Latest news with #MarineGeology
Miami Herald
5 days ago
- Science
- Miami Herald
Hidden inland boulder is proof of massive tsunami that hit Tonga 7,000 years ago
On the island of Tongatapu, the main island of Tonga, researchers scoured the southern coastline for evidence of violent weather events that occurred thousands of years ago. They were specifically looking for boulders, as they can only be carried ashore or moved by massive waves in 'high-energy events, such as tsunamis or storms,' according to a May 14 study published in the journal Marine Geology. Aerial photo revealed several boulders, but the largest was hidden from view. Local farmers speaking with the researchers told them of a boulder deep inland atop a cliff, covered by dense vegetation that obscured it from aerial view, and led them to it. 'I was so surprised; it is located far inland outside of our field work area,' study author and Ph.D. candidate Martin Köhler said in a news release from The University of Queensland's School of the Environment. 'It was quite unbelievable to see this big piece of rock sitting there covered in and surrounded by vegetation,' Köhler said. Researchers said 7,000 years ago, a tsunami about 164 feet tall— the height of the Arc de Triomphe, or a giant sequoia — dislodged the enormous rock and moved it 656 feet inland. At 45 feet long, 22 feet tall, 39 feet wide and weighing 1,300 tons, the 'exceptional' Maka Lahi is the world's largest cliff-top boulder, according to the study. Models suggest the tsunami was triggered by a landslide caused by an earthquake near the Tonga-Kermadec Trench, according to the study. 'Understanding past extreme events is critical for hazard preparation and risk assessment now and in the future,' coastal geomorphologist Annie Lau said in the release. According to Lau, the region has a 'long history of tsunamis triggered by volcanic eruptions and earthquakes along the underwater Tofua Ridge and the Tonga Trench.' The research team included Martin Köhler, Annie Lau, Koki Nakata, Kazuhisa Goto, James Goff, Daniel Köhler, Mafoa Penisoni.
Yahoo
7 days ago
- Climate
- Yahoo
There's a humongous boulder on a cliff in Tonga. Now we know how it got there.
When you buy through links on our articles, Future and its syndication partners may earn a commission. 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. Related: Dinosaur age tsunami revealed from tiny chunks of Japanese amber, study finds 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 Zealand's North Island — around 1,300 miles (2,000 kilometers) south west of Tonga — between 7,240 and 6,940 years ago. The Maka Lahi boulder may have moved because the wave's arrival coincided with an earthquake – a "coseismic" event. "It is possible that the earthquake not only generated a tsunami that inundated the North Island of New Zealand but also triggered a coseismic landslide, which in turn produced a separate tsunami that deposited Maka Lahi," the researchers wrote in the paper. The islands of Tonga are located in the South Pacific Ocean, a region that is extremely prone to tsunamis due to being surrounded by tectonic plate boundaries known as the "Ring of Fire." Subduction zones — where one plate is forced under another — or large underwater volcanic eruptions can generate powerful undersea earthquakes that can trigger tsunamis. The Tongan islands are located near the Tonga Trench, where the Pacific Plate is being subducted beneath the Indo-Australian Plate, making it especially vulnerable to tsunamis. RELATED STORIES —Record-shattering Tonga volcanic eruption wasn't triggered by what we thought, new study suggests —Tsunamis up to 90 feet high smash into New Zealand every 580 years, study finds —What's the difference between a tsunami and a tidal wave? In 2022, Tongatapu was hit by a 62.3 feet (19 m) tsunami triggered by the eruption of the Hunga Tonga–Hunga volcano, with water reaching as far as 0.62 miles (1 km) inland. "Tonga's most recent tsunami in 2022 killed 6 people and caused a lot of damage," Annie Lau, a coastal geomorphologist at the University of Queensland, said in the statement. The researchers hope that this discovery of how far such a large boulder was moved by a wave may help Tonga and surrounding South Pacific nations prepare for large tsunamis. "Understanding past extreme events is critical for hazard preparation and risk assessment now and in the future," Lau said. "The analysis strengthens our understanding of wave transportation of rocks to improve coastal-hazard assessments in tsunami-prone regions around the world."
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.
