Australasian Science: Australia's authority on science since 1938

Geology on the Up

By Stephen Luntz

Prof Jonathan Aitchison is rewriting the story of the world’s greatest mountain chain. Soon textbooks may need to follow.

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School students’ introduction to plate tectonics usually involves learning that India and Asia collided 55 million years ago, producing the Himalayas. However, Aitchison has found marine rocks in Tibet that are only 35 million years old.

If confirmed, Aitchison’s findings will ripple through geology because the Himalayas are considered the template for understanding the events that drove the formation of many more ancient mountain ranges. “We’re getting an idea of the rates at which things happen,” says Aitchison. “That will have implications for lots of other examples.”

Aitchison says that when plate tectonics first became accepted, the date for the India/Asia collision was estimated at 45 million years ago. However, it was subsequently observed that India’s northward motion slowed substantially 10 million years earlier. “People put one and one together and got an unrelated number,” says Aitchison.

The India/Asia collision has been thought of as a simple story of two large continental plates coming together, making it a textbook favourite. However, Aitchison notes: “In between was what is known as the neo-Tethyian ocean. No one really thought about what that ocean was like. When we look at the western Pacific Ocean we see ocean space can be very complicated, for example with the Philippine Sea plate.”

Aitchison imagines Asia and India converging...

The full text of this article can be purchased from Informit.