The Mekong river near Zaduo, Tibet highlands

The history of the deep valley that carries the Mekong River through the Tibetan highlands is debated, with monsoon rains proposed as one factor in its formation. Credit: Getty

Geology

How the mighty Mekong River dug deep

Intense monsoon rains might have played a part in sculpting the river’s valley.

The steep valley that the Mekong River follows through the southeastern Tibetan Plateau may owe its existence to profound climate disruptions millions of years ago.

The Mekong River is one of the world’s largest rivers in terms of water volume and sediment transport, but knowledge of its geological history is patchy. Junsheng Nie at Lanzhou University in Gansu, China, and his colleagues analysed the age of minerals in samples taken from the bedrock of the upper and middle Mekong. They also modelled the history of erosion by the river.

The results suggest that the river began to cut fast and deep into the Tibetan Plateau about 17 million years ago. There is no evidence of major tectonic activity at that time, but the period was marked by an exceptionally warm climate and intense East Asian summer monsoon rains. Strong rainfall and erosion, rather than surface uplift, might have facilitated the young Mekong’s rapid descent, the team says.