SIMPLE GEOLOGY OF THE ISLE OF WIGHT
How did it get like this?
The Island's history really begins not with its people but with its rocks. The best place to begin to study of the geology of the I.W. is probably in Sandown Bay where the bones of huge reptiles can still be found in the Wealden Clays which, like all rocks in the I.W., were laid down - layer upon layer - as a sedimentary rock under water, probably a shallow lagoon, dating back nearly 140 million years ago.
Also, in these ancient rocks, are many plant remains and, at Hanover Point (near Brook), the remains of an interesting petrified fossil log jam can be seen at low tide - where the early trees have turned into a forest of lignite: this can also be found in, both, Alum Bay and Whitecliff Bay: the only place to find "coal" in the Isle of Wight!
Since then, the whole area we know as the I.W. has been covered by sea water, huge rivers or lakes and risen up again no fewer than seven times: examples of how the island mass has sunken and risen again are illustrated by the raised beach at Bembridge and the marine gravel laid down on the bottom of the Pliocene Sea but now found on top of Chillerton Down some 167 metres (548 feet) above sea level. At present it is thought to be sinking again - all of which can be more readily understood by a visit to the I.W. Museum of Geology. Here, can be found evidence of the actual fossils of Dinosaurs, Iguanadon etc., as well as huge ammonites and many other fascinating specimens. For over a decade an Indian Professor could be seen just under Culver Cliff in Sandown Bay, each summer, searching - very successfully, for fossils in the Wealden clays.
Over an immense period of time huge deposits of chalk were being laid down at a rate of about 2.5 cms (1") per 2,500 years; the depth of the chalk thus indicates a deposit period of over 50 million years. On top of this other layers of sand, clays and gravel have been deposited, some of which have been tilted giving near vertical sections and which can be seen as coloured rocks at both Alum Bay and Whitecliff Bay.
This tilting of the rocks was caused by incredible pressures within the earth's crust which led to a gigantic buckling of all the bedded layers of rocks - at a time when the Alps mountains were formed some 22 million or so years ago. From this Folding about 644 kms (400 miles) away the ripples led to the uplifting of what is known as the "backbone of the Isle of Wight" and which divides the Island into two distinct geological parts -Cretaceous - in the south and Palaeogene in the northern half - with a variety of drift deposits on top.
Study of the Island's rocks reflect the changing environment and once the sedimentary process was completed some 35 million years ago there began a further build up of these drift deposits of the more geologically recent Pleistocene period which, aside the high relief, defined much of the shape of the Island.