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New Zealand's Tallest Mountain Shrinks by 100 Feet

Aoraki/Mount Cook
New Zealand's tallest mountain, Aoraki/ Mount Cook, is nearly 100 feet (30 meters) shorter than thought, according to GPS measurements by researchers at the University of Otago. (Image credit: Pascal Sirguey)

New Zealand's stunning Aoraki/Mount Cook, the country's tallest peak, is officially 98 feet (30 meters) shorter than previously thought, researchers with the University of Otago announced today (Jan. 15).

While currently officially listed as 12,316 feet (3,754 meters) tall, GPS data from an Otago-led climbing expedition reveal that Aoraki/Mount Cook is actually only 12,217 feet (3,724 m) high, the scientists said today.

Capped by a brilliant crown of snow and ice, Aoraki/Mount Cook towers above the Southern Alps on New Zealand's South Island. On Dec. 14, 1991, the peak was 12,349 feet (3,764 m) tall when a massive rock and ice avalanche cut 33 feet (10 m) off its top.

Since the avalanche, the ice crown has continued to collapse, the University of Otago scientists recently discovered.

"When it broke, the top of the ice cap was not in balance with the shape underneath," said Pascal Sirguey, a research scientist at the university and project leader for the research. "The ice eroded and changed a lot over the past 20 years," Sirguey told LiveScience's OurAmazingPlanet. "It's like when cookies crumble." [Video: New Zealand's Tallest Mountain Shorter Than Thought]

Sirguey and his collaborators first discovered their country's most famous peak had shrunk when they were building a digital elevation model of a nearby glacier. "That model, no matter what we did, didn't match the published elevation [of Aoraki/Mount Cook]," Sirguey said. "When you compare photos from then and now, it is also obvious, but no one had really noticed the change."

The team double-checked their measurements by climbing the mountain on Nov. 23, 2013, and measuring its height with GPS receivers, though they didn't ascend to the very top. Instead, they verified the height a few meters from the summit. A trigonometric survey — similar to the map-making done in the 1800s — also confirmed the height from lower elevations on Aoraki/Mount Cook.

Aoraki/Mount Cook after the 1991 avalanche. (Image credit: Trevor Chinn)

The indigenous Maori people of New Zealand, and the Ngãi Tahu tribe in particular, consider the mountain to be an ancestor and sacred. Stepping on the peak's highest point violates the mountain's sacred status (a status which is also protected by New Zealand's Department of Conservation). The research team also presented their results to the Ngãi Tahu tribe before publicly releasing the new height, Sirguey said.

And there is no reason to worry that Aoraki/Mount Cook will lose its place as New Zealand's tallest peak in the near future. It's still 75 feet (23 m) ahead of the second-place holder, Rarakiroa/Mount Tasman, and is growing about 0.4 inches (10 millimeters) every year thanks to grinding tectonic plates underneath New Zealand.

Email Becky Oskin or follow her @beckyoskin. Follow us OurAmazingPlanet @OAPlanet, Facebook and Google+. Original article at LiveScience's OurAmazingPlanet.

Becky Oskin
Contributing Writer
Becky Oskin covers Earth science, climate change and space, as well as general science topics. Becky was a science reporter at Live Science and The Pasadena Star-News; she has freelanced for New Scientist and the American Institute of Physics. She earned a master's degree in geology from Caltech, a bachelor's degree from Washington State University, and a graduate certificate in science writing from the University of California, Santa Cruz.