Latest news with #Tongatapu
RNZ News
6 days ago
- General
- RNZ News
Dengue fever cases in Tonga rise to 815
A dengue outbreak was declared in Tonga on 19 February. Photo: Tonga Ministry of Health Tonga's Ministry of Health says 22 new cases of dengue fever were picked up in recent tests, bringing the total cumulative cases to 815. The majority of the confirmed cases are on the main island, Tongatapu. Five people were currently in hospital,all in a stable condition. There have been no new deaths following the three reported to date, according to the Ministry of Health. A dengue outbreak was declared in the kingdom in February. The disease is spread by mosquitos. Outbreaks have also been declared in Samoa, Fiji and Cook Islands. Sign up for Ngā Pitopito Kōrero, a daily newsletter curated by our editors and delivered straight to your inbox every weekday.
RNZ News
25-05-2025
- Science
- RNZ News
Research shows Tonga's Maka Lahi boulder's journey
Photo: Supplied New research theorises that Tonga's Maka Lahi boulder was moved more than 200 metres inland by a tsunami around 7,000 years ago. Maka Lahi , meaning "Big Rock", is a limestone boulder measuring 6.7 metres tall and 14 metres wide, and weighing approximately 1180 tonnes. It is the second-largest boulder in Tonga, after Maui Rock , and sits at an elevation of 39 metres. The University of Queensland's School of the Environment PhD candidate Martin Köhler is one of the authors of the study published in Marine Geology . He said that he and his team were directed to the boulder local farmers. "We had been surveying the southern side of the island of Tongatapu, looking along the coastal cliffs at evidence of past tsunamis," Köhler said. "[The boulder] is located far inland, outside of our field work area, and must have been carried by a very big tsunami. "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." The researchers used numerical modelling to establish that wave heights of around 50 metres, and lasting around 90 seconds, would have been needed to dislodge it from its cliff-edge origin and move it to its resting place. This suggests its emplacement "likely resulted from a landslide-triggered tsunami event", researchers said. Several wave-transported boulders (weighing 0.6-1555 t) had previously been reported on Tongatapu. "The exceptional characteristics of the Maka Lahi boulder, including its dimensions, estimated mass of approximately 1180tn and its high elevation, rank it among the three largest coastal boulders globally and the largest cliff-top boulder in the world." Co-author Dr Annie Lau said Tonga had a long history of tsunamis triggered by volcanic eruptions and earthquakes along the underwater Tofua Ridge and the Tonga Trench. "The findings we have reported on the Maka Lahi boulder are the evidence of a tsunami in the Pacific region in the Holocene epoch, which began around 11,700 years ago," she said. "Understanding past extreme events is critical for hazard preparation and risk assessment now and in the future." The study said like other coastal boulders on Tongatapu such as Maui Rock on the west coast and the Haveluliku boulders on the east coast, Maka Lahi is also interpreted within a mythological framework as one of the " Maui throwing stones" believed to be deposited by the demi-god Maui , while chasing chicken(s) from 'Eua to Tongatapu, as described in a Tongan legend.
