New research indicates that the Maka Lahi boulder in Tonga was likely moved by a massive tsunami approximately 7,000 years ago. The study, conducted by the University of Queensland and published in May 2025, provides valuable insights into the region's history of extreme natural events and helps in assessing future risks.
The 1180-tonne limestone boulder, known locally as "Big Rock," is located 39 meters above sea level. Researchers created a 3D model of the boulder and identified its origin point on a cliff more than 30 meters above sea level. Numerical modeling suggests that waves around 50 meters high, lasting approximately 90 seconds, would have been necessary to move the boulder over 200 meters inland.
Dr. Annie Lau, a co-author from the University of Queensland, highlights that Tonga has a history of tsunamis caused by volcanic eruptions and earthquakes. Understanding these past events is crucial for preparing for future hazards and improving coastal-hazard assessments in tsunami-prone regions. The research emphasizes the importance of analyzing geological evidence to enhance these assessments.