Oct 16, 2026 12:46 AM
A Rock Dragged 90 Km Into Earth Came Back With a Temperature Story That Breaks The Models
https://www.sciencealert.com/a-rock-drag...the-models
EXCERPTS: Scientists have discovered a mysterious rock in eastern Papua New Guinea that traveled to the underworld roughly 4.4 million years ago. The story it has to tell is strange indeed.
As the rock journeyed deeper into our planet's interior, pushed by the forces of a subduction zone, its temperature did not do what scientists expected. At 45 kilometers below the surface, researchers estimate the rock became unusually warm, experiencing temperatures of about 700 °C (1,292 °F).
That's hotter than models predict subduction zones should be at that depth. But that's not all. When the rock reached more than 90 kilometers (56 miles) deep, its temperature only rose by a further 100 °C.
"What makes this rock so interesting is that it records two very different thermal conditions at different stages of its time deep inside Earth," says geologist Axel Schmitt from Curtin University in Australia. "At about 45 kilometers depth, the rock was surprisingly hot, but as it traveled deeper it entered an environment that was cooler than we would normally expect at that depth."
It's a small slice of evidence that has traveled a long way, and its journey could reveal important clues about what lies beneath our planet's surface. While it is generally true that Earth gets warmer the deeper you go, the temperature gradient isn't always clean and straight. The curious rock from Papua New Guinea is evidence of that.
[...] "One possibility is that intense shearing where the tectonic plates meet generates additional heat at relatively shallow depths." In other words, shearing forces where tectonic plates meet could be heating up shallow rocks more, relative to their pressure.
Another option, Schmitt explains, is that the system is young, and the subduction zone has not yet cooled to the lower temperatures scientists would expect.
"The findings suggest the thermal structure of these zones may be more complex than previously thought, helping scientists better understand how subduction operates over millions to billions of years," says Schmitt... (MORE - missing details)
PAPER: https://doi.org/10.1038/s41561-026-02110-1
https://www.sciencealert.com/a-rock-drag...the-models
EXCERPTS: Scientists have discovered a mysterious rock in eastern Papua New Guinea that traveled to the underworld roughly 4.4 million years ago. The story it has to tell is strange indeed.
As the rock journeyed deeper into our planet's interior, pushed by the forces of a subduction zone, its temperature did not do what scientists expected. At 45 kilometers below the surface, researchers estimate the rock became unusually warm, experiencing temperatures of about 700 °C (1,292 °F).
That's hotter than models predict subduction zones should be at that depth. But that's not all. When the rock reached more than 90 kilometers (56 miles) deep, its temperature only rose by a further 100 °C.
"What makes this rock so interesting is that it records two very different thermal conditions at different stages of its time deep inside Earth," says geologist Axel Schmitt from Curtin University in Australia. "At about 45 kilometers depth, the rock was surprisingly hot, but as it traveled deeper it entered an environment that was cooler than we would normally expect at that depth."
It's a small slice of evidence that has traveled a long way, and its journey could reveal important clues about what lies beneath our planet's surface. While it is generally true that Earth gets warmer the deeper you go, the temperature gradient isn't always clean and straight. The curious rock from Papua New Guinea is evidence of that.
[...] "One possibility is that intense shearing where the tectonic plates meet generates additional heat at relatively shallow depths." In other words, shearing forces where tectonic plates meet could be heating up shallow rocks more, relative to their pressure.
Another option, Schmitt explains, is that the system is young, and the subduction zone has not yet cooled to the lower temperatures scientists would expect.
"The findings suggest the thermal structure of these zones may be more complex than previously thought, helping scientists better understand how subduction operates over millions to billions of years," says Schmitt... (MORE - missing details)
PAPER: https://doi.org/10.1038/s41561-026-02110-1