Beneath the western Pacific, under the largest oceanic plateau on Earth, the Earth appears to keep a memory of its own violence. Listening to earthquakes from far away, researchers have read in the slowed and weakened passage of seismic waves the shapes of old magma channels, vertical fractures once filled with molten rock more than a hundred million years ago. The work reminds us that the great eruptions of the past did not vanish when they ended; they reshaped the rock beneath our feet, and some of that reshaping endures, waiting to be heard.
Seismic Waves Expose 100-Million-Year-Old Magma Pathways Beneath the Ontong Java Plateau
Channels that carried magma 100 million years ago may still be detectable today
Mark
So what did they actually find under the Ontong Java Plateau?
Mimi
Signs of ancient magma-filled fractures, called dike swarms, deep in the lithosphere. They're thought to be the channels magma used during the plateau's formation 110 to 120 million years ago.
Mark
How do you find that from the surface?
Mimi
By using high-frequency seismic waves from distant earthquakes. Passing through the plateau, they moved slower and weakened more than they do in normal oceanic crust.
Luke
Worth saying: nobody has sampled these dikes. It's an inference from wave behavior.
Mimi
True. But the team tested it with numerical models. Layered lithosphere alone didn't match the signals. Layers plus vertical dike-like structures did better.
Mark
And the slower speeds?
Mimi
They say thickness can't explain them, so they suggest magma chemically altered the surrounding mantle, leaving a lasting signature.
Luke
Notice the hedging. The source says minerals "may have" altered the rocks. That's a proposal, not a confirmed mechanism.
Mark
Why does it matter beyond this one plateau?
Mimi
It could refine how scientists model large volcanic provinces and how mantle plumes interact with older oceanic crust.
Luke
Whether it generalizes is still unknown. This is one plateau, and the article doesn't say other teams have replicated it.
Der Puls
- Seismic waves from distant earthquakes are behaving strangely as they cross a vast plateau in the western Pacific, slowing and weakening where they should not.
- Models built on ordinary layered oceanic rock fail to reproduce the signals, forcing scientists to reconsider what lies beneath the surface.
- Researchers are testing a new picture of vertical, dike-like magma pathways left from an eruption 110 to 120 million years ago.
- The findings are landing as a fresh clue into how mantle plumes interact with old ocean crust, though the evidence remains indirect and awaits confirmation from other datasets.
Beneath the western Pacific, under the largest oceanic plateau on Earth, the Earth appears to keep a memory of its own violence. Listening to earthquakes from far away, researchers have read in the slowed and weakened passage of seismic waves the shapes of old magma channels, vertical fractures once filled with molten rock more than a hundred million years ago. The work reminds us that the great eruptions of the past did not vanish when they ended; they reshaped the rock beneath our feet, and some of that reshaping endures, waiting to be heard.
Far below the western Pacific, beneath the largest oceanic plateau on Earth, researchers have found what looks like the preserved plumbing of an ancient volcanic event. The structures are dike swarms, vertical fractures that once carried magma, and they were found not by drilling but by listening to seismic waves from distant earthquakes.
The Ontong Java Plateau formed roughly 110 to 120 million years ago, and its volcanic origin has long been understood. What remained unclear was how such enormous volumes of magma travelled through the lithosphere to reach the surface. The seismic waves offered an answer of sorts. They crossed the plateau more slowly and lost more strength than they did over ordinary ocean crust, and standard layered models could not explain the recordings. Only when vertical, dike-like structures were added did the simulations match.
The researchers read these dikes as ancient conduits through which a deep mantle plume fed magma into older oceanic rock again and again. The pathways outlasted the volcanism itself. A second clue, the slower wave speeds, pointed toward chemical change: minerals carried by the molten material may have altered the surrounding mantle, leaving a lasting mark.
The study is careful about its limits. The evidence is interpretive, drawn from how waves behave rather than from direct sampling. Its value lies in suggesting new ways to study deep oceanic lithosphere, and the next step is whether similar seismic patterns appear in other volcanic provinces.
Deep under the western Pacific, beneath the largest oceanic plateau on Earth, researchers have found what appear to be the preserved plumbing of a volcanic event that ended more than 100 million years ago. The structures are called dike swarms: vertical fractures that were once filled with magma. They were identified from seismic data, not from drilling or direct sampling.
The work is described in a study titled "Dike Swarms in the Oceanic Lithosphere Beneath the Ontong Java Plateau," published in Advancing Earth and Space Sciences. Its central claim is that the channels created while the plateau was forming have survived across geological time, and that they can still be detected today.
The Ontong Java Plateau sits in the western Pacific and formed during an intense volcanic episode roughly 110 to 120 million years ago. Its volcanic origin has long been understood. What has been less clear is how such enormous volumes of magma moved through the Earth's lithosphere on their way to the surface.
To look at the plateau's interior, the researchers used high-frequency seismic waves generated by distant earthquakes. As those waves crossed the plateau, they behaved differently from waves passing through ordinary oceanic crust. They travelled more slowly and weakened more.
The team then tested possible explanations with numerical models. Models built only on layered oceanic lithosphere, the standard structure, could not reproduce the recorded signals. A better match came from a combination of the usual layered rock and vertically oriented, dike-like structures. In the researchers' interpretation, these dikes are the ancient conduits through which magma rose from a deep thermochemical mantle plume. The magma repeatedly entered older oceanic lithosphere, building a network of pathways that stayed in place after the volcanism stopped.
A second finding concerns speed. Seismic waves moved more slowly beneath the plateau than beneath nearby stretches of normal oceanic lithosphere, and the researchers said differences in thickness alone could not account for that. Their reading is that the magma changed the chemical makeup of the surrounding mantle. Minerals carried by the molten material may have altered the rock, leaving a lasting signature. On this account, the effects of the eruption reached well below the surface, into the planet's interior.
The study also speaks to a practical problem. Deep oceanic lithosphere is hard to study directly, because access is limited and drilling through large sections of rock is difficult. Seismic imaging offered a way in. The authors conclude that the plateau contains both layered lithosphere and preserved magma-filled dike swarms, evidence of how a thermochemical mantle plume interacted with existing oceanic crust.
The results may help refine models of how large volcanic provinces form and how they transform the lithosphere beneath them. The evidence is indirect, an interpretation of how waves behave, so the next test is whether other seismic datasets and models of similar provinces point to the same kind of structure.
Bemerkenswerte Zitate
Slower seismic speeds beneath the plateau could not be explained by thickness differences alone, and suggest magma altered the surrounding mantle's chemistry.— Researchers, as reported by The Economic Times
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