Around 8,150 years ago, the continental shelf off Norway collapsed and sent a mega-tsunami roaring across the North Sea. Evidence of the Storegga landslide on the Norwegian seabed – silent testimony to the three giant waves that crashed onto the shores around the North Sea, including the shores of Britain – have been identified. So has a lost land named Doggerland, a low-lying landmass that had lain between the United Kingdom and the Continent.
Understanding the mechanics of the Storegga Slide, and what damage the ensuing tsunamis did, matters less because it’s just interesting and more because it’s expected to happen again.
Now, a team mapping the North Sea floor off Britain reports on its findings in the journal of Antiquity. Lead author James Walker and Prof. Vincent Gaffney of the University of Bradford and colleagues add nuance to the crudely drawn picture, debunk a number of assumptions about Doggerland, its demise, and the impact of Storegga-type tsunamis on the coast of prehistoric Britain – where people on high land with a view of the sea would have seen the horror, but survived.
In fact, a chunk of the original landmass, which the authors call “Dogger Island,” apparently survived above the waves for centuries after the Storegga cataclysm. So did a huge tract of land the size of Wales, now submerged off Britain’s eastern coast, which the authors dub the “Dogger archipelago.”
In other words, the paradigm that the monster tsunami drowned Doggerland, its inhabitants and animals, and the northeastern coasts of Britain too, is at the least crude and inaccurate, the team suggests.
Working in the North Sea is abominable, landscape archaeologist and co-author Prof. Vincent Gaffney confides in Haaretz. "It’s cold and gray, and one can’t dive seriously in that water," he says.
For their great mapping project of landscapes at the bottom of the southern part of the North Sea – which, among other things, can indicate how the tsunami “behaved” when it hit Britain – the archaeologists availed themselves of seismic data from the oil and gas industry, as well as “dropping” cores deep into the sediment. Mediterranean Sea, we Israelis newly appreciate your charms.
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Anyway, in the area of the Dogger Archipelago off eastern Britain, their groundbreaking work has identified thousands of kilometers of paleo-riverbeds and streambeds, lakebeds, valleys and now-submerged marshland, Gaffney says. “It’s the largest prehistoric landscape in Europe,” he says, adding: “The landscapes we’ve mapped were bigger than some modern countries, before their inundation.” And they changed perceptions about Doggerland.
The myths of Doggerland
All this is key to understanding just what the Storegga Slide did to Doggerland, Britain’s eastern coastline and the Megalithic peoples living on both.
People assume that Doggerland was a great hulking (if low-lying) landmass between Britain and Continental Europe, and stayed that way until it was drowned by the tsunami. Not so.
Indeed, when ice levels were high and sea levels were low during the Ice Age, Doggerland was a land bridge between Denmark and Yorkshire. But people were not crossing that land bridge. Doggerland also would have been covered by glaciers and would have been uninhabitable.
As the glaciers retreated, Doggerland greened and it was gorgeous by the Mesolithic: thronged with plants, animals – and humans too, of whom evidence has been dredged up from the seabed. In fact, that’s how Doggerland was discovered: a fishing trawler dragged up a prehistoric harpoon from the seabed in 1931.
But throughout the period of plausible human habitation on Doggerland, it was shrinking. Following the Last Glacial Maximum about 16,000 years ago, deglaciation has been raising sea levels (and still is). By the time the Storegga tsunamis struck 8,150 years ago, all that remained of the great vaunted Doggerland was a small island, the new paper suggests – even though the level of the land would have risen after its glacier mass melted. (Heavy ice causes landmasses to sink; when they melt, the landmass may rise.)
The part we know today as Dogger Bank may have sunk below waves even before the tsunamis; and the part nearest Britain had been reduced to “essentially a big lump of land” off the eastern coast.
By around 9,000 years ago on the British coast, the rapidly rising sea levels – possibly as much as 4 meters, or 13 feet, in the space of just 200 years – would have reduced the uplands to islands, the authors say. That’s what the tsunamis hit there: islands. Nor did the tsunami, as some think, sever England from the Continent: that was caused by the rising sea levels of climate change.
