Rory Walsh explores the Early Jurassic geology, the ‘fata morgana’ mist illusion and the legends beneath Glastonbury Tor
Long before the famous music festival, pilgrims had been visiting Glastonbury for centuries. Saint Joseph of Arimathea is said to have come to the Somerset town with the Holy Grail. Welsh chronicles identified Glastonbury as the Vale of Avalon, the mythical King Arthur’s burial place. Other local legends include accounts of druids, goddesses and ley lines.
Many of them involve Glastonbury Tor, a conical mound rising 158 metres above the surrounding flat fields. At the top, a stone ruin stands like a giant chess piece. St Michael’s Church was built in the 14th century. Today, only the tower remains. It replaced an earlier wooden church destroyed by an earthquake on 11 September 1275. The tremors were felt in London and Wales.
Glastonbury Tor’s historic Welsh name was Ynys Wydryn or Isle of Glass. From a distance, it can resemble an island rising through a sea of mist. The tor overlooks the Somerset Levels. Low-lying and damp, some areas are only 0.2 metres above sea level. When dense, cold air on the Somerset Levels becomes trapped beneath layers of warmer air, a temperature inversion occurs. This bends rays of light, creating an optical illusion that makes the tor seem to float above the horizon. Italian sailors named the phenomenon ‘fata morgana’ after the Arthurian sorceress Morgan le Fay.
Glastonbury Tor was formed in the Early Jurassic Period, 200–175 million years ago, when a large rock ridge spanned the Somerset Levels. Millions of years of weathering and erosion broke it up, leaving behind the toughest outcrops. Glastonbury Tor endured because of its hard sandstone caprock. An iron-rich spring at the base still infuses the sandstone with iron oxides, making the rock even stronger.
While natural elements created Glastonbury Tor’s distinctive shape, the hill was also touched by human handiwork. Finds in the soil include Neolithic flint tools and fragments of Roman pottery. Distinct terraces ring the tor’s slopes. Whether created for farming or fortification, their origins remain unknown. The clearest sign of human activity lies further downhill.
Around 6,000 years ago, Glastonbury Tor punctured a vast watery landscape of boggy lakes and fens. Early settlers on the Somerset Levels lived in crannogs — island settlements with dwellings constructed of reeds and timber. Piecemeal land drainage took place during the Middle Ages. When steam pumps arrived in the 1840s, swathes of the Levels were given over to pasture. King Arthur’s watery grave became a drier land of legends.
