[Rockhounds] Earth’s Interior Is Cooling “Much Faster Than Expected”

[Kreigh Tomaszewski]

Researchers at ETH Zurich have demonstrated in the lab how well a mineral
common at the boundary between the Earth’s core and mantle conducts heat.
This leads them to suspect that the Earth’s heat may dissipate sooner than
previously thought.

The evolution of our Earth is the story of its cooling: 4.5 billion years
ago, extreme temperatures prevailed on the surface of the young Earth, and
it was covered by a deep ocean of magma. Over millions of years, the
planet’s surface cooled to form a brittle crust. However, the enormous
thermal energy emanating from the Earth’s interior set dynamic processes in
motion, such as mantle convection, plate tectonics, and volcanism.

Still unanswered, though, are the questions of how fast the Earth cooled
and how long it might take for this ongoing cooling to bring the
aforementioned heat-driven processes to a halt.

One possible answer may lie in the thermal conductivity of the minerals
that form the boundary between the Earth’s core and mantle.

This boundary layer is relevant because it is here that the viscous rock of
the Earth’s mantle is in direct contact with the hot iron-nickel melt of
the planet’s outer core. The temperature gradient between the two layers is
very steep, so there is potentially a lot of heat flowing here. The
boundary layer is formed mainly of the mineral bridgmanite. However,
researchers have a hard time estimating how much heat this mineral conducts
from the Earth’s core to the mantle because experimental verification is
very difficult.

Now, ETH Professor Motohiko Murakami and his colleagues from Carnegie
Institution for Science have developed a sophisticated measuring system
that enables them to measure the thermal conductivity of bridgmanite in the
laboratory, under the pressure and temperature conditions that prevail
inside the Earth.

https://scitechdaily.com/earths-interior-is-cooling-much-faster-than-expected/