Montana State geologist featured in CNN report about Himalayan mountain range

BOZEMAN - A Montana State University expert was quoted recently in a CNN article about the phenomenon of "river piracy" and its role in the uplift rate of Mount Everest and two nearby peaks in the Himalayan range.

Devon Orme, associate professor in MSU's Department of Earth Sciences in the College of Letters and Science, was asked by CNN writer Mindy Weisberger to comment on a paper by Chinese geologist Jin-Gen Dai, which was published Sept. 30 in the journal Nature Geoscience. The paper suggests that when a tributary of the Arun River was captured and diverted by the Kosi River in the Himalayas about 89,000 years ago, it changed the drainage patterns of the landscape. That, in turn, caused enough erosion in the valleys below Mount Everest to spark what is known as "isostatic rebound" - the upward lift of the landscape in response to decreased surface load.

As a tectonic sedimentologist, Orme studies landscapes formed by the collision of tectonic plates. She did her doctoral research in Tibet, where Eurasia and India converged 58 million to 60 million years ago to create the Himalayas. She is currently researching the erosional record of the region, which includes sampling river sands across Tibet, Nepal and Bhutan. Though Orme was not involved in the research reported by CNN, she and an MSU graduate student traveled to Nepal last December to sample sands in the Kosi and Arun rivers.

In the CNN article, which states that most of the Himalayan range is rising about 1 millimeter a year due to the continuing force of the plate collision, Orme said that Dai's findings offer a promising explanation for why Everest, along with nearby mountains Lhotse and Makalu, are rising about twice as fast as neighboring peaks.

"This paper convincingly highlights the interplay of surface and deeper tectonic processes in shaping high topography on Earth," Orme said.

She added, however, that because the findings are based on computer models, they will need to be verified by field research.

The article includes additional examples cited by Orme of river captures that have remodeled landscapes on Earth, including in the Amazon drainage basin and in two other regions of the Himalayas.

Orme, who joined the MSU faculty in 2017, has received numerous research grants from the National Science Foundation, including one that is funding her current research in the Himalayas. She is also the recipient of an NSF CAREER award, one of the most prestigious grants for researchers early in their careers.