It seems Dogger Bank may have protected these islands to its south. The highest terrain, as much as perhaps 1,000 square kilometers in area, may have been partly spared the battering, the authors say.
“If you were on the shore, it was not a good day for you,” the professor chuckles. But in higher areas (on the coast), the water would have retreated – because that’s what even the nastiest of tsunamis do: they race inland and then retreat. Some parts may not have been flooded at all. In the coastal section they call the archipelago, the tsunami was channeled down the glacial valleys, which took the water as much as 40 kilometers inland, based on deposits the team studied.
Following the archaeologists’ landscape reconstruction from the early Holocene (about 12,000 years ago) of Doggerland to the east and west, they think the story didn’t end with a bang but with a whimper. “Ultimately, it was climate change that killed Doggerland,” Gaffney sums up. By 7,000 years ago, the last of that wee island was under the waves and ditto the “Dogger archipelago.”
And some people would have survived. Perhaps, Gaffney speculates, some fully realized what it portends when the “ocean disappears” – that strange retreat of the water as a tsunami builds up force offshore. Maybe some managed to rush to high land. Maybe, maybe not. It is true that Mesolithic hunter-gatherers weren’t stupid: they were us without the Wikipedia entries on tsunamis. But how fast could they have escaped?
In any case, the team’s topographical analysis shows there were high lands that would have remained dry, from which people could have observed the madness raging below. And when it was all over, they would have returned to the land, picked up the pieces, reclaimed the land and carried on.
Until the rising seas drowned Dogger Island and the Dogger archipelago once and for all, a good 1,150 years after the Storegga cataclysm.
The shelf collapses
A key import of this work is that until we understand what Doggerland is, we cannot understand what the Storegga Slide did.
During the Storegga Slide, 3,200 cubic kilometers of land were displaced – an area greater than Scotland. In recent years, impacts of the ensuing tsunamis have been located all along the British coast north of Doggerland and elsewhere around the North Sea, though it’s difficult to identify underwater scars of even a mega-catastrophe thousands of years ago.
Even identifying the scars on land isn’t as easy as one might think: tsunamis may wash away their own evidence as they pull back! And cultural debris may be cleared away or utilized by returning people, or simply missed.
Making life even more complicated for researchers, the Storegga Slide coincided with the peak of the cold snap 8,200 years ago. Distinguishing which disaster caused what damage is another difficulty, the authors point out. They also note that while we assume the coastal areas 8,200 years ago were thronged with hunter-gatherers, such people left behind little material evidence even if they had permanent settlements. To date, only two Mesolithic sites on the British coast have been confirmed as underlying Storegga deposits, and only a few have been identified as being associated with the tsunami deposits.
As the authors put it: “The Storegga tsunami exemplifies the paradoxical scenario … whereby archaeological evidence for the impact of an unusually destructive force upon extant cultures remains elusive.”
As we said, all this matters because the Storegga Slide was not a one-off and it will pretty surely happen again. Some day. We don’t know why, but it appears that the mid-Norwegian continental margin has a nasty habit of sliding every 100,000 years or so. And so tsunamis thusly triggered will also recur. That is the key motivation behind mapping the damage.
The pre-Storegga slides of that kind were in deep time and we can’t predict when another may happen. In our lifetimes? Maybe, maybe not, but the Dutch – speaking of low-lying lands – are taking the thought of obtaining knowledge about it seriously, the professor notes.
Moreover, uncongenial as it may be, the North Sea has become crucial to the European economy – first for the fossil fuels found in its seabed, and now because of massive wind farms being erected there. Tsunamis might spare the terrified people on high enough hilltops, but they won’t spare industry. The more we know about the North Sea, its seabed and its history, and realize that it isn’t a constant but a dynamic environment, the better we may be able to weather future trouble.
As Gaffney has pointed out before: extreme events are not the fief of the past, but lie in our future as well.