Ancient debris key to Earth's secrets

An international team of researchers has uncovered new evidence about the formation of Earth arising from the collisions of tectonic plates.

Experts have known for years that the movement of tectonic plates caused continents to collide, resulting in a massive build-up of assorted geological 'debris', including great mountain belts and ranges.

The collisions began millions of years ago and some are still happening today. They resulted in some of the world's most stunning landscapes containing diverse varieties of rock that have baffled scientists - until now.

In a report of the research published in Nature, the scientists describe the impact of these collisions and, crucially, how evidence of these events is preserved largely intact in the Earth's crust for millions of years.

They say the results may lead to significant new insights into regions where data is incomplete.

This includes ancient, deeply-buried geological material beneath the Antarctic and Africa, and in regions such as the Himalayas, North America, Australia and South East Asia, where vast volumes of new crust have accumulated over the last 500 million years.

Although geologists are accustomed to finding unusual material mashed up in ancient mountain belts, what was not certain is how this happened. The researchers say classical geology focused on examining old rocks formed millions or sometimes billions of years ago in an attempt to piece information together.

But now, through vastly improved computer power, new avenues have opened up. The team combined advanced computer models with classical geological practices to gain new insights into rock sequences in eastern Australia.

The computer model gave scientists an accelerated simulation of synthetic rocks behaving in a digital Earth.

This indicated that rocks caught in collisions were swept in a huge arcing path, where they were stretched, rotated and dragged hundreds of kilometres from their original location - a process called subduction roll-back.

The team now intends to use the research results to analyse sites of more recent collisions such as has occurred in Alaska, where a block of rock in the region is being pulled into the subduction zone right now.