The geology of the Isle of Wight has attracted geologists for over two hundred years. In this small area one can begin to learn about the geological history and landscape development of southern England.
The north of the island is dominated by tertiary clays of the Palaeogene era (70-30 million years ago). The sands and clays of this period have formed the undulating landscape of the northern coastal plain.
The centre of the island mainly comprises a huge chalk ridge, which runs east to west across the island and is the deepest bed of chalk in Britain. This rock formation was formed around 65 million years ago. Chalk is formed from the mineral remains of tiny marine organisms in the sea and is chemically relatively pure calcium carbonate. It contains minute fossils that can be seen under a microscope.
The oldest rock formations on the island, found to the south of the chalk ridge, are from the Cretaceous period; the earliest of these are the Wealden Group, which were formed between 127 and 121 million years ago. The Wealden Group is composed of alternating sandstones and clays.
The cliffs at Yaverland, at the eastern end of Sandown Bay, offer one of the best opportunities to observe the meeting of the Wealdon Group sandstones at Redcliff, on the left, with the chalk at Culver Cliff, on the right. Both of these rock formations are sedimentary rock.
Formation of Sedimentary Rocks
A river carries, or transports, pieces of broken rock as it flows along. When the river reaches a lake or the sea, its load of transported rocks settles to the bottom. The deposited rocks build up in layers, called sediments. This process is called sedimentation. The weight of the sediments on top squashes the sediments at the bottom and the water is squeezed out from between the pieces of rock and crystals of different salts form. The crystals form a sort of glue that sticks or cements the pieces of rock together. This process is called cementation. The stronger the cementation the stronger the rock.
Your tasks
To log this cache, you will need to complete the tasks below. Please message us with the info (rather than post it on your log). You can log a find once we have been sent a message. We may delete your log if your answer is way off the mark. You do not need to go down onto the beach for this Earthcache.
- With your back to the pier, look across the beach towards the cliffs. Describe the appearance of Redcliff and Culver Cliff. (different colours, visible layers, etc)
- Estimate the height of Culver Cliff, at its highest point.
- The cliff to the left is more prone to landslides and the one on the right is more prone to rock falls. Why do you think this is? (hint, cementation)
- Culver Cliff is at the eastern end of the island's chalk ridge. Do a little research and find out what is at the western end.
- As an optional extra, post a picture on your log of yourself and / or your GPSr at this end of Sandown Bay.