Forbes
22-05-2025
- Science
- Forbes
Researchers Stumble Over World's Largest Known Tsunami-Transported Rock
A 1,200 tons limestone boulder in Tonga is one of the largest known wave-transported rocks in the ... More world. Analysis has shown a boulder weighing almost 1,200 tons is one of the largest known wave-transported rocks in the world, providing new insights into the Pacific region's history and risk of tsunamis. During fieldwork on Tongatapu, the main island of the Tonga archipelago, searching for clues of past tsunamis, Ph.D. candidate Martin Köhler from the University of Queensland's School of the Environment was made aware by a farmer of a huge boulder — locally known as Maka Lahi meaning 'Big Rock' — hidden deep in the jungle. A survey quickly revealed that the boulder consists of fossiliferous limestone, a type of rock commonly found along the coast of the island. So-called erratic rocks, deposited far from their original source, are common in areas once occupied by a glacier. As the glacier melts, he leaves large boulders and debris behind. However, Tonga was never covered by ice. The only remaining force strong enough to move the boulder is a large wave. 'I was so surprised; it is located far inland and 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,' so Köhler. In a new study Köhler and other researchers show that the boulder was moved more than 200 meters inland by a tsunami around 7,000 to 10,000 years ago. Based on computer simulations, the researchers conclude that wave heights of around 50 meters lasting around 90 seconds were needed to dislodge it from its origin and move it to its resting place. 'Tonga has a long history of tsunamis triggered by volcanic eruptions,' explains coauthor Dr. Annie Lau, a coastal geomorphologist at the University of Queensland. Three years ago the previously unremarkable submarine volcano Hunga Tonga-Hunga Haʻapa erupted with the most powerful explosion since Krakatoa in 1883. The final blast triggered a tsunami as high as 20 meters above sea level. Most tsunamis are generated by earthquakes, when the seafloor shifts suddenly and displaces a large quantity of water, but they can also be triggered by a landslide, a volcanic eruption, or a meteor impact. Modern databases list more than 2.000 tsunamis in the last 4.000 years. Most of these records are based on historical documents. Geological evidence for tsunamis is surprisingly hard to find. 'Understanding past extreme events is critical for hazard preparation and risk assessment now and in the future,' so Dr. Lau. Local legends suggest that the islanders were well aware of this tsunami risk. According to one story, the boulders are there because the god Maui once tried to kill a monstrous chicken by throwing rocks from the sea on the island. The study,"Discovery of the world's largest cliff-top boulder: Initial insights and numerical simulation of its transport on a 30–40 m high cliff on Tongatapu (Tonga)," was published in the journal Marine Geology. Additional material and interviews provided by the University of Queensland.
Yahoo
22-05-2025
- Science
- Yahoo
Farmers lead Aussie research team to 'unreal' discovery on island
For 7,000 years, a giant boulder has been resting on a hilltop in the middle of a Pacific Island. When people first arrived in Tonga around 3,000 years ago, they began clearing land around it, and until recently, few knew of its existence. Australian-based researcher Martin Köhler had spent the day on the island of Tongatapu looking at smaller rocks they'd found using satellite images. The University of Queensland PhD candidate was working to understand how big the tsunamis were that thrust them from cliffs on the southern end of the island, further inland. 'On the last day of fieldwork in the late afternoon, we were talking to some farmers, and they said, 'Why aren't you looking at the much larger boulder further inl›and?',' Köhler recalled as he spoke to Yahoo News on Thursday. 'We were really interested, because a larger boulder further inland meant a much larger tsunami.' Köhler and his team followed the farmers past their crops of bananas, cassava, sweet potatoes, yam, and taro roots. When he stood at its base, he was shocked by its size. A photo taken later shows Köhler looking very small compared to the 1,200-tonne rock, which measured in at 14 metres long, 12 metres wide, and 6.7 metres high. 'I really couldn't believe the size and where it is — 200 metres inland is quite far for tsunami boulders. It was unreal,' he said. Prospector makes 'ripper' 90-year-old discovery in thick bush Item found among human skulls sheds new light on ancient civilisation Tense moment rare 35kg creature lowered into remote Aussie forest The University of Queensland team used computer modelling to determine how big the wave that carried the boulder from the edge of a cliff to the island's highest point. They calculated that a 50-metre-high wave, that was sustained for 90 seconds, would have been needed to shift the rock. While Tonga is still regularly hit by extreme weather events, a wave this big hasn't hit the island since humans arrived. Co-author Dr Annie Lau noted the 2022 tsunami killed six people and caused widespread damage. 'Understanding past extreme events is critical for hazard preparation and risk assessment, now and in the future,' she added. The research has been published in the journal Marine Geology. It's not the first sizeable tsunami rock found on Tongatapu. Another well-known boulder is considered a historical landmark on the island's northeastern coast. While it's bigger – measuring 30m long by 10m high – it wasn't moved ashore until 1917. Love Australia's weird and wonderful environment? 🐊🦘😳 Get our new newsletter showcasing the week's best stories.
