Edinburgh Castle

There is nothing unusual in the fact that Edinburgh has a castle in the middle of the city. Almost every European medieval city has one. Back in the day, you don’t have a formidable fortress to protect your settlement – you don’t have the settlement, as simple as that. What is unique about Edinburgh Castle, is that it sits on an extinguished volcano. Or, technically speaking, on a volcanic plug, which is even more unique. What happens is, magma, being liquid rock, sometimes solidifies within the vent of an active volcano, becoming one big boulder effectively plugging it. Then, over millions of years, erosion grazes off the volcano’s walls and leaves only the plug itself sticking out like a stand-alone rock. In case of Edinburgh Castle, the force that stripped off the mountain around the plug was a glacier. It was leaving the area at the end of the Ice Age, moving east and going over the volcano. The glacier sheared off pretty much anything that wasn’t solid basalt from the west side of the volcano, and left a long, elevated trail of debris to the east of the plug, making a ridge. Those specific formations are so common in this part of the world that they have a special name among geologists – a crag and tail formation. The crag in our case is standing in the middle of the otherwise level plain, providing perfect visibility over the surrounding area and easily defensible steep cliffs. No wonder, people realized these advantages from the early times, and settled on the top of the crag, now called Castle Rock, since 1000 BC. And this is when the story of Edinburgh Castle begins.