The discovery resolves a debate that has raged for decades: Can the core and underlying mantle exchange any material with the Earth’s surface?
The Earth’s core is not completely isolated from the rest of the layers. The material inside the core has the ability to leak out and “smear” to the ground. This process has been going on for the past 2.5 billion years.
The element Tunsten (W) ranked 74th in the periodic table is found abundantly in the Earth’s core with several chemical isotopes. By studying the isotopes W-182 (with 108 neutrons) and W-184 (with 110 neutrons), scientists concluded that they originated in the core.
Structures that make up the Earth. (Image: Wikipedia).
Another element, Hafnium (Hf) is found in the silicate-rich mantle of the Earth. With a half-life of 8.9 million years, Hafnium’s radioactive isotope Hf-182 decays to W-182. This means the overlay must have more W-182 than the core.
Therefore, the chemical exchange between the core and the mantle can be detected by comparing the W-182 and W-184 ratios of basalt soils in the ocean.
However, this Tungsten difference, if any, is also extremely small: The Tungsten-182 composition in the mantle and core is expected to differ by only about 200 parts per million (ppm). Fewer than five laboratories worldwide are capable of performing this type of analysis.
In addition, studying the planetary core is not easy, because it begins at a depth of about 2,900 km underground. The deepest holes man has ever dug is the Kola Superdeep well in Russia, only about 12.3km.
Layers of molten rock tend to spill down to the core. (Photo: Universal-sci).
So the researchers looked for another object to extrapolate: Layers of molten rock from the deep mantle at the Pilbara Craton, Western Australia, Réunion Island and the Kerguelen Archipelago in the Indian Ocean. These layers of molten rock tend to spill down to the core.
The researchers found that the W-182 to W-184 ratio of the core rock was higher than most rocks today in the mantle. While it is correct, the rock of the mantle should have this ratio higher.
Since the ratio of W-182 to W-184 is higher, it means that Tunsgten from the core has been rising to the surface for quite a long time.
The Earth is about 4.5 billion years old, however, the oldest rock layer of the planet’s crust does not have any significant changes in the Tungsten isotope. This suggests that between 4.3 billion and 2.7 billion years ago, there was little or no material exchange from the core and mantle.
But over the past 2.5 billion years, the tungsten isotope composition in the mantle has changed dramatically. The researchers say the oxygen produced by the organism may have affected Tungsten.
Today’s theories allege that the Earth’s core is the cause of the magnetic field that protects our planet from deadly cosmic radiation. (Photo: Livescience).
Layers of molten rock from the Earth’s crust carry an abundance of oxygen to the edge of the mantle and cause Tungsten to separate from the core, rising above the mantle.
Or it is possible that after the Earth formed, the core gradually solidified, causing the concentration of oxygen concentrated in the outer core to increase, causing material leakage. In that case, further studies of the phenomenon could tell us how the Earth’s core has evolved, and also reveal the origin of the main planet’s magnetic field.
Today’s theories allege that a molten core of iron and nickel is responsible for the magnetic field that protects our planet from deadly cosmic radiation.