New York Times
15-05-2025
- Science
- New York Times
How a Two-Story Boulder Ended Up on a 120-Foot-High Cliff
Just a stone's throw from the ocean, indeed. Small family farms dot the southern coast of Tongatapu, the largest island of Tonga in the South Pacific. But something lies amid the cassava and banana plants that doesn't belong: a staggeringly large, off-white boulder. The rock, which features prominently in Tongan mythology, was recently scrutinized by scientists. New results suggest that the object was transported inland thousands of years ago when tsunami waves breached a 120-foot cliff. That event might have been set in motion by an earthquake in the nearby Tonga-Kermadec Trench, the team reported last month in the journal Marine Geology. Seemingly out-of-place boulders are found in coastal regions around the world. From Japan to the Bahamas, scientists have spotted hulking rocks that simply don't seem to fit their surroundings. Researchers generally believe that such boulders were transported by moving water, and the powerful waves of tsunamis are often invoked as culprits. Last July, researchers traveled to Tongatapu to analyze several coastal boulders. On the last day of their planned fieldwork, the team received an unexpected tip from a group of Tongan farmers: A boulder, far larger than the ones the researchers were studying, lay nearby on farmland belonging to the Teisina family. That boulder turned out to be a behemoth — roughly the size of a two-story house. 'It was unreal,' said Martin Köhler, a geoscientist at the University of Queensland in Australia, who led the research. The rock, made of limestone, was also nearly completely camouflaged by vegetation. 'It looked like a hill,' said Mafoa Penisoni, a seismologist at Tonga Geological Services in Nuku'alofa, the country's capital, who accompanied the researchers. Mr. Köhler and his collaborators surveyed the rock, which is known locally as Maka Lahi or 'Big Rock.' The team calculated that it weighed more than 1,300 tons. It's surprising to find a tsunami-transported boulder that large, said Ricardo Ramalho, a geologist at Cardiff University in Wales, who was not involved in the study. 'Boulders this size are rare,' he said. The researchers also sampled formations growing on the sides of the boulder. Known as flowstone, they are akin to stalactites and stalagmites, and they build up slowly over time as limestone is dissolved by water. Maka Lahi is over 650 feet inland and sits atop a 12-story limestone cliff. As there's nothing taller around, the rock must have been dislodged from the edge of the cliff by one or more enormous waves, the team surmised. Using computer simulations, the researchers modeled waves of different heights that rolled in anywhere from every 10 to 600 seconds. The team found that waves of at least 160 feet high were required to dislodge the boulder from the cliff edge and send it rolling or sliding to its final resting place. That's far larger than the waves recorded for either the Indian Ocean tsunami in 2004 or the Tōhoku tsunami in 2011. Those tsunamis were caused by an earthquake, however, and the wave heights of such events are generally limited to a few tens of feet. So a tsunami caused by an earthquake probably wasn't the culprit in this case, said Annie Lau, a coastal geomorphologist at the University of Queensland and Mr. Köhler's thesis adviser. 'We're thinking it's likely a landslide tsunami.' When a large amount of material suddenly slides into the water — or something underwater rapidly shifts position — the result is a landslide-triggered tsunami. That's what happened in 2022, when the Hunga underwater volcano near Tonga erupted, sending waves roughly 50 feet tall into the northern coast of Tongatapu. Mr. Köhler and his team estimated that the massive waves that transported Maka Lahi struck about 7,000 years ago. That's based on the age of the flowstone growing on the lower half of the boulder. Because Tonga was settled only around 3,000 years ago, no humans were around to witness this event. 'It's older than the human occupation of Tonga,' Mr. Köhler said. It's impossible to know for sure what might have triggered massive waves that long ago, but there's geological evidence that large waves also inundated the North Island of New Zealand around 7,000 years ago. That event is believed to have been caused by an earthquake in the roughly 1,000-mile-long Tonga-Kermadec Trench that stretches from New Zealand to Tonga. Maybe that ground movement spurred a landslide near Tongatapu that launched the waves that ultimately transported Maka Lahi. Testing the idea will mean searching for evidence of a landslide. 'We need to look for the landslide scar,' Dr. Lau said. Such follow-up work is important, Dr. Ramalho said, for helping to reveal the triggering mechanisms and frequency of these kinds of hazards. And that's critical because such events are bound to happen again, he said. 'One day perhaps we'll be faced with an event like this.'
