Rethinking The Rise Of The Third Pole

Researchers from China have found that the Tibetan plateau—also known as the world’s Third Pole—rose to its current height much later than previously thought.

AsianScientist (Dec. 21, 2020) – While you may be more familiar with the North and South Poles, the vast, elevated Tibetan plateau is also home to the so-called Third Pole. Through fossil analysis, researchers from China have found evidence that the Third Pole grew to its modern height around 20 million years ago (Ma), instead of 40 Ma. Their study was published in Science Advances.

With an area of over 2.5 million square kilometers and an average height of 4,600 meters, the Tibetan plateau is the Earth’s most extensive elevated surface. As its ice fields contain the largest reserve of fresh water outside the polar region, the plateau is also known as the Third Pole. Accordingly, the Third Pole provides drinking water, power and irrigation for over 1.3 billion people in Asia—nearly one fifth of the world’s population.

Due to its location, the Third Pole exerts a significant influence on regional climate as well as biodiversity. Studying its geological evolution could therefore deepen our understanding of how the plateau contributes to the two processes. Among academic circles, it is widely believed that the plateau reached its current height as early as 40 Ma. However, the exact timeline remains hotly debated.

Hoping to settle the debate once and for all, researchers led by Dr. Fang Xiaomin from the Institute of Tibetan Plateau Research, Chinese Academy of Sciences (CAS) analyzed samples from the Lunpola Basin. Located in the plateau’s central area, the basin is home to well-preserved fossil soils, tropical plants and animals that can be used to estimate the history of geological uplift.

To calibrate the Third Pole’s age, the team studied changes in the magnetic properties and measured the ratio of radioactive carbon found in the basin’s fossil soils. Their analyses revealed that while low-elevation fossils were deposited 40 Ma, higher-elevation soils dated from about 25.5 to 21 Ma.

“This means that the Third Pole was still lower than 2300 m about 40 million years ago,” said Fang. “It only grew to 3500 m and above around 26 million to 21 million years ago.”

The team’s findings suggest that the Third Pole deformed and subsided around 40 Ma, and subsequently went through uplift at a much later period. Now that the dust has literally and figuratively settled, Fang and his colleagues are set to study the link between the plateau’s uplift and the evolution of Asian monsoons.

The article can be found at: Fang et al. (2020) Revised Chronology of Central Tibet Uplift (Lunpola Basin).


Source: Chinese Academy of Sciences; Photo: Unsplash.
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