This lonely headland between Edinburgh and Berwick is said by some to be the most important geological site in the world. It was the evidence that James Hutton needed 250 years ago to prove that the world is far older than the 6000 years claimed by interpreters of the Bible. He'd been watching the erosion of rocks on his farm and the deposition of sediment. He realised that sediment forms in horizontal layers with the youngest on top. The sandstone in the top picture is almost horizontal, just tilted slightly towards the sea. But look at the vertical layers in the picture below:
The rock in the vertical layers is greywacke. This was formed when there were avalanches of debris down the edge of the continental shelf into deep water. The rock is formed of coarse grit and is hard enough to resist erosion. Between the avalanches, layers of fine mudstone formed and these have been worn away to leaves the gaps you can see. Hutton realised that the greywacke formed first because it is under the sandstone. Earth movement tipped it on edge and then it was eroded. Later the sandstone formed. The lowest sandstone layers even have greywacke pebbles in. The unconformity shows that the rocks on Earth were not produced in one seamless event. The events described don't take 6000 years.
