.Introduction.

Originated by Dr John Catt

Having read this, if you want to learn more then the best source is the book
“Hertfordshire Geology and Landscape” edited by John Catt

Hertfordshire’s main topographic features, such as the Chiltern Hills and Vale of St. Albans, its valley patterns and soil types are all determined by the geological history of the area. These natural features in turn influence the county’s varied agriculture and semi-natural habitats and the distribution of its older towns, villages and industries.

Geological deposits are often divided into:

Solid Formations: the thicker and usually harder rocks formed in periods before about 2 million years ago.

Superficial Deposits, which were formed in the last 2 million years (the Quaternary Period) and are softer, thinner and partially cover the solid formations.