Monsoons change the motion of tectonic plates

Daisy Dumas in Australian Geographic: Long-term, natural climactic events can alter the motion of the earth's tectonic plates, according to new research. An international team - led by researchers from the Australian National University - found that intensifying monsoon activity has sped up the motion of the Indian plate, which crunched into the Eurasian plate to form the Himalayas 40 to 50 million years ago.

Over the past 10-15 million years, monsoons - which increase rainfall in northeast India by 4m annually and cause erosion - have sped up the anti-clockwise motion of the Indian plate by almost one centimetre per year, the researchers say. This is quite fast, considering tectonic plates move about the same rate at which fingernails grow.

"We were very excited," ANU's Dr Giampiero Iaffaldano told Australian Geographic. "This is the first time we have been able to make the link between what naturally happens to climate over millions of years and the motion of tectonic plates," he says. "While it was already known that plate tectonics can affect climate through events such as mountain uplift altering wind and rainfall patterns," Giampiero says. "Now we know that it can also operate the opposite way".

Monsoonal rain, says Giampiero, causes erosion of mountains, which reduces frictional forces along the plate boundary. This essentially allows the plates to move against each other more quickly - although he is quick to stress that it remains, nevertheless, a very slow process, taking millions of years.

Dr Jo Whittaker, a geophysicist at the University of Sydney, says the work has "implications for how scientists understand the forces driving the motion of the tectonic plates" - in particular, it is hoped the results may help to unlock the secrets of earthquake-prone regions…

Tectonic plates of the earth, from the USGS website