This was our first view of the 80 metre high limestone cliffs at Malham Cove. There used to be a waterfall over it at the end of the last ice age.
We climbed up steps to the limestone pavement on top of the cliffs. "I can't believe I'm standing where Harry Potter stood!" said the girl next to us. They used this location for filming The Deathly Hallows.
Limestone pavement is when the top layer of the old coral reef is eroded into blocks called clints. The deep gaps are called grykes. The grykes must be eroded by chemical weathering due to slightly acidic rain and by physical weathering - freeze/thaw. But they are so regular. Look at the lines running parallel to each other. I think that the weathering has happened along pre-existing weaknesses in the rock. I wondered if that had been caused by shear forces due to earth movements.
This is a map from the visitor centre. Apparently the limestone layer was bumped downwards by earth movements due to the North Craven Fault. Then the Middle Craven Fault was produced by earth movements that pushed the cliffs upwards. The cliffs are 80 metres high. It is about 3km between the faults. The Middle Craven Fault is supposed to be 36 km long. The volume of rock moved is thus about 9 billion cubic metres. The density of limestone is about 2500 kg per cubic metre. Thus it has a mass of about 20 billion tonnes. Think of a force that could shift that!
