The Earth is cooling faster than expected. Geologists from ETH Zurich have now been able to determine this using the thermal conductivity of the Earth’s mantle. According to this, the core transfers about 50% more heat to the mantle than previously assumed.
Hot core is a basic requirement for life on Earth
Life on Earth is also possible because the planet has life inside of it. Not only does the hot core of the Earth cause plate shifts, but mountains and volcanoes can also be traced back to this origin. In addition, the valuable protective factor of the Earth’s magnetic field should not be forgotten. This was also generated by underground currents. Layers of metal-bearing lava flow together in such a way that the planet is a giant dynamo and can block dangerous radiation from space using a strong magnetic field. According to some researchers, the complete cooling of the Earth’s core could cause our home planet to suffer the same fate as Mars.
The fact that this could one day be achieved is also due to the natural thermal conductivity of the cap. Bridgmanite is found largely in the transition zone between the mantle and the Earth’s core. This sticky layer of rock is constantly associated with iron-nickel lava, but is about 1,000 degrees Celsius hotter. “Because of the steep temperature gradient, this is the largest thermal limit on Earth, which raises the question of how quickly Earth loses heat and how long it can remain dynamically active,” say the researchers from ETH Zurich. In fact, the overall heat loss for the entire planet should depend on this limit.
Researchers had to mimic conditions in the heart of the Earth
To date, the measurement of thermal conductivity of bridgemanite has posed a significant problem. In order to determine how much heat the metal would absorb and release back, the scientists had to mimic the process underground and also consider the same conditions in terms of pressure and temperature. Swiss researchers have now managed to create exactly such a system by producing single-crystalline crystals of bridgemanite under high pressure and temperature and subjecting them to a pressure of 80 gigapascals using a diamond anvil cell. A laser can then be used to heat the crystals to a temperature of about 2,200°C.
The measurement can finally be made with a spectrometer. With this instrument, the outgoing radiation can be measured and conclusions can be drawn about the crystal lattice, thermal conductivity and heat.
About 5.3 Watts per meter and Kelvin (W/mK) are passed on by the metal. The researchers hypothesize that the overall thermal conductivity should be about 15.2 W/mK. The new findings are 1.5 times higher than previous geophysical estimates.
“Our results can give us a new perspective on the evolution of Earth’s dynamics,” says geologist Motohiko Murakami. “They suggest that Earth, like the other rocky planets Mercury and Mars, is cooling and becoming inactive much faster than expected.”
However, scientists have not been able to draw any conclusions about how long the Earth will be cold. “Under the present state of knowledge, the time of such events cannot be determined,” says the geologist. This will require more knowledge about the radioactive decay of the elements in the Earth’s core and about the process of mantle collecting.
Study link: https://www.sciencedirect.com/science/article/pii/S0012821X21005859
picture Eric Sucha employment pixabay
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