Basalt, the Edinburgh volcano

These photos show the remains of a 325 million-year-old volcanic island where the city of Edinburgh now stands. Only the lower parts of the volcano are now preserved after erosion.

This was one of many active volcanoes in the central Scotland Rift Valley during the Devonian and Carboniferous periods (around 300 to 400 million years ago), whose remains now form hills along the edges of the Scottish Lowlands.

 
1. Salisbury Crag - an ancient sill
2. Arthur’s Seat - core of the volcano
3. Castle Hill - a volcanic plug, once the vent of a parasitic cone