When most people think about rocks, they immediately conjour up a picture of hard, jagged igneous or metmorphic rocks, that give a dramatic setting to any landscape.
Essex, on the other hand, is not like that. We don’t have any mountains or volcanoes spewing out basalt or granite, but what we do have is just as facinating. If you look just a few meters beneath the surface, you will find sands and gravels that are slowly giving up their secrets about what happened to Essex during the last few glaciations – a time span of a few million years. During the intervening interglacials, these same layers have yielded fossils which have contributed greatly to our understanding of the ecosystems that flourished in these (geologically) brief interludes.
If you dig even deeper below the surface you will find evidence of what was happening, not just hundreds of thousands of years ago, but millions of years ago. Here, we encounter sands, clays, chalk and flints which are of world-wide importance in trying to make sense of what was happening to the world in general during the last 100 million years. Amongst other things, this is the time frame that encompasses the demise of the dinosaurs.
After a while, the student of Essex geology becomes aware of Essex’s pivotal role as an ‘edge land’ – a part of the world which has been subjected to a neverending series of inundations followed by withdrawals of the sea. This seesaw between land and sea has been in progress for hundreds of millions of years, and is still visible today, as the present day coast line of Essex is completely unrecognisable to that which existed even ten thousand years ago – and its still changing.
The interplay between the deep geology of Essex and its role as an ‘edge land’ has produced the surface geology illustrated below.
The story of how the present day rocks of Essex came to be is a facinating one. The outlines of story are captured in the following slide presentation, but please forgive the pun when we say that excellent as the presentation is, it only succeeds in scratching the surface!