A massive boulder perched hundreds of feet from the edge of a cliff in Tonga appears to have been transported by an ancient tsunami, making it one of the biggest rocks moved by a wave on Earth.
The boulder, which was discovered in 2024 on the southern coast of the Tongan island of Tongatapu, sits 656 feet (200 meters) inland from the cliff edge, at an elevation of 128 feet (39 m) above sea level. And it is enormous, measuring 45.9 x 39.3 x 22 feet (14 x 12 x 6.7 meters) and weighing over 1,300 tons (1,180 metric tons) .
It’s the world’s largest cliff-top boulder and was first identified by locals. “We had been surveying the southern side of the island of Tongatapu looking along the coastal cliffs at evidence of past tsunamis,” lead author Martin Köhler, a researcher at the University of Queensland in Australia, said in a statement. “We were talking to some farmers when they directed us to this boulder.”
But exactly how the big rock ended-up on a cliff was unclear. “I was so surprised,” Köhler said. “It is located far inland outside of our field work area and must have been carried by a very big tsunami. It was quite unbelievable to see this big piece of rock sitting there covered in and surrounded by vegetation.”
According to a new study published online on 21 April in the journal Marine Geology, the boulder — named Maka Lahi, which is Tongan for “big rock” — may have been deposited in its unlikely home by a huge tsunami that struck the island around 7,000 years ago.
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The researchers measured the boulder’s properties then modeled how large a wave would have needed to be in order to deposit such a large rock so far inland. They suggested that the boulder originally sat at the cliff’s edge, but was washed inland by a tsunami wave that lasted around 90 seconds and was up to 164 feet (50 m) tall – almost the height of Niagara Falls.
“We made a 3D model and then went back to the coast and found the spot the boulder could have come from, on a cliff over 30 metres above the sea level,” Köhler said.
Based on dating methods involving isotopes present in the rock, Köhler and colleagues believe that the boulder was likely washed to its current location a minimum of 6,891 years ago, plus or minus 97 years. This date aligns with evidence of a huge tsunami that hit on New…
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