by Kate S. Zalzal Monday, March 20, 2017
England’s iconic White Cliffs of Dover tower 100 meters over the English Channel and, historically, were often the first and last view of England for sea-faring travelers. New research investigating the erosion history of the steep chalk cliffs suggests that they have been retreating far faster over the last 150 years than they once did.
Scientists measured beryllium-10 concentrations in rocks on the coastal platforms at the base of the cliffs. The beryllium — which is produced when cosmic rays bombard oxygen in exposed rocks — acts as a “rock clock”: The longer the rocks are exposed, the more beryllium-10 accumulates.
Using the measurements, the researchers determined the likely pace of coastal retreat over time dating back nearly 7,000 years. They found that retreat rates between 2 and 6 centimeters per year prevailed for most of the Holocene, but that significantly higher rates of retreat began 200 to 500 years ago. Historical records indicate that retreat rates have recently increased even faster, with erosion estimates of 22 to 32 centimeters per year during the last 150 years.
“What we’ve seen in this case is that the erosion has taken a big leap in the last few hundred years,” said Martin Hurst of the University of Glasgow in Scotland, lead author of the study published in Proceedings of the National Academy of Sciences, in a statement.
Hurst’s team did not explore in the study why cliff retreat has accelerated, but the researchers suggested in the paper that it could have started due to increased storminess associated with the climatic conditions of the Little Ice Age and continued because of beach thinning linked to human engineering and intervention projects on nearby coastlines in recent decades.
As sea levels rise, cliff erosion is likely to be an increasing threat to people and infrastructure along the coast of England, the team noted. “[This study] could help authorities make more informed decisions about coastal management,” Hurst said.
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