Sedimentary records link Himalayan erosion rates and monsoon intensity th...( Throughout history the changing fort...)

Throughout history, the changing fortunes of human societies in Asia have been linked to variations in the precipitation resulting from seasonal monsoons.

A new paper published online today in the journal Nature Geoscience suggests that variations in monsoon climate over longer time scales also influenced the evolution of the Himalaya mountain chain, the world's highest.

The climate over much of Asia is dominated by seasonal winds that carry moist air over the Pacific Ocean into East Asia and over the Indian Ocean into South Asia.

The East and South Asian monsoons are responsible for most of the rainfall in these regions. Although the time when these monsoon patterns were first established is unknown, many lines of evidence suggest that they first came about at least 24 million years ago.

The new study uses geochemical data from an Ocean Drilling Project sediment core extracted from the seafloor of the South China Sea to establish a record of the East Asian monsoon climate over that time interval.

"This synthesis of climate and tectonic studies, from Himalayan rocks to ocean floor sediments, has revealed the ancient history of a dynamic part of our planet," said James Dunlap, program director in the National Science Foundation (NSF)'s Division of Earth Sciences, which funded the research. "These results will guide us in our efforts to better understand the potential for change on Earth today."

Sediments in this core were eroded from the drainage area of the Pearl River system in China, according to Peter Clift, a geologist at the University of Aberdeen in Scotland and lead author of the paper. "Their chemistry records the relative intensity through time of chemical weathering in an area that received the bulk of its precipitation from East Asian monsoon storms."

Many researchers believe that a geologically "abrupt" uplift of the Tibetan Plateau--the largest high-altitude region on Earth,
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