The story of this record begins in 1973, when the late Emeritus Professor Bob Kirk of the University of Canterbury initiated a monitoring program on the Kaikōura Peninsula’s shore platforms. What started as an exercise in curiosity about how rock coastlines operate has since blossomed into an invaluable scientific legacy, carried forward through the decades by successive generations of researchers armed with increasingly sophisticated techniques. Professor Wayne Stephenson, from the University of Otago’s School of Geography, is among those who have continued this work, and he explains that the peninsula’s unique geological setting made it an ideal natural laboratory for understanding the interplay between tectonic forces and coastal processes.

When the 7.8 magnitude earthquake struck in November 2016, it lifted the Kaikōura Peninsula by approximately one metre. This sudden uplift had dramatic consequences for the coastal landscape: sections of the shore platform, previously shaped by the daily rhythms of the tides, were thrust out of the intertidal zone entirely, and a brand new marine terrace was created in a matter of moments. For geomorphologists, the event represented an extraordinary opportunity—an accidental experiment in tectonic coastal evolution, witnessed by a monitoring program that had already been running for more than forty years before the earthquake occurred.

The latest results from the ongoing monitoring effort reveal something unexpected: erosion rates on the newly uplifted surfaces more than doubled after the earthquake. This finding challenges assumptions about how coastal landscapes respond to tectonic events and provides, according to Stephenson, a rare and valuable example of how tectonics can reshape rock coasts in real time. “This shows that major earthquakes can rapidly alter the way coastlines evolve and provides a rare example of how tectonic events reshape rock coasts,” he says.

The significance of the Kaikōura findings extends far beyond the shores of New Zealand’s South Island. More than half of the world’s shoreline consists of rock, and coastlines in tectonically active regions are regularly uplifted by earthquakes. New Zealand, Japan, Chile, Alaska, the western United States, and the Mediterranean all experience coastal uplift events of the kind that transformed Kaikōura in 2016. While the specific erosion rates measured at Kaikōura are particular to that location’s geology and wave climate, the broader principles revealed by the study apply to rock coasts around the globe, offering insights into how these landscapes respond when tectonic forces suddenly redefine the boundary between land and sea.

Perhaps most strikingly, the researchers believe they are the first to provide direct measurements of coastal erosion processes both immediately before and after a major uplift event. This before-and-after perspective is exceedingly rare in the earth sciences, where events like large earthquakes typically occur without warning and without instrumentation in place. The Kaikōura record, however, captured the baseline conditions against which the post-earthquake changes could be measured with confidence, allowing the researchers to document dramatically altered erosion rates and processes with an authority that few other studies could claim.

But the research has also produced a finding with profound implications for how scientists reconstruct earthquake histories. The evidence of past earthquakes may disappear much more quickly than previously assumed. The uplifted coastline at Kaikōura began eroding rapidly after the earthquake, suggesting that newly formed marine terraces—features that geologists have long used to identify and date past seismic events—may not survive long enough to preserve a complete geological record. “The evidence for the 2016 event will disappear quickly and not be preserved,” Stephenson warns. In other words, the very features that scientists rely upon to reconstruct the magnitude and frequency of ancient earthquakes may be ephemeral, eroded away within timeframes far shorter than the geological record would suggest.

This realization carries significant weight for seismic hazard assessment. Marine terraces have served as a cornerstone of paleoseismology in uplifted coastal regions, providing a tangible record of past earthquake events that helps scientists estimate the frequency and magnitude of future ones. If such terraces can be erased by accelerated erosion within decades or centuries rather than persisting for millennia, then the geological record of past earthquakes may be systematically incomplete. Real-time measurement, the researchers argue, becomes all the more critical for understanding seismic hazards in coastal regions, precisely because the physical evidence of individual events may vanish before it can be properly documented.

Dr Sophie Horton, Senior Lecturer from the University of Canterbury’s School of Earth and Environment – Te Kura Aronukurangi, Te Whare Wananga o Waitaha, and a co-author of the study, emphasizes that the observations at the Kaikōura Peninsula now provide researchers with an essential baseline for understanding erosion on tectonically active coastlines. “Following the earthquake, Kaikōura Peninsula is now on a different trajectory of re-establishing an equilibrium, which may progress for some decades into the future,” she says. The coastline is, in effect, adjusting to its new position, and the pace and pattern of that adjustment will shape the landscape for generations.

Horton also highlights the unique advantage offered by the long monitoring record: “The benefit of having measurements both before and after an event like this means that we are in a much better position to fine-tune models of tectonic coastline dynamics with these observed measurements; something that has not really been achieved anywhere else in the world.” Models of coastal evolution have long struggled to incorporate the sudden, dramatic perturbations that earthquakes impose on shorelines. The Kaikōura data now offers modelers an unprecedented calibration dataset—one that spans the pre-seismic equilibrium, the moment of tectonic disruption, and the ongoing post-seismic adjustment.

The study also improves scientific understanding of how earthquakes, erosion, and sea-level processes interact to shape rock coasts more broadly. These three forces operate on vastly different timescales: earthquakes act in seconds, storms and wave erosion act over years and decades, and sea-level change unfolds over centuries and millennia. Kaikōura provides a rare window into how these timescales intersect, showing that a single event lasting mere minutes can reset the trajectory of coastal evolution for decades to come.

Underlying all of this science is a human story of dedication and intellectual inheritance. The researchers are unanimous in their commendation of Bob Kirk, whose pioneering measurements in the 1970s laid the foundation for everything that followed. “Bob’s curiosity in the 1970s about how rock coastlines operate has left an invaluable legacy on the discipline, and it’s great to see the work still being carried out at Kaikōura all these years later with new techniques and new students,” Stephenson reflects. It is a poignant reminder that some of the most valuable contributions to science come not from dramatic discoveries, but from the patient, sustained accumulation of observations—work that may not reveal its full significance until decades later, when the Earth itself provides an unforeseen experiment.

As the Kaikōura Peninsula continues to adjust to its new elevation, the monitoring program established half a century ago carries on, documenting every change. In doing so, it continues to hold answers not only for New Zealand, but for the millions of people who live along the tectonically active, rock-bound coastlines of the world.

News Publication Date: 3-Sep-2026

Web References: Not provided

References: Fifty Years of Shore Platform Erosion Monitoring at Kaikōura Peninsula, South Island, Aotearoa-New Zealand, Earth Surface Processes and Landforms, https://doi.org/10.1002/esp.70360