In 2024, researchers from Australia’s College of Queensland found a large 1,200-tonne rock greater than 200 metres inland on the island of Tongatapu.
Positioned within the island’s dense jungle, the rock measures 4 x 12 x 6.7 metres, and stands out as a geological anomaly on the southern coast of Tongatapu.
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As a part of a brand new examine, researchers have traced the origin of the Maka Lahi Rock to an enormous tsunami occasion that struck the island 7,000 years in the past. By means of 3D modelling and comparisons of the composition, they recognized the rock’s origin to a cliff face positioned 30 metres above sea degree alongside the island’s shoreline.
When the tsunami hit with wave heights exceeding 50 metres, the Maka Lahi Rock was dislodged from the cliff-edge origin and moved to its resting place 200 metres inland, making it the world’s largest recognized cliff-top boulder.
“It constitutes the earliest recognized Holocene tsunami within the Pacific, providing new insights into the long-term historical past of utmost wave occasions within the area. The Maka Lahi rock additionally represents the biggest cliff-top boulder and one of many largest coastal boulders globally,” mentioned the examine authors.
The examine additionally supplies a warning to the catastrophe planning on Tongatapu, because it demonstrates that it’s doable for a tsunami to envelope the island in areas of 30–40 metre elevation, requiring future issues to be given to the island’s tsunami evacuation maps.
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Co-author Dr. Annie Lau, a coastal geomorphologist, emphasised Tonga’s vulnerability to tsunamis triggered by seismic exercise alongside the Tofua Ridge and Tonga Trench. “Understanding previous excessive occasions is vital for hazard preparation and threat evaluation now and sooner or later.”
Header Picture Credit score : College of Queensland
Sources : University of Queensland
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