Geology
The Isle of Wight is made up of a wide variety of different rock types ranging from Early Cretaceous times (around 127 million years ago) to the middle of the Palaeogene (around 30 million years ago). The northern half of island is mainly made up of Tertiary clays, with the southern half formed of Cretaceous rocks (the chalk that forms the central east-west downs, as well as Upper and Lower Greensands and Wealden strata).
All the rocks found on the island are sedimentary – made up of mineral grains from previously existing rocks. These are consolidated to form the rocks that can be seen on the island today, such as limestone, mudstone and sandstone. Rocks on the island are very rich in fossils and many of these can be seen exposed on the beaches as the cliffs erode.
Cretaceous rocks on the island, usually red, show that the climate was previously hot and dry. This provided suitable living conditions for dinosaurs. Dinosaur bones and footprints can be seen in and on the rocks exposed around the island's beaches, especially at Yaverland and Compton Bay. As a result, the isle has been nicknamed Dinosaur Island.
Along the northern coast of the island there is a rich source of fossilised shellfish, crocodiles, turtles and mammal bones. The youngest of these date back to around 30 million years ago.
The geological structure is dominated by a large monocline which causes the marked change in age of strata from the northern younger Tertiary beds to the older Cretaceous beds of the south. This gives rise to a dip of almost 90 degrees in the chalk beds, seen best at the Needles.
About 10,000 years ago, the great ice sheets of the last Ice Age melted and the sea level rose. Probably about 7,000 years ago, the Isle of Wight became separated from the mainland.
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