Privileged planet: solid rock flows at 3,000 kilometers deep (Introduction)

by David Turell , Monday, June 09, 2025, 17:47 (2 days ago) @ David Turell

Part of what feeds volcanoes, mantle plate movements, & earthquakes:

https://www.sciencedaily.com/releases/2025/06/250608222155.htm

"Beneath Earth s surface, nearly 3,000 kilometers down, lies a mysterious layer where seismic waves speed up inexplicably. For decades, scientists puzzled over this D' layer. Now, groundbreaking experiments by ETH Zurich have finally revealed that solid rock flows at extreme depths, acting like liquid in motion. This horizontal mantle flow aligns mineral crystals called post-perovskite in a single direction, explaining the seismic behavior. It s a stunning leap in understanding Earth s deep inner mechanics, transforming a long-standing mystery into a vivid map of subterranean currents that power volcanoes, earthquakes, and even the magnetic field.

"A seismic mystery nearly 3,000 kilometers underground has finally been solved: researchers found that solid rock flows horizontally, aligning minerals and causing a shift in earthquake wave speeds. This changes our entire view of Earth’s deep interior.

"Earthquakes, volcanic eruptions, shifting tectonic plates -- these are all signs that our planet is alive. But what is revealed deep inside the Earth surprises laymen and scientists alike: Almost 3000 kilometers below the Earth's surface, solid rock is flowing that is neither liquid, like lava, nor brittle like solid rock. This is shown by a new study by geoscientists led by Motohiko Murakami,

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"For over 50 years, researchers have been puzzling over a strange zone deep inside the Earth -- the so-called D" layer, around 2700 kilometers beneath our feet. Earthquake waves suddenly behave differently there: their speed jumps as if they were traveling through a different material. What exactly happens at that layer of the mantle has been unclear for a long time, until now.

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"Using a sophisticated computer model, they finally discovered something important: depending on the direction in which the post-perovskite crystals point, the hardness of the mineral changes. Only when all the crystals of the mineral point in the same direction in the model are the seismic waves accelerated -- as can be observed in the D" layer at a depth of 2700 kilometers.

"In an unusual laboratory experiment at ETH Zurich, Murakami has now proven that post-perovskite crystals align themselves in the identical direction under enormous pressure and extreme temperatures. To do this, the researchers measured the speed of seismic waves in their experiment and were also able to reproduce the jump that occurs at the D" layer in the laboratory. "We have finally found the last piece of the puzzle," says Murakami.

"The big question is: what makes these crystals line up? The answer is that solid mantle rock that flows horizontally along the lower edge of the Earth's mantle. Researchers have long suspected that this movement -- a kind of convection like boiling water -- must exist but have never been able to prove it directly.

"Murakami and his colleagues have now also demonstrated experimentally that mantle convection of solid rock is present at the boundary between the core and the Earth's mantle, i.e. that solid -- not liquid -- rock flows slowly but steadily at this depth. "This discovery not only solves the mystery of the D" layer but also opens a window into the dynamics in the depths of the Earth," Murakami explains."

Comment: our planet is still alive and changing/evolving. It is doing it at a given rate we who live here can tolerate.