Lava flow jigsaw puzzle reveals the secrets of shifting continents

New research by Curtin University has revealed the Tuz Gölü Fault Zone -- a more than 200-kilometre-long geological structure visible from space -- is slowly pulling apart, providing a rare glimpse into the forces that shape Earth's crust when tectonic plates collide.

Lead Australian author Professor Axel Schmitt, from Curtin's John de Laeter Centre and School of Earth and Planetary Sciences, said the study solved a long-standing mystery about the fault's movement, in a breakthrough not just for assessing seismic hazards but also for improving global models of continental deformation.

"While Turkey is well known for its earthquake-prone strike-slip faults, this study confirms for the first time that the Tuz Gölü Fault is an extensional fault, meaning the land on either side is moving away from each other, rather than sliding sideways as was previously thought," Professor Schmitt said.

"Several lava flows from Hasandağ volcano flowed over the fault and cooled, and then were broken apart by earthquakes. We were able to reconstruct their original shape and determine their age. This allowed us to track how rocks that were once connected have shifted apart over time.

"Our findings unambiguously reveal the fault is pulling apart at a rate of about one millimetre per year, rather than shifting sideways. Understanding these movements is crucial not just for assessing volcanic and earthquake threats but also for improving global models of continental deformation."

The research team used cutting-edge techniques, including remote sensing data, the John de Laeter Centre's ion microprobe and helium dating at the Western Australia ThermoChronology Hub (WATCH) Facility to precisely date the lava flows and track their displacement over thousands of years.

Curtin co-author Associate Professor Martin Danišík, from the John de Laeter Centre, said tiny zircon crystals in the lava flows worked as geological clocks, capturing helium produced by the radioactive decay of tiny amounts of naturally occurring uranium and thorium.

"By measuring uranium, thorium and helium in zircon, we can accurately determine when the lava flows erupted, spilled across the fault and subsequently cooled," Associate Professor Danišík said.

Curtin co-author and remote sensing expert Janet Harvey, also from the John de Laeter Centre, said that since earthquakes on the Tuz Gölü Fault occur less frequently than those on the fast-moving plate boundary faults in northern and eastern Turkey, landscape deformation studies like this provide data that the modern seismic record alone cannot.

"The fault sits at a key location where the Eurasian, Arabian and African plates are all interacting," Ms Harvey said.

"Studying its movements helps us understand how strain is distributed when continents collide -- insights that can be applied elsewhere along the Alpine-Himalayan mountain belt and to other continental deformation zones around the world.

"This research highlights the importance of revisiting long-held geological assumptions and using modern techniques to precisely measure how continents respond to the immense pressures of tectonic collisions."

The study was co-authored by researchers from Konya Technical University (Turkey), Heidelberg University (Germany) and University of Toronto (Canada).