(ORDO NEWS) — Seismic observations have shown that at a depth of thousands of kilometers, on the border of the core and mantle, there are massive and dense “mountains” up to several tens of kilometers high.
Geologists consider them to be the remains of ancient oceanic plates.
The Earth‘s core lies at a depth of about 3,000 kilometers, hundreds of times lower than the deepest wells we can drill.
Therefore, perhaps the only way to study it remains seismography – the registration of seismic waves that create earthquakes.
Passing through the thickness of the Earth, they change characteristics depending on the density and other properties of the rock.
This made it possible to find out that the core is divided into a solid inner and a liquid outer, and in the very center there is another miniature “nucleolus”.
It is surrounded by a thin, only tens of kilometers, boundary layer separating the core and mantle.
Ancient oceanic plates of the earth’s crust may accumulate there, a new study by geologists from the University of Alabama has shown.
Professor Samantha Hansen’s team used a network of 15 seismographs deployed in Antarctica.
The data were collected over a period of three years, “examining” the southern side of the boundary between the core and the mantle.
The main attention of scientists was drawn to the ultra-low viscosity regions (Ultra-Low Velocity Zone, ULVZ) – extremely dense sections of the boundary, causing a sharp slowdown in seismic waves.
ULVZ can be imagined as something like mountain ranges with a height of several to tens of kilometers.
Geologists have suggested that they may be the remains of ancient oceanic plates of the lithosphere, which, over many millions of years, have sunk almost to the very core.
“We are literally seeing mountains at the core of the earth that in some places can be five times the height of Mount Everest,” said Edward Garnero, one of the authors of the new work.
Recall that the earth’s crust is composed of two different types of plates: continental and oceanic.
Oceanic plates constantly “grow” at mid-ocean ridges and sink down in subduction zones – for example, going under more massive crust on the margins of the continents.
The ULVZ areas recorded by scientists do not correspond to modern subduction zones. This allowed us to assume that they went deep into the bowels of a very distant past.
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