Isle of Wight Nostalgia - Geology - a brief introduction


Geology is a fascinating subject which can be enjoyed by most of us. It can at first appear complex, especially when an account is incomplete or is only half the story. While I cannot possibly relate the entire Earth Story here, I hope this page enables the reader to gain a basic understanding about the formation of the earth - which will in turn enhance your understanding of the geological features of the Island. This page could be written as a book or even several volumes so you will appreciate this is a very top-level account. There are scientific 'proofs' or theories which back up what I have written here. What is interesting is that most of the proofs come from branches of science which have nothing at all to do with Geology. The BBC book 'Earth Story' covers these ideas in more detail and if you are interested in the subject I recommend this book (click on the bookstore below for details).

To begin ...

The earth was formed 4,500,000,000 years ago - I'll skip how this is thought to have occurred - however the earth at this time was molten rock. The surface started to cool and solidify however extensive volcanic activity created a surface of lava rock. Below the surface, at greater pressures and temperatures the lava cooled slowly to form Granite. Thus the first rocks to be created had volcanic origins and are referred to as igneous rocks. Weathering and chemical reactions soon began to erode these rocks. The eroded material was carried to the lower levels by wind, rivers etc. where they began to accumulate in rivers, lakes & oceans.

Sea level change

We are sometimes concerned about small rises in sea level affecting our coastline. However over geological time, sea level has altered considerably. In some cases this has been due to landmasses sinking and rising - in other cases due to water freezing and accumulating at the polar caps. Depending on the depth of water at the time, different sedimentary rocks formed from the eroded materials deposited there. These sediments, when subjected to the pressure of the water above them, formed solid rocks.

The twisted earth

The solid earth is in fact being twisted and transformed by immense pressures. Entire continents form plates which literally move around. As one landmass is pushed or pulled from another, the land is slowly twisted and buckled. This manifests itself as earthquakes. Over millions of years the extent of this twisting can be awesome as we shall see.

The age of rocks

How old are rocks? Clearly the material from which they are formed is of the same age; However geologists can measure the age when rocks were transformed into their current states. Due to the twisting and buckling we can see many different rocks on the surface of the planet, each formed at different points during the evolution of the earth. Rocks contain fossils of those animals, insects, plants etc. that existed at the time the particular rock was formed. So investigating the surface of an area can provide an insight about the age of the surface rocks at each location - and suggest the type of fossil that the rock might yield.

Isle of Wight

Many geology books about the Island skip much geology relating to the first 99% of the earth's life as the rocks on the surface of the Island are relatively new. In fact all Island rocks are sedimentary and were all formed during the most recent 1% of the Earth's history. I hope this short account fill some of the gaps. You will see from the various geological pages on this site that despite the newness of the Islands surface, the geology is nonetheless truly amazing. This is due to the twisting and buckling described above and followed by yet more erosion - it has exposed a wide and interesting variety of different rock types, representing various geological times from the dinosaurs to the present.

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