The inner workings of the Earth shape the continents and islands we know on the surface — but many of the inner workings of the planet remain a mystery to even the most experienced researchers. One of those mysteries has been a characteristic — and hitherto unexplained — 60° bend in the Hawaiian-Emperor seamount chain, a mostly undersea mountain chain that stretches thousands of miles across the Pacific Ocean. Now, that mystery may have been solved — thanks, of course, to supercomputing.
“It’s been a holy grail to figure out why this change happened,” said Michael Gurnis, a professor of geophysics at the California Institute of Technology, in an interview with Jorge Salazar of the Texas Advanced Computing Center (TACC). Gurnis, along with colleagues from Caltech, New York University, Sydney University and Argonne National Laboratory, sought that grail.
The Hawaiian-Emperor seamount chain is thought to have originated from a tectonic plate traveling over a volcanic hotspot. For tens of millions of years, that plate traveled north; then, 50 million years ago, the plate and the mantle plume that formed the hotspot both shifted direction. “Maybe there’s an underlying physical reason why they would happen simultaneously,” Gurnis said.
“Going into the present study, we actually had a model which could explain the motion of the plume to the south and then stop abruptly, but we didn’t have a model that could explain how the plate could change its direction,” Gurnis explained. Then: “We discovered that there was another idea that had existed in the literature, but it wasn’t getting much attention.”
That new literature had pointed to a subduction zone near Russia that terminated around the same time the plume and the plate had shifted direction. Gurnis and his team built new models that incorporated this subduction zone, and ran them on supercomputers allocated by the Extreme Science and Engineering Discovery Environment (XSEDE).
The supercomputers in question: Stampede2 (10.7 Linpack petaflops) and Frontera (23.5 Linpack petaflops, and 13th on the most recent Top500 list). “Both XSEDE and Frontera are absolutely vital for our research,” Gurnis said. “This capability computing is essential. We’re spinning up projects with this collaboration that will be substantially larger than this, that are going to require something even beyond Frontera to compute.”
Once the models were built, the team successfully demonstrated that incorporating that Russian subduction zone could explain the shift of the plate in the Pacific. “We’ve shown with computer models for the first time how the Pacific plate can abruptly change direction from the north to the west,” Gurnis said.
To learn more, read the reporting from TACC’s Jorge Salazar here.