Recent studies reveal that Mount Everest’s growth has accelerated due to a rare geological phenomenon called river piracy.
This event has had a significant impact on the Himalayan landscape, reshaping the heights of several peaks.
Geological Background
Mount Everest, also known as Chomolungma, stands as one of Earth’s tallest peaks at 29,031.69 feet (8,848.86 meters) above sea level. Its formation started around 40 to 50 million years ago due to the collision of the India Plate and the Eurasian Plate, leading to the rise of the Himalayan mountain range.
This ancient collision continues to elevate the Himalayas even today. However, recent studies suggest that Everest’s growth has accelerated due to an unusual geological event: river piracy. This phenomenon involves a river capturing the flow of another river, drastically altering the landscape.
The Event of River Piracy
About 89,000 years ago, the Kosi River captured a tributary, the Arun River. This process, known as river piracy, caused significant geological changes. As the Kosi’s flow strengthened, it eroded more rock from the valleys around Everest, leading to an unexpected increase in the mountain’s height.
Researchers estimate that this river piracy event caused an uplift of Everest and two other peaks, Lhotse and Makalu, by at least 49 feet (15 meters) and potentially as much as 164 feet (50 meters).
Professor Jin-Gen Dai from China University of Geosciences highlighted that such changes in river systems could have profound impacts on landscapes, adding a new dimension to the understanding of mountain formation.
Link Between Erosion and Uplift
The connection between river erosion and peak uplift is well-documented, with examples in the Alps, Antarctica, and the Colorado Plateau. In these regions, erosion and uplift usually balance each other out.
However, when a river changes course suddenly, it triggers rapid erosion. This, in turn, causes nearby peaks to rise due to isostatic rebound. This balancing act means that as some parts of the landscape erode, others rise to compensate.
This phenomenon explains the unusual heights of Everest, Lhotse, and Makalu. The diversion of the Arun River also highlights the complex interplay between surface and deeper tectonic processes in shaping the Earth’s topography.
Further Evidence and Modern Parallels
Dr Devon A. Orme from Montana State University noted that river captures similar to the Arun and Kosi event are still occurring today. For instance, in the Amazon basin, ongoing river capture is shaping the region’s steep topography.
Ancient examples of river capture are evident around the Himalayas, causing Namche Barwa and Nanga Parbat regions to rise significantly over millions of years.
In modern times, a similar phenomenon was observed in Canada’s Yukon Territory, where the formation of a canyon caused a river to divert and dramatically change the landscape within just a few years.
Discovering the Puzzle
The researchers initially questioned the unusual course of the Arun River, which flows from east to west along the northern Himalayas before turning sharply south.
During an expedition, they found ancient lake sediments in the Arun River Basin, indicating significant past changes in water distribution. This suggested a possible river capture event.
Lead author Xu Han used computer models to simulate these landscape changes, revealing that the Kosi’s increased flow would have deepened its valleys and caused nearby peaks, including Everest, to rise.
Rapid Changes and Long-term Impacts
River capture, or piracy, can occur rapidly in geological terms, sometimes within just a few years or decades. This rapid change can significantly alter the landscape.
Compared to river piracy, erosion and uplift are slower processes. However, they continue to influence Everest, Lhotse, and Makalu over long periods.
Calculating the exact duration of these effects remains challenging, but the research underscores the complex dynamics of Earth’s surface.
Ongoing Evolution of Everest
Even as tectonic forces and isostatic rebound push Everest upward, weathering and glacier movement simultaneously wear it down.
Understanding the formation and evolution of Everest helps scientists grasp broader Earth dynamics, which is crucial as climate change and shifting weather patterns continue to transform the planet’s landscapes.
River piracy has played a crucial role in the unexpected growth of Mount Everest and its neighbouring peaks.
Understanding these geological processes highlights the complexity of Earth’s dynamic evolution and could provide insights into future landscape changes.
