Mountain ranges are not just majestic landscapes; they have a profound impact on our climate and the diverse ecosystems that call them home. As warm air rises and cools on the windward side, it creates rainfall and snow. However, on the leeward side, a phenomenon known as rain shadow occurs, resulting in deserts. The formation of mountain ranges has always fascinated climate scientists and researchers who study past climates.
That fascination is about to intensify with a groundbreaking study published in the journal Nature Geoscience. Researchers from the Stanford Doerr School of Sustainability have used a unique technique to measure historic altitudes in sedimentary rocks, challenging long-held assumptions about the formation of one of the world’s most iconic mountain ranges, the Himalayas.
“The controversy lies in what existed ‘before’ the Himalayas were formed,” explains Page Chamberlain, a professor at the Doerr School of Sustainability and senior author of the study. “Our research reveals that the edges of the tectonic plates were already significantly high before the collision that created the Himalayas, averaging about 3.5 kilometers.”
“That’s more than 60% of their current height,” adds Daniel Ibarra, the paper’s first author and a postdoctoral researcher from Chamberlain’s lab, who is now an assistant professor at Brown University. “This discovery challenges previous assumptions and could revolutionize our understanding of past climate and biodiversity.”
These findings will require a recalibration of ancient climate models and prompt a closer examination of other important mountain ranges, such as the Andes and the Sierra Nevada.
Unveiling the Past with a Unique Technique
The reason this debate is gaining momentum is due to the difficulty of measuring past topographic altitudes, a field known as paleoaltimetry. It is a complex task with limited proxies available in the geological record. However, the Stanford team, in collaboration with researchers from China University of Geosciences, found a solution.
By analyzing the isotopic composition of rocks, experts can determine the altitude at which they were formed. The chemical composition of precipitation changes as it rises towards the mountain peaks, with heavier isotopes falling out first. This technique, known as triple oxygen analysis, provides valuable insights into ancient altitudes.
However, oxygen 17, the key isotope for this analysis, is incredibly rare, making this research even more challenging. “There are maybe eight labs in the world that can do this analysis,” says Chamberlain. “It took us three years to obtain meaningful and consistent results.”
Redefining Tectonic Shifts
Thanks to a grant from the Heising-Simons Foundation, the team successfully adapted the technique to paleoaltimetry and conducted a proof-of-concept study in Sun Valley, Idaho, in 2020. With the methodology established, they turned their attention to the Himalayas.
By analyzing quartz veins from lower altitudes in southern Tibet, the researchers discovered that the foundations of the Gangdese Arc were already much higher than previously believed, long before any tectonic collision occurred.
“Experts have always believed that massive tectonic collisions were necessary to create elevations like those found in the Himalayas,” says Ibarra. “This study challenges that notion and opens up new avenues of research.”
The study’s contributing authors include Yuan Gao, Jingen Dai, and Chengshan Wang from China University of Geosciences. Chamberlain is also affiliated with Bio-X and the Stanford Woods Institute for the Environment.
