New Geological Study Rewrites History Of The World’s Highest Peaks

A team of researchers at the Stanford Doerr School of Sustainability has used the isotopic makeup of minerals to show that one of the world’s most familiar mountain ranges, the Himalayas, did not form as experts have long assumed.

With 14 peaks rising to an elevation of over 8,000 meters, the Himalayas contain some of the tallest mountains in the world, towering over the Tibetan Plateau, the world’s highest and largest plateau above sea level with an average elevation exceeding 4,500 meters.

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“The controversy rests mainly in what existed ‘before’ the Himalayas were there,” explains Page Chamberlain, professor of Earth and planetary sciences, and senior author of the study. “Our study shows for the first time that the edges of the two tectonic plates were already quite high prior to the collision that created the Himalayas—about 3.5 kilometers on average.”

“That’s more than 60 percent of their present height,” added Daniel Ibarra, Ph.D., a postdoctoral researcher from Chamberlain’s lab, first author of the paper, and now an assistant professor at Brown University.

In the classic model, the Himalaya mountain range formed when the Indian subcontinent collided northward with Eurasia about 50 million years ago, closing the ocean between the two landmasses and pushing crust fragments upwards.

“Experts have long thought that it takes a massive tectonic collision, on the order of continent-to-continent scale, to produce the sort of uplift required to produce Himalaya-scale elevations,” explains Ibarra. “This study disproves that and sends the field in some interesting new directions.”

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The researchers looked at oxygen isotopes preserved in minerals to determine the altitude at which they formed, reconstructing the topography of the Himalayas before the continent collision.

Almost all minerals contain traces of oxygen in their crystalline structure, as does H₂O or water. Oxygen exists in three stable isotopes: oxygen 16, 17, and 18. Oxygen isotopes behave chemically in an identical manner, but due to the slight mass difference, water molecules containing heavy oxygen isotopes tend to evaporate and precipitate at different rates. A mineral formed at a lower altitude near the ocean will show a higher level of heavy isotopes, and a mineral formed at a high altitude will be depleted in heavy isotopes in favor of lighter ones.

Sampling quartz (SiO₂) veins from southern Tibet and using oxygen analysis, the team showed that the foundations of the Gangdese Arc—a major geological unit at the base of the Himalaya mountains—were already much higher than anticipated. Substantial uplift occurred by 63 to 61 million years ago. This uplift was probably caused by oceanic crust sliding beneath the two continental plates at a low angle before the collision of the Indian and Eurasian continents.

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“This new understanding could reshape theories about past climate and biodiversity,” Ibarra concludes. The formation of the Himalayan mountains as an effective barrier for rain and atmospheric currents has long been seen as an important factor shaping weather patterns over Asia and the Indian Ocean. But the new paleo-topographic reconstruction, with high-elevation terrain predating their formation, will likely lead to new paleoclimatic assumptions. It could also beget closer scrutiny of other key mountain ranges, such as the Andes and the Sierra Nevada, formed in a similar manner by the collision of Earth’s tectonic plates.