Previously, it was thought that uplift of the Himalaya and the Tibetan plateau about 45 million years ago was responsible for the desert’s dry climate, as they blocked the flow of moisture-laden air from the Indian Ocean. However, newly analysed soil samples suggest that much of the desert dried out more recently.
A team of scientists from Stanford and Rocky Mountain College in Montana measured the relative level of carbon isotopes in samples collected in Mongolia, using the results as a proxy for past rainfall. The data showed a decline 30 million years ago when the Hangay mountains emerged, and a further dip five to ten million years ago during the formation of the Altai range. ‘What these smaller mountains did was expand the Gobi north and west into Mongolia,’ said Jeremy Caves, who was involved in the study.
The study suggests that the two ranges, which are located to the north of the Gobi, created a rain shadow, blocking wetter air from entering Central Asia. ‘As a result, the northern and western sides of these ranges are wet,’ said Caves, ‘while the southern and eastern sides are dry.’
This story was published in the February 2014 edition of Geographical Magazine