Gizmodo
22-05-2025
- Science
- Gizmodo
How Did This 1,300-Ton Boulder Travel Up a Cliff? Scientists Just Figured It Out
A giant boulder in Tonga rode a wave from an ancient tsunami 7,000 years ago. The 1,300-ton rock traveled a distance twice the size of a football field, swept away by the sheer force of the wave, according to a new study. But this was no ordinary giant rock. It was also sitting on a 100-foot (30-meter) tall cliff before surfing to its new location—hinting at a past mega-tsunami that swept the region. In July of 2024, Martin Kohler, a PhD candidate from the University of Queensland, and his team were doing fieldwork on Tonga's cliffs, searching for evidence of past tsunamis. In particular, they were looking for large boulders that could have been carried inland, which can tell researchers a lot about the history of tsunamis in earthquake-prone regions, like Tonga. On one of their last field days, some local farmers told the researchers about a boulder they might be interested in. The rock, familiar to locals as Maka Lahi, or literally 'large rock,' had never been studied by scientists. It had likely eluded previous satellite searches for tsunami-swept rocks because of its thick coat of vegetation. The boulder was made of coral reef limestone breccia, hinting that it had come from somewhere near the coast. 'I was so surprised; it is located far inland outside of our field work area and must have been carried by a very big tsunami,' Kohler said in a statement. The researchers' findings were published in the journal Marine Geology. The researchers later found a huge gash in a 100-foot (30-meter) tall cliff near the ocean, around 650 feet (200 meters) away from the boulder's current position. They also determined the rock was deposited 6,891 years ago, before humans settled on Tonga. The researchers measured the boulder at 45 by 40 by 20 feet (14 by 12 by 7 meters) high, roughly the size of a two-story house. It now has the honor of being the third largest tsunami-swept rock in the world. And it's the largest boulder known to have surfed a tsunami from a cliff. The team then used computer modeling to figure out roughly how tall the ancient tsunami that carried Maka Lahi must have been. They concluded that the tsunami was, at minimum, 164 feet (50 meters) tall and would have taken about a minute and a half to pass. The tsunami likely reached speeds of over 70 miles per hour (113 kilometers per hour). It was huge and very powerful, and the researchers think a landslide, rather than an earthquake, initially triggered the wave. Tonga sees a lot of geologic activity that can trigger tsunamis, like the devastating tsunami in 2022. Understanding more about the mechanics of past tsunamis can help researchers better prepare for future events, co-author Annie Lau, a coastal geomorphologist at the University of Queensland, said in a statement. 'The analysis strengthens our understanding of wave transportation of rocks to improve coastal-hazard assessments in tsunami-prone regions around the world,' Lau said.
Yahoo
12-03-2025
- Science
- Yahoo
Scientists Found 52-Foot-Tall Underground Ripples From the Asteroid That Killed the Dinosaurs
Some 66 million years after the Chicxulub asteroid impact kickstarted the Cretaceous–Paleogene (K-T) extinction, scientists are still finding stunning evidence of its destruction. In 2021, researchers spotted 'megaripples' nearly one mile below the surface, suggesting that the megatsunami created by the impact left behind geologic formations as the waves collided with the continental shelf. Now, the authors have expanded the search and found evidence of megaripples in a 900-square-mile area throughout the Gulf of Mexico, along with their varying formations along the upper shelf and the deep sea. Of the five mass extinctions that have impacted our planet in the past 500 million years, the Cretaceous–Paleogene (K-T) extinction event certainly delivers on dramatic flair. On a spring day some 66 million years ago, a six-mile-wide asteroid smashed down just north of what is now Mexico's Yucatan Peninsula. This sudden impact created tsunamis stretching one mile tall and racing outward from the asteroid's dino-killing blow. As those waves raced toward present-day Louisiana (which was largely underwater at the time), they achieved most of their gargantuan height as they reached the ramp of the continental shelf. In 2021, using seismic data gathered by the oil and natural gas company Devon Energy, scientists led by Gary Kinsland from the University of Louisiana at Lafayette found evidence of this geologic trauma in the form of 52-foot-tall 'megaripples' located one mile underground—an area of rock associated with the end-Cretaceous period. Initially surveying a 77-mile area, Kinsland and his team determined that these subterranean ripples likely formed as the asteroid-generated megatsunamis disturbed sediment near the shore. Now, a new study from the same team reveals that these 'megaripples'—roughly spaced up to one kilometer apart—can be found both further up the shelf of what is now central Louisiana and further down in deeper waters of the Gulf of Mexico. The scientists behind this new paper found evidence of megaripples in a larger, 900-square-mile area, and explain that these formations vary depending on where the tsunami impacted sediments along the paleo-shelf. The results of the study were published in the journal Marine Geology. 'The megaripples are different on the slope, at the shelf break and further up the shelf,' Kinsland, the lead author of the new study, told Live Science. 'This is important information in modeling of tsunami, in prediction of future tsunami interactions with shelves and in the understanding of the Chicxulub tsunami.' As the study explains, the largest of these megaripples can be seen along the paleo-shelf break—the area where the Gulf's depth dramatically increases down the slope of the continental shelf toward the deep sea. The way that waves interact with the continental shelf is a well-known process known as the 'Van Dorn effect,' which describes how waves surge over a shelf. The study also discovered that megaripples further inland were more weakly asymmetric, suggesting the waves' behavior changed as they entered shallower waters. Conversely, megaripples in the deep sea took on varied shapes, likely as a result of interactions with faults and collapses, according to Live Science. 'From the coverage of the three areas here in Louisiana we infer that the buried northern Gulf of Mexico shelf system, from Texas to Florida, is covered with megaripples from at least the paleo-slope up to the paleo-bathymetry where Gulf storms would have eroded the megaripples after their formation,' the team said in a press statement. While this gives scientists a better understanding of how the Chicxulub impact tsunami affected the region, it also provides a stunningly powerful example of how tsunamis interact with continental shelves. And if our worst fears are ever realized, it may help us prepare for future asteroid encounters during Earth's never-ending journey through the universe. You Might Also Like The Do's and Don'ts of Using Painter's Tape The Best Portable BBQ Grills for Cooking Anywhere Can a Smart Watch Prolong Your Life?
