, Warden Hill and Shappenhoe Clappers. The countryside is varied with hills and valleys, open fields and woodland. The area is characterised by dry valleys or combe cut escarpments, one of the other features of the area besides the Dry Valley, Scarp cut slopes, is the Bedfordshire farmland stretching between the Chilterns and the Greensands Ridge. The best locations to walk the dry valleys are around Pegsdon and Barton.