David Keys, The Independent, 16 August 1988
Most of north Britain appears to have been rendered uninhabitable more than 3000 years ago by a catastrophe resembling the "nuclear winter" that some scientists believe would follow a nuclear war.
Research by archaeologists in Scotland and Northern Ireland suggests that the population of the northern half of Britain was reduced by more than 90 percent by a volcanic eruption that hurled vast quantities of dust into the atmosphere, partially blotting out sunlight and causing climatic changes that made agriculture impossible in upland areas.
The volcano responsible was Mount Hekla in Iceland. About 1150 BC, it erupted and spewed an estimated 12 cubic kilometres of volcanic dust into the stratosphere.
Research by two British climatologists, Dr. Chris Sear and Dr. Mick Kelly, of the University of East Anglia climatic research unit, suggests that the dust veil may well have created an area of low pressure and low temperature over the British Isles. This, the research indicates, led to extremely high rainfall, which combined with cold weather, would have made agricultural life impossible in areas such as the Scottish Highlands, the southern uplands, the Pennines, the Lake District and Wales.
"The evidence shows that nothing short of an environmental catastrophe on the scale of a nuclear winter took place in the latter half of the twelfth century BC," according to the Scottish Historic Buildings and Monuments Central Excavation Unit.
The catastrophe was so sudden and severe that it appears to have forced hundreds of thousands of people to leave their upland homes to seek a new life in the already inhabited valleys and lowlands.
Widespread warfare would have followed – and in the latter half of the twelfth century BC, valley settlements start to be fortified. As populations competed for food, conflict would have spread and large numbers of displaced people would have exerted pressure on neighbouring tribes. There may have been a "domino effect" over a considerable period, with each displaced group displacing its neighbours. In general, in northern Britain the tribal "dominoes" would have tended to fall in a southerly direction – the direction in which most agriculturally viable land existed.
The dramatic worsening of the weather after the eruption of Hekla appears to have been the final blow that rendered many of Britain’s upland areas uninhabitable.
Scotland was the hardest hit. For several centuries before the eruption, the Scottish Highlands had been under severe environmental stress as a result of long-term climatic changes; but only when all of or most harvests began to fail would upland settlements have become impossible.
Archaeologists have considerable evidence that a catastrophe hit northern Britain in the twelfth century BC and that some undefended lowland or valley settlements suddenly became fortified at around the same time.
- At Strath of Kildonan, Caithness, excavations revealed that 80 hamlets – a total of about 1000 huts – were suddenly deserted by their inhabitants.
- On the south-west corner of the isle of Arran, five small villages were deserted and replaced by a single fortified settlement.
- On the island of North Uist, 15 villages and hamlets were abandoned.
- At Dryburn Bridge, a lowland site in East Lothian, the inhabitants fortified their settlement.
- At Eildon Hill, in the Scottish Borders, and at Broxmouth, East Lothian, the inhabitants of open settlements built sturdy palisades to protect their villages.
Evidence for the Hekla eruption and its disastrous climatic effects has been discovered in three places: under the surface of the Greenland icecap, in Irish peat bogs, and on the Scottish islands.
In Greenland, the eruption’s acid fallout remains to this day, forming a datable layer on what was the twelfth century BC icecap surface, more than 1800 feet under its present surface.
In Ireland, an examination of tree-ring data from ancient oaks buried in peat bogs has revealed that tree growth slowed down dramatically at times of major northern hemisphere volcanic eruptions, including that of Hekla at around 1150 BC. The vital tree-ring discoveries were made by Dr. Michael Baillie and Dr. Martin Munro of the palaeoecology centre at Queen’s University, Belfast.
In the past few weeks, on the Hebridean island of South Uist and in Shetland, a joint team from Edinburgh and Sheffield Universities has unearthed a layer of tephra – volcanic dust – which fell from the sky at the time of the Hekla eruption.