Buzz
As Buddhist nun Pema Chödron eloquently expressed, “Everything—every tree, every blade of grass, all creatures, humans, structures, and even inanimate objects—is in a constant state of transformation.” While geological changes often occur over timescales imperceptible to us, some transformations are rapid. Recent studies indicate that the chalk cliffs along England’s southern coastline are eroding at a rate 10 times faster than in the past. These findings were detailed in the Proceedings of the National Academy of Sciences.
The stunning Seven Sisters cliffs, with their sweeping curves along the British coastline, are a magnet for tourists and photographers. Despite their tranquil beauty, these cliffs pose significant risks.
Chalk, being one of the softest minerals, is highly susceptible to erosion, particularly under the relentless force of ocean waves. The area has experienced major landslides, including significant events in 1999 and 2001, and a dramatic cliff collapse in May 2016 that sent massive amounts of rock tumbling into the sea. (“While we encourage visitors to enjoy East Sussex’s stunning coastline,” the Seven Sisters Country Park website advises, “we remind everyone to prioritize their safety and exercise caution.”)
Coastal erosion has emerged as a critical concern in an era of rising sea levels. The challenge lies in analyzing phenomena that, by their very nature, have disappeared. Even massive rockfalls eventually disintegrate and are dispersed by ocean currents.
However, traces of the ancient coastline linger in the remaining rock formations. Geologists employed a method known as cosmogenic nuclide dating, which assesses cosmic radiation levels in rocks to determine their age and exposure duration. This technique helps reconstruct the rock's movement and transformation over time.
The white cliffs are interspersed with durable, chemically stable flint—a rock that serves as a more reliable historical record than the softer chalk. Researchers collected flint samples along a transect from the cliff face to the shoreline, ensuring a comprehensive analysis.
The flint samples were ground into fine particles and analyzed using a cosmogenic nuclide array to uncover their age and geological history.
Using this data, the team incorporated it into a coastal erosion model, enabling them to estimate the cliffs' erosion rates over thousands of years.
The study revealed that the coastline is eroding rapidly, though this accelerated pace is a relatively new phenomenon. Historically, the cliffs eroded at a consistent rate of 2 to 6 centimeters annually, as noted in the research. However, in recent centuries, this rate has surged dramatically, now reaching 22 to 32 centimeters per year.
The exact cause of this shift remains uncertain. One potential factor is natural climate change, particularly during the Little Ice Age from the 14th to 19th centuries, when wave activity intensified. Additionally, the cliffs have grown more susceptible to erosion over the past few centuries due to the depletion of protective sediment by ocean currents and human interventions.
