Darwin - FDC

On Ascension it was the geology that interested Darwin, recording his experiences and findings in the third chapter of his ‘Volcanic Islands’. Of particular interest was the Devil’s Riding School, shown on the First Day Cover. Situated on the South Westerly part of Ascension, evidence has revealed that there once was a lake but it dried out and subsided in the centre due to volcanic eruptions. Darwin visited the area and collected samples from a layer of pinkish pumiceous ash, which was full of the siliceous remains of diatoms and 25 other types of plant material; evidence to show the lake had existed. It was later discovered by other geologists that the volcanic ash beds were composed of finely pulverized rock in sub-horizontal bands of white, pink and buff colour, representing successive discrete phases of eruptions. One layer contains the curious concretions called ‘Devil’s Eyeballs’ by islanders, and another containing the abundant remains of organic life. Darwin was fascinated by the area and that’s why it has become a place of Outstanding Natural Beauty and Geological Interest.