The Isle of Portland sticks out into the English Channel and is attached to the mainland by Chesil Beach. It is subject to the full wrath of the storms that plague one the busiest shipping lane in the world. The cliffs of Portland are constantly under attack from the waves.
This diagram shows how the Isle of Portland is vulnerable to coastal erosion. The Sea erodes the Kimmeridge Clay and Portland Sand easily; this leaves the strong Portland Stone above to be undercut causing it to collapse. The Kimmeridge Clay underlies the Isle of Portland and as the clay is eroded away the coastline is continually causing landslides. The wind around Portland tends to be in a southwesterly direction, this drives the waves onto the West coast that is becoming increasingly eroded. Whilst the West coast is being eroded the natural barrier of the Isle of Portland is protecting the East coast. The quieter waters on the Eastern shore help form of a natural harbour.
Here you can see Portland Harbour, the bay behind is where the sailing for London 2012 Olympics will take place. You can see how if a strong Easterly storm struck the island it would cause a lot of damage to the less well-protected Eastern shore. At the southern point of the Isle of Portland there is potential for another land form to appear, one which is more famously associated with the most Western point on the Isle of Wight, The Needles.
The Needles are made up of chalk and were once attached to mainland Isle of Wight. Similarly to the creation of Lulworth Cove, it all started with a weakness in the rock which evolved into a cave, the arch of the cave would have fallen in creating the well known towers of stone. The key difference between Lulworth Cove and The Needles is that The Needles were formed on a headland, and Lulworth Cove was eroded inland.
The Diagram above shows how what resulted in a stump started as a cave. The cave is eroded away and enlarged until it eventually goes through the headland creating an arch. As time goes by the arch will be eroded and collapse into the sea leaving a stack, this is then further eroded away until all that is left is a stump, which in turn will be eroded away until there is nothing to show that land used to be there.
Key Words
Cave Arch Stack Stump Headland
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