50 Years Celebration Book

Celebrating 50 Years with 50 Geological Sites

Editors Michael Lambert and Nick Pierpoint

This book celebrates the 50th anniversary of the Hertfordshire Geological Society in 2025.

It is a collection of 50 full-page illustrations that, taken together, tell the story of Hertfordshire’s geological past. Most of the objects and locations shown are ones that readers can easily visit and, in the accompanying text, we’ve tried to be clear and understandable, with geological terminology kept to a minimum.

It will be available later this year.

Readers can use the book in two ways:

As a resource you can dip into: discovering a story that interests you and a place you might want to visit.
As a chronological account of the county’s geological past.

Seven Themes

The book is arranged into seven themed sections (the numbers relate to location on the map below) . The first four are roughly in time order, from oldest to youngest.

1. Well Bore Dicovery

We start with a glimpse down a borehole, to see the most ancient rocks buried deep underground.

Tring No.6 TD Lowere Palaeozoic

2. Chalk

Then comes the Chalk: the oldest rock to reach the surface, which was formed on the seafloor 100-66 million years ago, when giant marine reptiles swam across Hertfordshire and dinosaurs inhabited the nearby land.

Sink hole, St Albans

Hertfordshire: Key Towns with some of the sites typical of those which will be detailed in the book.

3. Tertiary

We then move forward into the Tertiary period, 66-2.6 million years ago, when the county was re-invaded by the sea and Hertfordshire Puddingstone, our greatest claim to geological fame, was formed.

Visitors to Little heath Pit - GA, 1919

4. Glacial

Next, we describe sites and objects from the recent, glacial period, which had such a profound impact on the county’s current landscape.

Royston Erratic, Milstone Grit

In the three final sections, we examine human interactions with the geology, aspects of landscape, and a collection of curios that defy categorisation.

5. Human & Geology

Hertfordshire Puddingstone Rotary Quern

6. Landscape

The Herfordshire Bourne

7. Curious

Scotts Grotto in Ware

Some Examples Of Sites Easily Accessible To The Public:

Hill End Chalk Pit (near Hitchin, 8 on map) is of national stratigraphic and international palaeontological importance.

The quarry is the type locality of the Hitch Wood Hardground at the top of the Chalk Rock. This hardground is exceptionally fossiliferous here, and has probably yielded more fossils of all groups (notably ammonites) than any other Chalk Rock locality.

Little Heath Pit (near Berkhamsted, 3 on map) provides a glimpse of the time, 2.8 million years ago, when the sea extended westwards and the Chilterns and much of Hertfordshire were under water

The beds of sands and gravels were first described by Charles Gilbert in 1919 as mostly beach deposits of Pliocene age.

The Ware Museum collection (7 on map) includes Ichthyosaurus ribs and vertebrae preserved in a nodule from the Oxford Clay.

That stratum was deposited about 160 million years ago, and is exposed at the surface around Ely, 50 miles to the north of Ware. The boulder was transported to Ware by the Anglian Ice Sheet some 450,000 years ago

Behind the hamlet of Water End (9 on map) lies the largest collection of active swallow holes (also called dolines) in the United Kingdom.

What could be more spectacular in a geomorphologic context than watching water literally disappear in front of your eyes in a gurgling vortex? They are the only ones in chalk that are a permanent feature of the landscape.

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