Scientists at The Australian National University (ANU) are helping to improve understanding of how rocks in Earth's hot, deep interior enable the motions of tectonic plates, which regulate the water cycle that is critical for a habitable planet.

Research team leader Professor Ian Jackson said tectonic plates were continuously created at mid-ocean ridges and destroyed when they sink back into the Earth's mantle.

"Plate tectonics is responsible for diverse geological phenomena including continental drift, mountain building and the occurrence of volcanoes and earthquakes," said Professor Jackson from the ANU Research School of Earth Sciences.

The stirring of the Earth's interior, which is responsible for the plate motions at the surface, has resulted in the Earth's gradual cooling over its 4.5 billion-year life.

He said defects allowed the normally strong and hard minerals of the Earth's deep interior to change their shape and flow like viscous fluid on geological timescales.

"We have found that flaws in the regular atomic packing in the dominant upper-mantle mineral, called olivine, that become more prevalent under oxidising conditions, substantially reduce the speeds of seismic waves," Professor Jackson said.

Seismic waves, caused by earthquakes, are used to image the Earth's deep interior in a manner similar to medical CAT scanning.

"Our new findings challenge a long-held theory that defects involving water absorption in these normally dry rocks could control both their viscosity and seismic properties," Professor Jackson said.

ANU Research School of Earth Sciences (RSES) PhD scholar Chris Cline is the lead author of the study undertaken in collaboration with RSES colleagues and Professor Ulrich Faul at the Massachusetts Institute of Technology in the United States.

The team used specialised equipment in a laboratory at ANU to make synthetic specimens similar to upper mantle rocks and measured their rigidity, which controls seismic wave speeds, under conditions simulating those of the Earth's mantle.

Professor Jackson said the research was particularly relevant to environments where old, cold, and oxidised tectonic plates sink into the Earth's hot interior.

"We have the potential to help map the extent of oxidised regions of the Earth's mantle that play such an important role in the chemical evolution of Earth," he said.

Research paper

Related Links
Australian National University
Tectonic Science and News

Tweet

Thanks for being here; We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain. With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords. Our news coverage takes time and effort to publish 365 days a year. If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.
SpaceDaily Contributor $5 Billed Once credit card or paypal		SpaceDaily Monthly Supporter $5 Billed Monthly paypal only

Unique diamond impurities indicate water deep in Earth's mantle
Las Vegas NC (SPX) Mar 12, 2018
A UNLV scientist has discovered the first direct evidence that fluid water pockets may exist as far as 500 miles deep into the Earth's mantle. Groundbreaking research by UNLV geoscientist Oliver Tschauner and colleagues found diamonds pushed up from the Earth's interior had traces of unique crystallized water called Ice-VII. The study, "Ice-VII inclusions in Diamonds: Evidence for aqueous fluid in Earth's deep Mantle," was published Thursday in the journal Science. In the jewelry busin ... read more