The Tibetan Plateau supposedly rose as the Indian continent smashed into Eurasia about 50 million years ago. But the latest study of fossils and oxygen isotopes in the region's rocks shows that parts of southern Tibet were already as tall as they are today before the collision.

The findings challenge the conventional wisdom of what happens when continents collide, and because of the role of mountains in weather systems, also imply that the Asian monsoons could have been going on for much longer than previously assumed.

The Tibetan Plateau covers an area about one-quarter as large as the United States, with an average elevation of 5,000 metres. To the south, it is ringed by the Himalayas, which include the highest peaks in the world. How and when such a gigantic region rose up has been a matter of intense debate for decades.

To get a glimpse of topography of ancient Tibet, a team led by Ding Lin, a geologist at the Chinese Academy of Sciences’ Institute of Tibetan Plateau Research in Beijing, analysed 55-million-year-old rocks from the Linzhou Basin, about 50 kilometres northeast of Lhasa in Tibet.

The team measured the isotopes of oxygen from ancient rain and snow that would have been preserved in the rock. “As clouds climb up a mountain slope, water vapour with the heavier oxygen isotope, oxygen-18, rains out first,” says Ding. The higher the elevation, the less oxygen-18 precipitates, whereas the opposite holds for oxygen-16. Thus, the ratio of the two isotopes is a measure of elevation.

Fitzroy Gardens in Melbourne, Australia, takes on an ethereal quality in the light of a streetlamp, emanating deep hues of jade and emerald. “It reminds me of somewhere magical out of a fairy-tale story, a small piece of tranquility in the middle of a bustling city,” writes Luke Aveil, a contributor to Your Shot. Named after Sir Charles Augustus Fitzroy, the gardens receive over two million visitors each year.

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