Edinburgh castle is built on a granite plug. A volcano erupted in Edinburgh millions of years ago. The volcano became blocked when molten magma cooled and solidified within the vent. Millions of years later the sea level rose and sedimentary rocks were laid down. As the sea level fell again, the softer sedimentary rocks were eroded away leaving the more resistant granite plug as a higher area of land. This became an ideal defence site and a castle was built.
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- First broadcast:
- 21 February 2008
The students could plan what they would use the volcanic plug feature in the landscape for, should the castle not be on there. They also could look at the concept of hard and soft rock, and be given photographs to determine the hardness of the rock and why. Students could also list the advantages and disadvantages of living near an active or extinct volcano.