Hidden coastal uplift in New Zealand caused by ancient earthquake

This groundbreaking study expands our understanding of New Zealand's geological history and highlights the lasting impact of ancient earthquakes on coastal species.
Abdul-Rahman Oladimeji Bello
Crashing waves on Whites Bay beach near Rarangi in Marlborough region, New Zealand
Crashing waves on Whites Bay beach near Rarangi in Marlborough region, New Zealand


Beneath the sun-kissed shores of New Zealand's Rarangi, a team of intrepid scientists from the University of Otago embarked on a quest to unravel the mysteries of the past. 

Armed with cutting-edge laser mapping technology and the remarkable clues hidden within the genes of bull kelp, they made a groundbreaking discovery: a concealed world of coastal uplift, silently molded by an ancient earthquake.

New Zealand, despite its rich history of geological exploration, still harbors enigmatic stories waiting to be unearthed—stories of earthquakes that have shaped the very fabric of the land. 

The researchers stumbled upon an unseen coastal bench, majestically perched one meter above the Azure Sea. It was a subtle testament to the seismic forces that had acted upon this land.

In a conversation with co-author Professor Jon Waters from the Department of Zoology, he emphasized the significance of this study in unraveling the mysteries of Aotearoa's landscapes and the consequences of seismic activity. 

"Rarangi is also a very popular summer swimming spot, rather than some obscure or remote location, and the evidence of coastal uplift was hiding in plain sight," Professor Waters says.

The research team utilized LiDAR mapping, an innovative remote sensing technology that accurately models ground elevation, alongside genetic analysis of bull kelp samples obtained from the uplifted coastline. 

Their meticulous examination revealed a previously unknown bench, approximately 3.3 feet (1 meter) above sea level, uplifted by an earthquake. 

The genetic analysis of kelp below the bench uncovered a significant anomaly. This indicated the extinction of the species in the area following the earthquake. Subsequently, the area was recolonized by kelp drifting from 186 miles (300 kilometers) to the south.

Estimating the time of the earthquake

Based on their findings, the researchers estimate that the earthquake responsible for the uplift occurred between 2,000 and 3,000 years ago. This remarkable discovery showcases the kelp's potential to serve as a geological record of disturbance events.

Surprisingly, the uplifted coastal zone in Rarangi is located near a well-known active fault. While previous researchers had quantified several major earthquakes in the vicinity, this specific area had previously eluded their attention. 

This research is part of an ongoing Marsden-funded project aimed at assessing the impacts of earthquakes on coastal species. The combined approaches of genetics and geology have proven highly effective in pinpointing this previously unknown site of coastal uplift in New Zealand.

It underscores the dynamic nature of the country and highlights how earthquake uplifts leave lasting signatures in coastal species.

As we continue to explore the intersections of genetics, geology, and remote sensing technologies, we can expect more surprising revelations about our planet's ancient events. 

The discovery in Rarangi serves as a testament to the potential for groundbreaking scientific discoveries hidden in plain sight, waiting for curious minds to uncover them.

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